Keysight N5465A InfiniiSim Waveform Transformation Toolset

Keysight N5465A InfiniiSim Waveform Transformation Toolset
Keysight N5465A InfiniiSim
Waveform Transformation Toolset
Software
User's Guide
Notices
© Keysight Technologies, Inc. 2009-2015
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Ed ition
April 2015
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Contents
1 InfiniiSim Waveform Transformation Toolset
Starting InfiniiSim / 6
InfiniiSim Overview / Theory / 9
For Example: Removing a Cable's or Fixture's Insertion Loss / 9
InfiniiSim Features / 10
Measurement Circuit / Simulation Circuit Concept / 11
Correction Transfer Functions / 12
Circuit Model Block Configurations / 13
Using the InfiniiSim Wizard / 15
General Setup / 15
Select Model / 15
Measurement Block Setup / 16
Simulation Block Setup / 17
Observation Nodes / 18
Save File / 18
Creating a Transfer Function From a Model (2 Port) / 19
Application Presets (2 Port) / 20
Circuit Diagram View (2 Port) / 21
Circuit Source and Load Impedances (2 Port) / 23
Defining a Block (2 Port) / 24
Measurement and Simulation Node Locations (2 Port) / 36
Creating a Transfer Function From a Model (4 Port) / 38
Application Presets (4 Port) / 39
Circuit_Diagram View (4 Port) / 40
Circuit Source and Load Impedances (4 Port) / 42
Defining a Block (4 Port) / 43
Measurement and Simulation Node Locations (4 Port) / 56
Generating / Saving a Transfer Function File / 58
InfiniiSim Plots / 59
Frequency Response Plot / 60
Impulse Response Plot / 60
Step Response Plot / 62
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InfiniiSim Examples / 64
Removing the Insertion Loss of a Cable / 64
Simulating Crosstalk / 69
InfiniiSim Warning / Error Messages / 74
InfiniiSim Concepts / 80
S-Parameter Files / 80
Transfer Function Files / 82
Using the Bandwidth Limit Control / 83
InfiniiSim Reference Information / 86
InfiniiSim Setup Dialog Box / 86
InfiniiSim Model Setup Dialog Box / 88
Circuit Source and Load Impedances Dialog Box / 88
InfiniiSim Block Setup Dialog Box / 88
InfiniiSim Sub-circuit Block Setup Dialog Box / 88
InfiniiSim Node Setup Dialog Box / 89
Index
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Keysight N5465A InfiniiSim Waveform Transformation Toolset Software User's Guide
Keysight N5465A InfiniiSim Waveform Transformation Toolset Software
User's Guide
1 InfiniiSim Waveform
Transformation Toolset
Starting InfiniiSim / 6
InfiniiSim Overview / Theory / 9
Using the InfiniiSim Wizard / 15
Creating a Transfer Function From a Model (2 Port) / 19
Creating a Transfer Function From a Model (4 Port) / 38
Generating / Saving a Transfer Function File / 58
InfiniiSim Plots / 59
InfiniiSim Warning / Error Messages / 74
InfiniiSim Examples / 64
InfiniiSim Concepts / 80
InfiniiSim Reference Information / 86
NOTE
You must have either the InfiniiSim Basic or InfiniiSim Advanced application installed on your
oscilloscope to have access to these features.
The Basic version of InfiniiSim allows you to use only one block in your
measurement/simulation circuits (building these circuits is discussed in other InfiniiSim
topics) while the Advanced version contains all of the InfiniiSim capabilities.
Application Notes
See Also
•
"The ABCs of De-Embedding"
•
"De-embedding and Embedding S-Parameter Networks"
•
"De-embedding Techniques in Advanced Design Systems"
If you prefer to view a PDF version of this help, see "InfiniiSim User's Guide".
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InfiniiSim Waveform Transformation Toolset
Starting InfiniiSim
For an overview and theory of the InfiniiSim Waveform Transformation Toolset, see
“InfiniiSim Overview / Theory" on page 9.
To enter the InfiniiSim application:
1 Open the Channel dialog box. This dialog box can be accessed by:
NOTE
•
Choosing Setup > Channel 1... (or Channel 2, Channel 3, or Channel 4 depending
on the channel you want to use InfiniiSim on).
•
Clicking the channel buttons located directly above the waveform window.
You can also use InfiniiSim on a differential or common-mode channel by checking the
Differential box near the top of the Channel dialog box before proceeding to the next step.
2 After opening the Channel dialog box, set the entry controls for your specific
setup. The InfiniiSim entry controls are shown in this screen shot:
InfiniiSim is enabled by selecting either the 2 Port or 4 Port options within the
InfiniiSim section of the Channel dialog box. If you select 4 Port, you need to
specify whether it is two channel or one channel.
Additionally, if you are using 4 Port one channel InfiniiSim, you need to use the
Port Extraction controls to specify how to properly model your setup. This is a
transfer function port extraction.
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For channels 1 or 2:
•
Use Ports 1 -> 2 — you are using a single-ended path (port 1 to port 2) for the
4 port one channel analysis.
•
Use Ports 3 -> 2 — you are using a single-ended path (port 3 to port 2) for the
4 port one channel analysis.
•
Differential — you are using the differential path through the 4 port device.
•
Common Mode — you are using the common-mode path through the 4 port
device.
For channels 3 or 4:
•
Use Ports 3 -> 4 — you are using a single-ended path (port 3 to port 4) for the
4 port one channel analysis.
•
Use Ports 1 -> 4 — you are using a single-ended path (port 1 to port 4) for the
4 port one channel analysis.
•
Differential — you are using the differential path through the 4 port device.
•
Common Mode — you are using the common-mode path through the 4 port
device.
3 Click the Band wid th Limit... button and set the desired bandwidth. Bandwidth
limiting is independent of InfiniiSim waveform transformations and can be
applied to measured or simulated waveforms. It is implemented using a FIR
(finite impulse response) filter that has a size (time span) determined by the
filter size controls located inside the InfiniiSim Setup dialog box. For more
information, see: “Using the Bandwidth Limit Control" on page 83.
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4 Once you have selected the 2 Port or 4 Port options and set the Band wid th Limit,
click Setup... to open the InfiniiSim Setup dialog box.
5 If you already have a transfer function created, you can apply it simply by using
the Transfer Function File Name field to browse and select the file. Then, set the
other related controls (see “InfiniiSim Setup Dialog Box" on page 86).
If you need to create a transfer function:
•
And would like a wizard to guide you through the process, click Setup
Wizard....
For more information, see “Using the InfiniiSim Wizard" on page 15.
•
And would like to go through the process without guidance, click Create
Transfer Function from Model....
For more information, see:
8
•
“Creating a Transfer Function From a Model (2 Port)" on page 19
•
“Creating a Transfer Function From a Model (4 Port)" on page 38
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InfiniiSim Waveform Transformation Toolset
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InfiniiSim Overview / Theory
The InfiniiSim Waveform Transformation Toolset provides a flexible and accurate
way to render waveforms anywhere in a digital serial data link. InfiniiSim
transforms waveforms you actually measured into waveforms you wanted to
measure, but were unable to for some reason. The highly configurable system
modeling in InfiniiSim lets you:
•
Remove the deleterious effects of unwanted channel elements.
•
Simulate waveforms with channels models inserted.
•
View waveforms at physically unprobeable locations.
•
Compensate for the loading of probes and other circuit elements.
Next: “For Example: Removing a Cable's or Fixture's Insertion Loss" on page 9.
For Example: Removing a Cable's or Fixture's Insertion Loss
Many times your device under test (DUT) cannot be immediately accessed by your
measurement instrument. Instead, signals from the DUT must pass through
devices such as cables or fixtures before being measured. Therefore, you end up
measuring a combination of the DUT signal and the effects added from the various
other devices used to access the DUT. It would be great if you could isolate the
DUT and only measure its performance. InfiniiSim can be used to do just this.
One thing InfiniiSim lets you do is extract the DUT's signal from the measured
signal. For example, look at the following representation of a measurement.
The node that is indicated by the dotted line is the location you want to measure,
but the cable distorts this measurement. InfiniiSim can extract the undistorted
DUT signal from the distorted measured signal.
In a similar manner, you could use InfiniiSim to do the exact opposite — add the
effects of a cable or fixture to a measured signal. For example, SATA requires that a
10 m (30 ft) cable be used in the testing. However, this is a large and cumbersome
cable to use. It would be easier to simply take the measurement without the cable
and then add the effects of the 10 m cable into the measurement.
Next: “InfiniiSim Features" on page 10.
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InfiniiSim Features
InfiniiSim can perform the waveform transformation of inserting a cable or fixture
(see “For Example: Removing a Cable's or Fixture's Insertion Loss" on page 9), but
it can do much more. InfiniiSim is a general transformation tool that can be used to
produce more accurate results for a variety of problems. InfiniiSim provides default
configurations (called "application presets") for many common use models as well
as general purpose configurations for the advanced user. For example, you can:
10
•
Remove a channel element insertion loss — Modeled with one block of loss (blocks
are described in detail later) such as from a cable or fixture between a digital
source and the oscilloscope. The inverse gain of the block (S21-1) is determined,
and its time response is convolved with the acquired signal.
•
Insert a channel element insertion loss — Modeled with one block of loss, such as
from a standard cable model, that is inserted before the oscilloscope. The gain
of the block (S21) is determined, and its time response is convolved with the
acquired signal.
•
Remove scope input reflection — Modeled using two blocks — one for the
transmitter source and the other for the oscilloscope input (so the oscilloscope
input reflection can be removed).
•
Remove all effects of a channel element — By using S-parameter models of source
and oscilloscope load, the effects of a channel element are totally removed.
This is different from "removing insertion loss" in that the interactions between
the elements are taken into account. This provides the most accurate way to
remove a channel element.
•
Add all effects of a channel element — By using S-parameter models of source and
oscilloscope load, a complete insertion of a channel element is performed. This
is different from "inserting a channel element insertion loss" in that the
reflective interactions between the elements are taken into account. This
provides the most accurate rendering to insert a channel element.
•
Measurement node relocation — Measurement node relocation lets you view any
voltage waveform in a circuit by moving the observation node to any location
you desire. This is an "in situ" analysis so it is not a "removal" or "insertion"
viewpoint.
•
Remove load ing effects of an oscilloscope probe — To remove the loading effects of
a probe, a topology of circuit blocks is given that lets probe models be
considered in the measurement. An oscilloscope probe, while it might be
defined as "high impedance", really does have a loading effect on the circuit.
This effect can be taken into account and removed.
•
General purpose configuration — General-purpose topologies are provided for
greater flexibility. General purpose probe, 6 block, and 9 block topologies are
available with user defined measurement and simulation points. Additionally,
each block can be defined as having a combination of up to three elements in
cascade, series, or parallel arrangements giving you 27 total possible circuit
elements to define for the most sophisticated scenarios.
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Next: “Measurement Circuit / Simulation Circuit Concept" on page 11.
Measurement Circuit / Simulation Circuit Concept
InfiniiSim accomplishes its tasks (see “InfiniiSim Features" on page 10) through
the use of correction transfer functions. When using InfiniiSim, you define two
electrical circuits.
•
One circuit, the measurement circuit, models the actual physical electrical circuit
that produced the measured waveform.
•
The other circuit, the simulation circuit, models a hypothetical electrical circuit
that exhibits the electrical characteristics that you wished to have measured.
You can build these two circuits using the InfiniiSim GUI shown below. This is one
of the simplest 2-port models you can create. (The GUI also lets you develop much
more complex models as discussed later in other InfiniiSim topics.)
The values highlighted in light blue define the measurement circuit while the
values in light orange define the simulation circuit. In the above example, the
single-block model is used to represent the connection between the DUT and the
oscilloscope, and can be defined in a variety of ways (S-parameters, RLC circuits,
open, thru, lossless transmission line, etc.). When using more complex preset
configurations, you can move the measurement and simulation nodes to a variety
of locations within the model.
InfiniiSim analyzes these the measurement and simulation circuits and generates a
correction transfer function which, when applied to the measured waveform,
produces the desired simulated waveform on the oscilloscope's display.
The convolution process used by InfiniiSim requires that the measurement circuit
and the simulation circuit be linear and time-invariant (these are small-signal
analysis requirements).
Next: “Correction Transfer Functions" on page 12.
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Correction Transfer Functions
You now have a basic idea of what InfiniiSim can do, and you know that it
generates transfer functions from the two circuits you define in the application (see
“Measurement Circuit / Simulation Circuit Concept" on page 11), but how exactly
does it do this, and what is a transfer function?
A correction transfer function represents the ratio (in the frequency domain)
between voltage waveforms defined by two different conditions — one defined by
the measurement circuit, and the other defined by the simulation circuit. For any
given application, the correction transfer function can be calculated from circuit
models you create or loaded directly from a transfer function file.
If you create the transfer function through circuit models, you first create the
measurement and simulation circuits in the InfiniiSim GUI. The response of the two
circuits due to a stimulus from the same voltage source is calculated at their
specified observation nodes. The transfer function is then calculated from the ratio
(in the frequency domain) of the simulation node's response divided by the
measurement node's response. This ratio can then be convolved (in the time
domain) with the measured waveform in order to convert it into the desired
simulated waveform.
Note that in 4-port mode, there are actually two sources and observation nodes in
each circuit. In this case, the ratio of node voltages becomes a matrix division
operation generating a set of four frequency domain functions that are convolved
with the two measured waveforms to produce the desired simulated waveforms.
It is also important to realize that transfer function files and S-parameter files are
not the same thing. S-parameter files represent complete electrical models of
physical elements and can be used to define specific model blocks within the
circuit models. Transfer function files represent the relationship between measured
and simulated voltage waveforms. For more information, see “S-Parameter
Files" on page 80 and “Transfer Function Files" on page 82.
InfiniiSim can be used on differential signals as well as single-ended signals.
•
In single-ended applications, the measurement and simulation circuits are
constructed from 2-port network model blocks and the analysis is performed
on each oscilloscope channel independently.
•
In differential applications, you must decide whether to use 2-port analysis or
4-port analysis. 2-port analysis can be used on differential signals or
common-mode signals independently, but it does not include cross-coupling
components between the differential and common-mode signals.
Note that you would use 2-port analysis on a differential signal if that signal is
being converted to a single oscilloscope channel input by a differential probe.
Next: “Circuit Model Block Configurations" on page 13.
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Circuit Model Block Configurations
There are a wide variety of configurations possible using the InfiniiSim GUI. This
section describes three of the "application preset" configurations to give you a
brief overview of how they are used.
Remember that the model blocks in these configurations are used to represent a
certain device and can be defined in a variety of ways (S-parameters, RLC circuits,
open, thru, lossless transmission line, etc. — defining a circuit model block is
discussed in more detail under the "Creating a Transfer Function From a Model"
topics).
•
One Block for Simplest Path Compensation
The configuration shown below is a basic one-block model. Many times you
simply want to compensate for the loss of a channel element such as a cable or
fixture. This one-block model can perform this task. It can also be extended to a
remove/replace operation by changing the simulation parameters.
•
Three Block Analysis for True Channel Element Removal and Insertion
When the most precision for a single channel element removal / insertion is
required, you need at least the 3-block model (an example of a 3-block model
is shown below). This model uses block descriptions for transmitter (T) and
receiver (S) as well as the channel (C) to describe the full system. The inclusion
of the transmitter and receiver blocks enable the most complete waveform
rendering by including the reflective S-parameter elements in the mathematical
calculation of the transfer function used to transfer from the measurement (M)
to the simulated measurement (S).
•
General Purpose Configuration
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InfiniiSim Waveform Transformation Toolset
The InfiniiSim waveform transformation toolset includes three general-purpose
topologies to enable detailed tailoring of the description of your circuit:
For More
Information
14
•
For probe modeling, the general-purpose probe topology is used.
•
For SMA differential probe usage, the general-purpose 6-block model is
used in the majority of cases.
•
For those very sophisticated applications (for example, using both high
impedance probes and differential SMA probe heads), the general purpose
model can be used to describe these complex cases.
Now that you have a seen a high-level explanation of the InfiniiSim Waveform
Transformation Toolset, refer to the following topics for a more detailed look at the
controls as well as additional information regarding the InfiniiSim application.
•
“Starting InfiniiSim" on page 6
•
“Using the InfiniiSim Wizard" on page 15
•
“Creating a Transfer Function From a Model (2 Port)" on page 19
•
“Creating a Transfer Function From a Model (4 Port)" on page 38
•
“Generating / Saving a Transfer Function File" on page 58
•
“InfiniiSim Plots" on page 59
•
“InfiniiSim Warning / Error Messages" on page 74
•
“InfiniiSim Examples" on page 64
•
“InfiniiSim Concepts" on page 80
•
“InfiniiSim Reference Information" on page 86
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Using the InfiniiSim Wizard
The InfiniiSim Wizard helps you quickly set up InfiniiSim by walking you through
the necessary steps.
•
“General Setup" on page 15
•
“Select Model" on page 15
•
“Measurement Block Setup" on page 16
•
“Simulation Block Setup" on page 17
•
“Observation Nodes" on page 18
•
“Save File" on page 18
Clicking the Cancel button will undo any selections or changes.
General Setup
InfiniiSim consists of two circuits:
•
The Measurement Circuit is a description of what your system actually is.
•
The Simulation Circuit is a description of what you want your system to be like.
InfiniiSim creates a transfer function to convert between the Measurement Circuit
(real) and the Simulation Circuit (desired).
For example, you may be using a cable that is having undesired effects on your
oscilloscope measurements. In the Measurement Circuit, there would be a block
that describes the electrical characteristics of the cable (such as an RLC circuit or
S-parameter file). In the Simulation Circuit, it would just be a "Thru" because
InfiniiSim creates a transfer function that compensates for the electrical impact of
the cable. This means the waveforms shown on the oscilloscope are what you
would be seeing if the cable had no electrical impact at all.
These are the colors for the Measurement (light blue) and Simulation Circuits (light
orange).
Select Model
Select the InfiniiSim model you want to use.
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For more information on the various InfiniiSim models, see “InfiniiSim Features" on
page 10.
Measurement Block Setup
When you have selected the "Add/remove insertion loss of a fixture or cable"
InfiniiSim models, the next step in the InfiniiSim Wizard lets you set up the
measurement block.
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For more information on measurement circuits and setting them up, see:
•
“Measurement Circuit / Simulation Circuit Concept" on page 11
•
“Correction Transfer Functions" on page 12
•
“Defining a Block (2 Port)" on page 24
•
“Defining a Block (4 Port)" on page 43
Simulation Block Setup
When you have selected the "Add/remove insertion loss of a fixture or cable"
InfiniiSim models, the next step in the InfiniiSim Wizard lets you set up the
simulation block.
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For more information on simulation circuits and setting them up, see:
•
“Measurement Circuit / Simulation Circuit Concept" on page 11
•
“Correction Transfer Functions" on page 12
•
“Defining a Block (2 Port)" on page 24
•
“Defining a Block (4 Port)" on page 43
Observation Nodes
The Observation Nodes are indicated by the "M" and "S" icons shown below.
•
Measurement Observation Node
•
Simulation Observation Node
•
Both Measurement and Simulation Nodes
The Measurement Node corresponds to the location in the circuit where you
actually measured the original signal.
The Simulation Node corresponds to the location in the circuit where you wished
you could have measured the signal.
An Observation Node can be moved by clicking the node where you want it to go.
However, there are situations where a node cannot be made into an Observation
Node.
Save File
Enter the name of the transfer function file. This file is created by InfiniiSim based
upon the Measurement and Simulation models you have specified. To use these
models again, just use select this file instead of running this wizard.
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Creating a Transfer Function From a Model (2 Port)
This section describes how to generate a transfer function from a model using the
InfiniiSim Model Setup dialog box (accessed by clicking the Create Transfer Function
from Model... button in the “InfiniiSim Setup Dialog Box" on page 86).
(No models are shown in the InfiniiSim Model Setup dialog box's default view
above because the Application Preset field is set to None.)
Follow these steps to create a transfer function from a model:
1 Select one of the application presets. See “Application Presets (2 Port)" on
page 20.
2 In the Transfer Function File (Not Saved) field, specify the name of the transfer
function file you will create.
3 (Optional) Select the circuit diagram view. See “Circuit Diagram View
(2 Port)" on page 21.
4 Specify the circuit source and load impedances. See “Circuit Source and Load
Impedances (2 Port)" on page 23.
5 Define measurement circuit and simulation circuit blocks. See “Defining a Block
(2 Port)" on page 24.
6 Specify measurement and simulation node locations. See “Measurement and
Simulation Node Locations (2 Port)" on page 36.
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7 Click Save Transfer Function to generate and save the transfer function file.
NOTE
The transfer function you create in this dialog box is not saved until you click the Save
Transfer Function button. If you close the dialog box without saving, your transfer function is
not applied.
See: “Generating / Saving a Transfer Function File" on page 58.
Application Presets (2 Port)
The first field in the InfiniiSim Model Setup dialog box is labeled Application Preset.
This drop-down field gives you a variety of preset configurations you can work with
to build your own model. The available preset configurations for InfiniiSim Basic
and InfiniiSim Advanced are:
•
None (Basic and Advanced)
•
Add insertion loss of a fixture or cable (Basic and Advanced)
•
Remove insertion loss of a fixture or cable (Basic and Advanced)
•
Remove scope input reflection (Advanced)
•
Add all effects of a fixture or cable (Advanced)
•
Remove all effects of a fixture or cable (Advanced)
•
Replace one channel element with another (Advanced)
•
Relocate the observation node of a measurement (Advanced)
•
Remove load ing effects of a probe (Advanced)
•
Remove load ing effects of a DDR interposer and probe (Advanced)
•
Relocate the observation node of a probed measurement (Advanced)
•
General purpose probe (Advanced)
•
General purpose 6 blocks (Advanced)
•
General purpose 9 blocks (Advanced)
To understand the basic components that make up these configurations, look at a
very simple example. The following circuit appears in the InfiniiSim Model Setup
dialog box when you set the Application Preset field to Add Insertion Loss of a Fixture or
Cable.
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Notice that some values are highlighted light blue and some highlighted red.
These correspond to the measurement and simulation circuit respectively.
•
Measurement Circuit — This circuit models the actual physical circuit that
produced the measured waveform.
•
Simulation Circuit — This circuit models a hypothetical electrical circuit that
exhibits your desired electrical characteristics.
In other words, the measurement circuit is what you actually measured and the
simulation circuit is what you wish you would have been able to measure.
InfiniiSim analyzes these two circuits and generates a correction transfer function
which, when convolved with the measured waveform, produces the desired
simulated waveform. For more information on transfer functions and how InfiniiSim
generates them, see “InfiniiSim Overview / Theory" on page 9 and “Transfer
Function Files" on page 82.
Circuit Diagram View (2 Port)
If you look under the Circuit Diagram View section in the InfiniiSim Model Setup
dialog box, you see that you have three viewing options.
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Measurement & Simulation
Circuits
Measurement Circuit Only
Simulation Circuit Only
These choices let you build/view the measurement circuit, the simulation circuit, or
both at the same time.
It is important to note that these circuit model representations in the GUI are
simplified for ease of viewing. If we were being explicit, the model blocks in the
circuit would look like the following for a 2-port device:
The diagrams in the GUI are completely interactive so you can click various
sections or components and make adjustments.
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Circuit Source and Load Impedances (2 Port)
The resistor on the left side of the circuit shown below corresponds to the
impedance of the transmitter. It is defaulted to 50 Ω, but you can change this if
needed. Simply place your cursor over the resistor (it highlights to indicate you are
on top of it) and click.
You then see the following Circuit Source and Load Impedances dialog box.
The Circuit Source and Load Impedances dialog box lets you specify all of the
source and load impedances within both the measurement and simulation circuits.
Note that if we did not have the Apply to All box checked, the Add Insertion Loss
application preset (used in the screen shot above) would grey-out the load
impedance controls because the oscilloscope load impedance is always 50 Ω.
If you want all impedances in both measurement and simulation circuits to be
identical, simply check the Apply to All box and set the All Impedance value. All of
the other impedances are then changed to match this one.
Note that by using one of the 3-block models (for example, the Add/Remove All
Effects of a Fixture or Cable application preset), you can apply an arbitrarily complex
transmitter and/or oscilloscope impedance using the additional model blocks
dedicated to forming the transmitter source impedance and oscilloscope input
impedance.
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Note that any termination block located adjacent to a source or load resistor (like
the T block and S block above) can have 1 port S-parameter files assigned to them
in 2 port InfiniiSim mode. These are the only locations in a 2 port InfiniiSim circuit
where you can place 1 port S-parameter (s1p) files. Likewise, termination blocks
can be defined by 2 port S-parameter files in 4 port mode. You can also use a
1 port S-parameter file for a 4 port application which will apply that s1p to s11 and
s33 and set s13 and s31 to zero.
Defining a Block (2 Port)
The blocks used in creating the measurement and simulation circuits may be used
to model various components (cable loss, probe loading, a fixture, etc.).
InfiniiSim assigns letters and names to the blocks in the legend for a typical use
scenario depending upon the application preset chosen. These names are just a
convenience for referring to blocks and an example of how the block may be used.
However, you can define them any way you like. You can change these names by
using the Block Name control inside the Block Setup dialog box (accessed by
clicking one of the blocks).
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While blocks represent different parts of the circuit, they have the exact same
definition controls to choose from and are simply called different types to help you
understand what they might represent in your circuit. The termination blocks, T
and S, are different in one respect — those blocks can be defined by return loss
only S-parameter files (1 port file in 2 port InfiniiSim analysis mode).
When you click a block, the InfiniiSim Block Setup dialog box opens.
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The first section (Measurement/Simulation Circuit), lets you specify whether you are
currently defining a block in the measurement circuit or the simulation circuit. For
instance, if you select Simulation Circuit in this section and then set the Block Type to
Ideal Thru, then the corresponding block in the simulation circuit is set to a Thru
block.
The Block Name control lets you customize the name of the block.
The bottom section (Block Type) is where you actually define the block. There are
six choices in this section.
•
Ideal Thru — Nothing happens to the signal as it passes through a Thru block. It
is as though the block was not there and port 1 is shorted directly to port 2.
•
Open — When you set the block to open, no signal passes through it. It is as
though port 1 and port 2 form an open circuit.
•
RLC — This lets you set up the block as a RLC (resistor, inductor, capacitor)
network. See “RLC Block Type (2 Port)" on page 26.
•
S-parameter File — If you have an S-parameter file that models a fixture, cable,
probe, or device in your circuit, you can load it into InfiniiSim and use it for the
block definition. See “S-Parameter File Block Type (2 Port)" on page 27.
•
Transmission Line (Lossless) — This defines the block as an ideal lossless
transmission line. This block is defined by a characteristic impedance value and
a time delay value. See “Transmission Line Block Type (2 Port)" on page 30.
•
Combination Of Sub-circuits — This selection lets you use up to three blocks in
place of the one. These three sub-blocks can be arranged in cascade, parallel,
or series. See “Combination of Sub-Circuits Block Type (2 Port)" on page 30.
•
Probe — This selection models the effects of the probe that is connected to the
current InfiniiSim channel. The model is inserted in series with the signal path
and is used when the measured or simulated signal travels through the probe to
the input of the oscilloscope. See “Probe Block Type (2 Port)" on page 33.
•
Probe Load — This selection allows the modeling of a probe load in shunt with
the signal path. This model is used when the measured or simulated signal
does not travel through the probe, but is only loaded by a probe from a different
channel. See “Probe Load Block Type (2 Port)" on page 34.
Once your circuits are built, select the appropriate measurement node location
and the desired simulation node location (see “Measurement and Simulation
Node Locations (2 Port)" on page 36), then generate, save, and apply the
correction transfer function (see “Generating / Saving a Transfer Function File" on
page 58).
RLC Block Type (2 Port)
When you select RLC for the block type, additional controls appear at the bottom
of the dialog box.
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For Circuit Element, you can choose:
•
Series Thru
•
Parallel Thru
•
Series Shunt
•
Parallel Shunt
When you select one of these options, the basic circuit configuration is shown in
the dialog box (see screen shot above).
After selecting the configuration of the RLC circuit, you can set the values for the
Resistance, Inductance, and Capacitance. If you do not want to use an inductor or
capacitor in your RLC circuit, do not check the boxes located next to each entry.
S-Parameter File Block Type (2 Port)
When you select S-parameter File for the block type, additional controls appear at
the bottom of the dialog box.
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You can click the S-parameter File field to browse to your saved S-parameter files.
S-parameter files are typically generated using a vector network analyzer or circuit
simulator, for example, and then saved on the oscilloscope hard drive. These can
be files that model fixtures, cables, devices, or probes in your circuit. InfiniiSim
accepts both Touchstone files (.s1p, .s2p, .s4p) and CITIfile (.cti) files.
By default, the oscilloscope expects port 1 to be on the left of the block and port 2
to be on the right. However, this may not match the way the data is defined in your
S-parameter file. Therefore, you can check the Flip Model box to switch ports 1 and
2.
If you select a 4-port S-parameter file (.s4p file) in this step (remember we are
performing a 2-port InfiniiSim analysis in this topic), the oscilloscope needs to
know how to interpret the data in the S-parameter file (because there are more
than two ports worth of information contained in a 4-port file). In this case, you see
the additional 4-Port Numbering and Port Extraction controls.
The 4 Port Numbering control lets you specify how the data is arranged in the 4-port
S-parameter file. There is an industry standard numbering system:
However, you can tell InfiniiSim that your file actually uses the following
numbering system.
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You can also use the Flip Model box to flip the numbers between the right side and
the left side.
Flip Model
4 Port Numbering
No
1-2, 3-4
No
1-3, 2-4
Yes
1-2, 3-4
Yes
1-3, 2-4
How Ports are Connected in Block
The Port Extraction field tells InfiniiSim how to extract a 2-port model from the
4-port S-parameter file and use it in your 2-port transformation.
For example, if you select 1-2, 3-4 for the 4-port Numbering field, you are offered the
following choices:
•
Use Ports 1 -> 2 — this means you are only extracting the port 1 and 2
information from the 4-port S-parameter file (one single-ended path through
the differential model)
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•
Use Ports 3 -> 4 — this means you are only extracting the port 3 and 4
information from the 4-port S-parameter file (the other single-ended path
through the differential model)
•
Differential — this means you are extracting port D1 and port D2 of a
mixed-mode view of the file (differential path through the 4-port file)
•
Common Mode — this means you are extracting port C1 and port C2 of a
mixed-mode view of the file (common-mode path through the 4-port file)
For additional information regarding the reading of S-parameter files, see
“S-Parameter Files" on page 80.
Transmission Line Block Type (2 Port)
When you select Transmission Line (Lossless) for the block type, two additional fields
appear for setting the Characteristic Impedance of the transmission line in your
model block as well as its Propagation Delay.
Combination of Sub-Circuits Block Type (2 Port)
The Combination Of Sub-circuits selection lets you use a combination of three
sub-blocks in place of one block. When you make this selection, additional
controls appear at the bottom of the dialog box.
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You have the following three choices for how to set up the three individual blocks
that now make up the one circuit block (pictures show connections for two of the
three blocks for simplicity).
Cascade
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Parallel
Series
Once you select one of these three configurations, you can click each individual
block and define what type of block it is.
When you click one of the sub-blocks a new InfiniiSim Sub-circuit Block Setup
dialog box appears where you can define its type
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Notice that you can choose between Thru, Open, RLC, S-parameter File, Transmission
Line, and an option called Unused. Unused simply means that this particular
sub-block is not used (letting you use 2 sub-blocks instead of three, for example).
Using the Unused setting has a different effect on this specific block depending on
which configuration is being used.
•
For the Cascade structure, for example, Unused acts like a Thru block.
•
For the Parallel structure, Unused acts like an Open block.
Probe Block Type (2 Port)
The Probe block type selection models the effects of the probe that is connected to
the current InfiniiSim channel. The model is inserted in series with the signal path
and is used when the measured or simulated signal travels through the probe to
the input of the oscilloscope.
You can select the Probe block type only in the blocks that are intended to model
the oscilloscope input (for example, the ones circled in yellow below).
A probe must be connected to the channel in order for the Probe block type
selection to be active.
When you make the Probe block type selection, the appropriate probe input
impedance file is automatically selected, based on your selections in the Probe
Configuration dialog box.
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Probe Load Block Type (2 Port)
The Probe Load block type selection lets you model a probe load in shunt with the
signal path. This model is used when the measured or simulated signal does not
travel through the probe, but is only loaded by a probe from a different channel.
The Probe Load block type is not allowed in those blocks that are intended to model
the oscilloscope input (for example, the ones not circled in yellow below).
When the Probe Load block type is selected it does two things: port 1 and 2 of the
block are connected together (like an Ideal Thru) and the supplied S-parameter
file is used to describe the shunt impedance loading the connected ports.
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Probe Load block
1
ports of the
model block
2
1
2
Zt
S-parameter File
for impedance loading
When you make the Probe Load block type selection, additional controls appear at
the bottom of the dialog box:
•
S-parameter File — Used to describe an impedance loading.
If a 1-port S-parameter (s1p) file is selected, you can ignore port 2 of the load
and the Termination Impedance (Zt).
If a 2-port S-parameter (s2p) file is selected, port 2 of the load is as shown, and
the desired Termination Impedance (Zt) should be entered.
On Infiniium oscilloscopes with the Windows 7 operating system, input
impedance files in are located in the "C:\Users\Public\Documents\Infiniium\
Filters\Probes\InfiniiMax" directory.
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•
Termination Impedance — Again, with a 1-port S-parameter (1sp) file, you can
ignore the Termination Impedance (Zt). With a 2-port S-parameter (s2p) file,
the desired Termination Impedance (Zt) should be entered.
•
Flip Model — If your S-parameter file has a different port ordering, you can check
this box to switch ports 1 and 2.
Measurement and Simulation Node Locations (2 Port)
You can also change the location of the measurement and simulation nodes. The
measurement node corresponds to the location in the circuit where you actually
measured the original signal. The simulation node corresponds to the location in
the circuit where you wished you could have measured the signal.
Look at the model below that shows both the measurement and simulation circuit
view. The light blue circle labeled M is the measurement node and the light orange
circle labeled S is the simulation node.
In this 1-block model, the measurement and simulation nodes cannot be moved
anywhere else in the circuit (there are no empty node locations in the circuit)
because this simple preset only lets you add insertion loss of a device.
However, in more complex configurations such as the General purpose 6 blocks
application preset configuration shown below, you can change the location of the
measurement and/or simulation node.
To change the nodes, click one of the empty node locations; then, select either
Move the Measurement Node here or Move the Simulation Node here from the InfiniiSim
Node Setup dialog box (as shown below).
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Creating a Transfer Function From a Model (4 Port)
This section describes how to generate a transfer function from a model using the
InfiniiSim Model Setup dialog box (accessed by clicking the Create Transfer Function
from Model... button in the “InfiniiSim Setup Dialog Box" on page 86).
(No models are shown in the InfiniiSim Model Setup dialog box's default view
above because the Application Preset field is set to None.)
Follow these steps to create a transfer function from a model:
1 Select one of the application presets. See “Application Presets (4 Port)" on
page 39.
2 In the Save Transfer Function File As field, specify the name of the transfer function
file you will create.
3 (Optional) Select the circuit diagram view. See “Circuit_Diagram View
(4 Port)" on page 40.
4 Specify the circuit source and load impedances. See “Circuit Source and Load
Impedances (4 Port)" on page 42.
5 Define measurement circuit and simulation circuit blocks. See “Defining a Block
(4 Port)" on page 43.
6 Specify measurement and simulation node locations. See “Measurement and
Simulation Node Locations (4 Port)" on page 56.
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7 Generate and save the transfer function file.
NOTE
The transfer function you create in this dialog box is not saved until you click the Save
Transfer Function button. If you close the dialog box without saving, your transfer function is
not applied.
See: “Generating / Saving a Transfer Function File" on page 58.
Application Presets (4 Port)
The first field in the InfiniiSim Model Setup dialog box is labeled Application Preset.
This drop-down field gives you a variety of preset configurations you can work with
to build your own model. The available preset configurations for InfiniiSim Basic
and InfiniiSim Advanced are:
•
None (Basic and Advanced)
•
Add insertion loss of a fixture or cable (Basic and Advanced)
•
Remove insertion loss of a fixture or cable (Basic and Advanced)
•
Remove scope input reflection (Advanced)
•
Add all effects of a fixture or cable (Advanced)
•
Remove all effects of a fixture or cable (Advanced)
•
Replace one channel element with another (Advanced)
•
Relocate the observation node of a measurement (Advanced)
•
Remove load ing effects of a probe (Advanced)
•
Remove load ing effects of a DDR interposer and probe (Advanced)
•
Relocate the observation node of a probed measurement (Advanced)
•
General purpose probe (Advanced)
•
General purpose 6 blocks (Advanced)
•
General purpose 9 blocks (Advanced)
To understand the basic components that make up these configurations, look at a
very simple example. The following circuit appears in the InfiniiSim Model Setup
dialog box when you set the Application Preset field to Add Insertion Loss of a Fixture or
Cable.
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Notice there are some values highlighted light blue and some highlighted red.
These correspond to the measurement and simulation circuit respectively. Let us
first define what we mean by each of these circuits.
•
Measurement Circuit — This circuit models the actual physical circuit that
produced the measured waveform.
•
Simulation Circuit — This circuit models a hypothetical electrical circuit that
exhibits your desired electrical characteristics.
In other words, the measurement circuit is what you actually measured and the
simulation circuit is what you wish you would have been able to measure.
InfiniiSim analyzes these two circuits and generates a correction transfer function
which, when convolved with the measured waveform, produces the desired
simulated waveform. For more information on transfer functions and how InfiniiSim
generates them, see “InfiniiSim Overview / Theory" on page 9 and “Transfer
Function Files" on page 82.
Circuit_Diagram View (4 Port)
If you look under the Circuit Diagram View section in the InfiniiSim Model Setup
dialog box, you see that you have three viewing options.
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Measurement & Simulation
Circuits
Measurement Circuit Only
Simulation Circuit Only
These choices let you build/view the measurement circuit, the simulation circuit, or
both at the same time.
It is important to note that these circuit model representations in the GUI are
simplified for ease of viewing. If we were being explicit, the model blocks in the
circuit would look like the following for a 4-port device:
The diagrams in the GUI are completely interactive so you can click various
sections or components and make adjustments.
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Circuit Source and Load Impedances (4 Port)
The resistor on the left side of the circuit shown below corresponds to the
impedance of the transmitter. It is defaulted to 50 Ω, but you can change this if
needed. Simply place your cursor over the resistor (it thickens to indicate you are
on top of it) and click.
You then see the following Circuit Source and Load Impedances dialog box.
The Circuit Source and Load Impedances dialog box lets you specify all of the
source and load impedances within both the measurement and simulation circuits.
Note that if we did not have the Apply to All box checked, the Add Insertion Loss
application preset (used in the screen shot above) would grey-out the load
impedance controls because the oscilloscope load impedance is always 50 Ω.
If you want all impedances in both measurement and simulation circuits to be
identical, simply check the Apply to All box and set the All Impedance value. All of
the other impedances are then changed to match this one.
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Note that by using one of the 3-block models (for example, the Add/Remove All
Effects of a Fixture or Cable application preset), you can apply an arbitrarily complex
transmitter and/or oscilloscope impedance using the additional model blocks
dedicated to forming the transmitter source impedance and oscilloscope input
impedance.
Please note that any termination block located adjacent to a source or load
resistor (like the T block and S block above) can have 1 port S-parameter files
assigned to them in 2 port InfiniiSim mode. These are the only locations in a 2 port
InfiniiSim circuit where you can place 1 port S-parameter (s1p) files. Likewise,
termination blocks can be defined by 2 port S-parameter files in 4 port mode. You
can also use a 1 port S-parameter file for a 4 port application which will apply that
s1p to s11 and s33 and set s13 and s31 to zero.
Defining a Block (4 Port)
The blocks used in creating the measurement and simulation circuits may be used
to model various components (cable loss, probe loading, a fixture, etc.).
InfiniiSim assigns letters and names to the blocks in the legend for a typical use
scenario depending upon the application preset chosen. These names are just a
convenience for referring to blocks and an example of how the block may be used.
However, you can define them any way you like. You can change these names by
using the Block Name control inside the Block Setup dialog box (accessed by
clicking one of the blocks).
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While blocks represent different parts of the circuit, they have the exact same
definition controls to choose from and are simply called different types to help you
understand what they might represent in your circuit. The termination blocks, T
and S, are different in one respect — those blocks can be defined by return loss
only S-parameter files (2 port file in 4 port InfiniiSim analysis mode). You can also
use a 1-port S-parameter (s1p) file for a 4 port application which will apply that
s1p to s11 and s33 and set s13 and s31 to zero.
When you click a block, the InfiniiSim Block Setup dialog box opens.
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The first section (Measurement/Simulation Circuit), lets you specify whether you are
currently defining a block in the measurement circuit or the simulation circuit. For
instance, if you select Simulation Circuit in this section and then set the Block Type to
Ideal Thru, then the corresponding block in the simulation circuit is set to a Thru
block.
The Block Name control lets you customize the name of the block.
Next, you need to select the Block Port Type.
Using full 4-port S-parameter models is often necessary because they include
cross-coupling components between all four ports in the model. However, it is
sometimes more convenient to split the 4-port model into two uncoupled 2-port
models. You can, for example, choose to use two 2-port S-parameter files to
model a pair of coaxial cables. Another example is when you have an accurate
S-parameter file for the differential path through a device, but not for the
common-mode path. You can use a 2-port differential S-parameter file to model
the differential path through the device and an RLC block to model the
common-mode path.
Consequently (in 4 port analysis mode), you can select these block port types:
•
(2) 2 Port — You can define the 4-port model blocks as a combination of two
uncoupled 2-port model blocks — one for the path between ports 1 and 2 and
one for the path between ports 3 and 4.
In this case, you can define each 2-port Block Type independently to be an Ideal
Thru, Open, RLC, Transmission Line (Lossless), S-parameter File, or Combination Of
Sub-circuits.
•
(2) 2 Port Differential — You can define the 4-port model block as a combination
of two different uncoupled 2-port model blocks — one for the differential path
through the device and one for the common-mode path through the device.
In this case, you can define each 2-port Block Type independently to be an Ideal
Thru, Open, RLC, Transmission Line (Lossless), S-parameter File, or Combination Of
Sub-circuits.
•
4 Port — This uses a standard 4 port model.
In this case, you can define the Block Type to be an Ideal Thru, Open, 4-port
S-parameter File, or Combination Of Sub-circuits. RLC and Transmission Line (Lossless)
block types are not available in 4-port Block Port Type mode.
The bottom section (Block Type) is where you actually define the block. There are
six choices in this section.
•
Ideal Thru — Nothing happens to the signal as it passes through a Thru block. It
is as though the block was not there and port 1 is shorted directly to port 2.
•
Open — When you set the block to open, no signal passes through it. It is as
though port 1 and port 2 form an open circuit.
•
RLC — This lets you set up the block as a RLC (resistor, inductor, capacitor)
network. See “RLC Block Type (4 Port)" on page 46.
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•
S-parameter File — If you have an S-parameter file that models a fixture, cable,
probe, or device in your circuit, you can load it into InfiniiSim and use it for the
block definition. See “S-Parameter File Block Type (4 Port)" on page 47.
•
Transmission Line (Lossless) — This defines the block as an ideal lossless
transmission line. This block is defined by a characteristic impedance value and
a time delay value. See “Transmission Line Block Type (4 Port)" on page 49.
•
Combination Of Sub-circuits — This selection lets you use up to three blocks in
place of the one. These three sub-blocks can be arranged in cascade, parallel,
or series. See “Combination of Sub-Circuits Block Type (4 Port)" on page 50.
•
Probe — This selection models the effects of the probe that is connected to the
current InfiniiSim channel. The model is inserted in series with the signal path
and is used when the measured or simulated signal travels through the probe to
the input of the oscilloscope. See “Probe Block Type (4 Port)" on page 53.
•
Probe Load — This selection allows the modeling of a probe load in shunt with
the signal path. This model is used when the measured or simulated signal
does not travel through the probe, but is only loaded by a probe from a different
channel. See “Probe Load Block Type (4 Port)" on page 54.
Once your circuits are built, select the appropriate measurement node location
and the desired simulation node location (see “Measurement and Simulation
Node Locations (4 Port)" on page 56), then generate, save, and apply the
correction transfer function (see “Generating / Saving a Transfer Function File" on
page 58).
RLC Block Type (4 Port)
The RLC block type is only available in the (2) 2 Port and (2) 2 Port Differential port
type modes. In the (2) 2 Port mode, either single-ended path of the model block
can be defined by a 2 port RLC model. In the (2) 2 Port Differential mode, either
the differential or common-mode paths can be defined by a 2 port RLC model.
When you select RLC for the Block Type (not available in 4 port Block Port Type
mode) and the Block Port Type is set to (2) 2 Port Differential, the dialog box looks like
the following.
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In the Circuit Element section, there are four configuration options (Series Thru,
Parallel Thru, Series Shunt, and Parallel Shunt). When you select one of these options,
the basic circuit configuration is shown in the dialog box (see screen shot above).
After selecting the configuration of the RLC circuit, you can set the values for the
resistor, inductor, and capacitor using the fields to the right. To use an inductor or
capacitor in your RLC circuit, check the corresponding box and then enter the
value.
S-Parameter File Block Type (4 Port)
When you select S-parameter File for the block type, additional controls appear in
the dialog box.
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You can click the S-parameter File field to browse to your saved S-parameter files.
S-parameter files are typically generated using a vector network analyzer or circuit
simulator, for example, and then saved on the oscilloscope hard drive. These can
be files that model fixtures, cables, devices, or probes in your circuit. InfiniiSim
accepts both Touchstone files (.s1p, .s2p, .s4p) and CITIfile (.cti) files.
InfiniiSim can read 4 port or 2 port files in 4 Port Block Port Type mode. It can read
4 port, 2 port, and 1 port files in (2) 2 Port or (2) 2 Port Differential Block Port Type
mode. If you use a 1-port S-parameter (s1p) file for a 4 port application, that s1p
will apply to s11 and s33 and set s13 and s31 to zero. Additional information about
reading S-parameter files can be found in “S-Parameter Files" on page 80.
By default, the oscilloscope expects ports 1 and 3 to be on the left side of the
block (if you have the Block Port Type set to 4 Port) and ports 2 and 4 to be on the
right. However, this may not match the way the data is formatted in your
S-parameter file. Therefore, you can check the Flip Model box to have the ports
switch sides.
You may also see the 4 Port Numbering control depending upon your settings. The
4 Port Numbering control lets you specify how the data is arranged in the 4-port
S-parameter file. There is an industry standard numbering system:
However, you can tell InfiniiSim that your file actually uses the following
numbering system.
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You can also use the Flip Model box to flip the numbers between the right side and
the left side.
Flip Model
4 Port Numbering
No
1-2, 3-4
No
1-3, 2-4
Yes
1-2, 3-4
Yes
1-3, 2-4
How Ports are Connected in Block
For additional information regarding the reading of S-parameter files, see
“S-Parameter Files" on page 80.
Transmission Line Block Type (4 Port)
When you select Transmission Line (Lossless) for the block type, two additional fields
appear for setting the Characteristic Impedance of the transmission line in your
model block as well as its Propagation Delay.
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Combination of Sub-Circuits Block Type (4 Port)
The Combination Of Sub-circuits selection lets you use a combination of three
sub-blocks in place of one block. When you make this selection, additional
controls appear at the bottom of the dialog box.
You have the following three choices for how to combine the three individual
blocks that now make up the one circuit block: Cascade, Parallel, and Series.
In (2) 2 Port and (2) 2 Port Differential port type modes, the blocks combine as shown
below (pictures show 2 port connections with two blocks for simplicity).
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Cascade
Parallel
Series
In 4 Port port type mode, the 4 port blocks combine as shown below (pictures show
connections for two of the three blocks for simplicity):
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Once you select one of these three configurations, you can click each individual
block and define what type of block it is.
When you click one of the sub-blocks a new InfiniiSim Sub-circuit Block Setup
dialog box appears where you can define its type
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Notice that you can choose between Ideal Thru, Open, RLC, S-parameter File,
Transmission Line, and an option called Unused. Unused simply means that this
particular sub-block is not used (letting you use 2 sub-blocks instead of three, for
example).
Using the Unused setting has a different effect on this specific block depending on
which configuration is being used:
•
For the Cascade structure, for example, Unused acts like a Thru block.
•
For the Parallel structure, Unused acts like an Open block.
Probe Block Type (4 Port)
The Probe block type selection models the effects of the probe that is connected to
the current InfiniiSim channel. The model is inserted in series with the signal path
and is used when the measured or simulated signal travels through the probe to
the input of the oscilloscope.
You can select the Probe block type only in the blocks that are intended to model
the oscilloscope input (for example, the ones circled in yellow below).
A probe must be connected to the channel in order for the Probe block type
selection to be active.
When you make the Probe block type selection, the appropriate probe input
impedance file is automatically selected, based on your selections in the Probe
Configuration dialog box.
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Probe Load Block Type (4 Port)
The Probe Load block type selection lets you model a probe load in shunt with the
signal path. This model is used when the measured or simulated signal does not
travel through the probe, but is only loaded by a probe from a different channel.
The Probe Load block type is not allowed in those blocks that are intended to model
the oscilloscope input (for example, the ones not circled in yellow below).
When the Probe Load block type is selected it does two things: port 1 and 2 of the
block are connected together (like an Ideal Thru) and the supplied S-parameter
file is used to describe the shunt impedance loading the connected ports.
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Probe Load block
1
ports of the
model block
2
1
2
Zt
S-parameter File
for impedance loading
When you make the Probe Load block type selection, additional controls appear at
the bottom of the dialog box:
•
S-parameter File — Used to describe an impedance loading.
If a 1-port S-parameter (s1p) file is selected, you can ignore port 2 of the load
and the Termination Impedance (Zt).
If a 2-port S-parameter (s2p) file is selected, port 2 of the load is as shown, and
the desired Termination Impedance (Zt) should be entered.
On Infiniium oscilloscopes with the Windows 7 operating system, input
impedance files in are located in the "C:\Users\Public\Documents\Infiniium\
Filters\Probes\InfiniiMax" directory.
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•
Termination Impedance — Again, with a 1-port S-parameter (1sp) file, you can
ignore the Termination Impedance (Zt). With a 2-port S-parameter (s2p) file,
the desired Termination Impedance (Zt) should be entered.
•
Flip Model — If your S-parameter file has a different port ordering, you can check
this box to switch the selected 4-port numbering.
•
4 Port Numbering — If your S-parameter file has a different port ordering, you can
check this box to switch the selected 4-port numbering.
Measurement and Simulation Node Locations (4 Port)
You can also change the location of the measurement and simulation nodes. The
measurement node corresponds to the location in the circuit where you actually
measured the original signal. The simulation node corresponds to the location in
the circuit where you wished you could have measured the signal.
Look at the model below that shows both the measurement and simulation circuit
view. The light blue circle labeled M is the measurement node and the light orange
circle labeled S is the simulation node.
In this 1-block model, the measurement and simulation nodes cannot be moved
anywhere else in the circuit (there are no other large black dots or nodes in the
circuit) because this simple preset only lets you add insertion loss of a device.
However, in more complex configurations such as the General purpose 6 blocks
application preset configuration shown below, you can change the location of the
measurement and/or simulation node.
To change the nodes, click one of the empty node locations; then, select either
Move the Measurement Node here or Move the Simulation Node here from the InfiniiSim
Node Setup dialog box (as shown below).
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Generating / Saving a Transfer Function File
Once you have your measurement and simulation circuits built (see “Creating a
Transfer Function From a Model (2 Port)" on page 19 or “Creating a Transfer
Function From a Model (4 Port)" on page 38), you are ready to generate and save
your transfer function file.
In the upper right corner of the InfiniiSim Model Setup dialog box, click the Save
Transfer Function... button. This saves the transfer function file to the name (and to
the location) specified in the Save Transfer Function File As field.
After you click the Save Transfer Function button, a window appears telling you that
InfiniiSim is computing the transfer function. If it successfully computes the
transfer function, the following message appears.
If InfiniiSim does not successfully compute the transfer function and instead gives
you an error/warning message, see “InfiniiSim Warning / Error Messages" on
page 74 for information regarding each of these messages and possible corrective
actions.
Close all of the dialog boxes and you will see the simulated waveform on your
oscilloscope's display. You can toggle back and forth between the measured
waveform and the simulated waveform by entering the Channel dialog box (Setup >
Channel N...) and turning InfiniiSim on or off (by selecting either Off, 2 Port, or 4 Port).
Note that when comparing simulated waveforms to measured waveforms
(InfiniiSim On/Off), you should use bandwidth limiting to see the transformation
difference only (see the “Starting InfiniiSim" on page 6 topic for more information
on the bandwidth limiting feature).
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InfiniiSim Plots
Frequency Response Plot / 60
Impulse Response Plot / 60
Step Response Plot / 62
When InfiniiSim is enabled, the InfiniiSim window appears on your oscilloscope's
display.
Click this Type drop-down menu to see plots of the frequency response of the
original measured signal, the simulated signal, and the filter applied by InfiniiSim.
You can also see the impulse response and step response plots of the transfer
function as well.
Use the Graphs control to specify how many plots you want to see in the InfiniiSim
window.
These plots are useful when setting some of the controls in the “InfiniiSim Setup
Dialog Box" on page 86.
You can right-click in a plot to go directly to the InfiniiSim Setup or InfiniiSim
Model Setup dialog boxes.
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You can drag a rectangle within a plot to zoom. After you zoom, there will be an
Undo Zoom selection in the plot to return to the original view.
Frequency Response Plot
This plot serves two basic functions. First, it lets you see the measured signal's
frequency response, the simulated signal's frequency response (the signal after
InfiniiSim transforms the measured signal), and the applied transfer function's
frequency response. By investigating this plot, you can see whether they make
sense for the specific setup you defined. Sometimes errors in the transformation or
problems with the transfer function can be found by investigating this plot.
This plot also helps you determine what value to use for the bandwidth limit.
Remember from the discussion on the bandwidth limit, you need to determine at
what frequency your signal's frequency response is mostly just noise (if you are
using this control). By investigating these plots, you can determine this and set the
bandwidth limit accordingly.
Impulse Response Plot
The Impulse Response plot shows a time-domain perspective of the transfer
function and is useful in determining how to set the Max Time Span control (found in
“InfiniiSim Setup Dialog Box" on page 86).
For an example of how the Impulse Response plot lets you decide what to set the
Max Time Span control to, look at the following simplified plot.
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As you can see, there are large sections of the impulse response that are just flat
and, therefore, contribute insignificantly to the simulated waveform. If you see this,
you may be able to increase your measurement update rate by reducing the Max
Time Span control.
For example, the screen shot above was captured with the Max Time Span being set
to 8 ns. You can reduce this until you get to a point where most of these flat
regions are not shown. You can open the InfiniiSim Setup dialog box by
right-clicking the plot area and selecting Setup Channel N InfiniiSim.... Then, you can
move this dialog box to a portion of the display such that you can see both the
dialog box and the impulse response plot at the same time. Then, simply reduce
the Max Time Span control until the flat sections are no longer shown. For example,
reducing the control to 3 ns yields the following view of the plot.
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As you can see, there are still some flat regions on either side, but they have been
dramatically reduced.
If you show the Impulse Response plot and you do not see any flat regions on
either side, you may need to increase the Max Time Span control until you start to
see some flat regions. If increasing the Max Time Span control does not change the
filter's actual time span, it may be limited by one or more of your S-parameter
files.
Also, please note that you do not have to change both the Max Time Span and the
Min Frequency Resolution controls. When you adjust the Max Time Span control, the
Min Frequency Resolution field automatically adjusts (because they are reciprocals of
each other).
Step Response Plot
The Step Response plot is the integration of the Impulse Response plot just
discussed. It shows you basically the same information, but in a different way. This
plot is also useful in setting the Max Time Span control. In fact, it is normally more
useful in predicting how the transfer function affects your measured waveform.
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The screen shot above shows large flat areas. You may need to reduce the Max Time
Span control in this instance.
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InfiniiSim Examples
Removing the Insertion Loss of a Cable / 64
Simulating Crosstalk / 69
Removing the Insertion Loss of a Cable
One of the key features of the Keysight N5465A InfiniiSim Waveform
Transformation Toolset is the flexibility it offers you in terms of the broad range of
models you can build using its GUI.
The easiest way to learn how to use a flexible application such as this is to first
investigate a very simple case and then progress to more advanced models as you
get more of a feel for the application and its user interface.
This example walks you through a very simple model you can build using the
InfiniiSim application to help you become more familiar with the basic controls.
The Problem:
Removing the
Insertion Loss of a
Cable
For our simple example, let us assume we have the following setup.
DUT
Oscilloscope
A
B
cable
The locations marked A and B are the nodes in our measurement. We cannot
connect the oscilloscope directly to node A to measure the signal at that location.
Instead, we need a cable to connect to the DUT which means we actually end up
measuring what the signal looks like at node B after it has passed through the
cable. We would like, however, to display the waveform at A if possible.
The Solution Using
InfiniiSim
We are now going to walk through the process to accomplish this using InfiniiSim
in a step-by-step fashion. Again, understanding this basic model makes it easier to
understand how to use the controls when you use it on more complex problems.
Let us assume the cable is connected to Channel 1 on your oscilloscope.
Therefore, click the Channel 1 setup button located directly above the waveform
window.
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This opens the Channel dialog box. Under the InfiniiSim section, select 2 Port (we
assume the signal passing through the cable is single-ended). Then, click the
Band wid th Limit button and set the limit to 4 GHz because we assume our signal to
noise ratio past 4 GHz is low (either we already know this or we determined it from
the “Frequency Response Plot" on page 60). Click the Setup... button to open the
InfiniiSim Setup dialog box.
We now want to create our transfer function from a model (we do not have a
transfer function previously saved) so click the Create Transfer Function from Model...
button. This opens the InfiniiSim Model Setup dialog box.
For our simple example, we choose the Remove Insertion Loss of a Fixture or Cable as
the use model from the Application Preset field. This is because we only have one
device we are trying to negate and we do not care about multiple reflection effects.
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Once you select this use model, you see the following circuit view in the dialog
box.
Now, we need to set up the two circuits: the measurement circuit and the
simulation circuit.
The measurement circuit represents the real physical setup that created the
measured waveform. For our example, this would mean there is a cable connected
between the DUT and the oscilloscope and we can only measure the signal
coming from the DUT after it has passed through the cable.
Let us assume we measured the S-parameters for the cable using a network
analyzer and they are saved to a file named "cable.s2p". Then, we know we are
going to set the measurement view of the model block in the above circuit to this
S-parameter file.
This makes sense if you follow along the measurement circuit — first the signal
leaves the transmitter (the DUT), travels through the cable (the block has the same
characteristics as the cable because we built a S-parameter file for the cable and
are using it for the block), and is then measured at the front end of the oscilloscope
(the measurement - or M - node).
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To get it set up like this, click the C block to open the InfiniiSim Block dialog box.
Then, select the Measurement Circuit option in the Circuit section. Under Block Type,
choose S-parameter File and then click the S-parameter File field, navigate to where
you saved the file on the oscilloscope, and click Load. Because the S-parameters
represent a cable, S21 = S12, checking the Flip Model option should have no effect.
Because the Simulation circuit block is defaulted to Ideal Thru for this application
preset, we do not need to change it. If you think about the simulation we want to
perform, it makes sense that the block needs to be defined as a Thru (meaning
that the block acts as though it is not there). Remember in the measurement
circuit that we had the signal exiting the DUT, passing through the cable, and
entering the oscilloscope. We could only measure it at the front end of the
oscilloscope. We actually wished we could have measured the signal before it
entered the cable so we could remove any loss induced by the cable.
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Therefore, if we set the simulation circuit to Ideal Thru, we have the following
situation. The signal will leave the transmitter (the DUT), not pass through any
cable (since the block is defined as a Thru), and then immediately enter the
oscilloscope's front end. You can now see that we have removed the cable from
the circuit and are, in effect, moving the oscilloscope's front end to be connected
directly to the DUT.
Now, you have the measurement and simulation circuits built appropriately for
your model. In the InfiniiSim Model Setup dialog box, click the Save Transfer
Function As field and enter the name you want to give the transfer function file.
Then, click the Save Transfer Function... button and InfiniiSim starts generating and
saving the transfer function file. Once it is complete, you can then close all of the
dialog boxes to see your simulated waveform on the oscilloscope's display.
Remember that this simulated waveform is what the signal looked like with no
cable present between the DUT and the oscilloscope.
You can also click the InfiniiSim tab to see the various plots associated with your
signal, the simulated signal, and the transfer function.
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Simulating Crosstalk
The simplest way to simulate crosstalk is by applying a 6-port transfer function to
three measured signals; a victim and 2 aggressors as shown in the following figure.
(aggressor)
Meas Ch 1
1
2
(victim)
Meas Ch 3
3
4
(aggressor)
Meas Ch 4
5
6
Xtalk. tf6
Sim Ch 3
(victim)
However, InfiniiSim cannot handle 6-port transfer functions. But, you can simulate
crosstalk with two 4-port transfer functions using the setup shown in the following
figure.
(aggressor)
Meas Ch 1
1
(victim)
Meas Ch 3
3
2
Xtalk1. tf4
4
Sim Ch 3
+
(unused) Meas Ch 2
1
(aggressor) Meas Ch 4
3
2
Func1
(victim)
Sim Ch 2
Xtalk2. tf4
4
First, create two 4-port TFs (transfer functions) from two 4-port S-parameter
models. Then, apply the two 4-port TFs to three measured signals in order to
produce two simulated waveforms that can be added together using a waveform
math function.
The following figures show how to configure InfiniiSim.
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From the Channel 3 Setup dialog box, select InfiniiSim 4 Port (Channels 1 & 3). Then,
click Setup... to open the InfiniiSim Setup dialog box shown below.
If Xtalk1.tf4 already exists, then select it as the Transfer Function File. Otherwise, you
have to create it from S-parameter models. To create it from models, click Create
Transfer Function from Model... to open the InfiniiSim Model Setup dialog box; then,
choose the Add insertion loss of a fixture of cable application preset, and rename the
Save Transfer Function File As to "Xtalk1.tf4".
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Then, click the Channel model block to open its Block Setup dialog box. Configure
the Simulation Circuit to use your desired S-parameter file. The Measurement
Circuit should remain defined to an Ideal Thru.
The S-parameter models you use to model crosstalk can be measured directly
from your device or exported from your personal simulation tools. In either case,
use the following configurations when measuring or simulating the S-parameter
crosstalk models, in which the unused ports are terminated into 50 ohms.
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(aggressor)
1
VNA Port 1
2
Xtalk1.s4p
VNA Port 3
VNA Port 2
50
50
3
4
VNA Port 4
1
2
VNA Port 2
(victim)
(unused)
VNA Port 1
50
VNA Port 3
50
(aggressor)
Xtalk2.s4p
3
VNA Port 4
4
50
50
Now, close the Block Setup dialog box and click Save Transfer Function. After it
completes calculating and saving the new TF, close the Model Setup dialog box
and the InfiniiSim Setup dialog box.
Next, open the Channel 2 Setup dialog box and configure InfiniiSim as shown
below.
Then, configure the InfiniiSim Setup dialog box and generate the Xtalk2.tf4
transfer function using a procedure similar to that explained for Xtalk1.tf4.
Finally, combine the two simulated waveforms into the resultant crosstalk
waveform using the "add" math function:
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Note that although the example just described only used two aggressors, a third
could be added by simply using the port 1 input of Xtalk2.tf4.
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InfiniiSim Warning / Error Messages
Sometimes you can get a warning or error message when attempting to create a
transfer function. Please refer to the alphabetized list below for the meaning of
each of these messages as well as suggested corrective actions.
1 port Files Allowed at Source and Load Blocks Only
In 2 port InfiniiSim, you are only allowed to use 1 port files in the location circled
below.
In other words, you can only use them for Transmitter, Receiver, and Scope /
Probe blocks. If you try to use a 1-port file anywhere else, you get this error.
2 port Files Allowed at Source and Load Blocks Only
In 4 port InfiniiSim, you are only allowed to use 2-port files in the location circled
below.
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In other words, you can only use them for Transmitter, Receiver, and Scope /
Probe blocks. If you try to use a 2-port file anywhere else, you get this error.
Calculation Aborted
This error indicates that you chose to abort the transfer function computation
before it was written to a file.
Cannot Read 4 Port Data From a 2 Port File
This error means that you have attempted to load 2-port file data into a 4-port
model block. If you want to define a 4-port block with 2-port files, you need to use
the (2) 2 Port or (2) 2 Port Differential Block Port Type settings.
DEFAULT_FREQUENCY_RESOLUTION Value is Too Small
The DEFAULT_FREQUENCY_RESOLUTION value provided in the S-parameter file
is too small and yields more than the allowed 100,000 frequency points (see
“S-Parameter File Keywords" on page 81).
Files May Only Contain a Single Data Package
Each CITIfile file may only model a single device.
File Not Found
This indicates that the file is not where you are telling InfiniiSim it is located or it
has the wrong name.
Impedance of All Ports Must Be the Same
The .cti format lets you specify a unique port impedance for each port. However,
they must all be the same for InfiniiSim; otherwise, you get this error.
Invalid Data Format (DBANGLE, MAGANGLE, RI only)
You are only allowed to use DBANGLE, MAGANGLE, or RI data value formats with
CITIfile files. If you use any other data format, you get this error message.
Invalid Data Format (DB, MA, RI only)
You are only allowed to use BE, BD, MA, or RI data value formats with ATF and
Touchstone files. If you use any other data format, you get this error message.
Invalid File Format
InfiniiSim could not recognize the indicated S-parameter file format.
Invalid File Name
This indicates that the file extension is wrong or invalid for the type of file needed.
Invalid Frequency Units (Hz, kHz, MHz, GHz only)
You are only allowed to use Hz, kHz, MHz, and GHz in your S-parameter file. If you
use anything else, you get this error.
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Invalid Output Name
This means you probably gave the Save As file name an improper file extension.
Invalid RETURN_LOSS_INTERPRETATION Value
The RETURN_LOSS_INTERPRETATION value in the S-parameter file must be set to
either SCOPE, PROBE, SERIES_RLC, SHUNT_RLC, or DEFAULT (see “S-Parameter
File Keywords" on page 81).
Less Than 2 Data Points in the File
You must have at two least data points in your S-parameter and transfer function
files.
Signal Amplitude at Measurement Node is Too Small
This message usually means you made a mistake when setting up your
measurement circuit (example, placed an open circuit block somewhere between
the source and measurement nodes). This may also occur if an S-parameter file in
the measurement circuit has a resonant 'suck-out' that the transfer function is
trying to compensate for.
What this warning means is that the voltage seen at the measurement node is very
small. It could be that your specific setup does indeed cause this to occur and
there was no error made, but more often than not, you should go back and check
your measurement circuit setup.
Transfer Function Data Must Contain a 0 Hz Point
This is not true for S-parameter files, but is true for transfer function files.
Unspecified Error
An internal error was detected by InfiniiSim. Please contact Keysight Technical
Support.
Unspecified File Read Error
This indicates that the file has an invalid format.
Unspecified File Write Error
An internal error was detected in InfiniiSim. Please contact Keysight Technical
Support.
Unstable or Ill-cond itioned Circuit Definition
When you get this message it means one of your circuits is invalid. This warning
indicates that an infinite voltage is present in the circuit (analogous to an
oscillation) or in other words, the gain becomes infinite.
Warning: File Data Truncated to 100 kpts
This warning means there are too many points in your S-parameter file. You need
to reduce the number of points.
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Warning: Frequency Resolution May Be Too Large for Slow Time Constants
This is similar to the warning immediately below except that instead of a model's
long time delay causing the problem, it is the model's slow time constants. These
kind of models require finer frequency resolution. Therefore, you need to have a
finer sampling of frequencies in your S-parameter file.
Warning: Frequency Resolution May Be Too Large for Time Delay
S-parameter models that have long time delays require finer frequency resolution
because the model's impulse response needs to be longer. This warning indicates
that your S-parameter file may not have enough resolution to accurately represent
the modeled device. Therefore, you need to have a finer sampling of frequencies in
your S-parameter file.
If you see the this warning and your S-parameter file does not contain a DC
frequency, InfiniiSim may not extrapolate the DC values correctly. InfiniiSim looks
at the lowest frequency points in the file in order to determine if each DC value
should be a positive or negative. If the frequency resolution in the file is so large
compared to the time delay of the S-parameter model that it causes the phase
linear component (delay component) of the phase variation to change more than
90 degrees per frequency step, then the DC value will have the wrong polarity.
When the DC value of the insertion loss is incorrectly determined to be negative,
but it should actually be positive, you will likely also see the "Transfer function
appears to invert the signal" warning message.
Warning: Interpolated S-parameters Limited to 100 kpts
This warning indicates that the interpolation performed by InfiniiSim on your file
data results in too many points. InfiniiSim sets the resolution by looking at the
separation between the last two points in the file. If these values are too close
together then it can cause the resolution to be too fine.
There is also a command you can place within the S-parameter file that forces
InfiniiSim to have a different resolution than that specified by the frequency
spacing in the file (see “S-Parameter Files" on page 80). If you used this command
and set it to too fine of a resolution, this could result in this warning message.
Warning: Non-uniformly Sampled Data
If you give InfiniiSim S-parameter files with uniformly spaced points, it uses the
data as is (if there is only one file). If your points are not uniformly spaced (for
example, log sweep), InfiniiSim will try to interpret the points, but you may get a
bad result (especially if you are using a pure log sweep — not recommended). If
you have a nonuniform spacing between the points in your S-parameter file,
InfiniiSim sets the resolution by looking at the separation between the last two
points in the file. See “S-Parameter Files" on page 80.
Warning: Transfer Function Appears to Invert Signal
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This warning typically happens with 4 port InfiniiSim. There is one particular
non-standard port ordering that can cause the 4 port model to invert the signal
polarity. Unfortunately, this uncommon port ordering cannot be corrected with any
combination of the Flip Model and 4 Port Numbering controls.
Again, it could be that your specific setup does indeed cause signal polarity
inversion to occur and there was no error made (for example, if you are modeling
an inverting amplifier), but more often than not there is a problem with the
S-parameter file port ordering.
If you see the "Frequency resolution may be too large for the time delay" and the
S-parameter file does not contain a DC frequency, InfiniiSim may not extrapolate
the DC values correctly. InfiniiSim looks at the lowest frequency points in the file in
order to determine if each DC value should be a positive or negative. If the
frequency resolution in the file is so large compared to the time delay of the
S-parameter model that it causes the phase linear component (delay component)
of the phase variation to change more than 90 degrees per frequency step, then
the DC value will have the wrong polarity. When the DC value of the insertion loss
is incorrectly determined to be negative, but it should actually be positive, you will
likely also see this "Transfer function appears to invert the signal" warning
message.
Warning: Transfer Function Gain is Unusually Large
This warning indicates that the voltage seen at the simulation node is huge when
compared with the voltage seen at the measurement node (when driven by the
same source). This usually means you made a mistake when setting up your
measurement circuit (example, placed an open circuit block somewhere that is
preventing the source from driving the measurement node) so you should first
check your measurement circuit to ensure there are no errors. This may also occur
if an S-parameter file in the measurement circuit has a resonant 'suck-out' that the
transfer function is trying to compensate.
It could be that your specific setup does indeed cause a large gain in the transfer
function. Examination of the frequency response plot can help verify if it is correct
(see “Frequency Response Plot" on page 60).
Warning: Unrecognized ATF File Version (A.01.00 Only)
This warning indicates that InfiniiSim does not support the ATF file you are
attempting to use. InfiniiSim only supports A.01.00 ATF files.
Warning: Unrecognized CITIfile Version (A.01.00 and A.01.01 Only)
This warning indicates that InfiniiSim does not support the CITIfile you are
attempting to use. InfiniiSim only supports A.01.00 and A.01.01 CITIfiles.
Invalid S-Param file name: '<empty string>'
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When you are saving a transfer function, this error dialog box appears if no
S-parameter File name is specified in the InfiniiSim Block Setup dialog box (which
appears after clicking the measurement/simulation block in the InfiniiSim Model
Setup dialog box).
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InfiniiSim Concepts
S-Parameter Files / 80
Transfer Function Files / 82
Using the Bandwidth Limit Control / 83
S-Parameter Files
S-parameter files describe electrical n-port network models of physical devices as
a tabular list of complex S-parameter values at specific frequencies. Formatted as
ASCII text, S-parameter files are easily viewed or edited using any text-based file
editor. InfiniiSim supports two standard file formats:
•
Touchstone (version 1.1).
Touchstone files are identified by the file extensions .s1p, .s2p, or .s4p.
•
CITIfile (version A.01.00 and A.01.01).
CITIfile files are identified by either .cti or .cit.
In addition, InfiniiSim supports only CITIfiles that contain a single data package
(each file may model only a single device).
InfiniiSim requires model information at DC (0 Hz). However, S-parameter files
often do not contain DC values, especially if they originate from network analyzer
measurements. When files do not contain DC values, InfiniiSim will, by default,
copy the file's lowest frequency values to 0 Hz and set their phase components to
zero. This technique may not always yield appropriate DC S-parameter values.
Ideally, you should measure or simulate the true DC values and manually add
them to the S-parameter file with a text editor.
InfiniiSim also requires S-parameter values that are uniformly spaced in frequency
with a spacing or resolution that is small enough to accurately represent the
slowest time constants and time delays exhibited by the modeled device.
However, this does not mean that all S-parameter files must contain uniformly
spaced frequency data. Uniformly spaced file data is usually preferred, but not
required if you are knowledgeable about how InfiniiSim interprets file data.
In the absence of the special InfiniiSim keyword
DEFAULT_FREQUENCY_RESOLUTION (see “S-Parameter File Keywords" on
page 81), InfiniiSim checks the data to ensure that it is uniformly sampled in
frequency (with exception to the interval between DC and the next lowest
frequency point) and generates a warning if the data is not uniformly sampled. If
the DEFAULT_FREQUENCY_RESOLUTION keyword is accompanied by a numeric
value, the data is resampled using linear interpolation and the frequency resolution
specified by that value. Otherwise, InfiniiSim resamples the file data using a
frequency resolution equal to the frequency interval between the last two
frequency points in the file.
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InfiniiSim expects S-parameter files to list their values in monotonically increasing
frequency order and ignores those values at which frequencies are less than or
equal to the frequencies of previously listed values. InfiniiSim also truncates all file
data to a maximum of 100,000 frequency points.
InfiniiSim calculates transfer functions using only full 2-port (in 2-port analysis
mode) or 4-port (in 4-port analysis mode) S-parameter models that contain both
return loss and insertion loss information. However, those blocks that model
source impedance or load impedance (transmitter source, oscilloscope/probe, or
oscilloscope input) can be defined by S-parameter files which contain only return
loss information. In the absence of the special InfiniiSim keyword
RETURN_LOSS_INTERPRETATION, InfiniiSim assumes that the return loss data
models a simple passive shunt RLC circuit and calculates the insertion loss of the
same circuit that would produce the file data.
Selecting a 1-port S-parameter (s1p) file for a 4 port application applies that s1p
to s11 and s33, and sets s13 and s31 to zero.
S-Parameter File Keywords
The following are the currently supported optional keywords you can place in your
S-parameter files. InfiniiSim scans S-parameter files for special keywords which
communicate to InfiniiSim how the data within the file was generated or how it
should be interpreted. The format of these lines differs slightly between
Touchstone and CITIfile files in that they must be proceeded by an exclamation
point (!) within Touchstone files. InfiniiSim keywords are case insensitive and
permit additional comments on the same line.
#DSO DEFAULT_FREQUENCY_RESOLUTION <value>
where <value> may be a numeric value in Hz or the text strings AUTO or
AUTOMATIC.
In the absence of this keyword, InfiniiSim checks the data to ensure that it is
uniformly sampled in frequency (with exception to the interval between DC and the
next lowest frequency point) and generates a warning if the data is not uniformly
sampled. If <value> is a numeric value, the data is resampled using linear
interpolation and the frequency resolution specified by <value>. Otherwise,
InfiniiSim resamples the file data using a frequency resolution equal to the
frequency interval between the last two frequency points in the file. If <value> is
equal to either of the text strings (AUTO or AUTOMATIC), InfiniiSim does not report
a warning about non-uniformly sampled data.
#DSO RETURN_LOSS_INTERPRETATION <string>
where <string> is one of the following legal strings: SCOPE, PROBE, SERIES_RLC,
SHUNT_RLC, or DEFAULT.
In the absence of this keyword, InfiniiSim assumes that the return loss data models
a simple passive shunt RLC circuit and calculates the insertion loss of the same
circuit that would produce the file data (S21 = 12 = 1 + S11, S22 = S11).
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When <string> equals SERIES_RLC, InfiniiSim assumes that the return loss data
models a simple passive series RLC circuit (S21 = S12 = 1 - S11, S22 = S11).
When <string> equals SCOPE, InfiniiSim assumes that the return loss data models
an oscilloscope input (S21 = 1, S12 = S22 = 0).
When <string> equals PROBE, InfiniiSim assumes that the return loss data models
a probe input (S21 = 1 + S11, S12 = 0, S22 = -1).
When <string> equals DEFAULT, InfiniiSim uses its default interpretation without
creating the default return loss warning.
Transfer Function Files
Transfer function files describe the relationship between two sets of time varying
node voltages as a tabular list of complex transfer function values at specific
frequencies. Formatted as ASCII text, transfer function files are easily viewed or
edited using any text-based file editor. InfiniiSim supports a single proprietary
transfer function file format:
•
ATF (version A.01.00) derived from the Touchstone 1.1 format.
ATF files are identified by the file extensions .tf2 or .tf4.
All transfer function files must include values at DC (0 Hz).
InfiniiSim requires transfer function values that are uniformly spaced in frequency
with a spacing or resolution that is small enough to accurately represent the
slowest time constants and time delays exhibited by the modeled device.
However, this does not mean that all transfer function files must contain uniformly
spaced frequency data. Uniformly spaced file data is usually preferred, but not
required if you are knowledgeable about how InfiniiSim interprets file data.
In the absence of the special InfiniiSim keyword
DEFAULT_FREQUENCY_RESOLUTION (see “Transfer Function File Keywords" on
page 83), InfiniiSim checks the data to ensure that it is uniformly sampled in
frequency (with exception to the interval between DC and the next lowest
frequency point) and generates a warning if the data is not uniformly sampled. If
the DEFAULT_FREQUENCY_RESOLUTION keyword is accompanied by a numeric
value, the data is resampled using linear interpolation and the frequency resolution
specified by that value. Otherwise, InfiniiSim resamples the file data using a
frequency resolution equal to the frequency interval between the last two
frequency points in the file.
InfiniiSim expects transfer function files to list their values in monotonically
increasing frequency order and ignores those values at which frequencies are less
than or equal to the frequencies of previously listed values. InfiniiSim also
truncates all file data to a maximum of 100,000 frequency points.
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Transfer Function File Keywords
The following are the currently supported optional keywords you can place in your
transfer function files. InfiniiSim scans transfer function files for special keywords
which communicate to InfiniiSim how the data within the file was generated or
how it should be interpreted. InfiniiSim keywords are case insensitive and permit
additional comments on the same line.
! #DSO ATF_FILE_VERSION <string>
The value of <string> represents the format version of the ATF file.
! #DSO DEFAULT_FREQUENCY_RESOLUTION <value>
where <value> may be a numeric value in Hz or the text strings AUTO or
AUTOMATIC.
In the absence of this keyword, InfiniiSim checks the data to ensure that it is
uniformly sampled in frequency (with exception to the interval between DC and the
next lowest frequency point) and generates a warning if the data is not uniformly
sampled.
If <value> is a numeric value, the data is resampled using linear interpolation and
the frequency resolution specified by <value>. Otherwise, InfiniiSim resamples the
file data using a frequency resolution equal to the frequency interval between the
last two frequency points in the file.
If <value> is equal to either of the text strings (AUTO or AUTOMATIC), InfiniiSim
does not report a warning about non-uniformly sampled data.
! #DSO TRANSFER_FUNCTION_DEFINITION_STRING <string>
InfiniiSim uses this keyword to include a complete description of the circuit models
from which it calculates the transfer function file. When loading transfer function
file data, InfiniiSim checks for this keyword and if present, uses this information to
re-populate the circuit model descriptions.
Using the Bandwidth Limit Control
The Band wid th Limit... button requires some explanation so you know how to
properly set the value and whether or not it is required for your specific
application.
One way to understand the transformations InfiniiSim performs is in terms of the
frequency response of the cable, fixture, or probe your signal travels through.
Ideally, you would like to transmit a signal through a channel whose frequency
response was flat over the full bandwidth of the signal so every frequency
component of the signal was equally represented.
In practice, your frequency response plot may look something like the plot below
where the signal attenuates at higher frequencies (this is a very simplified
example).
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Some InfiniiSim applications attempt to remove or correct this insertion loss in the
channel. In those cases, the correction transfer function becomes the inverse of
the channel's insertion loss (dashed line in plot below) such that the product of the
"peaked" correction transfer function response and the channel response yields a
flat frequency spectrum (red line in plot below).
Now, in the above example, the response plot before InfiniiSim was applied was
very simplistic. A more realistic frequency response plot might look more like the
following:
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Notice that above a certain frequency (or bandwidth) there is very little signal and
mostly noise. If you apply a correction through InfiniiSim as discussed above, you
may end up excessively amplifying the noise. Setting the bandwidth in the
Bandwidth Limit dialog box lets you minimize this noise gain by attenuating the
resulting waveforms above the frequency where there is mostly just noise.
Examining the Frequency Response Plot helps you see what bandwidth you
should set this field to (see “Frequency Response Plot" on page 60).
Also, note that normally you do not need to set a bandwidth limit if you are adding
loss (applying the loss of a cable, etc.). However, if you are applying gain
(removing the loss of a cable, etc.), you may need to use the Bandwidth Limit
dialog box.
Click the Band wid th Limit... button to open the Bandwidth Limit dialog box. You can
then enter the value for this field.
Notice in the Channel dialog box, there is a box labeled Show Raw Channels. When
you use InfiniiSim, apply filters, or use differential channels, the signal displayed
on the oscilloscope may be very different from the signal entering the front end of
the oscilloscope. However, the oscilloscope triggers on the signal at the front end,
not the signal you see on screen. Also, the signal entering the front end is the one
that enters the ADC (analog to digital converter). Therefore, if you are having
problems triggering or if you want to ensure you are using the entire vertical range,
but not overdriving the ADC, you need to see this front end signal. Checking this
Show Raw Channels box turns off all of the transformations or filters applied to the
signal and shows you what the signal entering the oscilloscope looks like. You can
then make the necessary adjustments and uncheck this box to go back to the
signal you were viewing.
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InfiniiSim Reference Information
InfiniiSim Setup Dialog Box / 86
InfiniiSim Model Setup Dialog Box / 88
Circuit Source and Load Impedances Dialog Box / 88
InfiniiSim Block Setup Dialog Box / 88
InfiniiSim Sub-circuit Block Setup Dialog Box / 88
InfiniiSim Setup Dialog Box
•
Create Transfer Function — If you do not have a previously saved transfer function
to load, you can create a transfer function from a model (click Create Transfer
Function From Model...). For information on creating a transfer function from a
model, see “InfiniiSim Model Setup Dialog Box" on page 88.
•
Transfer Function File Name — Lets you select a Transfer Function File to apply. If you
have a previously saved transfer function or one you generated elsewhere, you
can click this field and load it. For an overview of transfer function files, see
“Transfer Function Files" on page 82.
Also in the Transfer Function File Name area is a control for including or removing
delay. Cables and fixtures delay the signal in time in addition to changing the
waveform's shape. This can make it difficult to compare the simulated and
measured waveforms because as you turn InfiniiSim on and off, the waveforms
are not aligned in time. This may make one or the other shift entirely off screen,
for example.
•
86
Include Fil ter Delay — Apply the delay imposed by the model to the waveform.
This selection will accurately shift the waveform in time according to the
model.
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•
Remove Fil ter Delay — Remove the delay imposed by the model on the
waveform. Because different frequencies can have different delays, this is an
approximation of the group delay. Use this mode to compare the response
correction of the signal with InfiniiSim turned on and off.
•
Include Trigger Corrected Delay — This selection applies the trigger's jitter error
correction after the de-embedding filter has been applied.
The Normalize Gain option removes any DC gain of the InfiniiSim transfer
function and can be used when modeling probes.
You may have to apply a different transfer function before the remaining
controls become visible.
•
Band wid th Limit — This is the same control located in the Bandwidth Limit dialog
box. It is duplicated here for convenience. See “Using the Bandwidth Limit
Control" on page 83.
•
Response Correction — This field linearly scales the amount of correction applied
to the non-DC frequency components of the measured signal. This lets you
trade off the amount of correction to apply through the transformation function
versus the increase in noise it may create at higher frequencies. In other words,
you can fine-tune the amount of high-frequency noise versus the sharpness of
the step response edge.
If you are making averaged mode measurements or applying a transfer function
that does not magnify the noise, use the full correction by setting this field to
100%. However, if you are working with eye diagrams or making jitter
measurements and the transfer function is magnifying the noise, you may want
to limit the correction by selecting a lower percentage.
Once you have your InfiniiSim-transformed signal displayed on screen, you can
adjust this value in the dialog box to see its effect on the signal.
It is also useful to display the frequency response plots and step response plot
while you adjust this field to see its effect on these plots. For instance, you can
see how the frequency response of the transformation filter changes as you
change the percentage. See “Frequency Response Plot" on page 60 and “Step
Response Plot" on page 62.
•
Fil ter Size — This area has two controls: Max Time Span and Min Frequency
Resolution. These two controls are reciprocals of each other and slaved
together, so as you set one to a lower value, the other one raises to a higher
value and vice versa. InfiniiSim applies the correction transfer function by
means of a FIR digital filter. The size of this filter determines the time span of
the transformation it can apply. However, there is a trade-off. Using a longer
filter corrects longer time constants, but it can take longer to calculate. By
default, InfiniiSim tries to choose a filter size that preserves the coarsest
frequency resolution used by all of the model blocks. However, you can limit the
filter size by reducing the Max Time Span value.
A quick summary of the two controls is:
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•
Increasing the Max Time Span control increases the maximum time span of
the correction transfer function's impulse response. Increasing this control
enables InfiniiSim to apply transformations which have slower time
constants. You can use either the Step Response or Impulse Response plot
(see page 59) to see if the time span is long enough to model your device
adequately.
•
Increasing the Min Frequency Resolution control makes the frequency
resolution less fine and automatically decreases the Max Time Span control
(which corresponds to a higher update rate). Therefore, you would do this if
you wanted a higher update rate with the trade-off of a shorter transfer
function impulse response. Generally, you want to set the Max Time Span
using the Step Response or Impulse Response plot (see page 59) and then
this Min Frequency Resolution is set automatically.
InfiniiSim Model Setup Dialog Box
If you are using 2-port models, see:
•
“Creating a Transfer Function From a Model (2 Port)" on page 19
If you are using 4-port models, see:
•
“Creating a Transfer Function From a Model (4 Port)" on page 38
Circuit Source and Load Impedances Dialog Box
If you are using 2-port models, see:
•
“Circuit Source and Load Impedances (2 Port)" on page 23
If you are using 4-port models, see:
•
“Circuit Source and Load Impedances (4 Port)" on page 42
InfiniiSim Block Setup Dialog Box
If you are using 2-port models, see:
•
“Defining a Block (2 Port)" on page 24
If you are using 4-port models, see:
•
“Defining a Block (4 Port)" on page 43
InfiniiSim Sub-circuit Block Setup Dialog Box
If you are using 2-port models, see:
•
“Combination of Sub-Circuits Block Type (2 Port)" on page 30
If you are using 4-port models, see:
•
88
“Combination of Sub-Circuits Block Type (4 Port)" on page 50
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InfiniiSim Node Setup Dialog Box
If you are using 2-port models, see:
•
“Measurement and Simulation Node Locations (2 Port)" on page 36
If you are using 4-port models, see:
•
“Measurement and Simulation Node Locations (4 Port)" on page 56
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Index
Numerics
2 Port InfiniiSim, 6
2-port vs. 4-port InfiniiSim analysis, 12
3-block circuit model, InfiniiSim, 13
4 Port InfiniiSim, 6
4-port numbering, S-parameter files, 28,
56
4-port vs. 2-port InfiniiSim analysis, 12
6-block circuit model (general-purpose),
InfiniiSim, 14
A
all effects of fixture or cable, 20, 39
application presets for 2-port InfiniiSim, 20
application presets for 4-port InfiniiSim, 39
ATF transfer function file format, 82
ATF_FILE_VERSION transfer function file
keyword, 83
B
bandwidth limit and InfiniiSim, 7
Bandwidth Limit control, using, 83
block definition, InfiniiSim 2 Port, 24
block definition, InfiniiSim 4 Port, 43
C
cable effects, 20, 39
cable effects, adding, 9
cable insertion loss, 9, 20, 39
channel element insertion loss,
inserting, 10
channel element insertion loss,
removing, 10
channel element, add all effects, 10
channel element, remove all effects, 10
channel element, replace one with
another, 20, 39
channels, show raw, 85
characteristic impedance of transmission
line, InfiniiSim 2 Port, 30
characteristic impedance of transmission
line, InfiniiSim 4 Port, 49
circuit diagram view, InfiniiSim 2 Port, 21
circuit diagram view, InfiniiSim 4 Port, 40
circuit model block configurations,
InfiniiSim, 13
Circuit Source and Load Impedances dialog
box, 88
CITIfile S-parameter file format, 80
Combination Of Sub-circuits block
definition, InfiniiSim 2 Port, 30
Combination Of Sub-circuits block
definition, InfiniiSim 4 Port, 50
common-mode signals and InfiniiSim, 6, 12
convolution process (InfiniiSim)
requirements, 11
correction transfer function, 11, 12, 84
crosstalk, simulating in InfiniiSimk, 69
D
DDR interposer and probe, loading
effects, 20, 39
DEFAULT_FREQUENCY_RESOLUTION
S-parameter file keyword, 80, 81
DEFAULT_FREQUENCY_RESOLUTION
transfer function file keyword, 82, 83
differential probe and InfiniiSim
analysis, 12
differential signals and InfiniiSim, 6, 12
differential SMA probe heads, InfiniiSim, 14
E
error messages, InfiniiSim, 74
F
filter delay, include, InfiniiSim transfer
function, 86
filter delay, remove, InfiniiSim transfer
function, 87
filter size, InfiniiSim, 87
fixture effects, 20, 39
fixture effects, adding, 9
fixture insertion loss, 9, 20, 39
flip model, S-parameter files, 28, 29, 36,
48, 49, 56, 78
frequency response plot, InfiniiSim, 60
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general purpose probe topologies, 10
general-purpose 6 blocks InfiniiSim
application preset, 20, 39
general-purpose 9 blocks InfiniiSim
application preset, 20, 39
general-purpose probe circuit model,
InfiniiSim, 14
general-purpose probe InfiniiSim
application preset, 20, 39
I
Ideal Thru block definition, InfiniiSim 2
Port, 26
Ideal Thru block definition, InfiniiSim 4
Port, 45
impedances, circuit source and load,
InfiniiSim 2 Port, 23
impedances, circuit source and load,
InfiniiSim 4 Port, 42
impulse response plot, InfiniiSim, 60
InfiniiSim Advanced application, 5
InfiniiSim analysis, 2-port vs. 4-port, 12
InfiniiSim application, starting, 6
InfiniiSim Basic, 5
InfiniiSim Block Setup dialog box, 88
InfiniiSim concepts, 80
InfiniiSim convolution process
requirements, 11
InfiniiSim Example: Simulating
Crosstalk, 69
InfiniiSim examples, 64
InfiniiSim features, 10
InfiniiSim license information, 5
InfiniiSim Model Setup dialog box, 88
InfiniiSim Node Setup dialog box, 89
InfiniiSim overview / theory, 9
InfiniiSim plot controls, 59
InfiniiSim Plots, 59
InfiniiSim Setup dialog box, 86
InfiniiSim Sub-circuit Block Setup dialog
box, 88
InfiniiSim user's guide, 5
InfiniiSim Warnings / Error Messages, 74
InfiniiSim Waveform Transformation
Toolset, 5
input reflection (oscilloscope), remove, 10
input reflection, oscilloscope, 20, 39
91
Index
insertion loss (channel element),
inserting, 10
insertion loss (channel element),
removing, 10
insertion loss of cable, removing with
InfiniiSim, 64
insertion loss of fixture or cable, 20, 39
insertion loss, simple InfiniiSim example, 9
Invalid S-Param file name, 78
K
keywords, S-parameter file, 81
keywords, transfer function file, 83
L
loading effects of DDR interposer
probe, 20, 39
loading effects of probe, 20, 39
M
measurement circuit, InfiniiSim, 11, 21, 40
measurement node location, InfiniiSim 2
Port, 36
measurement node location, InfiniiSim 4
Port, 56
measurement node relocation, 10
messages, InfiniiSim, 74
N
Normalize Gain, InfiniiSim setup, 87
notices, 5
O
observation node of a probed
measurement, 20, 39
observation node of measurement, 20, 39
one-block circuit model, InfiniiSim, 13
Open block definition, InfiniiSim 2 Port, 26
Open block definition, InfiniiSim 4 Port, 45
oscilloscope input reflection, 20, 39
oscilloscope input reflection, remove, 10
overview, InfiniiSim, 9
P
plot controls, InfiniiSim, 59
port extraction, InfiniiSim, 6
port extraction, S-parameter files, 29
Probe block definition, InfiniiSim 2 Port, 33
Probe block definition, InfiniiSim 4 Port, 53
92
Probe Load block definition, InfiniiSim 2
Port, 34
Probe Load block definition, InfiniiSim 4
Port, 54
probe loading effects, removing, 10
probe topologies, general purpose, 10
probe, loading effects, 20, 39
propagation delay of transmission line,
InfiniiSim 2 Port, 30
propagation delay of transmission line,
InfiniiSim 4 Port, 49
TRANSFER_FUNCTION_DEFINITION_STRING
transfer function file keyword, 83
Transmission Line block definition, InfiniiSim
2 Port, 30
Transmission Line block definition, InfiniiSim
4 Port, 49
trigger corrected delay, include, InfiniiSim
transfer function, 87
R
warning messages, InfiniiSim, 74
W
raw channels, show, 85
resonse correction, InfiniiSim, 87
RETURN_LOSS_INTERPRETATION
S-parameter file keyword, 81
RLC block definition, InfiniiSim 2 Port, 26
RLC block definition, InfiniiSim 4 Port, 46
S
scope input reflection, 20, 39
Show Raw Channels, 85
simulating crosstalk in InfiniiSim, 69
simulation circuit, InfiniiSim, 11, 21, 40
simulation node location, InfiniiSim 2
Port, 36
simulation node location, InfiniiSim 4
Port, 56
single-ended signals and InfiniiSim, 12
six-block circuit model (general-purpose),
InfiniiSim, 14
SMA differential probes, InfiniiSim, 14
S-parameter File block definition, InfiniiSim
2 Port, 27
S-parameter File block definition, InfiniiSim
4 Port, 47
S-parameter file keywords, 81
S-parameter files, 12, 80
step response plot, InfiniiSim, 62
T
termination block, InfiniiSim, 24, 25, 43,
44
theory, InfiniiSim, 9
three-block circuit model, InfiniiSim, 13
Touchstone S-parameter file format, 80
transfer function file keywords, 83
transfer function file, generating /
saving, 58
transfer function files, 12, 82
transfer function port extraction,
InfiniiSim, 6
transfer function, creating from 2-port
model, 19, 38
Keysight N5465A InfiniiSim Waveform Transformation Toolset Software User's Guide
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