Network Analysis Back to Basics
Network Analysis
Back to Basics
Objectives
Review RF basics (transmission lines, etc.)
Understand what types of measurements are made with vector
network analyzers (VNAs)
Examine architectures of modern VNAs
Provide insight into nonlinear
characterization of amplifiers,
mixers, and converters using a VNA
Understand associated calibrations
Application: Amplifiers test and Fixture
Simulator
Automation VBA example
Network Analysis is NOT.…
Router
Bridge
Repeater
Hub
Your IEEE 802.37 X.25 ASDN
switched-packet data stream
is running at 547 MBPS
with
-9
a BER of 1.523 X 10 . . .
What Are Vector Network Analyzers?
S21
Transmission
DUT
S11
S22
Reflection
Are stimulus-response test systems
S12
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
Magnitude
Provide the highest level
of measurement accuracy
RF Source
Phase
LO
R1
A
Test port 1
R2
B
Test port 2
Low
Integration
High
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
Resonators
Dielectrics
R, L, C's
Passive
RFICs
MMICs
T/R modules
Transceivers
Receivers
Tuners
Converters
Antennas
VCAs
Amplifiers
Switches
Multiplexers
Mixers
Samplers
Multipliers
VTFs
Modulators
VCAtten’s
Diodes
Transistors
Device type
Active
Complex
Device Test Measurement Model
RFIC Testers
Ded. Testers
VSA
SA
Response tool
RFIC test
Harm. Dist.
LO stability
Image Rej.
VNA
SNA
NF Mtr.
Full call
sequence
Pulsed S-parm.
Pulse profiling
NF
Imped. An.
Simple
Intermodulation
Distortion
Gain/flat. Compr'n
Phase/GD AM-PM
Isolation Mixers
Rtn loss Balance
Impedance d
S-parameters
TG/SA
Param. An.
NF
BER
EVM
ACP
Regrowth
Constell.
Eye
LCR/Z
I-V
Measurement plane
Absol.
Power
Power Mtr.
Det/Scope
DC
CW
Simple
Swept
Swept
freq
power
Noise
2-tone
Multi-tone
Complex
modulation
Stimulus type
Pulsed-
Protocol
RF
Complex
Lightwave Analogy to RF Energy
Incident
Reflected
Transmitted
Lightwave
DUT
RF
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, X-parameters
Ensure good match when absorbing
power (e.g., an antenna)
KPWR FM 97
The Need for Both Magnitude and Phase
S21
1. Complete characterization
of linear networks
S11
S22
S12
4. Time-domain characterization
2. Complex impedance
needed to design
matching circuits
Mag
Time
3. Complex values
needed for device
modeling
5. Vector-error correction
Error
Measured
Actual
6. X-parameter (nonlinear) characterization
Agenda
•
•
•
•
•
What measurements do we make?
Network analyzer hardware
Error models and calibration
Applications
Automation
Incident
Transmitted
DUT
SOURCE
Reflected
SIGNAL
SEPARATION
INCIDENT (R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
SHORT
OPEN
LOAD
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

High frequencies
Wavelength  or << length of transmission medium

Need transmission lines for efficient power transmission
 Matching to characteristic impedance (Z ) is very important for
o
low reflection and maximum power transfer
 Measured envelope voltage dependent on position along line

Transmission line Zo
Zo determines relationship between voltage and current waves
Zo is a function of physical dimensions and r
Zo is usually a real impedance (e.g. 50 or 75 ohms)
1.5
attenuation is
lowest at 77 ohms
1.4
1.3
normalized values
1.2
1.1
50 ohm standard
1.0
0.9
0.8
0.7
power handling capacity
peaks at 30 ohms
0.6
0.5
10
20
30
40
50
60 70 80 90 100
Characteristic impedance for coaxial
airlines (ohms)
Power Transfer Efficiency
RS
For complex impedances, maximum
power transfer occurs when ZL = ZS*
(conjugate match)
RL
Rs
+jX
Load Power
(normalized)
1.2
-jX
1
0.8
RL
0.6
0.4
0.2
0
0
1
2
3
4
5
6
7
8
9
10
RL / RS
Maximum power is transferred when RL = RS
Transmission Line Terminated with Zo
Zs = Zo
Zo = characteristic impedance
of transmission line
Zo
Vinc
Vreflect = 0! (all the incident power
is transferred to and
absorbed in the load)
For reflection, a transmission line terminated in Zo
behaves like an infinitely long transmission line
Transmission Line Terminated with Short, Open
Zs = Zo
V inc
o
Vreflect In-phase (0 ) for open,
o
out-of-phase (180 ) for short
For reflection, a transmission line terminated in a
short or open reflects all power back to source
Transmission Line Terminated with 25 Ohms
Zs = Zo
ZL = 25 W
Vinc
Vreflect
Standing wave pattern does not
go to zero as with short or open
High-Frequency Device Characterization
Incident
Transmitted
R
B
Reflected
A
TRANSMISSION
REFLECTION
Reflected
Incident
=
VSW
R
S-Parameters
S11, S22
Reflection
Coefficient
G, r
A
Transmitted
R
Incident
Return
Loss
Impedance,
Admittance
R+jX,
G+jB
=
B
R
Group
Delay
Gain / Loss
S-Parameters
S21, S12
Transmission
Coefficient
T,t
Insertion
Phase
Reflection Parameters
Reflection
Coefficient
G
Vreflected
=
=
Vincident
r
Return loss = -20 log(r ), r
=
F
=
ZL - Zo
ZL + Zo
G
Vmax
Vmin
Voltage Standing Wave
Ratio
Vmax
VSWR =
Vmin
=
1+r
1-r
Full reflection
(ZL = open, short)
No reflection
(ZL = Zo)
0
r
1
 dB
RL
0 dB
1
VSWR

Smith Chart Review
Polar plane
90
o
+jX
1.0
.8
.6
.4
0
+ 180 o
-
+R  
o
.2
0

0
-jX
-90 o
Rectilinear impedance plane
Constant X
Constant R
Z L = Zo
Smith Chart maps
rectilinear impedance
plane onto polar plane
G=
0
ZL =
Z L = 0 (short)
G= 1
±180
G =1
O
Smith chart
(open)
0
O
Transmission Parameters
V Incident
V Transmitted
DUT
Transmission Coefficient =
Insertion Loss (dB) = -20 Log
T
=
V Incident
VTrans
V Inc
Gain (dB) = 20 Log
V Trans
V Inc
V Transmitted
= -20 Log(t)
= 20 Log(t)
=
t
Linear Versus Nonlinear Behavior
A * Sin 360o * f (t - to)
A
Linear behavior:
Time
to
Sin 360o * f * t


A
phase shift =
to * 360o * f
Time
f
1
DUT
Input
Input and output frequencies are the
same (no additional frequencies created)
Output frequency only undergoes
magnitude and phase change
Frequency
Output
Nonlinear behavior:
f
1

Frequency
Time

f
1
Frequency
Output frequency may undergo
frequency shift (e.g. with mixers)
Additional frequencies created
(harmonics, intermodulation)
Criteria for Distortionless Transmission
Linear Networks
Linear phase over
bandwidth of
interest
Magnitude
Constant amplitude over
bandwidth of interest
Phase
Frequency
Frequency
Magnitude Variation with Frequency
F(t) = sin wt + 1/3 sin 3wt + 1/5 sin 5wt
Time
Time
Magnitude
Linear Network
Frequency
Frequency
Frequency
Phase Variation with Frequency
F(t) = sin wt + 1 /3 sin 3wt + 1 /5 sin 5wt
Linear Network
Time
Magnitude
Time
Frequency
0°
Frequency
-180°
-360 °
Frequency
Deviation from Linear Phase
Use electrical delay to remove
linear portion of phase response
Linear electrical length
added
Phase 45 /Div
RF filter response
Deviation from linear
phase
=
+
Frequency
Low resolution
o
o
Phase 1 /Div
(Electrical delay function)
Frequency
Frequency
High resolution
Group Delay
Frequency (w)
tg
Group delay ripple
Dw
to
Phase 
Average delay
D
Frequency
Group Delay=(tg)
-d 
dw

w

=
-1
360 o
*
d
df
in radians
in radians/sec
in degrees
f in Hertz (w = 2 p f)

Group-delay ripple indicates phase distortion

Average delay indicates electrical length of DUT

Aperture (Dw) of measurement is very important
Phase
Phase
Why Measure Group Delay?
f
f
-d 
dw
Group
Delay
Group
Delay
-d 
dw
f
f
Same peak-peak phase ripple can result in different group delay
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
V1 = h11I1 + h12V2
I2 = h21I1 + h22V2
Y-parameters
I1 = y11V1 + y12V2
I2 = y21V1 + y22V2
Z-parameters
V1 = z11I1 + z12I2
V2 = z21I1 + z22I2
h11 = V1
I1
V2=0
(requires short circuit)
h12 = V1
V2
I1=0
(requires open circuit)
Why Use S-Parameters?

Relatively easy to obtain at high frequencies






Measure voltage traveling waves with a vector network analyzer
Don't need shorts/opens (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 electronic-simulation tools
a1
S 21
Incident
b2
S11
Reflected
b1
Transmitted
DUT
Port 1
Transmitted
Port 2
S12
S22
Reflected
a2
Incident
b1 = S11 a1 + S12 a 2
b 2 = S21 a1 + S22 a 2
Measuring S-Parameters
a1
Forward
S 21 =
b1
Incident
a2 = 0
b1
= a
1
b
a2 = 0
2
= a
1
a2 = 0
a1 = 0
Z0
DUT
Load
b1
Load
DUT
Reflected
Transmitted
b2
Transmitted
21
Z0
S 11
Reflected
Incident
S 11 =
S
Incident
Transmitted
S 12
S 22 =
S 12 =
Reflected
Incident
Transmitted
Incident
S 22
b2
= a
2
b
1
= a
2
a1 = 0
b2
Reverse
Reflected
a2
Incident
a1 = 0
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
Measurements on Nonlinear Components
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
Scattering Parameters – Power Dependence
An early attempt at providing
some power-dependence
was the P2D files used in
ADS.
Unfortunately these files did
not properly capture nonlinear behavior except S11
and S21 compression,
nor did they predict
harmonics and IMD
33
X-parameters come from the
Poly-Harmonic Distortion (PHD) Framework
A1
A2
B1
B1k = F1k ( DC, A11 , A12 ,..., A21 , A22 ,...)
B2 k = F2 k ( DC, A11 , A12 ,..., A21 , A22 ,...)
Port Index
Harmonic (or carrier) Index
Spectral map of complex large input phasors to large complex output phasors
Black-Box description holds for transistors, amplifiers, RF systems, etc.
34
X-parameters Reduce to S-parameters
B21 ( A11 ) = X
dB
40
20
X
(F )
21
(F )
21
( A11 ) P + X
(S )
21,21
( A11 ) A21 + X
2
*
21
( A11 ) P A
[ X 21( F ) ( A11 )]  s21
/ | A11 |
| A11 |
(S )
X 21,21
0
(T )
21,21
| A11 | 0
(S )
X 21,21
( A11 )  s22
| A11 |0
-20
-40
-60
-25
X
-20 -15 -10
(T )
X 21,21
( A11 )  0
(T )
21,21
|A11| (dBm)
-5
| A11 |0
0
5
10
Reduces to (linear)
S-parameters in the
appropriate
limit
+
37
Agenda
•
•
•
•
•
What measurements do we make?
Network analyzer hardware
Error models and calibration
Applications
Automation
Incident
Transmitted
DUT
SOURCE
Reflected
SIGNAL
SEPARATION
INCIDENT (R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
SHORT
OPEN
LOAD
Generalized Network Analyzer Block Diagram
(Forward Measurements Shown)
Incident
Transmitted
DUT
SOURCE
Reflected
SIGNAL
SEPARATION
INCIDENT
(R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
Source
Incident
Transmitted
DUT
Reflected
SOURCE
SIGNAL
SEPARATION
INCIDENT (R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR




Supplies stimulus for system
Can sweep frequency or power
Traditionally NAs had one signal source
Modern NAs have the option for a second
internal source and/or the ability to control
external source.

Can control an external source as a local
oscillator (LO) signal for mixers and
converters

Useful for mixer measurements like
conversion loss, group delay
PROCESSOR / DISPLAY
Signal Separation
Incident
Transmitted
DUT
Reflected
SOURCE
SIGNAL
SEPARATION
• Measure incident signal for reference
• Separate incident and reflected signals
INCIDENT (R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
splitter
bridge
directional
coupler
Detector
Test Port
Directivity
Directivity is a measure of how well a directional coupler or
bridge can separate signals moving in opposite directions
(undesired leakage
signal)
(desired reflected
signal)
I
leakage
desired
C
result
Test port
L
Directional Coupler
Directivity = Isolation (I) - Fwd Coupling (C) - Main Arm Loss (L)
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
Advantage: less loss at low
frequencies
Disadvantages: more loss in main
arm at high frequencies and less
power-handling capability
Interaction of Directivity with the DUT
(Without Error Correction)
0
Data max
Directivity
30
Add in-phase
Device
60
Frequency
Data min
Add out-of-phase
(cancellation)
Device
Device
Directivity
Directivity
Return Loss
DUT RL = 40 dB
Data = vector sum
Detector Types:
Narrowband Detection - Tuned Receiver
RF
ADC / DSP
IF Filter
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

LO
10 MHz
26.5 GHz
Tuned Receiver Front Ends:
Mixers Versus Samplers
Incident
Transmitted
DUT
Reflected
SOURCE
SIGNAL
SEPARATION
INCIDENT (R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
Sampler-based front end
ADC / DSP
S
ADC / DSP
Mixer-based front end
It is cheaper and easier to make
broadband front ends using
samplers instead of mixers, but
dynamic range is considerably less
Harmonic
generator
f
frequency "comb"
Dynamic Range and Accuracy
Error Due to Interfering Signal
100
-
10
Error (dB, deg)
+
phase error
1
Dynamic range is
very important for
measurement
accuracy!
magn error
0.1
0.01
0.001
0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
Interfering signal or noise (dB)
-55
-60
-65
-70
T/R Versus S-Parameter Test Sets
S-Parameter Test Set
Transmission/Reflection Test Set
Source
Source
Transfer switch
R1
R
A
B
A
B
R2
Port 1
Port 2
Fwd



DUT
Port 1
Fwd
Fwd
RF comes out port 1; port 2 is receiver
Forward measurements only
Response, one-port cal available
Port 2



DUT
Rev
RF comes out port 1 or port 2
Forward and reverse measurements
Two-port calibration possible
Modern VNA Block Diagram (2-Port PNA-X)
+28V
J11
J10
J9
J8
rear panel
J7
+
-
J2
J1
LO
Source 2
OUT 1
Source 1
OUT 1
R1
OUT 2
Noise receivers
To receivers
Pulse
modulator
OUT 2
Pulse
modulator
R2
Pulse generators
A
B
1
2
3
4
Test port 1
Source 2
Output 1
Source 2
Output 2
DUT
Impedance tuner for noise
figure measurements
S-parameter receivers
RF jumpers
3–
13.5/
26.5
GHz
10 MHz 3 GHz
noise receivers
Mechanical switch
Test port 2
Processor / Display
Incident
Transmitted
DUT
Reflected
SOURCE
SIGNAL
SEPARATION
INCIDENT
(R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
• Markers
• Limit lines
• Pass/fail indicators
• Linear/log formats
• Grid/polar/Smith charts
• Time-domain transform
• Trace math
Achieving Measurement Flexibility
Channel
Channel
Trace
Trace
Trace
Trace
Trace
Trace
Window
Window
Trace (CH1)
Trace (CH1)
Trace (CH2)
Window
Window
Trace (CH3)
Trace (CH2)
Trace (CH4)
•
•
•
•
•
•
•
•
Trace
•
•
•
•
•
•
•
•
•
•
Parameter
Format
Scale
Markers
Trace math
Electrical delay
Phase offset
Smoothing
Limit tests
Time-domain transform
Sweep type
Frequencies
Power level
IF bandwidth
Number of points
Trigger state
Averaging
Calibration
Three Channel Example
Channel 1
Channel 2
Channel 3
frequency sweep (narrow)
frequency sweep (broad)
power sweep
S21
S21
S11
S11
Window
Window
S21
Window
Agenda
•
•
•
•
•
What measurements do we make?
Network analyzer hardware
Error models and calibration
Applications
Automation
Incident
Transmitted
DUT
SOURCE
Reflected
SIGNAL
SEPARATION
INCIDENT (R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
SHORT
OPEN
LOAD
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
Measurement Error Modeling
Systematic errors
• Due to imperfections in the analyzer and test setup
• Assumed to be time invariant (predictable)
• Generally, are largest sources or error
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
Errors:
SYSTEMATIC
Measured
Data
RANDOM
DRIFT
Unknown
Device
Systematic Measurement Errors
R
Directivity
A
B
Crosstalk
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
What is Vector-Error Correction?
Errors
Measured
Actual
Vector-error correction…
• Is a process for characterizing systematic error terms
• 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
Using Known Standards to Correct
for Systematic Errors

1-port calibration (reflection measurements)



Full two-port calibration (reflection and transmission measurements)



Only three systematic error terms measured
Directivity, source match, and reflection tracking
Twelve 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 cal-kit
Reflection: One-Port Model
RF in
Ideal
Error Adapter
RF in
1
ED = Directivity
S11A
S11M
ES
ED
S11M
ERT
To solve for error terms, we
measure 3 standards to generate
3 equations and 3 unknowns


S11A
ERT = Reflection tracking
ES = Source Match
S11M = Measured
S11A = Actual
S11A
S11M = ED + ERT
1 - ES S11A
Assumes good termination at port two if testing two-port devices
If using port two 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


Before and After A One-Port Calibration
Data after 1-port calibration
Data before 1-port calibration
Two-Port Error Correction
Reverse model
Port 1
Port 2
E RT'
Forward model
Port 1
a1
ED
EX
ES
S11A
b1
E RT
S22 A
S 12
ETT
EL
A
E D' = rev directivity
E S' = rev source match
E RT' = rev reflection tracking
EL' = rev load match
ETT' = rev transmission tracking
EX' = rev isolation

A
b2
A
S22 A
E S'
ED'
S12 A
EX'
a2
EL = fwd load match
ETT = fwd transmission tracking
EX = fwd isolation

S11
E TT'
b2
ED = fwd directivity
E S = fwd source match
ERT = fwd reflection tracking

E L'
b1
Port 2
S21A
S21
a1
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 a network analyzers!!!
S11a =
S
- ED
S
- ED '
S
- E X S12 m - E X '
( 11m
)(1 + 22m
E S ' ) - E L ( 21m
)(
)
E RT
E RT '
E TT
E TT '
S
S
S
- E D'
- ED '
- E X S12m - E X '
(1 + 11m
E S )(1 + 22m
E S ' ) - E L ' E L ( 21m
)(
)
E RT
E RT '
E TT
ETT '
(
S21a =
S21m - E X
E TT
)(1 +
S22 m - E D '
E RT '
( E S '- E L ))
S
S
S
- ED
- ED'
- E X S12 m - E X '
(1 + 11m
E S )(1 + 22m
E S ' ) - E L ' E L ( 21m
)(
)
E RT
E RT '
E TT
ETT '
S12a =
S
- EX '
S
- ED
( 12m
)(1 + 11m
( E S - E L ' ))
E TT '
E RT
S
- ED
S
- ED'
S
- E X S12m - E X '
(1 + 11m
E S )(1 + 22m
E S ' ) - E L ' E L ( 21m
)(
)
E RT
E RT '
E TT
E TT '
S22a =
S 22m - E D '
S11m - E D
S 21m - E X S12m - E X '
)( 1 +
ES ) - E L ' (
)(
)
E RT '
E RT
E TT
E TT '
S
- ED
S
- ED'
S
- E X S12m - E X '
(1 + 11m
E S )(1 + 22m
E S ' ) - E L ' E L ( 21m
)(
)
E RT
E RT '
E TT
ETT '
(
a2
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 two
DUTs with termination on output
LOAD
DUT
DUT
LOAD
Errors and Calibration Standards
UNCORRECTED
FULL 2-PORT
RESPONSE
1-PORT
SHORT
DUT
OPEN
thru



Convenient
Generally not accurate
No errors removed
LOAD
SHORT
OPEN
OPEN
LOAD
LOAD
DUT



Easy to perform
Use when highest
accuracy is not
required
Removes frequency
response error
DUT



ENHANCED-RESPONSE
Combines response and 1-port
 Corrects source match for transmission
measurements

SHORT
For reflection measurements
Need good termination for
high accuracy with two-port
devices
Removes these errors:
Directivity
Source match
Reflection tracking
thru
DUT


Highest accuracy
Removes these
errors:
Directivity
Source, load match
Reflection tracking
Transmission
tracking
Crosstalk
Calibration Summary
SHORT
Reflection
Test Set (cal type)
T/R
(one-port)

Reflection tracking

Directivity

Source match

Load match
S-parameter
OPEN
(two-port)
LOAD
Test Set (cal type)
Transmission
T/R
(response, isolation) (two-port)
error can be corrected

Transmission Tracking

Crosstalk

Source match

Load match
error cannot be corrected
*
enhanced response cal corrects
for source match during
transmission measurements
(
S-parameter
* )
Response versus Two-Port Calibration
Measuring filter insertion loss
After two-port calibration
After response calibration
Uncorrected
ECal: Electronic Calibration
• Variety of two- and four-port modules cover 300 kHz to 67 GHz
• Nine connector types available, 50 and 75 ohms
USB controlled
• Single-connection calibration

dramatically reduces calibration time

makes calibrations easy to perform

minimizes wear on cables and standards

eliminates operator errors
• Highly repeatable temperature-compensated
characterized terminations provide excellent accuracy
Microwave modules use a
transmission line shunted
by PIN-diode switches in
various combinations
ECAL User Characterizations
1. Select adapters for the
module to match the
connector configuration
of the DUT.
2. Perform a calibration
using appropriate
mechanical standards.
3. Measure the ECal
module, including
adapters, as though
it were a DUT
4. VNA stores resulting
characterization data
inside the module.
Thru-Reflect-Line (TRL) Calibration
We know about Short-Open-Load-Thru (SOLT) calibration... What is TRL?

A two-port calibration technique

Good for non-coaxial environments (waveguide, fixtures, wafer probing)

Characterizes same 12 systematic errors as the more common SOLT cal


Uses practical calibration standards that
are easily fabricated and characterized
Other variations: Line-Reflect-Match (LRM),
Thru-Reflect-Match (TRM), plus many others
TRL was developed for
non-coaxial microwave
measurements
Unknown-Thru Calibration
Analyzer
Port 1
DUT
Cal Methods are listed in order of
ascending accuracy (least accurate
first):
•
•
•
•
Uncharacterized Thru Adapter
Electronic Calibrator (Ecal)
Ecal with Unknown Thru
Mechanical with Unknown Thru
Cal
• Adapter Removal
Port 2
Analyzer
Port 1
Short
Open
Load
DUT
Thru
Port 2
Short
Open
Load
www.agilent.com/find/backtobasics
Network Analyzer Basics
Agenda
•
•
•
•
•
What measurements do we make?
Network analyzer hardware
Error models and calibration
Applications
Automation
Incident
Transmitted
DUT
SOURCE
Reflected
SIGNAL
SEPARATION
INCIDENT (R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
SHORT
OPEN
LOAD
VNA application examples
– RF amplifier test
– High-power measurement
76
RF amplifier test
Stability (K-factor)
Calculates stability (K-factor)
from all S-parameters with
equation editor
Gain compression
Sweeps both frequency and
input power level at PxdB
Harmonic Distortion
Performs real-time harmonics test
over frequency or input power
f1
High-power test
Performs accurate tests with
high-power input / output of DUT
VNA
Swept IMD
Performs IMD analysis over an
entire range of frequencies
f1 f2 f3
Pulsed-RF
Characterize pulsed
performance of devices
Efficiency (PAE)
Calculate power-added
efficiency (PAE)
The modern VNA is a more suited solution for many parametric tests of RF amplifiers.
77
What is gain compression?
DUT
•Parameter to define the transition between the linear and nonlinear region of an active device.
•The compression point is observed as x dB drop in the gain with VNA’s power sweep.
Gain (S21)
Output Power (dBm)
Sufficient power
level to drive DUT
Linear region
Compression
(nonlinear) region
Input Power (dBm)
Power is not high enough
to compress DUT.
Input Power (dBm)
Enough margin of source power capability
is needed for analyzers.
78
VNA Functions
Power sweep range
DUT
Ex.) RF amplifier - Gain compression point
Legacy VNA
Modern VNA
(Agilent/ HP 8753ES)
(Agilent E5072A)
S21
S21
8753’s sweep range
(i.e. -15 to +10 dBm)
:
• Power sweep range is limited within 25 dB
(i.e. -15 to 10 dBm).
• VNA’s output power is NOT high enough to
see compression point of DUT.
79
• VNA can drive up to +20 dBm, enough to
detect compression point.
•Wide power sweep range (>65 dB) enables
linear and nonlinear test with a single sweep.
VNA Functions
User Interface
Legacy VNA
Modern VNA
System Controller
• Manual parameter setup only.
• Customers need to develop their own
software for applications.
80
• Measurement wizard is provided using the VNA’s
built-in automated software environment (i.e. VBA;
Visual Basic for Applications)
• Easy setup for calibration / measurement.
• No external system controller is necessary.
VNA Functions
Measurement Wizard
•
•
•
81
Measurement wizard program speeds up measurements of RF amplifiers.
Key parameters of amplifiers: S-parameters, harmonics distortion, gain compression (CW or
Swept frequency), and swept-frequency IMD measurements.
Can be downloaded from www.agilent.com/find/enavba
VNA application examples
– RF amplifier test
– High-power measurement
82
Why high-power measurements?
• Components used for transmitting data in wireless communications
need to be tested with high-power signals under conditions similar
to actual operation. (may be beyond the measurement capability of
instruments!)
Diagram of RF interface in wireless communication
LNA Rx Filter
Antenna
Power Amp
Duplexer
Tx Filter Combiner
83
High-power Measurements
Temperature drift of a booster amp needs to be considered.
DUT’s actual input power (Pin)
Configuration with a booster amp
Input power (dBm)
System Controller
Power (drifted)
Target
power
level
SG
Booster
DUT
amp Pin
Power (initial)
tolerance
SA
Gain
Gain variation from
temperature drift
Frequency (Hz)
When temperature changes after setup / calibration,
input power levels are changed even out of tolerance!
Measurement Challenges:
• Power leveling - Eliminating short-term drift of a booster amplifier’s gain;
variation of input power to DUT.
84
High-power Measurements
Power leveling
DUT’s input power level should be within a specific target range - power leveling.
Configuration for input power leveling
DUT’s actual input power (Pin)
Input power (dBm)
System Controller
Leveled power
e.g. GPIB
SG’s power
is adjusted
Power (drifted)
Power
Sensor
Coupler
SG Booster
Pin DUT
SA
amp * Coupler to detect output
Target
power
level
tolerance
Frequency (Hz)
power of a booster amp
Measurement Challenges:
• Power leveling process takes very long time!
• Test configuration is complicated; necessary to lower overall cost of test systems.
85
VNA Function
Power leveling
VNA Function - Receiver leveling
• Adjusts the source power level using its receiver measurements.
• Replaces existing test systems for power leveling with reducing test complexity.
Leveling with rack & stack system
VNA’s receiver leveling
System Controller
e.g. GPIB
V
Power
Sensor
SG
Booster
amp
ATT
(Optional)
Coupler
Pin
DUT
SA
Booster
amp
Coupler
Pin
DUT
Receiver leveling offers fast and accurate leveling
to compensate a booster amp’s drift with a simple
connection.
86
High-power Measurements
Power leveling
Configuration of Power leveling
Leveled Input power (Pin)
Pin (dBm)
Receiver leveling ON
R1
ATT (Optional)
Booster amp
Coupler
Pin
+43 dBm
DUT
Receiver leveling OFF
0.1 dBm/div
Note: frequency sweep is performed to monitor Pin over frequency.
DUT’s Pin is accurately adjusted (i.e. within +-0.1 dBm) at
target power level of +43 dBm by using the VNA’s receiver
leveling.
87
Fixture Simulator
• Fixture Simulator
– Balanced measurements (Mixed-mode S-parameters)
– (De-)Embedding / port matching
– Setup wizard of fixture simulator
– Port matching utility program
Fixture Simulator
Actual
Calibration Plane
Zd
DUT
Zc
Data Process
Measured Sparameters
Port
Extension
Network Deembedding
Port reference
Z conversion
Port Matching
UnbalancedBalanced
Conversion
Differential
Port Z
conversion
Differential
Matching
circuit
Embedding
Balanced (Mixed-mode) S-parameter
Single-ended S-parameter
Single-ended
Balanced
Built-in Balanced Measurement
Balanced component examples:
SAW Filters (Unbal-Bal)
SAW Filters (Bal-Bal)
Differential Amplifiers
Baluns
Cable
Mixed-mode S-parameters
 S11 S12

S 21 S 22
 S 31 S 32

S 41 S 42
Measure
Single-ended S-parameters
S13 S14 

S 23 S 24
S 33 S 34

S 43 S 44
Simulate Hybrid Balun
to extract differential and common
DUT
Vdiff
Vcomm
Obtain
Mixed-mode S-parameters
(Balanced and Common-mode
S-parameters)
V1
V2
 S DD11 S DD12
S
 DD 21 S DD 22
 SCD11 SCD12

 SCD21 SCD22
S DC11
S DC 21
SCC11
SCC 21
S DC12 
S DC 22 
SCC12 

SCC 22 
Vdiff   A, B  V 1 

 = 
 *  
Vcomm   C , D  V 2 
Examples of Mixed-mode S-Parameters
Mixed-mode S21 for Bal-Bal
Sdd21
Sdc21
Mixed-mode S11
Sdd11
Mixed-mode S21 for Single to Bal
Scd21
Sds21
Scc21
Scs21
Sss11
Sds21
Ssd12
Sdd22
Ssc12
Sdc22
Sdc11
Scs21
Scd22
Scc22
Balanced SAW filter measurement example
Embedding/De-embedding and Port Z Conversion
Embedding
De-embedding
Measured
S-parameter
Measured
S-parameter
Additional
Network
Additional
Network
DUT
Undesired
Network
Undesired
Network
DUT
De-embedded
Response
Embedded Response
Complex Port Z Conversion
50
Measure
Simulate
DUT
DUT
50
R+jX
R+jX
Embedding / De-embedding
(De-)Embedding of 2-port circuits
Port 3
Port 1
DUT
Port 2
Port 4
(De-)Embedding of 4-port circuits
Port 1
Port 3
DUT
Port 2
Port 4
De-embedding
•Accurate characterization of the DUT is achieved by de-embedding Sparameter (*.s2p) of a fixture.
DUT
Connector
S21
Calibrated
system(cal
plane at cable
end)
RF Cable
Calibration
Plane
S11
S22
S12
Fixture
Create an S2p file
and de-embed
DUT
Embedding Virtual Networks
Virtual matching circuits
C1
Bal
SAW
Filter
Zi
L2
Zd
L1
C1
Zc
• Mathematically embed matching circuits on any ports as required.
• Predefined matching topologies or user defined S-parameters networks can
be embedded.
Balanced SAW Filter Measurement Example
Single-ended (unbalanced)
9x9 S-parameters, S11 to S33
Balanced S-parameters
(both differential and common modes)
Sss11
Ssd12
Ssc12
Sds21
Sdd22
Sdc22
Scs21
Scd22
Scc22
Measurement Specifications
Connections
Setup
• Single-ended : Port 1
1. Preset :
OK
• Balanced :
Port 2
2. Center :
942.5MHz
• Balanced :
Port 3
3. Span :
200MHz
4. Display :
Number of Traces: 9
Allocate Traces: |1|2|3|
|4|5|6|
|7|8|9|
Band Pass Filter(Single-ended)
F0 : 947.5MHz
PORT 2
PORT 1
50 ohm
Duplexer
PORT 1
50 ohm
PORT 2
F0(Tx) : 1880MHz
F0(Rx) : 1960MHz
50 ohm
ANT 50 ohm
R
x
PORT 3
50 ohm
T
x
Band Pass Filter(Balanced)
PORT 2
F0 : 942.5MHz
PORT 1
5. Select parameter & format as shown on next page
6. Adjust Scale
50 ohm
200 ohm
PORT 3
E5079A
s1
Handset Component Demo Kit
Agilent Restricted
Measure Single-ended S-parameters
Measurement parameters
S11
S21
S31
S12
S22
S32
S13
S23
S33
C1
Zi
Bal
SAW
Filter
L2
Zd
C1
Zc
Measured
S-parameter
Perform Full 3-port Calibration
C1
Zi
Bal
SAW
Filter
L2
Zd
C1
Zc
Measured
S-parameter
(w/Full-3 Cal)
Apply Port Extension
Electrical length
Port 1 : 180ps
Port 2 : 280ps
Port 3 : 280ps
C1
Zi
Bal
SAW
Filter
L2
Zd
C1
Zc
Apply port
extension
Measured
S-parameter
(w/Full-3 Cal)
Convert to Mixed-mode S-parameters
Measurement Parameters
Sss11
Sds21
Scs21
Ssd12
Sdd22
Scd22
C1
Ssc12
Sdc22
Scc22
Zi
Bal
SAW
Filter
L2
Zd
C1
Zc
Apply port
extension
Measured
S-parameter
(w/Full-3 Cal)
Convert to mixed-mode
S-parameter
Modify Port Characteristic Impedance
Port characteristic impedance
Port 1 : 50 ohms
Port 2 : 100 ohms
Port 3 : 100 ohms
C1
Zi
Bal
SAW
Filter
L2
Zd
C1
Zc
Apply port
extension
Measured
S-parameter
(w/Full-3 Cal)
Convert port
characteristic
impedance*
Convert to mixedmode S-parameter
* Differential & common impedance are
automatically calculated from defined
single-ended impedance.
Apply Port Matching
Matching specifications
Port 1 : none
Port 2 : Shunt L = 28nH
Port 3 : Shunt L = 28nH
C1
Zi
Bal
SAW
Filter
L2
Zd
C1
Zc
Apply port
extension
Apply matching Convert port
characteristic
circuit
impedance*
Measured
S-parameter
Convert to mixed(w/Full-3 Cal)
mode S-parameter
Save “State & Cal”
Measurement Specifications
Setup
Electrical length
1. Preset :
OK
2. Center :
942.5MHz
3. Span :
200MHz
Band Pass Filter(Singleended)
F0 : 947.5MHz
PORT 2
PORT 1
50 ohm
50
ohm
Duplexer
F0(Tx) :
1880MHz
F0(Rx) :
PORT 1 ANT 50 ohm
1960MHz
PORT 2
50 ohm
R
x
Port 1 : 180ps
Port 2 : 280ps
Port 3 : 280ps
Port characteristic impedance
Port 1 : 50 ohms
Port 2 : 100 ohms
Port 3 : 100 ohms
Matching specifications
PORT 3
50 ohm
T
x
Band Pass Filter(Balanced)
PORT 2
F0 : 942.5MHz
PORT 1
50 ohm
200 ohm
PORT 3
Port 1 : none
Port 2 : Shunt L = 28nH
Port 3 : Shunt L = 28nH
E5079A
s1
Handset Component Demo Kit
Agilent Restricted
Setup Wizard of Fixture Simulator
Fast and easy measurements with setup wizard
Available at Agilent website at http://www.agilent.com/find/enavba
Agenda
•
•
•
•
•
What measurements do we make?
Network analyzer hardware
Error models and calibration
Applications
Automation
Incident
Transmitted
DUT
SOURCE
Reflected
SIGNAL
SEPARATION
INCIDENT (R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
SHORT
OPEN
LOAD
Agilent IO Libraries Suite 16 provides
one tool for fast start-up
Suite 16
System set-up in
< 15 minutes
• Identify and set up LAN,
USB, GPIB, and converter
interfaces
• Identify and communicate
with instruments
• Change addresses and set
interface aliases
• Works with NI-488 software
and NI VISA I/O library
LAN eXtension for Instrumentation
LXI devices serve a web page
IP Address
Manufacturer
Model #
Serial #
Firmware rev.
IP Address
Domain name
etc.
Ability to
change the
IP address
Page 109
LXI Possibilities
Long
distance
operations
Higher
throughput
Flexible
triggering
No trigger
wires
Expert
Troubleshooting
Timestamp
all data
Parallel
operations
Eliminate
latency
Smart instruments
Asset
Management
Internal
network
Reduce
programming
Page 114
Software Integration
VEE Pro
Integrated
VBA Programming
Agilent SystemVue
Page 115
Agilent ADS
1/26/2011
Quick Demo Guide
ENA Series Network Analyzer - VBA Programming (UserMenu)
Procedure overview
1. Connect DUT to ENA
2. Launch VBA editor, and code VBA program
3. Run VBA Macro
4. Add bandwidth search module
5. Apply VBA macro to UserMenu buttons
Required Instrument and fixture
ENA series network analyzer (E5071C or E5061B)
N-Type Cable
In this demo…
• Code simple VBA macro for bandpass filter measurement
• Apply VBA macro to UserMenu buttons
2. Launch VBA editor, and code VBA program
a. Press [Macro setup] hard key then press VBA Editor soft key
VBA editor
b. Create module and code procedure
Click Insert in the menu bar then click Module
Code as shown below in Module1
Sub main()
Call Setup
End Sub
Band pass filter (BPF)
In this demo, we will use BPF (Center frequency =
1.09 GHz) but you can use another filter. Prepare
appropriate cable and adapter to connect between
ENA and DUT.
1. Connect DUT to ENA
DUT
Sub Setup()
SCPI.SYSTem.PRESet
SCPI.SENSe.FREQuency.CENTer = “1.09E9”
SCPI.SENSe.FREQuency.SPAN = “200E6”
SCPI.CALCulate.PARameter.Count = 2
SCPI.DISPlay.WINDow.Split = "D12"
SCPI.CALCulate.PARameter(2).DEFine = "S21"
SCPI.SENSe.BANDwidth.RESolution = 1000
MsgBox "Setup done"
SCPI.DISPlay.WINDow.TRACe(1).Y.SCALe.AUTO
SCPI.DISPlay.WINDow.TRACe(2).Y.SCALe.AUTO
End Sub
c. Save VBA program and exit VBA editor
Click
icon of the VBA editor. The Save As dialog box
appears. Specify the file name and location and click Save.
Click
icon of the VBA editor.
Figure1. DUT connection
3. Run VBA macro
Press [Macro Run] Hard key.
The ENA calles main() procedure, and this VBA program will set
up the measurement parameters as shown below.
Quick Demo Guide
4. Add Bandwidth Search Module
5. Apply VBA procedure to UserMenu buttons
6. Use UserMenu Buttons
a. Open VBA Editor
b. Modify Sub() procedure of Module1 as below code
a. Open VBA Editor
b. Modify Sub() procedure of Module1 as below code
a. Press “Setup” button to run Setup procedure
b. Press “Bandwidth” button to run Bandwidth_Search
procedure
Sub Main()
Call Setup
Call Bandwidth
End Sub
c. Add below procedure on Module1
Sub Bandwidth()
SCPI.CALCulate.PARameter(2).SELect
With SCPI.CALCulate.SELected.MARKer
.State = True
.FUNCtion.TYPE = "MAX"
.FUNCtion.EXECute
.BWIDth.State = True
End With
End Sub
Sub Main()
UserMenu.Item(1).enabled
UserMenu.Item(2).enabled
UserMenu.Item(1).Caption
UserMenu.Item(2).Caption
UserMenu.Show
End Sub
=
=
=
=
True
True
"Setup"
"Bandwidth"
c. Create UserMenu module
Click E5061B_Objects then Double-Click UserMenu
In the object box in the code window, select UserMenu as
shown below.
Tips: Command finder
Using command finder chapter of the help file, you can easily
find appropriate command for each button. To open help,
press [Help] hard key, then click Programing > Command
Reference > Command Finder.
d. Save VBA program and run
Click
icon, then
icon of the VBA editor
Press [Macro Run] hard key.
This code sets the measurement parameter, then make
bandwidth search function as below.
d. Code below procedure on UserMenu module
Private Sub UserMenu_OnPress(ByVal ID As
Long)
If ID = 1 Then Module1.Setup
If ID = 2 Then Module1.Bandwidth
UserMenu.Show
End Sub
e. Save program and run
Click
icon, then
icon of the VBA Editor
press [Macro Run] hard key.
www.agilent.com/find/ena_vba
Sample VBA(s) for the ENA
Agilent VNA Solutions
PNA-X, NVNA
Industry-leading performance
10 MHz to 13.5/26.5/43.5/50/67 GHz
Banded mm-wave to 2 THz
Test Accessories
PNA
Performance VNA
10 MHz to 20, 40, 50, 67, 110 GHz
Banded mm-wave to 2 THz
PNA-L
World’s most capable value VNA
300 kHz to 6, 13.5, 20 GHz
10 MHz to 40, 50 GHz
ENA
ENA-L
FieldFox
Mm-wave
solutions
World’s most popular
economy VNA
9 kHz to 4.5, 8.5 GHz
300 kHz to 20.0 GHz
Low cost VNA
300 kHz to 1.5/3.0 GHz
Up to 2 THz
PNA-X
receiver
8530A replacement
RF Analyzer
5 Hz to 4/6 GHz
PNA-X Customer Presentation
Last update:
Page 119
ENA Series Network Analyzers
New!
30 kHz to 4.5 / 8.5 GHz
E5072A
9 / 100 kHz to 4.5 / 6.5 / 8.5 GHz
300 kHz to 14 / 20 GHz
• 2-port
• Wide output power range
• Configurable test set
• 150 dB dynamic range
•
•
•
•
2-port & 4-port
Balanced meas.
Up to 20 GHz
Option TDR
E5071C
E5061B-3L5, LF-RF option
5 Hz to 3 GHz
E5061B-115 to 237, RF options
E5061B
100 kHz to 1.5 / 3 GHz
• Low-freq coverage
• Z-analysis function
• Low-cost simple RF NA
• 50 Ω & 75 Ω
Accurate Handheld VNA N9923A (4/6 GHz)
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Quad display
Page 121
CAT
Full 2 port vector network Analyzer
CalReady at each test port
Full 2 port QuickCal
O.01 dB/deg C Stability Spec
100 dB dynamic range
Power meter
Vector Voltmeter (1 – and 2-channel)
Distance to Fault
LAN, USB, mini SD
Vector volt Meter
Power Meter
Group/Presentation Title
Agilent Restricted
17 December 2012
APPENDIX
122
VNA application examples
– RF amplifier test
– High-power measurement
– Swept IMD measurement
– High-gain amp measurement
What is intermodulation distortion (IMD)?
• A measure of nonlinearity of amplifiers.
• Two or more tones applied to an amplifier and produce additional intermodulation products.
• The DUT’s output will contain signals at the frequencies: n*F1 +m *F2.
P(F1)
P(F2)
DeltaF
IM3 relative to
carrier (dBc)
F_IMD = n * F1 + m * F2
ex.)
•Lo F_IM3 = 2 * F1 - F2
•Hi F_IM3 = 2 * F2 - F1
•Lo F_IM5 = 3 * F1 - 2 * F2
•Hi F_IM5 = 3 * F2 - 2 * F1
•Lo F_IM7 = 4 * F1 - 3 * F2
•Hi F_IM7 = 4 * F2 - 3 * F1
P(2*F1-F2)
2*F1-F2
F1
F2
2*F2-F1
Frequency
Third-order Intercept Point (IP3)
• The third-order intercept point (IP3) or the third-order intercept (TOI) are often used as figures
of merit for IMD.
Output power (dBm)
P(F1)
OIP3
P(F2)
DeltaF
IM3 relative to
carrier (dBc)
Third-order product
(Slope 1:3)
Fundamental
(Slope 1:1)
P(2*F1-F2)
IIP3
2*F1-F2 F1
F2
2*F2-F1
Input power
(dBm)
Frequency
P(F1): Power level of low tone
P(F2): Power level of high tone
P(2*F1-F2): Power level of low-side IM3 signal
P(2*F2-F1): Power level of high-side IM3 signal
IP3 can be calculated by the equation using
low-side IM3:
IP3 (dBm) = P(F1) + (P(F2) - P(2*F1-F2)) / 2
When high-side IM3 is used, the equation is:
IP3 (dBm) = P(F2) + (P(F1) - P(2*F2-F1)) / 2
Intermodulation Distortion
2x SG + SA
• Using two SGs and a SA with CW signals.
• It requires a controller to synchronize
instruments.
• If many frequencies must be tested, test time
is increased dramatically.
SG + VNA
• ENA with frequency-offset mode (FOM) option
can set different frequencies at the source and
receiver.
• Real-time swept frequency IMD measurements
can be performed.
• Source power calibration and receiver calibration
is available with VNA for accurate absolute power
measurements.
VNA functions
Frequency Offset Mode
• Sets different frequency range for the source and receivers.
• Can be used for harmonics or intermodulation distortion (IMD) measurements with the VNA.
Frequency-offset Sweep
Normal Sweep
Source
(Port 1)
DUT
f1
Receiver
(Port 2)
f1
Source and receiver are tuned at the same
frequency range. (i.e. S-parameter).
Source
(Port 1)
DUT
f1
Receiver
(Port 2)
f2
Source and receiver are tuned at the different
frequency range (for harmonics, IMD test etc.)
IMD Measurement
Configuration of IMD measurement with VNA
SG
Measurement example (sweep delta)
USB/GPIB
Interface
10 MHz REF
f1 (SG)
VNA
f2 (ENA)
Attenuator
(Optional)
Lo IM3
f1 (SG)
f1
DUT
f_IM
(ENA)
f_IM
Combiner
f2 (ENA)
f2
Power levels of main tones and IM products in
swept frequencies can be monitored with the
VNA’s absolute measurements.
IMD Measurement Wizard for the E5072A
Key Features:
• Measurement macro running on the E5072A with intuitive GUI
• Quick setup of two-tone IMD measurements
• Control all necessary equipments from E5072A
–
MXG (connected via GPIB/USB interface)
–
Power meter & sensor (connected via GPIB/USB interface)
–
USB power sensor (connected directly to the ENA’s USB port)
• Guided calibration wizard
• Various measurement sweep types
–
Fixed F1 and Swept F2
–
Sweep Fc
–
Sweep DeltaF
• Various IMD measurement parameters
Available at: www.agilent.com/find/enavba
–
Absolute power of fundamental tones (in dBm)
–
Power levels of IMD products (absolute in dBm), Low or High-side IM (3rd, 5th, 7th)
–
Calculated third-order intercept point (IP3)
VNA application examples
– RF amplifier test
– High-power measurement
– Swept IMD measurement
– High-gain amp measurement
VNA Functions
Uncoupled Power
Independent built-in source attenuators to uncouple power level
•
•
•
Different output power level can be set for port 1 & 2 with independent source attenuators.
Easy characterization of high-gain power amp without external attenuators on output port.
More accurate reverse measurement (i.e. S12, S22) with wider dynamic range.
Example DUTs:
BTS repeaters, LNA, receivers.
R1
R2
A
B
ATT = 40 dB
(Port 1)
ATT = 0 dB
(Port 2)
0 dBm
-85 dBm
High-gain amp
High-gain amp measurement
DUT: High-gain (30 dB) RF Power amp
Coupled power
Uncoupled power
(Port 1 = Port 2 = -40 dBm)
(Port 1 = -40 dBm, Port 2 = 0 dBm)
S11
S12
S11
S12
S22
S22
S21
S21
K-factor
K-factor
More accurate S12 measurement with uncoupled
power results in better trace of calculated K-factor.
Resources
• Configuration Guide (5990-8001EN)
• Data Sheet (5990-8002EN)
• Quick Fact Sheet (5990-8003EN)
• Technical Overview (5990-8004EN)
• Application Note
– High-power measurement using the E5072A (5990-8005EN)
• ENA Series: www.agilent.com/find/ena
• E5072A Product page: www.agilent.com/find/e5072a
• Campaign page: www.agilent.com/find/e5072a_PR
• E5072A on YouTube: www.youtube.com/user/AgilentVNA#p/u/5/cA83A4qFEZU
Campaign page
YouTube page
THANK YOU!
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