Download Network Analyzer Basics

Network Analyzer Basics
Network Analyzer Basics
Network Analysis is NOT.…
Router
Bridge
Repeater
Hub
Your IEEE 802.3 X.25 ISDN
switched-packet data stream
is running at 147 MBPS with
-9
a BER of 1.523 X 10 . . .
Network Analyzer Basics
Network Analyzer Basics
Low
Dielectrics
R, L, C's
Passive
Complex
RFICs
MMICs
T/R modules
Transceivers
VSA
SA
Receivers
Tuners
Converters
VCAs
Amplifiers
Antennas
Switches
Multiplexers
Mixers
Samplers
Multipliers
Diodes
Device type
VCOs
VTFs
Oscillators
Modulators
VCAtten’s
RFIC test
Harm. Dist.
LO stability
Image Rej.
VNA
TG/SA
SNA
NF Mtr.
Param. An.
Power Mtr.
Transistors
Det/Scope
Full call
sequence
Pulsed S-parm.
Pulse profiling
NF
LCR/Z
I-V
Measurement
plane
Absol.
Power
Gain/Flatness
DC CW Swept Swept
freq
power
modulation
RF
Simple
Active
Intermodulation
Distortion
NF
BER
EVM
ACP
Regrowth
Constell.
Eye
Gain/Flat. Compr'n
Phase/GD AM-PM
Isolation
Rtn Ls/VSWR
Impedance
S-parameters
Imped. An.
Network Analyzer Basics
Noise
2-tone
Multi-
Complex
tone
Pulsed-
Stimulus type
Protocol
Complex
Network Analyzer Basics
Lightwave Analogy to RF Energy
Incident
Reflected
84000
Ded. Testers
Response
tool
Integration
Duplexers
Diplexers
Filters
Couplers
Bridges
Splitters, dividers
Combiners
Isolators
Circulators
Attenuators
Adapters
Opens, shorts, loads
Delay lines
Cables
Transmission lines
Waveguide
Resonators
Device Test Measurement Model
Simpl
e
High
What Types of Devices are Tested?
Why Do We Need to Test Components?
• Verify specifications of “building blocks” for more
complex RF systems
• Ensure distortionless transmission
of communications signals
Transmitted
– linear: constant amplitude, linear phase / constant group
delay
– nonlinear: harmonics, intermodulation, compression, AMto-PM conversion
Lightwave
• Ensure good match when absorbing
power (e.g., an antenna)
DUT
RF
KPWR
Network Analyzer Basics
Network Analyzer Basics
1
FM 97
Network Analyzer Basics
The Need for Both Magnitude and Phase
Agenda
S21
1. Complete
characterization of
linear networks
S11
S22
S12
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
5. Vector-error correction
Error
Base
Collector
Measured
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
Actual
Emitter
Network Analyzer Basics
Network Analyzer Basics
Transmission line Zo
Transmission Line Basics
-
I
•
•
•
Zo determines relationship between voltage and current
waves
Zo is a function of physical dimensions and εr
Zo is usually a real impedance (e.g. 50 or 75 ohms)
1.5
Twisted-pair
1.3
a
1.2
b
High frequencies
wavelength ≈ or << length of transmission
medium
need transmission lines for efficient power
transmission
matching to characteristic impedance (Z o) is
very important for low reflection and maximum
Network Analyzer Basics
power transfer
measured envelope voltage dependent on
εr
Coaxial
w2
Coplanar
50 ohm standard
1.0
0.9
0.8
power handling capacity
peaks at 30 ohms
0.6
w
0.5
10
20
30
40
50
60 70 80 90 100
characteristic impedance
for coaxial airlines (ohms)
Microstrip
Network Analyzer Basics
Transmission Line Terminated with Zo
Zs = Zo
Load Power
(normalized)
1.1
0.7
w1
RS
For complex impedances, maximum
power transfer occurs when ZL = ZS*
(conjugate match)
Rs
1.2
h
h
Power Transfer Efficiency
RL
attenuation is
lowest at 77 ohms
1.4
Waveguide
normalized values
+
Low frequencies
wavelengths >> wire length
current (I) travels down wires easily for efficient
power transmission
measured voltage and current not dependent on
position along wire
Zo = characteristic
impedance
of
transmission line
Zo
+jX
1
-jX
0.8
Vinc
0.6
RL
0.4
0.2
Vrefl = 0! (all the incident power
is absorbed in the load)
0
0
1
2
3
4
5
6
7
8
9
10
RL / RS
For reflection, a transmission line
terminated in Zo behaves like an infinitely
long transmission line
Maximum power is transferred when RL = RS
Network Analyzer Basics
Network Analyzer Basics
2
Network Analyzer Basics
Transmission Line Terminated with 25 Ω
Transmission Line Terminated with
Short, Open
Zs = Zo
Zs = Zo
ZL = 25 Ω
Vinc
Vinc
Vrefl
Network Analyzer Basics
Vrefl
In-phase (0o) for open,
out-of-phase (180o) for short
For reflection, a transmission line
terminated in a short or open reflects
all power back to source
Network Analyzer Basics
High-Frequency Device Characterization
Reflection Parameters
Reflection
Coefficient
Incident
Transmitted
R
Vreflected
Γ= V
incident
Return loss = -20 log(ρ),
B
Reflected
Standing wave pattern
does not go to zero as
with short or open
A
Reflected
Incident
=
A
Transmitted
R
Incident
SWR
S-Parameters
S11, S22
Reflection
Coefficient
Γ, ρ
Return
Loss
Impedance,
Admittance
R+jX,
G+jB
ρ
Φ
=
ZL − ZO
Z L + ZO
Γ
=
Voltage Standing Wave
Ratio
Emax
VSWR =
Emin
=
1+ρ
1-ρ
B
=
R
Group
Delay
Transmission
Coefficient
Τ,τ
Full reflection
(ZL = open, short)
No reflection
(ZL = Zo)
Gain / Loss
S-Parameters
S21, S12
ρ
Emax
Emin
TRANSMISSION
REFLECTION
=
ρ
1
∞ dB
RL
0 dB
1
VSWR
∞
0
Insertion
Phase
Network Analyzer Basics
Network Analyzer Basics
Smith Chart Review
Transmission Parameters
.
+jX
Polar plane
90
o
V Incident
DUT
1.0
.8
V Transmitted
.6
0
+R
.4
∞→
+ 180 o
-
o
.2
0
Transmission Coefficient =
∞
0
-jX
Rectilinear impedance
plane
-90
V
Constant X
Γ=
Γ= 1
V
0
±180
ZL =
Γ =1
O
(open)
0
Trans
Insertion Loss (dB) = - 20 Log
Constant R
Z L = 0 (short)
=
V Incident
=
o
Z L = Zo
Smith Chart maps
rectilinear
impedance
plane onto polar
plane
V Transmitted
Τ
V
O
Gain (dB) = 20 Log
V
Smith chart
Network Analyzer Basics
Network Analyzer Basics
3
Trans
Inc
= - 20 log
Inc
= 20 log
τ
τ
τ∠φ
Network Analyzer Basics
Criteria for Distortionless Transmission
Linear Networks
Linear Versus Nonlinear Behavior
A * Sin 360o * f (t - to)
A
Linear behavior:
Time
to
A
phase shift =
to * 360o * f
DUT
Input
Frequency
Magnitude
f
1
Time
Linear phase over
bandwidth of
interest
Constant amplitude over
bandwidth of interest
Output
Frequency
Phase
Sin 360o * f * t
input and output frequencies are
the same (no additional
frequencies created)
output frequency only undergoes
magnitude and phase change
Nonlinear behavior:
f
1
Frequency
Time
f
Frequency
1
output frequency may
undergo frequency shift
(e.g. with mixers)
additional frequencies
created (harmonics,
intermodulation)
Frequency
Network Analyzer Basics
Network Analyzer Basics
Phase Variation with Frequency
Magnitude Variation with Frequency
F(t) = sin wt + 1 /3 sin 3wt + 1 /5 sin 5wt
F(t) = sin wt + 1/3 sin 3wt + 1/5 sin 5wt
Linear Network
Time
Time
Time
Magnitude
Magnitude
Linear
Network
Frequency
Frequency
0°
Frequency
Frequency
-360°
Network Analyzer Basics
Deviation from Linear Phase
Group Delay
Use electrical delay to
remove linear portion of
phase response
Linear electrical length
added
RF filter response
Frequencyω
Average delay
∆φ
Phase 1 /Div
o
yields
Frequency
Group delay ripple
to
φ
Phase
Deviation from linear
phase
o
Phase 45 /Div
+
tg
∆ω
(Electrical delay function)
Low resolution
Frequency
-180°
Frequency
Network Analyzer Basics
Frequency
Time
Frequency
Group Delay (tg) =
−d φ
dω
Frequency
φ
ω
φ
High resolution
=
−1
360 o
*
dφ
df
in radians/sec
in degrees
f in Hertz (ω = 2 π f)
Network Analyzer Basics
Network Analyzer Basics
4
in radians
group-delay ripple indicates phase distortion
average delay indicates electrical length of DUT
aperture of measurement is very important
Network Analyzer Basics
Characterizing Unknown Devices
Using parameters (H, Y, Z, S) to characterize
devices:
Phase
Phase
Why Measure Group Delay?
f
f
−d φ
dω
Group
Delay
Group
Delay
−d φ
dω
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
H-parameters
Y-parameters
Z-parameters
conditions
V1 = h11I1 + h12V2
I1 = y11V1 + y12V2
V1 = z11I1 + z12I2
I2 = h21I1 + h22V2
I2 = y21V1 + y22V2
V2 = z21I1 + z22I2
f
f
Same p-p phase ripple can result in different
group delay
Network Analyzer Basics
V2=0
(requires short circuit)
h12 = V1
V2
I1=0
(requires open circuit)
Network Analyzer Basics
Measuring S-Parameters
Why Use S-Parameters?
h11 = V1
I1
Reflected
b1
b1
Transmitted
S 21 =
Incident
a2 = 0
b1
= a
1
b
Load
DUT
Reflected
Reflected
Incident
b2
Transmitted
21
Z0
S 11
Forward
S 11 =
S
Incident
a1
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
S 21
Incident
Transmitted
can easily import
and
use S-parameter
files in our electronica1
b2
simulation tools S11
a2 = 0
S 22 =
2
= a
1
a2 = 0
S 12 =
Reflected
Incident
Transmitted
Incident
b2
= a
2
b
a1 = 0
1
= a
2
a1 = 0
DUT
S22
Port 2 Reflected
Port 1
a2
Incident
S
Transmitted
12
a1 = 0
Z0
DUT
Load
b1 = S11a1 + S12 a 2
b1
b 2 = S21 a1 + S22 a 2
Network Analyzer Basics
Transmitted
S 12
S 22
b2
Reverse
Reflected
a2
Incident
Network Analyzer Basics
Equating S-Parameters with Common
Measurement Terms
Criteria for Distortionless Transmission
Nonlinear Networks
•
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
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
Frequency
Network Analyzer Basics
Network Analyzer Basics
5
Time
Frequency
Network Analyzer Basics
What is the Difference Between
Network and Spectrum Analyzers?
Measuring Nonlinear Behavior
8563A
LPF
SPECTRUM ANALYZER
.
RL 0 dBm
ATTEN
10 dB
10 dB / DIV
Measures
known
signal
Amplitude
8563A
Amplitude Ratio
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
SPECTRUM ANALYZER
GHz
9 k Hz -2 6.5
Measures
unknown
signals
Frequency
Frequency
9 k Hz -2 6.5 GHz
Network analyzers:
DUT
CENTER 20.00000 MHz
RB 30 Hz
VB 30 Hz
LPF
SPAN 10.00 kHz
ST 20 sec
Network Analyzer Basics
Spectrum analyzers:
measure components, devices,
circuits, sub-assemblies
contain source and receiver
display ratioed amplitude and phase
(frequency or power sweeps)
offer advanced error correction
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
Agenda
Generalized Network Analyzer
Block Diagram
Incident
What measurements do we make?
Network analyzer hardware
Error models and calibration
Example measurements
Appendix
Transmitted
DUT
SOURCE
Reflected
SIGNAL
SEPARATION
INCIDENT
(R)
REFLECTED
(A)
TRANSMITTED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
Network Analyzer Basics
Network Analyzer Basics
Incident
Source
Signal Separation
Transmitted
DUT
Reflected
SOURCE
SIGNAL
SEPARATION
INCIDENT ( R)
Supplies stimulus for system
Swept frequency or power
Traditionally NAs used separate
source
Most Agilent analyzers sold
today have integrated,
synthesized sources
REFL ECT ED
(A)
TRANSMITT ED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
•
•
measure incident signal for reference
separate incident and reflected signals
splitter
bridge
directional
coupler
Network Analyzer Basics
Network Analyzer Basics
6
Detector
Test Port
Network Analyzer Basics
Interaction of Directivity with the
DUT (Without Error Correction)
Directivity
Directivity is a measure of how well a
coupler can separate signals moving
in opposite directions
Data Max
Device
(desired reflected
signal)
Directivity
DUT RL = 40 dB
Return Loss
(undesired leakage
signal)
0
30
Add in-phase
60
Device
Frequency
Directivity
Directional Coupler
Network Analyzer Basics
Device
Test port
Data Min
Data = Vector Sum
Directivity
Add out-of-phase
(cancellation)
Network Analyzer Basics
Incident
Detector Types
Transmitted
Broadband Diode Detection
DUT
Reflected
SOURCE
Scalar broadband
(no phase
information)
Diode
SIGNAL
SEPARATION
INCIDENT ( R)
REFL ECT ED
(A)
TRANSMITT ED
(B)
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
DC
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
RF
AC
Tuned Receiver
IF = F LO ± F RF
RF
ADC / DSP
Vector
(magnitude and
phase)
IF Filter
LO
10 MHz
Network Analyzer Basics
26.5 GHz
Network Analyzer Basics
Narrowband Detection - Tuned Receiver
Comparison of Receiver Techniques
Broadband
(diode)
detection
ADC / DSP
0 dB
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
0 dB
Narrowband
(tuned-receiver)
detection
10 MHz
-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
26.5 GHz
Network Analyzer Basics
Network Analyzer Basics
7
Network Analyzer Basics
T/R Versus S-Parameter Test Sets
Dynamic Range and Accuracy
Source
Source
-
10
Transfer switch
+
Error (dB, deg)
S-Parameter Test Set
Transmission/Reflection Test Set
Error Due to Interfering Signal
100
Dynamic range
is very important
for measurement
accuracy!
phase error
1
magn error
0.1
R
R
B
A
Port 1
Port 2
0.01
Fwd
0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
-55
-60
-65
Fwd
RF always comes out port
1
port 2 is always receiver
response, one-port cal
Network Analyzer Basics
available
-70
Interfering signal (dB)
Network Analyzer Basics
Processor / Display
Incident
Port 2
Port 1
DUT
0.001
B
A
DUT
Rev
RF comes out port 1 or port
2
forward and reverse
measurements
two-port calibration
possible
Internal Measurement Automation
Transmitted
DUT
Simple: recall states
More powerful:
50 MH-20GHz
NETWORK ANYZER
ACTIVE
CHANNEL
C H 2 S TA R T 775. 000 000 MH z
C H 1 S TA R T 775. 000 000 MH z
Reflected
ENTRY
S TO P 925. 000 000 MH z
S TO P 925. 000 000 MH z
H ld
SOURCE
RESPONSE
PA S S
2
C or
P Rm
SIGNAL
SEPARATION
880.435 000 M H z
1
PA S S
1
REFL ECT ED
(A)
STIMULUS
H ld
TRANSMITT ED
(B)
P Rm
R CHANNEL
INSTRUMENT
STATE
D uplex er T est - Tx -A nt and Ant - Rx
T
R L
S
839.470 000 M H z
CH2
CH1
S 12
S 21
log MA G
log MA G
10 dB/
10 dB/
Test sequencing
1
C or
INCIDENT
(R)
R E F 0 dB
R E F 0 dB
HP-IB STATUS
1_ - 1.2468 dB
1_ - 1.9248 dB
PORT 1
PORT 2
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
CH2 START 775.000 000 MHz
CH1 START 775.000 000 MHz
STOP 925.000 000 MHz
STOP 925.000 000 MHz
Hld
PASS
2
IBASIC
Cor
markers
limit lines
pass/fail indicators
linear/log formats
grid/polar/Smith
charts
PRm
880.435 000 MHz
1
available on 8753/ 8720
families
keystroke recording
some advanced functions
ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 + - / * = < > ( ) & "" " , . / ? ; : ' [ ]
1 ASSIGN @Hp8714 TO 800
2 OUTPUT @Hp8714;"SYST:PRES; *WAI"
3 OUTPUT @Hp8714;"ABOR;:INIT1:CONT OFF;*WAI"
available on 8712 family
sophisticated programs
custom user interfaces
4 OUTPUT @Hp8714;"DISP:ANN:FREQ1:MODE SSTOP"
5 OUTPUT @Hp8714;"DISP:ANN:FREQ1:MODE CSPAN"
6 OUTPUT @Hp8714;"SENS1:FREQ:CENT 175000000 HZ;*WAI"
7 OUTPUT @Hp8714;"ABOR;:INIT1:CONT OFF;:INIT1;*WAI"
8 OUTPUT @Hp8714;"DISP:WIND1:TRAC:Y:AUTO ONCE"
9 OUTPUT @Hp8714;"CALC1:MARK1 ON"
PASS
Hld
10 OUTPUT @Hp8714;"CALC1:MARK:FUNC BWID"
11 OUTPUT @Hp8714;"SENS2:STAT ON; *WAI"
1
12 OUTPUT @Hp8714;"SENS2:FUNC 'XFR:POW:RAT 1,0';DET NBAN; *WAI"
1
Cor
PRm
13 OUTPUT @Hp8714;"ABOR;:INIT1:CONT OFF;:INIT1;*WAI"
Duplexer Test - Tx-Ant and Ant-Rx
839.470 000 MHz
CH2
CH1
S12
S21
log MAG
log MAG
10 dB/
10 dB/
REF 0 dB
REF 0 dB
14 OUTPUT @Hp8714;"DISP:WIND2:TRAC:Y:AUTO ONCE"
1_ -1.2468 dB
1_ -1.9248 dB
15 OUTPUT @Hp8714;"ABOR;:INIT1:CONT ON;*WAI"
16 END
Network Analyzer Basics
Network Analyzer Basics
Agilent’s Series of HF Vector Analyzers
Agilent’s LF/RF Vector Analyzers
Microwave
Combination NA / SA
8510C series
8720ET/ES series
13.5, 20, 40 GHz
economical
fast, small, integrated
test mixers, high-power
amps
110 GHz in coax
highest accuracy
modular, flexible
pulse systems
Tx/Rx module
test
4395A/4396B
RF
8712ET/ES series
1.3, 3 GHz
low cost
narrowband and
broadband
detection
IBASIC / LAN
E5100A/B
8753ET/ES series
500 MHz (4395A), 1.8 GHz (4396B)
impedance-measuring option
fast, FFT-based spectrum analysis
time-gated spectrum-analyzer option
IBASIC
standard test fixtures
3, 6 GHz
highest RF
accuracy
flexible hardware
more features
Offset and harmonic
RF sweeps
LF
Network Analyzer Basics
Network Analyzer Basics
8
180, 300 MHz
economical
fast, small
target markets: crystals, resonators, filters
equivalent-circuit models
evaporation-monitor-function option
Network Analyzer Basics
Agenda
Spectrum Analyzer / Tracking Generator
RF in
IF
8563A
SPECTRUM ANALYZER
9 k Hz -2 6.5 GHz
LO
DUT
Spectrum analyzer
TG out
f = IF
DUT
Tracking generator
Why do we even need error-correction and
calibration?
It is impossible to make perfect hardware
It would be extremely expensive to make hardware
good enough to eliminate the need for error
correction
Key differences from network analyzer:
What measurements do we
make?
Network analyzer hardware
Error models and calibration
Example measurements
Appendix
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)
Poorer accuracy
Small incremental cost if SA is required for other measurements
Network Analyzer Basics
Network Analyzer Basics
Measurement Error Modeling
Calibration Topics
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
C
AL
-C
RE
AL
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
Errors:
SYSTEMATIC
Measured
Data
Unknown
Device
RANDOM
DRIFT
Network Analyzer Basics
Network Analyzer Basics
Systematic Measurement Errors
Types of Error Correction
R
A
Crosstalk
Directivity
response (normalization)
simple to perform
only corrects for tracking errors
thru
stores reference trace in memory,
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
B
DUT
Frequency response
reflection tracking (A/R)
transmission tracking (B/R)
Source
Mismatch
Load
Mismatch
SHORT
S11a
Six forward and six reverse error
terms yields 12 error terms for twoport devices
Network Analyzer Basics
Network Analyzer Basics
9
thru
OPEN
S11m
LOAD
Network Analyzer Basics
What is Vector-Error Correction?
Reflection: One-Port Model
Error Adapter
Ideal
RF in
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
cal-kit
RF in
1
ED = Directivity
S11A
ED
S11A = Actual
To solve for error terms,
S11A
we measure 3 standards
S11M = ED +
to generate 3 equations
1
E
S S11A
ERT
and 3 unknowns
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
S11M = Measured
ERT
ES = Source Match
S11M
S11M
Network Analyzer Basics
Network Analyzer Basics
Two-Port Error Correction
Before and After One-Port Calibration
Reverse model
Forward model
0
Port 1
Port 1
EX
Port 2
S21
a1
data before 1-port
calibration
a1
20
S 21A
ES
ED
E RT
VSWR
EL' = rev load match
ETT' = rev transmission tracking
EX' = rev isolation
1.001
6000
12000
MHz
Network Analyzer Basics
A
S22
b2
E S'
A
ED'
a2
S12 A
E TT'
EX'
E D' = rev directivity
E S' = rev source match
E RT' = rev reflection tracking
S11
A
EL = fwd load match
ETT = fwd transmission tracking
EX = fwd isolation
b1
A
a2
ED = fwd directivity
E S = fwd source match
ERT = fwd reflection tracking
data after 1-port
calibration
60
EL
E L'
S 12
1.1
1.01
b2
ETT
S22 A
S11A
b1
40
Port 2
E RT'
2.0
Return Loss (dB)
ERT = Reflection tracking
S11A
ES
Each actual S-parameter is a function
of all four measured S-parameters
Analyzer must make forward and
reverse sweep to update any one Sparameter
Luckily, you don't need to know these
equations to use network analyzers!!!
S 22a =
E RT
E RT '
E TT
ETT '
(1 + 11m
E S )(1 + 22 m
E S ' ) − E L ' E L ( 21m
)(
)
S
S
− ED'
S
− E X S12 m − E X '
− ED
E RT '
E RT
ETT
E TT '
( 22m
)( 1 + 11m
E S ) − E L ' ( 21m
)( 12m
)
D
D
X
S
−E '
S
−E
S
−E
S
− EX '
S12a =
E RT
E RT '
E TT
E TT '
(1 + 11m
E S )(1 + 22 m
E S ' ) − E L ' E L ( 21m
)(
)
S
− ED
S
− ED'
S
− E X S12 m − E X '
E TT '
E RT
S
L
( 12m
)(1 + 11m
( E − E ' ))
S
− EX '
S
− ED
S21a =
E RT
E RT '
E TT
E TT '
(1 + 11m
E S )(1 + 22 m
E S ' ) − E L ' E L ( 21m
)(
)
− ED
− ED'
− E X S12 m − E X '
S
S
S
E TT
E RT '
(
)(1 +
( E S ' − E L ))
S21m − E X
S22 m − E D '
S11a =
E RT
E RT '
E TT
ETT '
(1 + 11m
E S )(1 + 22 m
E S ' ) − E L ' E L ( 21m
)(
)
S
− E D'
S
− ED '
S
− E X S12 m − E X '
E RT
E RT '
E TT
E TT '
S ') − EL(
( 11m
)(
1
+
E
)(
)
S
− ED
S 22 m − E D '
S 21m − E X S12 m − E X '
Network Analyzer Basics
Crosstalk: Signal Leakage Between
Test Ports During Transmission
Errors and Calibration Standards
DUT
UNCORRECTED
FULL 2-PORT
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
RESPONSE
DUT
OPEN
thru
Convenient
Generally not
accurate
No errors removed
LOAD
Easy to perform
Use when highest
accuracy is not
required
Removes
frequency
response error
ENHANCED-RESPONSE
DUT
LOAD
Network Analyzer Basics
Combines response and 1-port
Corrects source match for transmission
measurements
Network Analyzer Basics
10
SHORT
OPEN
OPEN
LOAD
LOAD
DUT
DUT
SHORT
DUT
LOAD
1-PORT
SHORT
For reflection
measurements
Need good termination for
high accuracy with twoport 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
Network Analyzer Basics
Calibration Summary
Reflection
Test Set (cal type)
T/R
Reflection tracking
Directivity
Source match
Load match
SHORT
Remember: convert all dB values to
linear for uncertainty calculations!
S-parameter
(one-port)
Reflection Example Using a One-Port Cal
(two-port)
OPEN
Directivity:
40 dB (.010)
T/R
DUT
S-parameter
(two-port)
(response, isolation)
.158
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
*
-20 * log (.158 - .100 - .010)
= 26.4 dB (+10.4 dB)
Network Analyzer Basics
Using a One-Port Cal + Attenuator
Load
match:
18 dB
(.126)
10 dB attenuator
(.316) SWR =
1.05 (.024)
Transmission Example Using Response
Cal
Measurement
uncertainty:
-20 * log (.158 + .039)
= 14.1 dB (-1.9 dB)
-20 * log (.158 - .039)
= 18.5 dB (+2.5 dB)
RL = 18 dB (.126)
RL = 14 dB (.200)
Thru calibration (normalization) builds error into
measurement due to source and load match interaction
DUT
16 dB RL (.158)
1 dB loss (.891)
.158
Calibration
Uncertainty
= (1 ± ρS ρL)
Low-loss bi-directional devices
generally require two-port
calibration
Worst-case error = .010 + .010 + .019 = .039 for low measurement uncertainty
(.891)(.316)(.126)(.316)(.891) = .010
(.891)(.024)(.891) = .019
= (1 ± (.200)(.126)
= ± 0.22 dB
Network Analyzer Basics
Network Analyzer Basics
Filter Measurement with Response Cal
Source match
= 14 dB (.200)
Measurement uncertainty:
-20 * log (.158 + .100 + .010)
= 11.4 dB (-4.6dB)
(.891)(.126)(.891) = .100
* )
Network Analyzer Basics
Directivity:
40 dB (.010)
20
16 dB RL (.158)
1 dB loss (.891)
Test Set (cal type)
Transmission
ρ or loss(linear) = 10 -dB
( )
Load
match:
18 dB
(.126)
LOAD
DUT
1 dB loss (.891)
16 dB RL (.158)
Measuring Amplifiers with a Response Cal
Load match
= 18 dB
(.126)
1
Source match
= 14 dB (.200)
DUT
16 dB RL
(.158)
Load match
= 18 dB
(.126)
1
(.126)(.158) = .020
(.126)(.158) = .020
(.126)(.891)(.200)(.891) = .020
(.158)(.200) = .032
(.158)(.200) = .032
Total measurement
uncertainty:
+0.60 + 0.22 = + 0.82 dB
-0.65 - 0.22 = - 0.87 dB
Total measurement
uncertainty:
+0.44 + 0.22 = + 0.66 dB
-0.46 - 0.22 = - 0.68 dB
Measurement uncertainty
= 1 ± (.020+.020+.032)
= 1 ± .072
= + 0.60 dB
- 0.65 dB
Network Analyzer Basics
Network Analyzer Basics
11
Measurement uncertainty
= 1 ± (.020+.032)
= 1 ± .052
= + 0.44 dB
- 0.46 dB
Network Analyzer Basics
Filter Measurements
using the Enhanced
Response Calibration
Effective source match =
35 dB!
DUT
1 dB loss (.891)
16 dB RL (.158)
Source
match = 35
dB (.0178)
Load match
= 18 dB
(.126)
Using the Enhanced Response
Calibration Plus an Attenuator
Calibration Uncertainty
= (1 ± ρS ρL)
10 dB attenuator (.316)
SWR = 1.05 (.024 linear or 32.4
dB)
Analyzer
load match =18 dB (.126)
Calibration Uncertainty
= (1 ± ρS ρL)
= (1 ±
(.0178)(.126)
= ± .02 dB
DUT
1 dB loss (.891)
16 dB RL (.158)
Source match
= 35 dB
(.0178)
1
Measurement uncertainty
= 1 ± (.020+.0018+.0028)
(.126)(.158) = .020
= 1 ± .0246
= + 0.211 dB
(.126)(.891)(.0178)(.891) = .0018
- 0.216 dB
= (1 ± (.0178)(.0366)
= ± .01 dB
Effective load match = (.316)(.316)(.126) + .024
= .0366 (28.7dB)
1
Measurement uncertainty
= 1 ± (.006+.0005+.0028)
= 1 ± .0093
(.0366)(.891)(.0178)(.891) = .0005 = ± 0.08 dB
(.0366)(.158) = .006
(.158)(.0178) = .0028
(.158)(.0178) = .0028
Total measurement
uncertainty:
0.22 + .02 = ± 0.24 dB
Total measurement
uncertainty:
0.01 + .08 = ± 0.09 dB
Network Analyzer Basics
Network Analyzer Basics
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
Source match
Load match
Refl. tracking
Trans. tracking
Isolation
= 47 dB
= 36 dB
= 47 dB
= .019 dB
= .026 dB
= 100 dB
Response versus Two-Port Calibration
Measuring filter insertion loss
CH1 S21&M log MAG
CH2 MEM log MAG
Reflection uncertainty
1 dB/
1 dB/
REF 0 dB
REF 0 dB
Cor
After two-port calibration
S11m = S11a ± ( ED + S11a 2 ES + S21a S12a EL + S11a (1 − ERT ))
= 0158
. ± (.0045 + 0158
. 2 *.0158 + 0891
. 2 *.0045 + 0158
. *.0022)
After response calibration
= 0.158 ± .0088 = 16 dB +0.53 dB, -0.44 dB (worst-case)
Transmission uncertainty
S21m = S21a ± S21a ( E I / S21a + S11a E S + S21a S12a E S E L + S22a E L + (1 − ETT ))
= 0891
. ± 0891
. (10−6 / 0.891 + 0158
. *.0158 + 0.8912 *.0158*.0045 + 0158
. *.0045+.003)
x2 1
= 0.891 ± .0056 = 1 dB ±0.05 dB (worst-case)
Network Analyzer Basics
•
•
2
STOP 6 000.000 MHz
START 2 000.000 MHz
Network Analyzer Basics
ECal: Electronic Calibration (85060/90 series)
•
Uncorrected
Cor
Variety of modules cover 30 kHz to 26.5 GHz
Six connector types available (50 Ω and 75
Ω)
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
Adapter Considerations
reflection from
adapter
leakage signal
desired signal
ρ
measured
= Directivity +
ρ
adapter +
ρ
DUT
Coupler directivity = 40 dB
85093A
Electronic Calibration Module
30 kHz - 6 GHz
Adapter
DUT
Termination
DUT has SMA (f) connectors
Worst-case
System Directivity
•
28 dB
Microwave modules use a
transmission line shunted by
PIN-diode switches in various
combinations
17 dB
14 dB
Network Analyzer Basics
Network Analyzer Basics
12
APC-7 calibration done here
Adapting from APC-7 to SMA
(m)
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
Calibrating Non-Insertable Devices
Swap Equal Adapters Method
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
(e.g.,
DUT
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
Port 1
Port 1
Port 1
Port 1
Network Analyzer Basics
Port 1
Calibration is very accurate and traceable
In firmware of 8753, 8720 and 8510 series
Also accomplished with ECal modules (85060/90)
Uses adapter with same connectors as DUT
Must specify electrical length of adapter to within
1/4 wavelength of highest frequency (to avoid
phase ambiguity)
Cal
Adapter
Port 1
Cal
Adapter
Adapter
B
Port 2
Adapter
B
Port 2
DUT
Port 2
2. Reflection cal using adapter B.
Adapter
B
Port 2
3. Measure DUT using adapter B.
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
Two variations: TRL (requires 4 receivers)
and TRL* (only three receivers needed)
Other variations: Line-Reflect-Match (LRM), Thru-Reflect-Match (TRM),
plus many others
TRL was developed for non-coaxial
microwave measurements
Port 2
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.
Cal Set 2
[CAL] [MORE] [MODIFY CAL SET]
[ADAPTER REMOVAL]
Port 1
Adapter
B
Thru-Reflect-Line (TRL) Calibration
Cal Set 1
Port 1
DUT
1. Transmission cal using adapter A.
Port 2
Network Analyzer Basics
Adapter Removal Calibration
Adapter
A
Accuracy depends on how well
the adapters are matched - loss,
electrical length, match and
impedance should all be equal
Port 2
DUT
DUT
Adapter
B
Port 2
3. Use ADAPTER REMOVAL
to generate new cal set.
4. Measure DUT without cal adapter.
Network Analyzer Basics
Network Analyzer Basics
Frequency Sweep - Filter Test
Agenda
CH1 S21
log MAG
10 dB/
REF 0 dB
CH1 S11
log MAG
5 dB/
REF 0 dB
Cor
What measurements do we make?
Network analyzer hardware
Error models and calibration
Example measurements
Appendix
Stopba
nd
rejectio
n
69.1 dB
START .300 000 MHz
STOP 400.000 000 MHz
CH1 S21
SPAN 50.000 MHz
CENTER 200.000 MHz
log MAG
1 dB/
REF 0 dB
Return loss
Cor
1
m1:
4.000 000
GHz 0.16 dB
m2-ref: 2.145 234 GHz
0.00 dB
ref
2
Cor
Insertion loss
x2 1
START 2 000.000 MHz
Network Analyzer Basics
Network Analyzer Basics
13
2
STOP 6 000.000 MHz
Network Analyzer Basics
Optimize Filter Measurements with
Swept-List Mode
Power Sweeps - Compression
Segment 3: 29 ms
(108 points, -10 dBm, 6000 Hz)
CH1 S 21
log MAG
12 dB/
REF 0 dB
PRm
PASS
Segment 5: 129 ms
(38 points, +10 dBm, 300 Hz)
Segment 1: 87 ms
(25 points, +10 dBm, 300 Hz)
Saturated output
power
Output Power (dBm)
Swept-list sweep: 349 ms
(201 pts, variable BW's & power)
Linear sweep: 676 ms
(201 pts, 300 Hz, -10
dBm)
Compression
region
Linear region
(slope = small-signal gain)
START 525.000 000 MHz
STOP 1 275.000 000 MHz
Input Power (dBm)
Segments 2,4: 52 ms
(15 points, +10 dBm, 300 Hz)
Network Analyzer Basics
Network Analyzer Basics
AM to PM Conversion
Power Sweep - Gain Compression
CH1 S21
1og MAG
1 dB/ REF 32 dB
30.991 dB
12.3 dBm
Amplitude
Measure of phase deviation caused by
amplitude
Power sweep variations
AM
(dB)
Mag(Am i
n)
DUT
1 dB
compression:
PM
(deg)
input power
resulting in 1 dB
drop in gain
1
0
Test Stimulus
Q
Time
Amplitude
AM
(dB)
START -10 dBm
CW 902.7 MHz
AM - PM Conversion
=
Mag(Pm
(deg/d
)
Mag(Am
out
B)
in)
STOP 15 dBm
Mag(AMo
ut)
PM
(deg)
Mag(Pm o
ut)
Time
Output
Response
Network Analyzer Basics
Log Mag
/M Phase
Agenda
1.0 dB/
5.0 deg/
Ch1:Mkr1
20.48 dB
Ch2:Mkr2
0.86 deg
Ref -115.7 deg
Ref 21.50 dB
-4.50 dBm
What measurements do we make?
Network analyzer hardware
Error models and calibration
Example measurements
Appendix
1.00 dB
2
1
Use transmission setup
with a power sweep
Display phase of S21
AM - PM = 0.86 deg/dB
2
1
1
Start -10.00 dBm
Start -10.00 dBm
I
AM to PM
conversion can
cause bit errors
Network Analyzer Basics
Measuring AM to PM Conversion
1:Transmission
2:Transmission
AM can be undesired:
supply ripple, fading, thermal
AM can be desired:
modulation (e.g. QAM)
CW 900.000 MHz
CW 900.000 MHz
Stop 0.00 dBm
Stop 0.00 dBm
Network Analyzer Basics
Network Analyzer Basics
14
Advanced Topics
time domain
frequency-translating devices
high-power amplifiers
extended dynamic range
multiport devices
in-fixture measurements
crystal resonators
balanced/differential
Inside the network analyzer
Challenge quiz!
Network Analyzer Basics
TDR Basics Using a Network Analyzer
Time-Domain Reflectometry (TDR)
What is TDR?
time-domain reflectometry
analyze impedance versus time
distinguish between inductive and
capacitive transitions
With gating:
analyze transitions
inductive
analyzer standards
transition
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
F
CH1 S 22
-1
Re
Cor
50 mU/ REF 0 U
20 GHz
f
t
6 GHz
impedance
t
∫ F(t)*dt
Integrate
0
time
capacitive
transition
TDR
F
Network Analyzer Basics
Cor
2
REF 0 U
1: -45.113 dB 0.947
GHz
2: -15.78 dB 6.000
GHz
Gate
1: 48.729 mU 638 ps
RISE TIME
29.994 ps
8.992 mm
STOP 1.5 ns
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 *
PRm
20 mU/
CH1 START 0 s
Ten Steps for Performing TDR
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
CH1 S11&M log MAG
5 dB/
REF 0 dB
Use two-port calibration
CH1 MEM Re
f
Network Analyzer Basics
Time-Domain Gating
-1
non-Zo transmission line
t
PRm
Cor
1/s*F(s)
Zo
2: 24.961 mU 668 ps
1
3: -10.891 mU 721 ps
2
3
Thru in time domain
CH1 START 0 s
Thru in frequency
domain, with and
without gating
1
STOP 1.5 ns
START .050 000 000 GHz
* If using two channels (even if coupled), these parameters must be set independently for
second channel
STOP 20.050 000 000 GHz
Network Analyzer Basics
Network Analyzer Basics
Time-Domain Transmission
Time-Domain Filter Tuning
RF Input
•
RF Output
CH1 S21 log MAG
Main Wave
Leakage
log MAG
•
Surface
Wave
Triple
Travel
CH1 S21
15 dB/ REF 0 dB
10 dB/ REF 0 dB
Cor
Cor
RF
Leakage
Triple
Travel
•
Gate off
Gate on
START -1 us
Deterministic method used for
tuning cavity-resonator filters
Traditional frequency-domain
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 time-domain
processing
STOP 6 us
Network Analyzer Basics
Network Analyzer Basics
15
Network Analyzer Basics
Filter Reflection in Time Domain
Tuning Resonator #3
•
•
•
•
•
Set analyzer’s center frequency
= center frequency of the filter
Measure S11 or S22 in the time
domain
Nulls in the time-domain response
correspond to individual resonators
in filter
•
•
Network Analyzer Basics
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
Frequency-Translating Devices
Medium-dynamic range
measurements (35 dB)
High-Power Amplifiers
High-dynamic range measurements
(100 dB)
Preamp
8753ES
FREQ OFFS
ON off
8753ES
8753ES
Source
LO
MENU
Ref In
Ref In
1
2
DOW N
CONVERTER
Filter
Ref out
UP
CONVERTER
Attenuator
Attenuator
Ref in
RF > LO
Preamp
Reference
mixer
AUT
DUT
R
RF < LO
Start: 900 MHz
Start: 100 MHz
Stop: 350 MHz
Stop: 650 MHz
LO power: 13 dBm
CH1 CONV MEAS
Filter
VIEW
MEASURE
Fixed LO: 1 GHz
B
A
Attenuator
RETURN
log MAG 10 dB/
DUT
REF 10 dB
Attenuator
AUT
Attenuat
or
+43 dBm max input (20 watts!)
8720ES Option 085
ESG-D4000A
START 640.000 000 MHz
Powe
r
splitt
er
85118A High-Power
Amplifier Test System
STOP 660.000 000 MHz
Network Analyzer Basics
Network Analyzer Basics
High-Dynamic Range Measurements
CH1 MEM
CH2 MEM
LOG
LOG
15 dB/
15 dB/
REF 3 dB
REF 3 dB
Multiport Device Test
•
•
PRm
Cor
Avg
10
8753 H39
CH1
CH2
PRm
S21
S12
log MA G
log MA G
10 dB/
10 dB/
REF 0 dB
REF 0 dB
1_ -1.9248 dB
1_ -1.2468 dB
839.470 000 MHz
PRm
Duplexer Test - Tx-Ant and Ant-Rx
Cor
1
Standard 8753ES
1
Hld
PASS
1
Cor
Avg
10
880.435 000 MHz
PRm
Cor
2
•
8753ES Special Option H16
CH1
CH2
START 775. 000 000 MHz
START 775. 000 000 MHz
PASS
Hld
CH1 STA RT 775.000 000 MHz
CH2 STA RT 775.000 000 MHz
STOP 1000. 000 000 MHz
STOP 1000. 000 000 MHz
Network Analyzer Basics
Network Analyzer Basics
16
STOP 925.000 000 MHz
STOP 925.000 000 MHz
Multiport analyzers and test sets:
improve throughput by reducing the
number of connections to DUTs with
more than two ports
allow simultaneous viewing of two paths
(good for tuning duplexers)
include mechanical or solid-state
switches, 50 or 75 ohms
degrade raw performance so calibration
is a must (use two-port cals whenever
possible)
Agilent offers a variety of standard and
custom multiport analyzers and test sets
Network Analyzer Basics
Test Set Cal Eliminates Redundant
Connections of Calibration Standards
SelfCal
Once a month:
perform a Test Set Cal with
external standards to remove
systematic errors in the analyzer,
test set, cables, and fixture
Test Set Cal
87050E/87075C Standard Multiport Test Sets
Through Connections
Reflection Connections
12-port
12-port
8-port
8-port
4-port
4-port
Fixture
DUT
•
•
•
•
•
Once an hour:
For use with 8712E family
automatically perform a SelfCal
using internal standards to
50 Ω: 3 MHz to 2.2 GHz, 4, 8, or 12 ports
remove systematic errors in the
analyzer and test set
75 Ω: 3 MHz to 1.3 GHz, 6 or 12 ports
Test Set Cal and SelfCal dramatically improve calibration
times
Systems offer fully-specified performance at test ports
0
Network Analyzer Basics
100
200
300
400
0
25
50
Test Set Cal
Traditional VNA Calibration
75
Network Analyzer Basics
In-Fixture Measurements
Characterizing Crystal Resonators/Filters
Measurement problem: coaxial calibration plane is not the
same as the in-fixture measurement plane
E5100A/B Network Analyzer
Ch1
Z: R
phase
40 / REF 0
1: 15.621 U
31.998 984 925 MHz
Min
Cor
Measurement
plane
Calibration
plane
Fixture
1
ED
ES
DUT
ET
Error correction with coaxial calibration
STA RT 31.995 MHz
SEG START
POINTS
STOP 32.058 MHz
POWER
IFBW
32.008 MHz
200
0 dBm
200Hz
> 2 32.052 MHz
32.058 MHz
200
0 dBm
200Hz
END
Loss
Phase shift
Mismatch
Example of crystal resonator
measurement
Network Analyzer Basics
Network Analyzer Basics
Balanced-Device Measurements
•
STOP
1 31.995 MHz
Traditional Scalar Analyzer
Incident
ATN-4000 series (4-port test set + software)
Transmitted
DUT
Reflected
•
•
•
•
•
•
SOURCE
measure tough singled-ended devices like couplers
measure fully-balanced or single-ended-to-balanced DUTs
characterize mode conversions (e.g. common-to-differential)
incorporates 4-port error correction for exceptional accuracy
works with 8753ES and 8720ES analyzers
more info at www.atnmicrowave.com
SIGNAL
SEPARATION
processor/display
INCIDENT ( R)
REFL ECT ED
(A)
TRANSMITT ED
(B)
RECEIVER / DETECTOR
source
PROCESSOR / DISPLAY
Example: 8757D/E
requires external detectors, couplers, bridges, splitters
good for low-cost microwave scalar applications
RF
R A
B
RF
Detector
R
Detector
Detector
Bridge
Channel Partner
Reflection
Network Analyzer Basics
Network Analyzer Basics
17
DUT
DUT
Termination
Transmission
A
B
Network Analyzer Basics
One Method of Measuring Coupler Directivity
Directional Coupler Directivity
Coupling Factor (fwd) x Loss (through arm)
Directivity =
1.0 (0 dB) (reference)
Isolation (rev)
Directivity (dB) = Isolation (dB) - Coupling Factor (dB) - Loss (dB)
50 dB
Test
port
50 dB
Coupler
35 dB (.018)
Directivity
Examples:
20 dB
Source
Directivity = 50 dB - 20 dB = 30 dB
30 dB
short
.018 (35 dB) (normalized)
Test
port
Directivity = 35 dB - 0 dB
Directivity = 50 dB - 30 dB - 10 dB = 10 dB
= 35 dB
10 dB
60 dB
20 dB
Test
port
Directivity = 60 dB - 20 dB - 10 dB = 30 dB
load
Source
10 dB
Network Analyzer Basics
Network Analyzer Basics
50 Ω
50 Ω
Detector
50 Ω
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
ADC / DSP
TRANSMITT ED
(B)
Mixer-based front end
It is cheaper and easier to make
broadband front ends using
samplers instead of mixers
Harmonic
generator
f
frequency "comb"
Network Analyzer Basics
Why Are Four Receivers Better Than Three?
TRL
R1
R
A
B
B
Port 2
3 receivers
more economical
TRL*, LRM* cals only
includes:
8753ES
8720ES (standard)
Port 2
Port 1
4 receivers
TRL*
assumes the source and load match of a test port are equal
(port symmetry between forward and reverse measurements)
this is only a fair assumption for three-receiver network analyzers
TRL
four receivers are necessary to make the required measurements
TRL and TRL* use identical calibration standards
In noncoaxial applications, TRL achieves better source and load match
correction than TRL*
What about coaxial applications?
SOLT is usually the preferred calibration method
coaxial TRL can be more accurate than SOLT, but not commonly used
R2
Port 1
TRL*
8720ES Option 400 adds
fourth sampler, allowing full
TRL calibration
Transfer switch
Transfer switch
REFL ECT ED
(A)
ADC / DSP
S
Source
SIGNAL
SEPARATION
INCIDENT ( R)
PROCESSOR / DISPLAY
Test Port
Source
SOURCE
Sampler-based front end
Three Versus Four-Receiver Analyzers
Transmitted
DUT
Reflected
RECEIVER / DETECTOR
Network Analyzer Basics
Incident
NA Hardware: Front
Ends, Mixers Versus
Samplers
Directional Bridge
A
Assume perfect
load (no
reflection)
more expensive
true TRL, LRM cals
includes:
8720ES (option 400)
8510C
Network Analyzer Basics
Network Analyzer Basics
18
Network Analyzer Basics
Challenge Quiz
Challenge Quiz (continued)
1. Can filters cause distortion in communications systems?
A. Yes, due to impairment of phase and magnitude response
B. Yes, due to nonlinear components such as ferrite inductors
C. No, only active devices can cause distortion
D. No, filters only cause linear phase shifts
E. Both A and B above
4. Maximum dynamic range with narrowband detection is defined as:
A. Maximum receiver input power minus the stopband of the device under test
B. Maximum receiver input power minus the receiver's noise floor
C. Detector 1-dB-compression point minus the harmonic level of the source
D. Receiver damage level plus the maximum source output power
E. Maximum source output power minus the receiver's noise floor
2. Which statement about transmission lines is false?
A. Useful for efficient transmission of RF power
B. Requires termination in characteristic impedance for low VSWR
C. Envelope voltage of RF signal is independent of position along line
D. Used when wavelength of signal is small compared to length of line
E. Can be realized in a variety of forms such as coaxial, waveguide, microstrip
5. With a T/R analyzer, the following error terms can be corrected:
A. Source match, load match, transmission tracking
B. Load match, reflection tracking, transmission tracking
C. Source match, reflection tracking, transmission tracking
D. Directivity, source match, load match
E. Directivity, reflection tracking, load match
3. Which statement about narrowband detection is false?
A. Is generally the cheapest way to detect microwave signals
B. Provides much greater dynamic range than diode detection
C. Uses variable-bandwidth IF filters to set analyzer noise floor
D. Provides rejection of harmonic and spurious signals
E. Uses mixers or samplers as downconverters
6. Calibration(s) can remove which of the following types of measurement error?
A. Systematic and drift
B. Systematic and random
C. Random and drift
D. Repeatability and systematic
E. Repeatability and drift
Network Analyzer Basics
Network Analyzer Basics
Answers to Challenge Quiz
Challenge Quiz (continued)
7. Which statement about TRL calibration is false?
A. Is a type of two-port error correction
B. Uses easily fabricated and characterized standards
C. Most commonly used in noncoaxial environments
D. Is not available on the 8720ES family of microwave network analyzers
E. Has a special version for three-sampler network analyzers
1. E
2. C
3. A
4. B
5. C
6. A
7. D
8. B
9. E
8. For which component is it hardest to get accurate transmission and
reflection measurements when using a T/R network analyzer?
A. Amplifiers because output power causes receiver compression
B. Cables because load match cannot be corrected
C. Filter stopbands because of lack of dynamic range
D. Mixers because of lack of broadband detectors
E. Attenuators because source match cannot be corrected
9. Power sweeps are good for which measurements?
A. Gain compression
B. AM to PM conversion
C. Saturated output power
D. Power linearity
E. All of the above
Network Analyzer Basics
Network Analyzer Basics
19