Network Analyzer Basics

Page 1

Network Analyzer Basics

Back to Basics Seminar

Electronics Measurement Group

George Trejo

Sales and Technical Support

Component Test Division

23-May-06

Network Analyzer Basics

23-May-06

Page 2

Network Analyzer Basics

Network Analyzer Basics

23-May-06

Page 3

Network Analysis is NOT.…

o r

B e

R a o I 8 X S s c p t t r m i r n a M

B o 5 X .

Network Analyzer Basics

23-May-06

What is a Vector Network Analyzer?

S

21

Vector network analyzers (VNAs)…

Transmission

Reflection

DUT

S

11

S

22

• Are stimulus-response test systems

S

12

• Characterize forward and reverse reflection and transmission responses

(S-parameters) of RF and microwave components

• Quantify linear magnitude and phase

• Are very fast for swept measurements

• Provide the highest level of measurement accuracy

RF Source

Magnitude

Phase

R1

LO

R2

Test port 1

A B

Test port 2

Network Analyzer Basics

23-May-06

Page 4

Page 5

What Types of Devices are Tested?

Duplexers

Diplexers

Filters

Couplers

Bridges

Splitters, dividers

Combiners

Isolators

Circulators

Attenuators

Adapters

Opens, shorts, loads

Delay lines

Cables

Transmission lines

Waveguide

Resonators

Dielectrics

R, L, C's

Passive

Antennas

Switches

Multiplexers

Mixers

Samplers

Multipliers

Diodes

Device type

RFICs

MMICs

T/R modules

Transceivers

Receivers

Tuners

Converters

VCAs

Amplifiers

VCOs

VTFs

Oscillators

Modulators

VCAtten’s

Transistors

Active

Network Analyzer Basics

23-May-06

Device Test Measurement Model

Page 6

RFIC Testers

Ded. Testers

TG/SA

SNA

NF Mtr.

Imped. An.

Param. An.

Power Mtr.

VSA

SA

VNA

Det/Scope

RFIC test

Harm. Dist.

LO stability

Image Rej.

Gain/Flat.

Phase/GD

Isolation

Rtn Ls/VSWR

Impedance

S-parameters

Compr'n

AM-PM

Mixers

Balanced

NF

Intermodulation

Distortion

BER

EVM

ACP

Regrowth

Constell.

Eye

Pulsed S-parm.

Pulse profiling

NF

LCR/Z

I-V

Measurement plane

Absol.

Power

Gain/Flatness

DC CW Swept Swept Noise 2-tone freq power

Simple

Stimulus type

Multitone

Complex Pulsedmodulation RF

Full call sequence

Protocol

Complex

Network Analyzer Basics

23-May-06

Page 7

Lightwave Analogy to RF Energy

Incident

Reflected

Transmitted

Lightwave

DUT

RF

Network Analyzer Basics

23-May-06

Page 8

Why Do We Need to Test Components?

Verify specifications of “building blocks” for more complex

RF systems

Ensure distortionless transmission of communications signals

• linear: constant amplitude, linear phase / constant group delay

• nonlinear: harmonics, intermodulation, compression, AM-to-PM conversion

Ensure good match when absorbing power (e.g., an antenna)

Network Analyzer Basics

23-May-06

Page 9

The Need for Both Magnitude and Phase

S

21

1. Complete characterization of linear networks

S

11

S

22

S

12

2. Complex impedance needed to design matching circuits

4. Time-domain characterization

Mag

3. Complex values needed for device modeling

High-frequency transistor model

Time

Base

Collector

5. Vector-error correction

Error

Measured

Actual

Emitter

Network Analyzer Basics

23-May-06

Agenda

What measurements do we make?

– Transmission-line basics

– Reflection and transmission parameters

– S-parameter definition

Network analyzer hardware

– Signal separation devices

– Detection types

– Dynamic range

– T/R versus S-parameter test sets

Error models and calibration

– Types of measurement error

– One- and two-port models

– Error-correction choices

– Basic uncertainty calculations

Example measurements

Appendix a1 b1

SOURCE

INCIDENT (R)

Incident

DUT

Reflected

REFLECTED

(A)

SIGNAL

SEPARATION

TRANSMITTED

(B)

RECEIVER / DETECTOR

Transmitted

PROCESSOR / DISPLAY

E

D

E

S

Port 1

E

X

S

11

A

S

21

A

S

22

A

Port 2

E

RT

S

12

A

E

TT b2 a

2

E

L

Network Analyzer Basics

23-May-06

Page 10

Transmission Line Basics

Low frequencies

+

I

-

 wavelengths >> wire length

 current (I) travels down wires easily for efficient power

 transmission measured voltage and current not dependent on position along wire

Page 11

High frequencies

 wavelength » or << length of transmission medium

 need transmission lines for efficient power transmission

 matching to characteristic impedance (Zo) is very important for

 low reflection and maximum power transfer measured envelope voltage dependent on position along line

Network Analyzer Basics

23-May-06

Transmission line Zo

Page 12

Z o determines relationship between voltage and current waves

Z o is a function of physical dimensions and

r

Z o is usually a real impedance (e.g. 50 or 75 ohms)

0.8

0.7

0.6

0.5

10

1.2

1.1

1.5

1.4

1.3

1.0

0.9

50 ohm standard attenuation is lowest at

77 ohms power handling capacity peaks at 30 ohms

20 30 40 characteristic impedance for coaxial airlines (ohms)

50 60 70 80 90 100

Network Analyzer Basics

23-May-06

Page 13

Power Transfer Efficiency

R

S

R

L

For complex impedances, maximum power transfer occurs when ZL = ZS*

(conjugate match)

1.2

1

0.8

0.6

0.4

0.2

0

0 1 2 3 4 5 6 7 8 9 10

R

L

/ R

S

Maximum power is transferred when RL = RS

Network Analyzer Basics

23-May-06

Transmission Line Terminated with Zo

Zs = Zo

Zo = characteristic impedance of transmission line

Zo

Page 14

V inc

Vrefl = 0! (all the incident power

is absorbed in the load)

For reflection, a transmission line terminated in Zo behaves like an infinitely long transmission line

Network Analyzer Basics

23-May-06

Transmission Line Terminated with Short, Open

Zs = Zo

V inc

Page 15

V refl

In-phase (0 o

) for open, out-of-phase (180 o

) for short

For reflection, a transmission line terminated in a short or open reflects all power back to source

Network Analyzer Basics

23-May-06

Transmission Line Terminated with 25

W

Zs = Zo

Z

L

= 25

W

Page 16

V inc

V refl

Standing wave pattern does not go to zero as with short or open

Network Analyzer Basics

23-May-06

High-Frequency Device Characterization

Incident

R

Reflected

A

REFLECTION

Reflected

Incident

=

A

R

SWR

S-Parameters

S

11

, S

22

Reflection

Coefficient

G, r

Return

Loss

Impedance,

Admittance

R+jX,

G+jB

Page 17

Transmitted

B

TRANSMISSION

Transmitted

Incident

=

B

R

Gain / Loss

S-Parameters

S

21

, S

12

Transmission

Coefficient

T, t

Insertion

Phase

Group

Delay

Network Analyzer Basics

23-May-06

Page 18

Reflection Parameters

Reflection

Coefficient

G

=

V reflected

V incident

Return loss = -20 log( r

),

No reflection

(Z

L

= Zo)

0

 dB

1

= r F r

=

G

E max

E min

=

Z

L

Z

L

-

Z

O

+

Z

O

Voltage Standing Wave Ratio

E max

VSWR =

E min r

RL

VSWR

=

1 + r

1 r

Full reflection

(Z

L

= open, short)

1

0 dB

Network Analyzer Basics

23-May-06

Smith Chart Review

+jX

0 +R

 

-jX

Rectilinear impedance plane

0

Smith Chart maps rectilinear impedance plane onto polar plane

Z = Z o

G

= 0

(short)

G

=

1

±180 O

Polar plane

90 o

-

+

180 o

.2

.4

.6

.8

1.0

0 o

-90 o

Constant X

Constant R

(open)

G

=

1

0

O

Smith chart

Network Analyzer Basics

23-May-06

Page 19

.

Page 20

Transmission Parameters

V

Incident

DUT

V

Transmitted

Transmission Coefficient =

T

=

V

Transmitted

V

Incident

Insertion Loss (dB) = - 20 Log

V

Trans

V

Inc

= - 20 log

t

=

t

Gain (dB) = 20 Log

V

Trans

V

Inc

= 20 log

t

Network Analyzer Basics

23-May-06

Page 21

Linear Versus Nonlinear Behavior

Sin 360 o

* f * t

Time

Input

DUT

f

1

Frequency

A to

A * Sin 360 o

* f (t - t o

)

Time

A phase shift = t o

* 360 o

* f f

1

Output

Frequency

Linear behavior: input and output frequencies are the same (no additional frequencies created) output frequency only undergoes magnitude and phase change f

1

Time

Frequency

Nonlinear behavior: output frequency may undergo frequency shift (e.g. with mixers) additional frequencies created (harmonics, intermodulation)

Network Analyzer Basics

23-May-06

Page 22

Criteria for Distortionless Transmission

Linear Networks

Constant amplitude

over bandwidth of interest

Linear phase

over bandwidth of interest

Frequency

Frequency

Network Analyzer Basics

23-May-06

Magnitude Variation with Frequency

F(t) = sin wt + 1/3 sin 3wt + 1/5 sin 5wt

Time

Time

Linear Network

Frequency

Page 23

Frequency

Frequency

Network Analyzer Basics

23-May-06

Phase Variation with Frequency

F(t) = sin wt + 1 /3 sin 3wt + 1 /5 sin 5wt

Linear Network

Time

Time

Page 24

Frequency

0

°

-180 °

-360

°

Frequency

Frequency

Network Analyzer Basics

23-May-06

Page 25

Deviation from Linear Phase

RF filter response

Use electrical delay to remove linear portion of phase response

Linear electrical length added

(Electrical delay function)

Deviation from linear phase

+ yields

Frequency

Low resolution

Frequency

Frequency

High resolution

Network Analyzer Basics

23-May-06

Page 26

Phase

Group Delay

Frequency

Dw w

D t g t o

Group Delay (t ) g

=

d

 d w

=

-

1

360 o

* d

 d f

 w

 in radians in radians/sec in degrees f in Hertz ( w = 2 p f)

Group delay ripple

Frequency

Average delay

 group-delay ripple indicates phase distortion average delay indicates electrical length of DUT aperture of measurement is very important

Network Analyzer Basics

23-May-06

Why Measure Group Delay?

-

d

d

w

f

-

d

d

w

f

Page 27

f

Same p-p phase ripple can result in different group delay

f

Network Analyzer Basics

23-May-06

Why Use S-Parameters?

Page 28

 relatively easy to obtain at high frequencies

 measure voltage traveling waves with a vector network analyzer don't need shorts/opens which can cause active devices to oscillate or self-

 destruct relate to familiar measurements (gain, loss, reflection coefficient ...)

 can cascade S-parameters of multiple devices to predict system

 performance can compute H, Y, or Z parameters from S-parameters if desired

 can easily import and use S-parameter files in our electronic-

simulation tools

Incident a

1

S

11

Reflected b

1

Transmitted

Port 1

S

21

DUT

S

12

Transmitted

Port 2

S

22

Reflected

Incident b

2 a

2 b

1

= S

11 a

1

+ S

12 a

2 b

2

= S

21 a

1

+ S

22 a

2

Network Analyzer Basics

23-May-06

Measuring S-Parameters

a

1

Forward

b

1

Incident

S

11

Reflected

S

11

S

21

=

Reflected

Incident

=

Transmitted

Incident

=

= b

1 a

1 b

2 a

1 a

2

= 0

a

2

= 0

S

21

DUT

Transmitted b

2

a

2

= 0

Z

0

Load

S

22

S

12

=

Reflected

Incident

=

Transmitted

Incident

=

= b

2 a

2 b

1 a

2 a

1

= 0

a

1

= 0

Z

0

Load

a

1

= 0 b

1

Transmitted

DUT

S

12

S

22

Reflected

Incident b

2 a

2

Reverse

Network Analyzer Basics

23-May-06

Page 29

Equating S-Parameters with Common

Measurement Terms

S11 = forward reflection coefficient (input match)

S22 = reverse reflection coefficient (output match)

S21 = forward transmission coefficient (gain or loss)

S12 = reverse transmission coefficient (isolation)

Remember, S-parameters are inherently complex, linear quantities -- however, we often express them in a log-magnitude format

Network Analyzer Basics

23-May-06

Page 30

Page 31

Agenda

What measurements do we make?

Network analyzer hardware

– Signal separation devices

– Detection types

– Dynamic range

– T/R versus S-parameter test sets

Error models and calibration

Example measurements

Appendix

A B

C

SOURCE

INCIDENT (R)

Incident

DUT

Reflected

SIGNAL

SEPARATION

REFLECTED

(A)

TRANSMITTED

(B)

RECEIVER / DETECTOR

Transmitted

PROCESSOR / DISPLAY

Network Analyzer Basics

23-May-06

Page 32

Generalized Network Analyzer Block

Diagram

Incident Transmitted

DUT

Reflected

SOURCE

INCIDENT (R)

REFLECTED

(A)

SIGNAL

SEPARATION

TRANSMITTED

(B)

RECEIVER / DETECTOR

PROCESSOR / DISPLAY

Network Analyzer Basics

23-May-06

Page 33

Source

Supplies stimulus for system

Swept frequency or power

Traditionally NAs used separate source

Most Agilent analyzers sold today have

integrated, synthesized

sources

Network Analyzer Basics

23-May-06

Signal Separation

• measure incident signal for reference separate incident and reflected signals

splitter directional coupler

Page 34

SOURCE

INCIDENT (R)

Incident

DUT

Reflected

REFLECTED

(A)

SIGNAL

SEPARATION

TRANSMITTED

(B)

RECEIVER / DETECTOR

Transmitted

PROCESSOR / DISPLAY

bridge

Detector

Test Port

Network Analyzer Basics

23-May-06

Page 35

Directivity

Directivity is a measure of how well a coupler can separate signals moving in opposite directions

(undesired leakage signal) (desired reflected signal)

Test port

Directional Coupler

Network Analyzer Basics

23-May-06

Page 36

30

0

Interaction of Directivity with the DUT

(Without Error Correction)

DUT RL = 40 dB

Data Max

Add in-phase

60

Frequency

Data Min

Add out-of-phase

(cancellation)

Directivity

Data = Vector Sum

Network Analyzer Basics

23-May-06

Detector Types

Page 37

RF

Diode

Scalar broadband

(no phase information)

DC

AC

RF

Tuned Receiver

IF = F

LO

 F

RF

ADC / DSP

IF Filter

LO

SOURCE

INCIDENT (R)

Incident

DUT

Reflected

REFLECTED

(A)

SIGNAL

SEPARATION

TRANSMITTED

(B)

RECEIVER / DETECTOR

Transmitted

PROCESSOR / DISPLAY

Vector

(magnitude and phase)

Network Analyzer Basics

23-May-06

Broadband Diode Detection

Easy to make broadband

Inexpensive compared to tuned receiver

Good for measuring frequency-translating devices

Improve dynamic range by increasing power

Medium sensitivity / dynamic range

Page 38

10 MHz

26.5 GHz

Network Analyzer Basics

23-May-06

Narrowband Detection - Tuned Receiver

ADC / DSP

Best sensitivity / dynamic range

Provides harmonic / spurious signal rejection

Improve dynamic range by increasing power,

 decreasing IF bandwidth, or averaging

Trade off noise floor and measurement speed

Page 39

10 MHz 26.5 GHz

Network Analyzer Basics

23-May-06

Comparison of Receiver Techniques

0 dB

Broadband

(diode) detection

0 dB

Narrowband

(tuned-receiver) detection

-50 dB -50 dB

-100 dB

-100 dB

-60 dBm Sensitivity

 higher noise floor

 false responses

< -100 dBm Sensitivity

 high dynamic range harmonic immunity

Dynamic range = maximum receiver power - receiver noise floor

Page 40

Network Analyzer Basics

23-May-06

Dynamic Range and Accuracy

Page 41

Error Due to Interfering Signal

100

10

-

+

1 phase error magn error

0.1

0.01

0.001

0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50 -55 -60 -65 -70

Interfering signal (dB)

Dynamic range is very important for measurement accuracy!

Network Analyzer Basics

23-May-06

T/R Versus S-Parameter Test Sets

Transmission/Reflection Test Set

Source

Source

S-Parameter Test Set

Transfer switch

R1

R

A

B

A

B

R2

Port 1 Port 2 Port 1

Port 2

Fwd

DUT

Fwd

DUT

Rev

RF always comes out port 1

 port 2 is always receiver

response, one-port cal available

RF comes out port 1 or port 2 forward and reverse measurements

two-port calibration possible

Page 42

Network Analyzer Basics

23-May-06

Processor / Display

SOURCE

INCIDENT (R)

Incident

DUT

Reflected

REFLECTED

(A)

SIGNAL

SEPARATION

TRANSMITTED

(B)

RECEIVER / DETECTOR

Transmitted

PROCESSOR / DISPLAY

CH1 S21

CH2 S12 log MAG log MAG

10 dB/

10 dB/

PRm

Cor

Duplexer Test - Tx-Ant and Ant-Rx

1

REF 0 dB

REF 0 dB

1_ -1.9248 dB

1_ -1.2468 dB

839.470 000 MHz

1

Hld

PRm

Cor

1

880.435 000 MHz

PASS

PASS

2

Hld

CH1 START 775.000 000 MHz

CH2 START 775.000 000 MHz

CH1 S21

CH2 S12 log MAG log MAG

10 dB/

10 dB/

PRm

Cor

Duplexer Test - Tx-Ant and Ant-Rx

1

REF 0 dB

REF 0 dB

1_ -1.9248 dB

1_ -1.2468 dB

839.470 000 MHz

1

 markers

 limit lines

 pass/fail indicators

 linear/log formats

 grid/polar/Smith charts

Hld

PRm

Cor

1

Hld

CH1 START 775.000 000 MHz

CH2 START 775.000 000 MHz

PASS

880.435 000 MHz

PASS

STOP 925.000 000 MHz

STOP 925.000 000 MHz

2

Page 43

Network Analyzer Basics

23-May-06

Achieving measurement flexibility

Channel

Trace

Trace

Channel

• Sweep type

• Frequency

• Power

• IF bandwidth

• Number of points

• Trigger state

• Averaging

• Calibration

Rules of 4:

RF Performance

Easy to learn and use

Powerful measurement configurations

Advanced connectivity

Flexible automation choices

32 independent measurement channels

26 windows to view traces and channels

8 active and 8 memory traces per window

4-parameter display needs only one channel

Exception: >4 traces per channel OK

Window

Global

• Trigger source

• Port extensions

• RF power on/off

Trace

• Parameter

• Format

• Scale

• Markers

• Trace math

• Electrical delay

• Phase offset

• Smoothing

• Limit tests

• Time-domain transform

Trace (CH1)

Window

Trace (CH3)

Window

Trace (CH1)

Trace (CH2)

Window

Trace (CH2)

Trace (CH4)

Network Analyzer Basics

23-May-06

Page 44

Three channel example

Channel 1

frequency sweep (narrow)

S11 S11 S21

Channel 2

frequency sweep (broad)

S21

Channel 3

power sweep

S21

Window

Page 45

Window Window

Network Analyzer Basics

23-May-06

Page 46

Agenda

What measurements do we make?

Network analyzer hardware

Error models and calibration

– measurement errors

– what is vector error correction?

– calibration types

– accuracy examples

– calibration considerations

Example measurements

Appendix a1 b1

E

D

E

S

Port 1

E

X

S

11

A

S

21

A

S

22

A

Port 2

E

RT

S

12

A

LOAD

OPEN

SHORT

E

TT b2 a

2

E

L

Network Analyzer Basics

23-May-06

The Need For Calibration

Why do we have to calibrate?

• It is impossible to make perfect hardware

• It would be extremely difficult and expensive to make hardware good enough to entirely eliminate the need for error correction

How do we get accuracy?

• With vector-error-corrected calibration

• Not the same as the yearly instrument calibration

What does calibration do for us?

• Removes the largest contributor to measurement uncertainty: systematic errors

• Provides best picture of true performance of DUT

Systematic error

Network Analyzer Basics

23-May-06

Page 47

Page 48

Measurement Error Modeling

Systematic errors

 due to

imperfections in the analyzer and test setup

 assumed to be time invariant (predictable)

Random errors

vary with time in random fashion (unpredictable) main contributors: instrument

noise, switch and connector repeatability

Drift errors

 due to system performance changing after a calibration has been done primarily caused by

temperature variation

Measured

Data

Errors:

SYSTEMATIC

RANDOM

DRIFT

Unknown

Device

Network Analyzer Basics

23-May-06

Systematic Measurement Errors

R

Directivity

A

Crosstalk

B

DUT

Frequency response

 reflection tracking (A/R) transmission tracking (B/R)

Source

Mismatch

Load

Mismatch

Six forward and six reverse error terms yields 12 error terms for two-port devices

Page 49

Network Analyzer Basics

23-May-06

Page 50

Types of Error Correction

response (normalization)

– simple to perform

– only corrects for tracking errors stores reference trace in memory, thru then does data divided by memory

vector

– requires more standards requires an analyzer that can measure phase accounts for all major sources of systematic error

S

11 a

S

11 m

SHORT

OPEN

LOAD

thru

Network Analyzer Basics

23-May-06

What is Vector-Error Correction?

Errors

Vectorerror correction…

Measured

• Is a process for characterizing systematic error terms

Actual

• Measures known electrical standards

• Removes effects of error terms from subsequent measurements

Electrical standards…

• Can be mechanical or electronic

• Are often an open, short, load, and thru, but can be arbitrary impedances as well

Network Analyzer Basics

23-May-06

Page 51

Calibration

Using Know Standards to Correct for Systematic Errors

Process of characterizing systematic error terms

 measure known standards remove effects from subsequent measurements

1-port calibration (reflection measurements)

 only 3 systematic error terms measured directivity, source match, and reflection tracking

Full 2-port calibration (reflection and transmission measurements)

12 systematic error terms measured usually requires 12 measurements on four known standards (SOLT)

Standards defined in cal kit definition file

 network analyzer contains standard cal kit definitions

CAL KIT DEFINITION MUST MATCH ACTUAL CAL KIT USED!

User-built standards must be characterized and entered into user calkit

Network Analyzer Basics

23-May-06

Page 52

Page 53

RF in

Reflection: One-Port Model

Ideal

RF in

Error Adapter

1

S

11

M

S

11

A

S

11

M

E

D

E

RT

E

S

S

11

A

E

D

E

RT

= Directivity

= Reflection tracking

E

S

= Source Match

S11

M

S11

A

= Measured

= Actual

To solve for error terms, we measure 3 standards to generate 3 equations and 3 unknowns

S

11M

= E

D

+ E

RT

S

11A

1 - E

S

S

11A

Assumes good termination at port two if testing two-port devices

If using port 2 of NA and DUT reverse isolation is low (e.g., filter passband):

 assumption of good termination is not valid two-port error correction yields better results

Network Analyzer Basics

23-May-06

Two-Port Error Correction

Forward model

Port 1

Reverse model

Port 2

E

RT' a1 b1

E

D

E

S

Port 1

E

X

S

11

A

S

21

A

S

22

A

Port 2

E

TT b2 a

2

E

L a

1 b1

E

TT'

E

L' S

11

A

S

21A

S

22

A

S

12

A

E

X'

E

S'

E

D' b2 a

2

E

D

E

S

E

RT

= fwd directivity

= fwd source match

= fwd reflection tracking

E

D'

E

S'

= rev directivity

= rev source match

E

RT'

= rev reflection tracking

E

RT

S

12

A

E

L

E

TT

E

X

= fwd load match

= fwd transmission tracking

= fwd isolation

E

L'

E

TT'

E

X'

= rev load match

= rev transmission tracking

= rev isolation

Each actual S-parameter is a function of all four measured S-parameters

Analyzer must make forward and reverse sweep to update any one

S-parameter

Luckily, you don't need to know these equations to use network analyzers!!!

=

( 1

(

S

11

m

ERT

-

ERT

-

E D

ES

)( 1

)( 1

S

22

m

-

ED

S

ERT

22

m

-

E RT

'

'

'

E D

'

ES

ES

' )

' )

-

-

E L

(

S

21

E L EL m

ETT

(

-

S

E X

21

m

)(

-

ETT

S

12

E X m

-

E X

'

)

ETT

'

)(

S

12

m

-

ETT

'

E X

'

)

S

21

a

=

( 1

S

11

m

-

ERT

E D

ES

(

S

21

m

-

E X

ETT

)( 1

S

22

m

-

ERT

)(

'

1

E D

'

S

22

m

-

ED

'

( '

ERT

'

ES

' )

-

E L

'

))

E L

(

S

21

m

-

ETT

E X

)(

S

12

m

-

ETT

'

E X

'

)

S

12

a

=

( 1

-

ERT

ES

(

S

)(

12

1

m

-

E

X

E RT

'

)( 1

ETT

S

'

22

m

-

E D

'

'

S

11

m

-

ERT

E

D

ES

' )

-

(

ES

-

E L

' ))

' (

S

21

m

-

E X

ETT

)(

S

12

m

-

E X

ETT

'

'

)

S

22

a

=

( 1

S

22

m

-

(

ERT

S

11

m

-

ED

'

E D

'

ERT

ES

)(

)( 1

1

ERT

S

22

m

-

E D

ERT

-

'

'

ES

)

-

E L

' (

ES

' )

-

S

21

m

-

E X

)(

S

12

m

E L EL

(

ETT

S

21

m

-

E X

ETT

)(

S

-

ETT

12

m

'

E X

-

ETT

'

'

)

E X

'

)

Network Analyzer Basics

23-May-06

Page 54

Page 55

Before and After One-Port Calibration

0

2.0

data before 1-port calibration

20

1.1

40

1.01

60 data after 1-port calibration

6000 12000

1.001

MHz

Network Analyzer Basics

23-May-06

Page 56

Crosstalk: Signal Leakage Between Test

Ports During Transmission

DUT

Can be a problem with:

 high-isolation devices (e.g., switch in open position)

 high-dynamic range devices (some filter stopbands)

Isolation calibration

 adds noise to error model (measuring near noise floor of system) only perform if really needed (use averaging if necessary)

 if crosstalk is independent of DUT match, use two terminations if dependent on DUT match, use DUT with termination on output

LOAD

DUT

DUT

LOAD

Network Analyzer Basics

23-May-06

Page 57

Reflection Example Using a One-Port Cal

Directivity:

40 dB (.010)

.158

(.891)(.126)(.891) = .100

Load match:

18 dB (.126)

DUT

16 dB RL (.158)

1 dB loss (.891)

Remember: convert all dB values to linear for uncertainty calculations!

r or loss

(linear)

= 10

( )

20

Measurement uncertainty:

-20 * log (.158 + .100 + .010)

= 11.4 dB (-4.6dB)

-20 * log (.158 - .100 - .010)

= 26.4 dB (+10.4 dB)

Network Analyzer Basics

23-May-06

Page 58

Directivity:

40 dB (.010)

.158

Using a One-Port Cal + Attenuator

Load match:

18 dB (.126)

10 dB attenuator (.316)

SWR = 1.05 (.024)

DUT

16 dB RL (.158)

1 dB loss (.891)

Measurement uncertainty:

-20 * log (.158 + .039)

= 14.1 dB (-1.9 dB)

-20 * log (.158 - .039)

= 18.5 dB (+2.5 dB)

(.891)(.316)(.126)(.316)(.891) = .010

(.891)(.024)(.891) = .019

Worst-case error = .010 + .010 + .019 = .039

Low-loss bi-directional devices generally require two-port calibration for low measurement uncertainty

Network Analyzer Basics

23-May-06

Transmission Example Using Response Cal

RL = 18 dB (.126)

RL = 14 dB (.200)

Thru calibration (normalization) builds error into measurement due to source and load match interaction

Calibration Uncertainty

= (1 ±

r

S

r

L

)

= (1 ± (.200)(.126)

= ± 0.22 dB

Page 59

Network Analyzer Basics

23-May-06

Page 60

Filter Measurement with Response Cal

Source match =

14 dB (.200)

DUT

1 dB loss (.891)

16 dB RL (.158)

Load match =

18 dB (.126)

1

(.126)(.158) = .020

(.126)(.891)(.200)(.891) = .020

Total measurement uncertainty:

+0.60 + 0.22 = + 0.82 dB

-0.65 - 0.22 = - 0.87 dB

(.158)(.200) = .032

Measurement uncertainty

= 1 ± (.020+.020+.032)

= 1 ± .072

= + 0.60 dB

- 0.65 dB

Network Analyzer Basics

23-May-06

Page 61

Measuring Amplifiers with a Response Cal

Source match =

14 dB (.200)

DUT

16 dB RL (.158)

Load match =

18 dB (.126)

1

Total measurement uncertainty:

+0.44 + 0.22 = + 0.66 dB

-0.46 - 0.22 = - 0.68 dB

(.126)(.158) = .020

(.158)(.200) = .032

Measurement uncertainty

= 1 ± (.020+.032)

= 1 ± .052

= + 0.44 dB

- 0.46 dB

Network Analyzer Basics

23-May-06

Filter Measurements using the Enhanced

Response Calibration

Source match =

35 dB (.0178)

Effective source match = 35 dB!

DUT

1 dB loss (.891)

16 dB RL (.158)

Load match =

18 dB (.126)

1

(.126)(.158) = .020

(.126)(.891)(.0178)(.891) = .0018

(.158)(.0178) = .0028

Calibration Uncertainty

=

(1 ±

r

S

r

L

)

= (1 ± (.0178)(.126)

= ± .02 dB

Measurement uncertainty

= 1 ± (.020+.0018+.0028)

= 1 ± .0246

= + 0.211 dB

- 0.216 dB

Total measurement uncertainty:

0.22 + .02 = ± 0.24 dB

Network Analyzer Basics

23-May-06

Page 62

Using the Enhanced Response

Calibration Plus an Attenuator

10 dB attenuator (.316)

SWR = 1.05 (.024 linear or 32.4 dB)

Analyzer load match =18 dB (.126)

Calibration Uncertainty

=

(1 ±

r

S

r

L

)

= (1 ± (.0178)(.0366)

= ± .01 dB

Source match =

35 dB (.0178)

DUT

1 dB loss (.891)

16 dB RL (.158)

Effective load match = (.316)(.316)(.126) + .024

= .0366 (28.7dB)

1

(.0366)(.158) = .006

(.0366)(.891)(.0178)(.891) = .0005

Measurement uncertainty

= 1 ± (.006+.0005+.0028)

= 1 ± .0093

= ± 0.08 dB

(.158)(.0178) = .0028

Total measurement uncertainty:

0.01 + .08 = ± 0.09 dB

Network Analyzer Basics

23-May-06

Page 63

Calculating Measurement Uncertainty

After a Two-Port Calibration

DUT

1 dB loss (.891)

16 dB RL (.158)

Corrected error terms:

(8753ES 1.3-3 GHz Type-N)

Directivity = 47 dB

Source match = 36 dB

Load match = 47 dB

Refl. tracking = .019 dB

Trans. tracking = .026 dB

Isolation = 100 dB

S

11

m

Reflection uncertainty

=

=

S

11

a

(

E

D

S

11

a

2

E

S

S

21

a

S

12

a

E

L

S

11

a

( 1

-

E

RT

))

.

(.

0045

.

2

*.

0158

.

2

*.

0045

.

*.

)

= 0.158 ± .0088 = 16 dB +0.53 dB, -0.44 dB (worst-case)

Page 64

Transmission uncertainty

S

21

m

=

S

21

a

=

.

S

21

a

(

E

I

/

S

21

a

S E

11

a S

S S

21

a

12

E E a S L

S

22

E a L

( 1

E

TT

))

.

(

-

6

/ .

.

*.

.

2

*.

*.

.

*.

= 0.891 ± .0056 = 1 dB

±0.05 dB (worst-case)

.

)

Network Analyzer Basics

23-May-06

Page 65

Comparison of Measurement

Examples

Reflection

Calibration type

One-port

One-port + attenuator

Two-port

Measurement uncertainty

-4.6/10.4 dB

-1.9/2.5 dB

-0.44/0.53 dB

Calibration type

Response

Enhanced response

Enh. response + attenuator

Two port

Transmission

Calibration uncertainty Measurement uncertainty Total uncertainty

0.22 dB

0.60/-0.65 dB 0.82/-0.87

0.02 dB

0.01 dB

-----

0.22 dB

0.08 dB

0.24

0.09

0.05

Network Analyzer Basics

23-May-06

Page 66

Response versus Two-Port Calibration

Cor

Measuring filter insertion loss

CH1 S 21 &M log MAG

CH2

MEM log MAG

1 dB/

1 dB/

REF 0 dB

REF 0 dB

After two-port calibration

After response calibration

Uncorrected

Cor x2 1

START 2 000.000 MHz

STOP 6 000.000 MHz

2

Network Analyzer Basics

23-May-06

Page 67

ECal: Electronic Calibration (85060/90 series)

Variety of modules cover 30 kHz to 26.5 GHz

Six connector types available (50

W and 75

W

)

Single-connection

 reduces calibration time

 makes calibrations easy to perform minimizes wear on cables and standards

 eliminates operator errors

Highly repeatable temperature-compensated terminations provide excellent accuracy

Microwave modules use a transmission line shunted by PIN-diode switches in various combinations

Network Analyzer Basics

23-May-06

Page 68

ECal: Electronic Calibration

300 kHz to 26.5 GHz module

10 MHz to 67 GHz module

Control ECal directly from the PNA or ENA

Network Analyzers via USB

Nine connector types available

Ideal calibration technique for manufacturing

Mixed-connectors available

 Type-N 50 ohm, 3.5 mm and 7-16

N4690 Series, 2-port Microwave ECal

85090 Series, 2-port RF ECal

N4431B, 4-port RF ECal

Network Analyzer Basics

23-May-06

Adapter Considerations

reflection from adapter desired signal leakage signal r

measured

=

Directivity +

r

adapter

+

r

DUT

Coupler directivity = 40 dB

Adapter

DUT

Termination

DUT has SMA (f) connectors

Worst-case

System Directivity

Adapting from APC-7 to SMA (m)

APC-7 calibration done here

28 dB

17 dB

14 dB

APC-7 to SMA (m)

SWR:1.06

APC-7 to N (f) + N (m) to SMA (m)

SWR:1.05 SWR:1.25

APC-7 to N (m) + N (f) to SMA (f) + SMA (m) to (m)

SWR:1.05 SWR:1.25 SWR:1.15

Network Analyzer Basics

23-May-06

Page 69

Page 70

Calibrating Non-Insertable Devices

When doing a through cal, normally test ports mate directly

 cables can be connected directly without an adapter

 result is a zero-length through

What is an insertable device?

 has same type of connector, but different sex on each port has same type of sexless connector on each port (e.g. APC-7)

What is a non-insertable device?

 one that cannot be inserted in place of a zero-length through has same connectors on each port (type and sex)

 has different type of connector on each port waveguide on one port, coaxial on the other)

What calibration choices do I have for non-insertable devices?

 use an uncharacterized through adapter use a characterized through adapter (modify cal-kit definition) swap equal adapters adapter removal

Network Analyzer Basics

23-May-06

Swap Equal Adapters Method

Port 1

DUT

Port 1

Adapter A

Port 2

Port 2

Accuracy depends on how well the adapters are matched - loss, electrical length, match and impedance should all be equal

1. Transmission cal using adapter A.

Port 1

Adapter

B

Port 2

2. Reflection cal using adapter B.

Page 71

Port 1

DUT

Adapter

B

Port 2

3. Measure DUT using adapter B.

Network Analyzer Basics

23-May-06

Adapter Removal Calibration

Page 72

Calibration is very accurate and traceable

In firmware of 8753, ENA and PNA series

Also accomplished with ECal modules

Uses adapter with same connectors as DUT

Port 1

Must specify electrical length of adapter to within 1/4 wavelength of highest frequency (to avoid phase ambiguity)

Port 1

Port 1

Cal

Adapter

Cal Set 1

Adapter

B

Port 2

Cal

Adapter

Adapter

B

Cal Set 2

[CAL] [MORE] [MODIFY CAL SET]

[ADAPTER REMOVAL]

Port 2

DUT

1. Perform 2-port cal with adapter on port 2.

Save in cal set 1.

2. Perform 2-port cal with adapter on port 1.

Save in cal set 2.

3. Use ADAPTER REMOVAL to generate new cal set.

Port 2

Port 1 DUT

Adapter

B

Port 2

4. Measure DUT without cal adapter.

Network Analyzer Basics

23-May-06

Compromises of Traditional Non-Insertable Methods

Swap equal adapters

Calibration

Measurement

• Need phase matched adapters of different sexes (e.g., f-f, m-f)

• Errors introduced from loss and mismatch differences of adapters

Use characterized thru

Known S-parameters

• Two-step process (characterize thru, then use it during calibration)

• Need a non-insertable cal to measure S-parameters of characterized thru

Perform adapter removal cal

2-port cal 2

2-port cal 1

• Accurate but many steps in calibration (need to do two 2-port calibrations)

Add adapters after cal, then, during measurement…

• Use port extensions – doesn’t remove adapter mismatch effects

• De-embed adapters (S-parameters known) – similar to characterized thru

Network Analyzer Basics

23-May-06

Page 73

Page 74

Thru-Reflect-Line (TRL) Calibration

We know about Short-Open-Load-Thru (SOLT) calibration...

What is TRL?

A two-port calibration technique

Good for noncoaxial environments (waveguide, fixtures, wafer probing)

Uses the same 12-term error model as the more common SOLT cal

Uses practical calibration standards that are easily fabricated and characterized

TRL (requires 4 receivers)

TRL was developed for

non-coaxial microwave

measurements

Other variations: Line-Reflect-Match (LRM),

Thru-Reflect-Match (TRM), plus many others

Network Analyzer Basics

23-May-06

Non-Insertable ECal Modules

ECal resolves many, but not all non-insertable situations

Network Analyzer Basics

23-May-06

Page 75

Errors and Calibration Standards

UNCORRECTED RESPONSE 1-PORT FULL 2-PORT

DUT

Convenient

Generally not accurate

No errors removed thru

SHORT

OPEN

LOAD

DUT

Easy to perform

Use when highest accuracy is not required

Removes frequency response error

DUT

For reflection measurements

Need good termination for high accuracy with two-port devices

Removes these errors:

Directivity

Source match

Reflection tracking

SHORT

OPEN

LOAD

ENHANCED-RESPONSE

Combines response and 1-port

Corrects source match for transmission measurements thru

DUT

Highest accuracy

Removes these errors:

Directivity

Source, load match

Reflection tracking

Transmission tracking

Crosstalk

SHORT

OPEN

LOAD

Network Analyzer Basics

23-May-06

Page 76

Page 77

Calibration Summary

Reflection

Reflection tracking

Directivity

Source match

Load match

Test Set (cal type)

T/R

(one-port)

S-parameter

(two-port)

error can be corrected error cannot be corrected

*

enhanced response cal corrects for source match during transmission measurements

SHORT

OPEN

LOAD

Transmission

Transmission Tracking

Crosstalk

Source match

Load match

Test Set (cal type)

T/R

(response, isolation)

S-parameter

(two-port)

Network Analyzer Basics

23-May-06

Internal Measurement Automation

Simple: recall states

More powerful:

Test sequencing

– available on 8753

– keystroke recording

– some advanced functions

Windows-compatible programs

– available on PNA Series

– Visual Basic, VEE, LabView, C++, ...

Visual Basic for Applications

– available on ENA Series

Visual Basic for Applications on ENA

Network Analyzer Basics

23-May-06

Page 78

Page 79

Agilent’s Series of HF Vector Analyzers

MW

PNA series

20, 40, 50, 67 GHz

Configurable test set

Offset and harmonic RF sweeps

Extendable to 325GHz

Mixer calibration, antenna test

Up to 4-ports with external test sets

PNA-L series

6, 13.5, 20, 40, 50GHz

Configurable test set

Offset and harmonic RF sweeps

Internal 4-port, 20GHz version

RF

ENA series

3, 8.5 GHz

Internal 2- or 4-ports

Built-in balanced measurements

Offset and harmonic RF sweeps

8753ET/ES series

30kHz - 3, 6 GHz

Flexible hardware

Offset and harmonic

RF sweeps

Network Analyzer Basics

23-May-06

Page 80

RF

Agilent’s LF/RF Vector Analyzers

Combination NA / SA

4395A/4396B

500 MHz (4395A), 1.8 GHz (4396B) impedance-measuring option fast, FFT-based spectrum analysis time-gated spectrum-analyzer option

IBASIC standard test fixtures

LF

ENA-L Series

1.3, 3 GHz

S-parameter or T/R test set

Fast, small

Target markets: crystals, resonators, filters

E5100A/B

180, 300 MHz

Economical

Fast, small

Target markets: crystals, resonators, filters

Equivalent-circuit models

Evaporation-monitor-function option

Network Analyzer Basics

23-May-06

Mixer Measurement Parameters

Conversion loss

Conversion compression

Conversion phase

Group delay

Isolation/SWR

Two tone third-order intermodulation distortion

RF

LO

IF

Page 81

Network Analyzer Basics

23-May-06

Agilent Multiport Solution Overview

• General purpose multiport components

– Duplexer, Triplexer, power divider, LAN cable etc.

– Multiple multiport device test

• Multiport components in Handset and WiLAN

– Filter bank (multi SAW filter module)

– Switch module in multi-band handset and Wireless LAN

• High-power device testing

– Switch linearity of FEM for GSM handset

Page 82

Network Analyzer Basics

23-May-06

Agilent Multiport Solution Overview

20-Port

18-Port

Special handling multiport test sets are also available

E5091A-016 13 or 16-port

Z5623A-K66 14-port

16-Port

14-Port

87075C

6/12-port

(75 ohm)

87050E

4/8/12-port

12-Port

E5091A-009 9-port

10-Port

8-Port

Z5623A-K64 6-port

(High-power)

PNA 4-port

Opt. 550 with N44xxB

6-Port

ENA 3/4-port

4-Port

PNA-L 4-port

1.3 GHz 2.2 GHz 3.0 GHz 8.5GHz

20 GHz 40 GHz 50 GHz 67 GHz

Network Analyzer Basics

23-May-06

Page 83

Appendix

Page 84

Network Analyzer Basics

23-May-06

Page 85

Characterizing Unknown Devices

Using parameters (H, Y, Z, S) to characterize devices:

 gives linear behavioral model of our device measure parameters (e.g. voltage and current) versus frequency under various source and load conditions (e.g. short and open circuits) compute device parameters from measured data predict circuit performance under any source and load conditions

H-parameters

V

1

= h

11

I

1

+ h

12

V

2

I

2

= h

21

I

1

+ h

22

V

2

Y-parameters

I

1

= y

11

V

1

+ y

12

V

2

I

2

= y

21

V

1

+ y

22

V

2

Z-parameters

V

1

= z

11

I

1

+ z

12

I

2

V

2

= z

21

I

1

+ z

22

I

2 h

11

= V

1

I

1

V

2

=0 h

12

= V

1

2

I

1

=0

(requires short circuit)

(requires open circuit)

Network Analyzer Basics

23-May-06

Criteria for Distortionless Transmission

Nonlinear Networks

Saturation, crossover, intermodulation, and other nonlinear effects can cause signal distortion

Effect on system depends on amount and type of distortion and system architecture

Time

Time

Page 86

Frequency

Frequency

Network Analyzer Basics

23-May-06

Page 87

Measuring Nonlinear Behavior

Most common measurements:

 using a network analyzer and power sweeps

 gain compression

AM to PM conversion

 using a spectrum analyzer + source(s)

 harmonics, particularly second and third intermodulation products resulting from two or more

RF carriers

RL 0 dBm ATTEN 10 dB

8563A

SPECTRUM ANALYZER 9 kHz - 26.5 GHz

10 dB / DIV

LPF

LPF

DUT

CENTER 20.00000 MHz SPAN 10.00 kHz

RB 30 Hz VB 30 Hz ST 20 sec

Network Analyzer Basics

23-May-06

What is the Difference Between

Network

and

Spectrum

Analyzers?

8563A

SPECTRUM ANALYZER 9 kHz - 26.5 GHz

Page 88

Measures known signal

Frequency

Network analyzers:

 measure components, devices, circuits, sub-assemblies contain source and receiver display ratioed amplitude and phase

(frequency or power sweeps) offer advanced error correction

Measures unknown signals

Frequency

Spectrum analyzers:

 measure signal amplitude characteristics carrier level, sidebands, harmonics...) can demodulate (& measure) complex signals are receivers only (single channel) can be used for scalar component test (no

phase) with tracking gen. or ext. source(s)

Network Analyzer Basics

23-May-06

Spectrum Analyzer / Tracking Generator

RF in

Page 89

IF

LO

DUT

Spectrum analyzer

TG out f = IF

DUT

Tracking generator

Key differences from network analyzer:

One channel -- no ratioed or phase measurements

More expensive than scalar NA (but better dynamic range)

Only error correction available is normalization (and possibly open-short averaging)

Less accurate

Small incremental cost if SA is required for other measurements

8563A SPECTRUM ANALYZER 9 kHz - 26.5 GHz

Network Analyzer Basics

23-May-06

Comparing Unknown Thru and Adapter Removal

1.85 f-f adapter comparison

0.00

-0.03

-0.05

-0.08

-0.10

-0.13

-0.15

-0.18

-0.20

-0.23

-0.25

0.00

10.00

70.00

20.00

30.00

40.00

Frequency GHz

1.85 adapter removal cal

50.00

1.85 unknown thru cal

60.00

Network Analyzer Basics

23-May-06

Page 90

Agenda

What measurements do we make?

Network analyzer hardware

Error models and calibration

Example measurements

Filter tests

Gain compression

AM to PM conversion

Appendix

Page 91

Network Analyzer Basics

23-May-06

Cor

CH1 S21

Frequency Sweep - Filter Test

log MAG 10 dB/ REF 0 dB

CH1 S11 log MAG

69.1 dB

Stopband rejection

5 dB/

REF 0 dB

Page 92

START .300 000 MHz STOP 400.000 000 MHz

CENTER 200.000 MHz log MAG

1 dB/ REF 0 dB

Cor

1 ref m1: 4.000 000 GHz -0.16 dB m2-ref: 2.145 234 GHz 0.00 dB

2

Insertion loss

Cor x2 1

START 2 000.000 MHz STOP 6 000.000 MHz

2

SPAN 50.000 MHz

Return loss

Network Analyzer Basics

23-May-06

Optimize Filter Measurements with Swept-

List Mode

Segment 3: 29 ms

(108 points, -10 dBm, 6000 Hz)

12 dB/ REF 0 dB

PRm

CH1 S21 log MAG

Linear sweep: 676 ms

(201 pts, 300 Hz, -10 dBm)

Swept-list sweep: 349 ms

(201 pts, variable BW's & power)

PASS

Segment 5: 129 ms

(38 points, +10 dBm, 300 Hz)

Segment 1: 87 ms

(25 points, +10 dBm, 300 Hz)

START 525.000 000 MHz STOP 1 275.000 000 MHz

Segments 2,4: 52 ms

(15 points, +10 dBm, 300 Hz)

Network Analyzer Basics

23-May-06

Page 93

Page 94

Power Sweeps - Compression

Saturated output power

Compression region

Linear region

(slope = small-signal gain)

Input Power (dBm)

Network Analyzer Basics

23-May-06

Page 95

Power Sweep - Gain Compression

CH1 S21 1og MAG 1 dB/ REF 32 dB 30.991 dB

12.3 dBm

0

1

1 dB compression:

input power resulting in 1 dB drop in gain

START -10 dBm CW 902.7 MHz STOP 15 dBm

Network Analyzer Basics

23-May-06

Page 96

AM

(dB)

Amplitude

AM to PM Conversion

Measure of phase deviation caused by amplitude variations

Power sweep

Mag(Am

in

)

DUT

AM can be undesired: supply ripple, fading, thermal

AM can be desired: modulation (e.g. QAM)

PM

(deg)

Test Stimulus

Time

Amplitude

Q

AM

(dB)

Mag(AM

out

)

AM - PM Conversion =

Mag(Pm

Mag(Am

out

)

in

)

(deg/dB)

PM

(deg)

Output Response

Time

Mag(Pm

out

)

I

AM to PM conversion can cause bit errors

Network Analyzer Basics

23-May-06

Page 97

Measuring AM to PM Conversion

1:Transmission

2:Transmission

Log Mag 1.0 dB/

/M Phase 5.0 deg/

Ref 21.50 dB

Ref -115.7 deg

Ch1:Mkr1 -4.50 dBm 20.48 dB

Ch2:Mkr2 1.00 dB 0.86 deg

1

2

Use transmission setup with a power sweep

Display phase of S21

AM - PM = 0.86 deg/dB

Start -10.00 dBm

Start -10.00 dBm

1

CW 900.000 MHz

CW 900.000 MHz

2

Stop 0.00 dBm

Stop 0.00 dBm

1

Network Analyzer Basics

23-May-06

Page 98

Agenda

What measurements do we make?

Network analyzer hardware

Error models and calibration

Example measurements

Appendix

Advanced Topics time domain frequency-translating devices high-power amplifiers extended dynamic range multiport devices in-fixture measurements crystal resonators balanced measurements

Inside the network analyzer

Challenge quiz

RF

LO

IF

Network Analyzer Basics

23-May-06

Page 99

Zo

Time-Domain Reflectometry (TDR)

What is TDR?

 time-domain reflectometry

 analyze impedance versus time

 distinguish between inductive and capacitive transitions

With gating:

 analyze transitions analyzer standards inductive transition capacitive transition non-Zo transmission line

time

Network Analyzer Basics

23-May-06

Page 100

TDR Basics Using a Network Analyzer

 start with broadband frequency sweep (often requires microwave VNA) use inverse-Fourier transform to compute time-domain resolution inversely proportionate to frequency span

Time Domain Frequency Domain

CH1 S 22 Re 50 mU/ REF 0 U

F

-1

Cor

20 GHz

t f

6 GHz

0

 t

F(t)*dt

Integrate

1/s*F(s)

TDR

t

F

-1

f f

CH1 START 0 s STOP 1.5 ns

Network Analyzer Basics

23-May-06

Time-Domain Gating

TDR and gating can remove undesired reflections (a form of error

correction)

Only useful for broadband devices (a load or thru for example)

Define gate to only include DUT

Use two-port calibration

CH1 S11 &M log MAG 5 dB/ REF 0 dB

PRm

Cor

2

CH1 MEM Re

PRm

Cor

RISE TIME

29.994 ps

8.992 mm

20 mU/ REF 0 U

1

1: 48.729 mU

2: 24.961 mU

638 ps

668 ps

3: -10.891 mU 721 ps

Gate

1: -45.113 dB 0.947 GHz

2: -15.78 dB 6.000 GHz

2

3

CH1 START 0 s

Page 101

Thru in time domain

STOP 1.5 ns

1

START .050 000 000 GHz

Thru in frequency domain, with and without gating

STOP 20.050 000 000 GHz

Network Analyzer Basics

23-May-06

Page 102

Ten Steps for Performing TDR

1.

Set up desired frequency range (need wide span for good spatial resolution)

2. Under SYSTEM, transform menu, press "set freq low pass"

3. Perform one- or two-port calibration

4. Select S11 measurement *

5. Turn on transform (low pass step) *

6. Set format to real *

7. Adjust transform window to trade off rise time with ringing and overshoot *

8. Adjust start and stop times if desired

9. For gating:

 set start and stop frequencies for gate

 turn gating on *

 adjust gate shape to trade off resolution with ripple *

10. To display gated response in frequency domain

 turn transform off (leave gating on) * change format to log-magnitude *

* If using two channels (even if coupled), these parameters must be set independently for second channel

Network Analyzer Basics

23-May-06

Cor

Time-Domain Transmission

RF Input

CH1 S21 log MAG

RF Output

Triple Travel

Main Wave

Leakage

10 dB/ REF 0 dB

CH1 S21 log MAG

Cor

RF Leakage

15 dB/ REF 0 dB

Surface

Wave

Triple

Travel

Gate off

Gate on

START -1 us STOP 6 us

Network Analyzer Basics

23-May-06

Page 103

Page 104

Time-Domain Filter Tuning

Deterministic method used for tuning cavity-resonator filters

Traditional frequencydomain tuning is very difficult:

 lots of training needed may take 20 to 90 minutes to tune a single filter

Need VNA with fast sweep speeds and fast timedomain processing

Network Analyzer Basics

23-May-06

Page 105

Filter Reflection in Time Domain

Set analyzer’s center frequency

= center frequency of the filter

Measure S

11 domain or S

22 in the time

Nulls in the time-domain response correspond to individual resonators in filter

Network Analyzer Basics

23-May-06

Page 106

Tuning Resonator #3

Easier to identify mistuned resonator in time-domain: null #3 is missing

Hard to tell which resonator is mistuned from frequency-domain response

Adjust resonators by minimizing null

Adjust coupling apertures using the peaks in-between the dips

Network Analyzer Basics

23-May-06

Mixers and Converters

Basic Mixer

f1

RF

LO

IF

f3 f1 + f2 f1 - f2 f2 f1

Converter

RF

LO

IF

f3

 Up converter: f3 > f1

 Down converter: f3 < f1

 Upper mixing product: f3 = f1 + f2

 Lower mixing product: f3 = f1 – f2 f2

Network Analyzer Basics

23-May-06

Page 107

Mixer Measurement Parameters

Conversion loss

Conversion compression

Conversion phase

Group delay

Isolation/SWR

Two tone third-order intermodulation distortion

RF

LO

IF

Page 108

Network Analyzer Basics

23-May-06

Page 109

Conversion Loss

Conversion loss (dB) =

Function of LO power

10 log

RF power(mW)

IF power(mW)

RF

LO

IF

A

Conversion Loss

IF

RF

LO

f

Network Analyzer Basics

23-May-06

Conversion Loss

Swept IF

A

Conversion Loss

IF RF LO

f

Page 110

Fixed IF

A

Conversion Loss

IF RF

LO

f

Fixed RF

A

Conversion Loss

IF

RF LO

f

Network Analyzer Basics

23-May-06

Conversion Compression

Compression Region

Conversion Loss (dB) 1-dB Compression Point

IF Power (dB)

RF Input Power [dBm]

Page 111

Network Analyzer Basics

23-May-06

Conversion Phase

Theoretical reference signal

Measurement with

MUT inserted

Page 112

Phase reference plane

B

C t t

Remember:

Phase is a relative

measurement

Must be made on

two signals with the same frequency

Network Analyzer Basics

23-May-06

Group Delay

• Customers who measure phase are typically interested in the group delay ripple

• Mathematical derivative of phase measurement

Group delay ripple t g t o

Average delay

Frequency

Page 113

Network Analyzer Basics

23-May-06

PNA & ENA Network Analyzers Mixer Calibration

Techniques

Vector-Mixer Calibration

Most accurate measurements of phase and absolute group delay

Removes magnitude and phase errors for transmission and reflection measurements

Scalar-Mixer Calibration

Highly accurate conversion-loss measurements with simple setup and calibration

Removes mismatch errors during calibration and measurements by combining 2-port and power-meter calibrations

Network Analyzer Basics

23-May-06

Page 114

Balanced Mixer Measurements

Vector-mixer characterization VBA macro offers

Agilent patented

balanced mixer characterization

Balanced mixer measurements require two calibration mixer/filter

Both mixer/filters are characterized with VBA macro

Network Analyzer Basics

23-May-06

Page 115

Page 116

High Power Amplifier Setup Diagram

Based on PNA Network Analyzers

Example: PNA output power enough to drive amplifier.

Network Analyzer Basics

23-May-06

Page 117

High Power Amplifier Setup Diagram

Based on PNA Network Analyzers

Example: PNA output power NOT enough to drive amplifier. Need to add pre-amplifier to boost power levels.

Source

Switch/Splitter

R1

-20 dBm

60 dB source attenuator

10 dB steps

60 dB source attenuator

10 dB steps

R2

+15 dBm

-20 dBm

A B

-20 dBm

+25 dBm

+40 dBm

10 dB

+5 dBm

+5 dBm

20 dB

+10 dBm

+0 dBm

Pre-amp

(30 dB gain)

+30 dBm

20 dB

+30 dBm

+50 dBm

10 dB

Attenuator

Network Analyzer Basics

23-May-06

Page 118

High-Dynamic Range Measurements

0

-10

-20

-30

-40

-50

-60

-70

-80

-90

-100

-110

-120

-130

-140

-150

800 980

MHz

Take advantage of extended dynamic range with directreceiver access

Network Analyzer Basics

23-May-06

Agilent Multiport Solution Overview

• General purpose multiport components

– Duplexer, Triplexer, power divider, LAN cable etc.

– Multiple multiport device test

• Multiport components in Handset and WiLAN

– Filter bank (multi SAW filter module)

– Switch module in multi-band handset and Wireless LAN

• High-power device testing

– Switch linearity of FEM for GSM handset

Page 119

Network Analyzer Basics

23-May-06

Page 120

In-Fixture Measurements

Measurement problem: coaxial calibration plane is not the same as the in-fixture measurement plane

Calibration plane

Fixture

E

D

E

S

E

T

Error correction with coaxial calibration

Loss

Phase shift

Mismatch

Measurement plane

DUT

Network Analyzer Basics

23-May-06

Error Correction Choices

New! Automatic

Port Extensions

Port Extensions

De-embedding

Normalization

(response cal)

Easier

Lower

Difficulty

Accuracy

Full 2/3/4-port corrections

(SOLT, TRL, LRM...)

Harder

Higher

Page 121

Network Analyzer Basics

23-May-06

APE = Automatic Port Extensions

First solution to apply both electrical delay and insertion loss to enhance port extensions

First approach to give reasonable alternative to building in-fixture calibration standards or de-embedding fixture

APE accounts for loss and phase of fixture transmission lines

Network Analyzer Basics

23-May-06

Page 122

Automatic Port Extensions

– Step 1

First, perform coaxial calibration at fixture connectors to remove errors due to VNA and test cables

At this point, only the fixture loss, delay and fixture mismatch remain as sources of error.

Coaxial calibration reference planes

Network Analyzer Basics

23-May-06

Page 123

Automatic Port Extensions

– Step 2

After coaxial calibration, connect an open or short to portion of fixture being measured

Perform APE: algorithm measures each portion of fixture and computes insertion loss and electrical delay

Values calculated by APE are entered into port extension feature

Now, only fixture mismatch remains as source of error

(dominated by coaxial connector).

Coaxial calibration reference planes

Open or short placed at end of each transmission line

Ports extended

Network Analyzer Basics

23-May-06

Page 124

Page 125

With and Without Automatic Port Extensions

Delay & loss compensation

(values computed by APE)

With Automatic

Port Extension

Without Automatic

Port Extension

Network Analyzer Basics

23-May-06

Fixturing

Page 126

Fixturing features are similar for Agilent ENA and PNA network analyzers.

Network Analyzer Basics

23-May-06

Port Matching

Page 127

Port matching feature is same as embedding

Network Analyzer Basics

23-May-06

Differential Port Matching

Page 128

Network Analyzer Basics

23-May-06

Characterizing Crystal Resonators/Filters

E5100A/B Network Analyzer

Page 129

Ch1

Z: R phase 40 / REF 0 1: 15.621 U

Cor

31.998 984 925 MHz

Min

1

START 31.995 MHz

SEG START STOP POINTS POWER IFBW

1 31.995 MHz

> 2

32.052 MHz

END

32.008 MHz

32.058 MHz

STOP 32.058 MHz

200

200

0 dBm

0 dBm

Example of crystal resonator measurement

200Hz

200Hz

Network Analyzer Basics

23-May-06

Page 130

What are Balanced Devices?

Ideally, respond to differential and reject common-mode signals

Gain = 1

Differential-mode signal

Balanced to single-ended

Common-mode signal

(EMI or ground noise)

Gain = 1

Differential-mode signal

Fully balanced

Common-mode signal

(EMI or ground noise)

Network Analyzer Basics

23-May-06

Page 131

What about Non-Ideal Devices?

Mode conversions occur...

Differential to commonmode conversion

+

Generates EMI

Susceptible to EMI

Common-mode to differential conversion

Network Analyzer Basics

23-May-06

Page 132

So What?

RF and digital designers need to characterize:

Differential to differential mode (desired operation)

Mode conversions (undesired operation)

Operation in non-50-ohm environments

Other differential parameters:

• common-mode rejection ratio

• K-factor

• phase/amplitude balance

• conjugate matches

Network Analyzer Basics

23-May-06

Agilent Solutions for Balanced Measurements

D = differential mode

C = common mode

Now integrated in ENA and PNA FW

Data presented as mixed-mode Sparameters

Excellent dynamic range and accuracy

Many important features such as time domain, impedance renormalization, user parameters...

Network Analyzer Basics

23-May-06

Page 133

Who Needs Balanced Measurements

Wireless Communications

• Balanced topology less susceptible to EMI, noise

• Less shielding required

• RF grounding less critical

• Better RF performance, smaller, lighter phones

• LVDS extends battery life

Signal Integrity

• Verify waveform quality of high speed digital signals

• Engineers primarily interested in time-domain analysis

Page 134

Network Analyzer Basics

23-May-06

Target Devices

RF/Microwave Components

Balanced filters

Differential/push-pull amplifiers

Baluns

Balanced transmission lines

Cable connectors

Couplers

*

, circulators

*

, splitters/combiners

*

Page 135

* single-ended devices that need 4-port error correction

Network Analyzer Basics

23-May-06

Target Devices

Digital Design

PCB backplanes

PCB interconnects

Sockets, packages

High-speed serial interconnects

(Ethernet, Firewire, Infiniband,

USB …)

Page 136

Network Analyzer Basics

23-May-06

Agenda

What measurements do we make?

Network analyzer hardware

Error models and calibration

Example measurements

Appendix

Inside the network analyzer

RF Source

R1

Test port 1

A

LO

R2

B

Test port 2

Page 137

Network Analyzer Basics

23-May-06

Traditional Scalar Analyzer

processor/display source

SOURCE

INCIDENT (R)

Incident

DUT

Reflected

REFLECTED

(A)

SIGNAL

SEPARATION

TRANSMITTED

(B)

RECEIVER / DETECTOR

Transmitted

PROCESSOR / DISPLAY

Example: 8757D requires external detectors, couplers, bridges, splitters good for low-cost microwave scalar applications

Reflection

Detector

Bridge

DUT

RF R A B

Termination

Transmission

RF

R A B

Detector

DUT

Detector

Network Analyzer Basics

23-May-06

Page 138

Page 139

50 dB

50 dB

60 dB

Directional Coupler Directivity

20 dB

Test port

Directivity =

Coupling Factor

(fwd) x Loss

(through arm)

Isolation

(rev)

Directivity (dB) = Isolation (dB) - Coupling Factor (dB) - Loss (dB)

Examples:

Directivity = 50 dB - 20 dB = 30 dB

30 dB

20 dB

10 dB

Test port

Test port

Directivity = 50 dB - 30 dB - 10 dB = 10 dB

Directivity = 60 dB - 20 dB - 10 dB = 30 dB

10 dB

Network Analyzer Basics

23-May-06

One Method of Measuring Coupler Directivity

1.0 (0 dB) (reference)

Source

Coupler Directivity

35 dB (.018) short

.018 (35 dB) (normalized)

Directivity = 35 dB - 0 dB

= 35 dB

Source

Page 140 load

Assume perfect load

(no reflection)

Network Analyzer Basics

23-May-06

Page 141

Directional Bridge

50

W

50

W

Detector

50

W

Test Port

50-ohm load at test port balances the bridge -- detector reads zero

Non-50-ohm load imbalances bridge

Measuring magnitude and phase of imbalance gives complex impedance

"Directivity" is difference between maximum and minimum balance

Network Analyzer Basics

23-May-06

NA Hardware: Front Ends,

Mixers Versus Samplers

ADC / DSP

SOURCE

INCIDENT (R)

Incident

DUT

Reflected

REFLECTED

(A)

SIGNAL

SEPARATION

TRANSMITTED

(B)

RECEIVER / DETECTOR

Transmitted

PROCESSOR / DISPLAY

Sampler-based front end

S

ADC / DSP

Mixer-based front end

Harmonic generator

frequency "comb"

f

It is cheaper and easier to make broadband front ends using samplers instead of mixers

Page 142

Network Analyzer Basics

23-May-06

Mixers Versus Samplers: Time Domain

Sampler

Narrow pulse

(easier to resolve noise)

LO

RF

Single-balanced mixer (x1)

Wide pulse

(tends to average noise)

LO

RF

Page 143

Sampler

LO pulse

Mixer

LO

Network Analyzer Basics

23-May-06

Mixers Versus Samplers: Frequency Domain

A

Sampler

. . .

IF

f

Note: frequencies not to scale

A x1

Mixer x3

f

Network Analyzer Basics

23-May-06

Page 144

IF

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