Download Network Analyzer Basics

Network Analyzer Basics
Network Analyzer Basics
Copyright
2000
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
Copyright
2000
Lo w
Integration
High
W hat Types of Devices are Tested?
Duplexers
Diplexers
Filters
Couplers
Bridges
Splitters, dividers
Co mbiners
Isolators
Circulators
Attenuators
Adapters
Opens, shorts, loads
Delay lines
Cables
Trans mission lines
W aveguide
Resonators
Dielectrics
R, L, C's
Passive
Network Analyzer Basics
RFICs
M MICs
T/R modules
Transceivers
Receivers
Tuners
Converters
VC As
A m plifiers
Antennas
S witches
M ultiplexers
Mixers
Sa mplers
M ultipliers
Diodes
Device type
VC Os
VTFs
Oscillators
M odulators
VC Atten’s
Transistors
Active
Copyright
2000
Co mplex
Device Test Measurement Model
84000
RFIC test
Ded. Testers
VSA
Response
tool
SA
Harm. Dist.
L O stability
Image Rej.
VNA
SNA
NF Mtr.
NF
Imped. An.
Simpl
e
Full call
sequence
Pulsed S-parm.
Pulse profiling
Gain/Flat. Co mpr'n
Phase/GD A M-P M
Isolation
Rtn Ls/VS W R
Impedance
S-parameters
TG/SA
Param. An.
Intermodulation
Distortion
NF
BER
EV M
A CP
Regrowth
Constell.
Eye
LCR/Z
I-V
Measure ment
plane
Absol.
Po wer
Gain/Flatness
Power Mtr.
Det/Scope
DC
CW
Swept
freq
modulation
Simple
Network Analyzer Basics
Swept
power
RF
Noise
2-tone
Multi-
Stimulus type
Complex
tone
Pulsed-
Protocol
Co mplex
Copyright
2000
Lightwave Analogy to RF Energy
Incident
Transmitted
Reflected
Lightwave
D UT
RF
Network Analyzer Basics
Copyright
2000
W hy Do W e Need to Test Components?
• Verify specifications of “building blocks” for more
complex RF systems
• Ensure distortionless transmission
of com munications signals
– linear: constant amplitude,linear phase / constant group
delay
– nonlinear: harmonics,intermodulation, compression, AMto-PM conversion
• Ensure good match when absorbing
power (e.g., an antenna)
KPWR
Network Analyzer Basics
FM 97
Copyright
2000
The Need for Both Magnitude and Phase
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
E mitter
Network Analyzer Basics
Actual
Copyright
2000
Agenda
●
●
●
●
●
Network Analyzer Basics
W hat measurem ents do we make?
➨ Transmiss
ion-line basics
➨ Ref
lection and transmission
parameters
➨ S-parameter def
inition
Network analyzer hardware
➨ Signal separat
ion devices
➨ Detect
ion types
➨ Dynamic range
➨ T/R versus S-parameter tes
t sets
Error models and calibration
➨ Types of measurement er
ror
➨ One- and two-por
t models
➨ Error
-correction choices
➨ Basic uncer
tainty calculations
Exa mple measurements
Appendix
Copyright
2000
Transmission Line Basics
+
I
-
Low frequencies
re length
● wavelengths >> wi
I)travels down wires easily for efficient
● current (
power transmission
ltage and current not dependent on
● measured vo
position along wire
High frequencies
r << length oftransmission
● wavelength ≈ o
medium
ransmission lines for efficient power
● need t
transmission
isticimpedance (Zo) is
● matching to character
very importantforlow reflection and maximu m
Network Analyzer Basics
power transfer
measured envelope voltage dependenton
Copyright
2000
Transmission line Zo
•
•
Zo determines relationship between voltage and current
waves
Zo is a function of physical dimensions and εr
Zo is usually a realimpedance (e.g. 50 or 75 ohms)
1.5
Twiste d-pair
attenuation is
lowest at 77 ohms
1.4
Wave guide
1.3
a
1.2
b
εr
Coaxial
h
normalized values
•
1.1
1.0
0.9
0.8
h
0.7
w1
Network Analyzer Basics
power handling capacity
peaks at 30 ohms
0.6
w
w2
Coplanar
50 ohm standard
0.5
10
Microstrip
20
30
40
50
60 70 80 90100
characteristicimpedance
for coaxial airlines (ohms)
Copyright
2000
Power Transfer Efficiency
RS
For co mplex im pedances, maximu m
power transfer occurs when ZL = ZS*
(conjugate match)
RL
Rs
Load Power
(normalized)
1.2
+jX
1
-jX
0.8
0.6
RL
0.4
0.2
0
0
1
2
3
4
5
6
7
8
9
10
RL / RS
Maximu m power is transferred when RL = RS
Network Analyzer Basics
Copyright
2000
Transmission Line Terminated with Zo
Zs = Zo
Zo = characteristic
impedance
of
transmission line
Zo
V inc
Vrefl = 0! (allthe incident power
is absorbed in the load)
For reflection, a transmission line
terminated in Zo behaves like an infinitely
long transmission line
Network Analyzer Basics
Copyright
2000
Transmission Line Terminated with
Short, Open
Zs = Zo
V inc
Vrefl
In-phase (0o) for open,
out-of-phase (180o) for short
For reflection, a trans mission line
terminated in a short or open reflects
all power back to source
Network Analyzer Basics
Copyright
2000
Transmission Line Terminated with 25 Ω
Zs = Zo
ZL = 25 Ω
V inc
Vrefl
Standing wave pattern
does not go to zero as
with short or open
Network Analyzer Basics
Copyright
2000
High-Frequency Device Characterization
Incident
Transmitted
R
B
Reflected
A
TRA NS MISSIO N
REFLECTION
Reflected
Incident
=
SWR
S-Parameters
S11, S22
Reflection
Coefficient
Γ, ρ
Network Analyzer Basics
A
Transmitted
R
Incident
Return
Loss
Impedance,
Ad mittance
R+jX,
G+jB
B
=
R
Group
Delay
Gain / Loss
S-Parameters
Transmission
S21, S12
Coefficient
Τ,τ
Insertion
Phase
Copyright
2000
Reflection Parameters
Reflection
Coefficient
Γ
Vreflected
=
=ρ
Vincident
Return loss = -20 log(ρ),
ρ
Φ
=
ZL − ZO
ZL + ZO
Γ
=
E max
E min
Voltage Standing Wave
Ratio
E max
VS W R =
E min
=
1+ρ
1-ρ
Full reflection
(ZL = open, short)
No reflection
(ZL = Zo)
0
ρ
1
∞ dB
RL
0 dB
1
VS W R
∞
Network Analyzer Basics
Copyright
2000
S mith Chart Review
.
o
+jX
90
Polar plane
1.0
.8
.6
0
+R
.4
∞→
+ 180o
-
o
.2
0
∞
0
-jX
-90o
Rectilinear impedance
plane
Constant X
Constant R
Z L = Zo
S mith Chart maps
rectilinear
impedance
plane onto polar
plane
Network Analyzer Basics
Γ=
0
ZL =
Z L = 0 (short)
Γ= 1
Γ =1
O
±180
(open)
0
S mith chart
Copyright
2000
O
Transmission Parameters
V Incident
V Transmitted
D UT
Transmission Coefficient =
VTransmitted
Τ
V
=
V Incident
Trans
Insertion Loss (dB) = - 20 Log
V
V
Gain (dB) = 20 Log
V
Network Analyzer Basics
Trans
= - 20 log
=
τ∠φ
τ
Inc
= 20 log
τ
Inc
Copyright
2000
Linear Versus Nonlinear Behavior
A * Sin 360o * f (t - to)
A
Linear behavior:
●
Time
to
Sin 360o * f * t
A
Time
f
1
D UT
Input
●
phase shift =
to * 360o * f
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
Network Analyzer Basics
1
Frequency
output frequency may
undergo frequency shift
(e.g. with mixers)
additionalfrequencies
created (harmonics,
intermodulation)
Copyright
2000
Criteria for Distortionless Transmission
Linear Networks
Linear phase over
bandwidth of
interest
Magnitude
Constant amplitude over
bandwidth ofinterest
Phase
Frequency
Frequency
Network Analyzer Basics
Copyright
2000
Magnitude Variation with Frequency
F(t) = sin wt + 1/3 sin 3wt + 1/5 sin 5wt
Time
Time
Magnitude
Linear
Network
Frequency
Network Analyzer Basics
Frequency
Frequency
Copyright
2000
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 °
Frequency
-360 °
Network Analyzer Basics
Copyright
2000
Deviation from Linear Phase
Use electrical delay to
remove linear portion of
phase response
Phase 45 /Div
RF filter response
Deviation from linear
phase
o
o
(Electrical delay function)
+
Frequency
Low resolution
Network Analyzer Basics
yields
Frequency
Phase 1 /Div
Linear electricallength
added
Frequency
High resolution
Copyright
2000
Group Delay
Frequency
ω
tg
Group delay ripple
∆ω
to
φ
Phase
Average delay
∆φ
Frequency
Group Delay (tg)=
−d φ
dω
φ
ω
φ
=
−1
360 o
dφ
*df
in radians
in radians/sec
●
●
●
group-delay ripple indicates phase distortion
average delay indicates electricallength of DUT
aperture of measurement is very important
in degrees
f in Hertz (ω = 2 π f)
Network Analyzer Basics
Copyright
2000
Phase
Phase
W hy Measure Group Delay?
f
f
φ
ω
−d φ
dω
Group
Delay
Group
Delay
−d
d
f
f
Sa me p-p phase ripple can resultin different
group delay
Network Analyzer Basics
Copyright
2000
Characterizing Unknown Devices
Using param eters (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
pred
ict circu
itperformance
under any source
andmeters
load
Y-parameters
Z-para
H-para
meters
cond
V1 i
=tions
h11I1 + h12V2
I1 = y11V1 + y12V2
V1 = z11I1 + z12I2
I2 = h21I1 + h22V2
Network Analyzer Basics
I2 = y21V1 + y22V2
V2 = z21I1 + z22I2
h11 = V1
I1
V2=0
(requires short circuit)
h12 = V1
V2
I1=0
(requires open circuit)
Copyright
2000
W hy Use S-Parameters?
relatively easy to obtain at high frequencies
ltage traveling waves with a vector network analyzer
■ measure vo
't need shorts/opens which can cause active devices to oscillate
■ don
or self-destruct
late to familiar measurements (gain,loss, reflection coefficient...)
● re
f multiple devices to predict system
● can cascade S-parameters o
performance
rom S-parameters if desired
● can co mpute H, Y, or Z parameters f
S 21
Incident
Transmi
tedin our electronicilyimpor
t
and
use
S-parameter
filtes
● can eas
a1
b2
simulation tools S11
●
D UT
Reflected
b1
Port 1
Transmitted
Port 2
S 12
S 22
Reflected
a2
Incident
b1 = S 11a1 + S 12 a 2
b2 = S21 a1 + S 22 a 2
Network Analyzer Basics
Copyright
2000
Measuring S-Parameters
a1
b1
S
11
21
=
=
Transmitted
Incident
a2 = 0
b1
= a
1
b
= a
Load
D UT
Reflected
Reflected
Incident
b2
Transmitted
21
Z0
S 11
Forward
S
S
Incident
a2 = 0
S
22
Reflected
Incident
=
2
1
a2 = 0
S
12
=
Transmitted
Incident
a1 = 0
Z0
b2
= a
2
b
= a
a1 = 0
1
2
a1 = 0
b2
D UT
Load
S 22
Reverse
Reflected
a2
b 1 Transmitted
Network Analyzer Basics
S 12
Incident
Copyright
2000
Equating S-Parameters with Com mon
Measurement Terms
S11
S22
S21
S12
= forward reflection coefficient (input match)
= reverse reflection coefficient (output m atch)
= forward transmission coefficient (gain or loss)
= reverse transmission coefficient (isolation)
Re me mber, S-para m eters are
inherently co mplex, linear
quantities -- however, we often
express the m in a log-magnitude
format
Network Analyzer Basics
Copyright
2000
Criteria for Distortionless Transmission
Nonlinear Networks
•
•
Saturation, crossover,
intermodulation, and other nonlinear
effects can cause signal distortion
Effect on system depends on amount
and type of distortion and system
arch
itecture
Time
Frequency
Network Analyzer Basics
Time
Frequency
Copyright
2000
Measuring Nonlinear Behavior
Most com m on measurements:
● using a network analyzer and
power sweeps
➨ gain compress
ion
➨ A M to PM convers
ion
rum analyzer +
● using a spect
source(s)
➨ harmonics, par
ticularly second
and third
➨ in
termodulation products resulting
from two or more RF
carriers
8563A
LPF
LPF
Network Analyzer Basics
SPE CT R U M AN A LYZ E R
RL 0 dBm
ATTEN
10 dB
10 dB / DIV
9 kHz - 26.5 GHz
DUT
CENTER 20.00000 MHz
RB 30 Hz
VB 30 Hz
SPAN 10.00 kHz
ST 20 sec
Copyright
2000
W hat is the Difference
Between Network and
Spectrum Analyzers?
.
Measures
known
signal
A mplitude
A mplitude Ratio
8563A
measure components,
devices,
circuits, sub-assemblies
● conta
in source and receiver
● disp
lay ratioed amplitude and
phase
(frequency or power sweeps)
● of
fe
rlyzer
advanced
error
Network
Ana
Basics
correction
●
9 kHz - 26.5
Measures
unknown
signals
Frequency
Network analyzers:
SPE CT R U M AN A LYZ E R
G Hz
Frequency
Spectru m analyzers:
●
●
●
●
measure signal amplitude
characteristics
carrierlevel, sidebands,
harmonics...)
can demodulate (& measure)
complex signals
are receivers only (single channel)
Copyright
can be used for scalar component
2000
test (no
h ) itht ki
t
Agenda
●
●
●
●
●
Network Analyzer Basics
W hat measurements do we make?
Network analyzer hardware
Error models and calibration
Example measurements
Appendix
Copyright
2000
Generalized Network Analyzer
Block Diagram
Incident
Transmitted
D UT
Reflected
S O U R CE
SIGN AL
SEPA R ATION
INCIDENT
(R)
REFLECTED
(A)
TRA NS MITTED
(B)
RE CEIVER / DETECTO R
PR O CESS O R / DISPLAY
Network Analyzer Basics
Copyright
2000
Source
●
●
●
●
Supplies stimulus for system
Swept frequency or power
Traditionally NAs used separate
source
Most Agilent analyzers sold
today have integrated,
synthesized sources
Network Analyzer Basics
Copyright
2000
Incident
Transmitted
D UT
Signal Separation
Reflected
SOURCE
SIGN AL
SEP A R ATION
INCIDENT (R)
REFLECTED
(A)
TRA NS MITTED
(B)
R E C EIVER / DETECT O R
P R O C ESS O R / DISPLAY
measure incident signal for reference
• separate incident and ref
lected signals
•
splitter
bridge
directional
coupler
Network Analyzer Basics
Detector
Test Port
Copyright
2000
Directivity
Directivityis a measure of how well a
coupler can separate signals moving
in opposite directions
(undesired leakage
signal)
(desired reflected
signal)
Test port
Directional Coupler
Network Analyzer Basics
Copyright
2000
Interaction of Directivity with the
D UT (Without Error Correction)
0
Data Max
Directivity
Device
Return Loss
D UT RL = 40 dB
30
Add in-phase
60
Network Analyzer Basics
Device
Device
Directivity
Frequency
Data Min
Add out-of-phase
(cancellation)
Data = Vector Sum
Directivity
Copyright
2000
Incident
Transmitted
Detector Types
D UT
Reflected
SOURCE
Diode
Scalar broadband
(no phase
information)
SIGN AL
SEP A R ATION
INCIDENT (R)
REFLECTED
(A)
TRA NS MITTED
(B)
R E C EIVER / DETECT O R
P R O C ESS O R / DISPLAY
DC
RF
AC
Tuned Receiver
IF = F LO ± F RF
RF
AD C / DSP
Vector
(magnitude and
phase)
IF Filter
LO
Network Analyzer Basics
Copyright
2000
Broadband Diode Detection
Easy to make broadband
● Inexpensive compared to tuned receiver
ing frequency-translating devices
● Good for measur
ing power
● Improve dynamic range by increas
tivity / dynamic range
● Mediu m sensi
●
10 MHz
26.5 GHz
Network Analyzer Basics
Copyright
2000
Narrowband Detection -Tuned Receiver
AD C / DSP
Best sensitivity / dynamic range
ides harmonic / spurious signal
● Prov
rejection
ing
● Improve dynamic range by increas
power, decreasing IF bandwidth, or
averaging
f noise floor and
● Trade of
measurement speed
●
10 MHz
Network Analyzer Basics
26.5 GHz
Copyright
2000
Co mparison of Receiver Techniques
Broadband
(diode)
detection
0 dB
0 dB
-50 dB
-50 dB
-100 dB
-100 dB
-60 dBm Sensitivity
higher noise floor
● fa
lse responses
●
Narrowband
(tuned-receiver)
detection
< -100 dBm Sensitivity
high dynamic range
● harmonic immuni
ty
●
Dyna mic range = maximum receiver power receiver noise floor
Network Analyzer Basics
Copyright
2000
Dynamic Range and Accuracy
Error Due to Interfering Signal
100
-
Error (dB, deg)
10
+
phase error
Dyna mic range
is very important
for measurem ent
accuracy!
1
magn error
0.1
0.01
0.001
0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
-55
-60
-65
-70
Interfering signal (dB)
Network Analyzer Basics
Copyright
2000
T/R Versus S-Parameter Test Sets
S-Para meter Test Set
Trans mission/Reflection Test Set
Source
Source
Transfer switch
R
R
B
A
Port 1
Port 2
Fwd
Port 2
Port 1
Fwd
D UT
RF always comes out port
1
● por
t 2 is always receiver
● response, one-port ca
l
Network Analyzer Basics
available
●
B
A
●
●
●
D UT
Rev
RF comes out port 1 or port
2
forward and reverse
measurements
Copyright
two-port calibration 2000
possible
Processor / Display
Incident
Transmitted
D UT
50 MH-20GHz
NETWORK ANYZER
A CTIVE
C H A N N EL
Reflected
CH 1
CH 2
S 21
S 12
log MA G
log MA G
10 dB /
10 dB /
S O U R CE
E NT RY
1_ -1.9248 dB
1_ -1.2468 dB
RE F 0 dB
RE F 0 dB
R ES P O N S E
839.470 000 MH z
P Rm
Duplexer T est - Tx-Ant and A nt-Rx
Cor
1
1
Hld
SIGNAL
SEP A R ATION
P AS S
1
880.435 000 MH z
STIMUL US
R CHA N N EL
INSTR U M E NT
STATE
P Rm
Cor
2
INCIDENT
(R)
REFLECTED
(A)
T
TRA NS MITTED
(B)
P AS S
Hld
HP-IB STAT US
CH 1 S T AR T 775.000 000 MH z
CH 2 S T AR T 775.000 000 MH z
S TO P 925.000 000 MH z
S TO P 925.000 000 MH z
P O RT 1
P O RT 2
RECEIVER / DETECTO R
PR O CESS O R / DISPLAY
CH1
CH2
S21
S12
log MAG
log MAG
10 dB/
10 dB/
1_ -1.9248 dB
1_ -1.2468 dB
REF 0 dB
REF 0 dB
839.470 000 MHz
PRm
Duplexer Test - Tx-Ant and Ant-Rx
Cor
1
markers
● l
imitlines
● pass/
failindicators
● l
inear/log formats
● gr
id/polar/Smith
charts
●
Network Analyzer Basics
1
Hld
PASS
1
880.435 000 MHz
PRm
Cor
2
PASS
Hld
CH1 START 775.000 000 MHz
CH2 START 775.000 000 MHz
STOP 925.000 000 MHz
STOP 925.000 000 MHz
Copyright
2000
R L
S
Internal Measurement Automation
Simple: recallstates
More powerful:
●
Test sequencing
■
■
■
●
available on 8753/ 8720
families
keystroke recording
some advanced functions
IBASIC
■
■
■
available on 8712 family
sophisticated programs
custom user interfaces
ABC DEF G HIJKLM N O P Q RSTUV W X YZ0123456789 + -/* = < > ( ) & "" ",./ ? ;:'[]
1 ASSIGN @ Hp8714 TO 800
2 OUTPUT @ Hp8714;"SYST:PRES; *WAI"
3 OUTPUT @ Hp8714;"ABOR;:INIT1:CONT OFF;*WAI"
4 OUTPUT @ Hp8714;"DISP:ANN:FRE Q1:M O DE SSTOP"
5 OUTPUT @ Hp8714;"DISP:ANN:FRE Q1:M O DE CSPAN"
6 OUTPUT @ Hp8714;"SENS1:FRE Q:CENT 175000000 HZ;*WAI"
7 OUTPUT @ Hp8714;"ABOR;:INIT1:CONT OFF;:INIT1;*W AI"
8 OUTPUT @ Hp8714;"DISP:WIND1:TRAC:Y:AUTO ONC E"
9 OUTPUT @ Hp8714;"CALC1:MARK1 ON"
10 OUTPUT @ Hp8714;"CALC1:MARK:FUNC B WID"
11 OUTPUT @ Hp8714;"SENS2:STAT ON; *WAI"
12 OUTPUT @ Hp8714;"SENS2:FUNC 'XFR:PO W:RAT 1,0';DET NBAN; *WAI"
13 OUTPUT @ Hp8714;"ABOR;:INIT1:CONT OFF;:INIT1;*W AI"
14 OUTPUT @ Hp8714;"DISP:WIND2:TRAC:Y:AUTO ONC E"
15 OUTPUT @ Hp8714;"ABOR;:INIT1:CONT ON;*WAI"
16 END
Network Analyzer Basics
Copyright
2000
Agilent’s Series of HF Vector Analyzers
Microwave
8510C series
8720ET/ES series
●
●
●
●
●
13.5, 20, 40 GHz
economical
fast, small,integrated
test mixers, high-power
amps
●
●
●
●
RF
8712ET/ES series
●
●
●
●
1.3, 3 GHz
low cost
narrowband and
broadband
detection
IBASIC / LAN
8753ET/ES
series
●
●
●
●
●
Network Analyzer Basics
110 GHz in
coax
highest
accuracy
modular,
flexible
pulse systems
Tx/Rx module
test
3, 6 GHz
highest RF
accuracy
flexible
hardware
more features
OffseCopyr
t and
ight
2000
harmonic RF
sweeps
Agilent’s LF/RF Vector Analyzers
Co mbination NA / SA
4395A/4396B
●
●
●
●
●
●
500 MHz (4395A), 1.8 GHz (4396B)
impedance-measuring option
fast, FFT-based spectrum analysis
time-gated spectrum-analyzer option
IBASIC
standard test fixtures
E5100A/B
●
●
LF
●
●
●
●
Network Analyzer Basics
180, 300 MHz
economical
fast, small
target markets: crystals, resonators, filters
equivalent-circuit models
evaporation-monitor-function option
Copyright
2000
Spectrum Analyzer / Tracking Generator
RF in
IF
8563A
SPE CT R U M AN A LYZ E R
9 kHz - 26.5 GHz
LO
DUT
Spectrum analyzer
TG out
f = IF
D UT
Tracking generator
Key differences from network analyzer:
●
●
●
●
●
one channel -- no ratioed or phase measurements
More expensive than scalar NA (but better dynamic range)
Only error correction available is normalization (and possibly
open-short averaging)
Poorer accuracy
S mallincremental costif SA is required for other measurements
Network Analyzer Basics
Copyright
2000
Agenda
W hat measurements do
we make?
● Network analyzer
hardware
● Error models and
calibration
● Example measurements
● Appendix
W hy do we even need error-correction and
calibration?
● I
tisimpossible to make perfect hardware
● I
t would be extremely expensive to make
hardware
good enough to eliminate the need for error
correction
●
Network Analyzer Basics
Copyright
2000
Calibration Topics
W hat measurements do we
make?
● Network analyzer hardware
● Error models and ca
libration
● measurement er
rors
● what is vector er
ror
correction?
● cal
ibration types
● accuracy examples
● cal
ibration considerations
● Example measurements
● Appendix
●
Network Analyzer Basics
Copyright
2000
Measurement Error Modeling
CA
L
-C
RE
AL
Systematic errors
● due to imperfect
ions in the analyzer and test setup
● assumed to be t
ime invariant (predictable)
Rando m errors
● vary wi
th time in random fashion (unpredictable)
● main cont
ributors: instrument noise, switch and
connector repeatability
Drift errors
● due to system per
formance changing aftera calibration
has been done
● pr
imarily caused by temperature variation
Errors:
Measured
Data
Network Analyzer Basics
SYSTE M ATIC
RAN D O
M
DRIF
T
Unknown
Device
Copyright
2000
Systematic Measurement Errors
R
A
Directivity
B
Crosstalk
D UT
Frequency response
● re
flection tracking (A/R)
● t
ransmission tracking (B/R)
Source
Mismatch
Load
Mismatch
Six forward and six reverse error
terms yields 12 error terms for twoport devices
Network Analyzer Basics
Copyright
2000
Types of Error Correction
●
response (normalization)
simple to perform
only corrects fortracking errors
thru
stores reference trace in me mory,
then does data divided by me mory
vector
requires more standards
requires an analyzer that can measure phase
accounts for all major sources of systematic error
■
■
■
●
■
■
■
SHORT
S11a
OPEN
S11m
Network Analyzer Basics
thru
LOAD
Copyright
2000
W hat is Vector-Error Correction?
●
Process of characterizing systematic error terms
measure known standards
remove effects from subsequent measurements
● 1-port cal
ibration (reflection measurements)
only 3 systematic error terms measured
directivity, source match, and reflection tracking
● Ful
l 2-port calibration (reflection and transmission
measurements)
12 systematic error terms measured
usually requires 12 measurements on four known
standards (SOLT)
● Standards def
ined in cal kit definition file
network analyzer contains standard cal kit definitions
C AL KIT DEFINITION MUST MATC H A CTU AL CAL
KIT USED!
Network Analyzer Basics
User-built standards must be characterized and
entered into user al kit
■
■
■
■
■
■
■
■
■
Copyright
2000
Reflection: One-Port Model
Error Adapter
RF in
Ideal
RF in
1
E D = Directivity
S11A
ES
ED
E RT = Reflection tracking
E S = Source Match
S11 M
S11 M
S11A
E RT
S11 M = Measured
S11A = Actual
●
●
To solve for error terms,
S11A
we measure 3 standards
S11 M = ED +
to generate 3 equations
1 - ES S11A
E RT
and 3 unknowns
Assumes good termination at porttwo iftesting two-port devices
If using port 2 of NA and DUT reverse isolation islow (e.g.,filter passband):
assumption of good termination is not valid
two-port error correction yields better results
■
■
Network Analyzer Basics
Copyright
2000
Before and After One-Port Calibration
0
2.0
data before 1-port
calibration
1.1
VS W R
Return Loss (dB)
20
40
1.01
data after 1-port
calibration
60
1.001
6000
Network Analyzer Basics
M Hz
12000
Copyright
2000
Two-Port Error Correction
Reverse model
Forward model
Port 1
Port 2
E RT'
Port 1
EX
Port 2
S 21
a1
a1
ED
ES
S 21A
S 11 A
b1
E RT
S 22
S 12
ETT
A
EL
E L'
b2
S 11
b1
A
b2
A
S 22
A
E S'
E D'
a2
a2
S 12 A
E TT'
E X'
A
ED = fwd directivity
E S = fwd source match
E RT = fwd reflection tracking
E L = fwd load match
E TT = fwd transmission tracking
E X = fwd isolation
E D' = rev directivity
E S' = rev source match
E RT' = rev reflection tracking
E L' = rev load match
E TT' = rev transmission tracking
E X' = rev isolation
Each actual S-parameter is a
function
of allfour measured
S-parameters
● Analyzer must make forward
and reverse sweep to update
any one S-parameter
● Lucki
ly, you don't need to know
these equations to use network
Network Analyzer Basics
analyzers!!!
S11a =
S
S
S
− ED
− ED '
− E X S12 m − E X '
( 11m
)(1 + 22 m
)(
)
E S ' ) − E L ( 21m
E TT '
E TT
E RT '
E RT
S
S
S
− E D'
− ED '
− E X S12 m − E X '
(1 + 11m
)(
)
E S ' ) − E L ' E L ( 21m
E S )(1 + 22 m
E TT '
E TT
E RT '
E RT
S21a =
S22 m − E D '
S21m − E X
)(1 +
( E S ' − E L ))
E RT '
E TT
S
S
S
− E X S12 m − E X '
− ED
− ED'
(1 + 11m
)(
)
E S ' ) − E L ' E L ( 21m
E S )(1 + 22m
E RT '
E RT
E TT
E TT '
S12 a =
S
− EX '
S
− ED
( 12m
)(1 + 11m
( E S − E L ' ))
E TT '
E RT
S
S
S
− ED
− ED'
− E X S12m − E X '
(1 + 11m
)(
)
E S ' ) − E L ' E L ( 21m
E S )(1 + 22 m
E TT '
E TT
E RT '
E RT
(
●
(
S22 a =
(1 +
S 22m − E D '
E RT '
)( 1 +
S 21m − E X S12 m − E X '
S11m − E D
)(
)
ES ) − E L ' (
E TT '
E TT
E RT
S 21m − E X S12 m − E X '
S 22 m − E D '
S11m − E D
)(
)
ES ' ) − E L ' E L (
E S )(1 +
E TT '
E TT
E RT '
E RT
Copyright
2000
●
Crosstalk: Signal Leakage
Between Test Ports During
ion
CanTransmiss
be a problem wi
th:
D UT
high-isolation devices (e.g., switch in open position)
high-dynamic range devices (some filter
stopbands)
● Iso
lation calibration
adds noise to error model(measuring near noise
floor of system)
only perform ifreally needed (use averaging if
necessary)
if crosstalk is independent of DUT match, use two
terminations
if dependent on DUT match, use DUT with
termination on output
■
■
■
■
■
■
LOAD
Network Analyzer Basics
D UT
D UT
LOAD
Copyright
2000
Errors and Calibration Standards
U N C O R RE CTED
FULL 2-PORT
RESP O NSE
1-PORT
SHORT
D UT
OPEN
thru
●
●
●
LOAD
Convenient
Generally not
accurate
No errors removed
●
Easy to perform
Use when highest
accuracy is not
required
Re moves
frequency
response error
●
●
●
EN H A N CE D-RESP O NSE
Co mbines response and 1-port
Corrects source match for transmission
measurements
Network Analyzer Basics
OPEN
OPEN
LOAD
LOAD
D UT
●
●
SHORT
D UT
●
●
SHORT
For reflection
measurements
Need good termination for
high accuracy with twoport devices
Re moves these errors:
Directivity
Source match
Reflection tracking
thru
D UT
●
●
Highest accuracy
Re moves these
errors:
Directivity
Source,load
match
Reflection tracking
Transmission
tracking
Copyrigh
t lk
Cross
ta
2000
Calibration Summary
Reflection
Test Set (cal type)
T/R
SHORT
S-parameter
(one-port)
(two-port)
OPEN
●
Reflection tracking
●
Directivity
●
Source match
●
Load match
LOAD
Test Set (cal type)
Trans mission
T/R
S-parameter
(two-port)
(response, isolation)
error can be corrected
●
Trans mission Tracking
●
Crosstalk
●
Source match (
●
Load match
error cannot be corrected
* enhanced response cal corrects
for source match during
transmission measurements
Network Analyzer Basics
* )
Copyright
2000
Reflection Example Using a One-Port Cal
Load
match:
18 dB
(.126)
Directivity:
40 dB (.010)
.158
(.891)(.126)(.891) = .100
Re me mber: convert all dB
values to linear for
dB lat
uncertainty ca
(-lcu
) ions!
D UT
ρ orloss(linear) = 10
20
16 dB RL (.158)
1 dB loss (.891)
Measure ment uncertainty:
-20 * log (.158 + .100 + .010)
= 11.4 dB (-4.6dB)
-20 * log (.158 -.100 -.010)
= 26.4 dB (+10.4 dB)
Network Analyzer Basics
Copyright
2000
Using a One-Port Cal +
Attenuator
Directivity:
40 dB (.010)
.158
Load
match:
18 dB
(.126)
10 dB attenuator
(.316) S W R =
1.05 (.024)
Measure ment
uncertainty:
-20 * log (.158 +
.039)
= 14.1 dB (-1.9 dB)
-20 * log (.158 -.039)
= 18.5 dB (+2.5 dB)
D UT
16 dB RL (.158)
1 dB loss (.891)
Low-loss bi-directional devices
generally require two-port
(.891)(.024)(.891) = .019
calibration
Worst-case error = .010 + .010 + .019 = .039
for low measure ment uncertainty
(.891)(.316)(.126)(.316)(.891) = .010
Network Analyzer Basics
Copyright
2000
Transmission Example Using Response
Cal
RL = 18 dB (.126)
RL = 14 dB (.200)
Thru calibration (normalization) builds error
into measurement due to source and load
match interaction
Calibration
Uncertainty
=(1 ± ρS ρL)
= (1 ± (.200)(.126)
= ± 0.22 dB
Network Analyzer Basics
Copyright
2000
Filter Measurement with Response Cal
Source match
= 14 dB (.200)
DUT
1 dB loss (.891)
16 dB RL (.158)
Load match
= 18 dB
(.126)
1
(.126)(.158) = .020
(.126)(.891)(.200)(.891) = .020
(.158)(.200) = .032
Total measure ment
uncertainty:
+0.60 + 0.22 = + 0.82
dB
-0.65 - 0.22 = - 0.87
Network Analyzer Basics
dB
Measurement uncertainty
= 1 ± (.020+.020+.032)
= 1 ± .072
= + 0.60 dB
- 0.65 dB
Copyright
2000
Measuring Amplifiers with a Response Cal
Source match
= 14 dB (.200)
DUT
16 dB RL
(.158)
Load match
= 18 dB
(.126)
1
(.126)(.158) = .020
(.158)(.200) = .032
Total measure ment
uncertainty:
+0.44 + 0.22 = + 0.66
dB
-0.46 - 0.22 = - 0.68
Network Analyzer Basics
dB
Measurement uncertainty
= 1 ± (.020+.032)
= 1 ± .052
= + 0.44 dB
- 0.46 dB
Copyright
2000
Filter Measurements
using the Enhanced
Response Calibration
Effective source match =
35 dB!
Source
match = 35
dB (.0178)
DUT
1 dB loss (.891)
16 dB RL (.158)
Load
match =
18 dB
(.126)
Calibration Uncertainty
=(1 ± ρS ρL)
= (1 ±
(.0178)(.126)
= ± .02 dB
1
Measurement uncertainty
= 1 ± (.020+.0018+.0028)
(.126)(.158) = .020
= 1 ± .0246
= + 0.211 dB
(.126)(.891)(.0178)(.891) = .0018
- 0.216 dB
(.158)(.0178) = .0028
Total measurem ent
uncertainty:
0.22 + .02 = ± 0.24 dB
Network Analyzer Basics
Copyright
2000
Using the Enhanced Response
Calibration Plus an Attenuator
10 dB attenuator (.316)
S W R = 1.05 (.024 linear or 32.4
dB)
Analyzer
load match =18 dB (.126)
Source match
= 35 dB
(.0178)
DUT
1 dB loss (.891)
16 dB RL (.158)
Calibration Uncertainty
=(1 ± ρS ρL)
= (1 ±
(.0178)(.0366)
= ± .01 dB
Effective load match = (.316)(.316)(.126) + .024
= .0366 (28.7dB)
1
Measurement uncertainty
= 1 ± (.006+.0005+.0028)
(.0366)(.158) = .006
= 1 ± .0093
(.0366)(.891)(.0178)(.891) = .0005 = ± 0.08 dB
(.158)(.0178) = .0028
Total measurem ent
uncertainty:
0.01 + .08 = ± 0.09 dB
Network Analyzer Basics
Copyright
2000
Calculating Measurement
Uncertainty After a Two-Port DUT
1 dB loss (.891)
Calibration
16 dB RL (.158)
Corrected error terms:
(8753ES 1.3-3 GHz Type-N)
Directivity
dB
Source match =
Load match
dB
Refl.tracking =
dB
Trans. tracking
.026 dB
Isolation
=
=
47
Reflection uncertainty
36 dB
2
=
47 S 11m = S11a ± ( E D + S11a E S + S 21a S12 a E L + S11a (1 − E RT ))
.019
= 0.158 ± (.0045 + 0.158 2 *.0158 + 0.8912 *.0045 + 0.158*.0022 )
= 0.158 ± .0088 = 16 dB +0.53 dB, -0.44 dB (worst-case)
=
100 dB
Trans mission uncertainty
S 21m = S 21a ± S 21a ( E I / S 21a + S11a E S + S 21a S12 a E S E L + S 22 a E L + (1 − E TT ))
= 0.891 ± 0.891(10 −6 / 0.891 + 0.158*.0158 + 0.8912 *.0158*.0045 + 0.158*.0045+.003)
= 0.891 ± .0056 = 1 dB ±0.05 dB (worst-case)
Network Analyzer Basics
Copyright
2000
Response versus Two-Port Calibration
Measuring filter insertion loss
C H1 S21& M
C H2 M E M
log MA G
log MA G
Cor
1 dB/
1 dB/
REF 0 dB
REF 0 dB
After two-port calibration
After response calibration
Cor
x2 1
START 2 000.000 MHz
Network Analyzer Basics
Uncorrected
2
ST OP 6 000.000 MHz
Copyright
2000
ECal: Electronic Calibration (85060/90
series)
•
•
•
Variety of modules cover 30 kHz to 26.5
G Hz
Six connector types available (50 Ω and
σα
75 Ω)
Single-connection
reduces calibration time
makes calibrations easy to perform
minimizes wear on cables and
standards
eliminates operator errors
Highly repeatable temperatureMicrowave modules use a
compensated terminations provide
transmission line shunted by
excellent accuracy
PIN-diode switches in various
85093A
Electronic Calibration Module
30 kHz - 6 GHz
■
■
■
■
•
combinations
Network Analyzer Basics
Copyright
2000
Adapter
reflection from
Considera
t
ions
desired signal
adapter
leakage signal
ρ
m easured = Directivity +
ρ
adapter +
ρ
D UT
Coupler directivity = 40 dB
Adapter
W orst-case
System Directivity
28 dB
17 dB
14 dB
Network Analyzer Basics
D UT
Termination
D UT has SMA (f) connectors
AP C-7 calibration done here
Adapting from APC-7 to SMA
(m)
APC-7 to SMA (m)
S W R:1.06
APC-7 to N (f) + N (m) to SMA (m)
S W R:1.05
S W R:1.25
APC-7 to N (m) + N (f)to SMA (f) + SMA (m) to (m)
S W R:1.05
S W R:1.25
S W R:1.15
Copyright
2000
Calibrating Non-Insertable
Devices
W hen doing a through cal, normally test ports
m ate directly
● cables can be connected d
irectly without an
adapter
● resul
tis a zero-length through
W hat is an insertable device?
● has same type of connector, but d
ifferent sex on
each port
● has same type of sex
less connector on each
port (e.g. APC-7)
W hat is a non-insertable device?
● one that cannot be inser
ted in place of a zerolength through
● has same connectors on each por
t (type and
sex)
● has d
ifferent type of connector on each port
(e.g., waveguide on one port, coaxial on
Network Analyzer Basics
the other)
W hat alibration hoi es do I have for non-
D UT
Copyright
2000
Swap Equal Adapters Method
Port 1
Port 1
Adapter
A
Port 1
Port 1
Port 2
D UT
D UT
Network Analyzer Basics
Accuracy depends on how well
the adapters are matched -loss,
electrical length, match and
impedance should all be equal
1. Transmission cal using adapter A.
Port 2
Adapter
B
Port 2
2. Reflection cal using adapter B.
Adapter
B
Port 2
3. Measure D UT using adapter B.
Copyright
2000
Adapter Re moval Calibration
●
●
●
●
●
Calibration is very accurate and traceable
In firmware of 8753, 8720 and 8510 series
Port 1
Also accomplished with ECal modules (85060/90)
Uses adapter with same connectors as DUT
Must specify electricallength of adapter to within
1/4 wavelength of highest frequency (to avoid
phase ambiguity)
Cal
Adapter
Port 1
D UT
Port 2
Adapter Port 2
B
1. Perform 2-port cal with adapter on port2.
Save in cal set 1.
Adapter
B
2. Perform 2-port cal with adapter on port1.
Save in cal set 2.
Cal Set 1
Port 1
Cal
Adapter
Port 2
Cal Set 2
[CAL] [MORE] [MODIFY CAL SET]
[ADAPTER RE M O VAL]
Port 1
Network Analyzer Basics
D UT
Adapter
B
Port 2
3. Use ADAPTER RE M O VAL
to generate new cal set.
4. Measure DUT without cal adapter.
Copyright
2000
Thru-Reflect-Line (TRL) Calibration
W e know about Short-Open-Load-Thru (SOLT) calibration...
W hat is TRL?
● A two-por
t calibration technique
● Good for noncoaxia
l environments (waveguide,
fixtures, wafer probing)
● Uses the same 12term error model as the more
com mon SOLT cal
● Uses pract
ical calibration standards tha
t was developed for nonTRL
are easily fabricated and characterized
coaxial microwave
● Two var
iations: TRL (requires 4 receivers) measurements
and TRL* (only three receivers needed)
● Other var
iations: Line-Reflect-Match (LRM),
Thru-Reflect-Match (TR M), plus many others
Network Analyzer Basics
Copyright
2000
Agenda
●
●
●
●
●
Network Analyzer Basics
W hat measurements do we make?
Network analyzer hardware
Error models and calibration
Example measurements
Appendix
Copyright
2000
Frequency Sweep - Filter Test
CH1 S 21
log MAG
10 dB/
REF 0 dB
CH1 S 11
log MAG
5 dB/
REF 0 dB
Cor
Stopba
nd
rejectio
n
69.1 dB
START .300 000 MHz
STOP 400.000 000 MHz
CH1 S 21
SPAN 50.000 MHz
CENTER 200.000 MHz
log MAG
1 dB/
REF 0 dB
Return loss
Cor
4.000 1000 GHz -
m1:
0.16 dB
m2-ref: 2.145 234 GHz
0.00 dB
ref
2
Cor
Insertion loss
x2 1
2
START 2 000.000 MHz
Network Analyzer Basics
STOP 6 000.000 MHz
Copyright
2000
Optimize Filter Measurements with
Swept-List Mode
Segment 3: 29 ms
(108 points, -10 dBm, 6000 Hz)
CH1 S 21
log MAG
12 dB/
REF 0 dB
PRm
S wept-list sweep: 349
ms
(201 pts, variable B W's &
power) PASS
Linear sweep: 676
ms
(201 pts, 300 Hz, -10
dB m)
Segment 5: 129 ms
(38 points, +10 dBm, 300 Hz)
Segment 1: 87 ms
(25 points, +10 dBm, 300 Hz)
START 525.000 000 MHz
STOP 1 275.000 000 MHz
Segments 2,4: 52 ms
(15 points, +10 dBm, 300 Hz)
Network Analyzer Basics
Copyright
2000
Output Power (dBm)
Power Sweeps -Co mpression
Saturated output
power
Co mpression
region
Linear region
(slope = small-signal gain)
Input Power (dB m)
Network Analyzer Basics
Copyright
2000
Power Sweep -Gain Compression
C H1 S21
1og MA G
1 dB/ REF 32 dB
30.991 dB
12.3 dBm
1 dB
co mpression:
1
0
START -10 dB m
Network Analyzer Basics
C W 902.7 MHz
input power
resulting in 1 dB
drop in gain
ST OP 15 dB m
Copyright
2000
A M to PM Conversion
A mplitude
Measure of phase deviation caused by
a Power
mplisweep
tude variations
●
AM
(dB)
Mag(Ami
n)
●
D UT
A M can be undesired:
supply ripple,fading, thermal
A M can be desired:
modulation (e.g. QA M)
PM
(deg)
Test Stimulus
Q
Time
A mplitude
AM
(dB)
A M - PM Conversion
=
Mag(P m
(deg/d
)
Mag(A
m B)
out
in)
Mag(AM o
ut)
PM
(deg)
Mag(Pm o
ut)
Output
Response
Network Analyzer Basics
Time
I
A M to PM
conversion can
cause bit errors
Copyright
2000
Measuring AM to PM Conversion
1:Transmission
Log Mag 1.0 dB/
2:Transmission /M Phase
5.0 deg/
Ch1:Mkr1
20.48
dB
Ch2:Mkr2
0.86 deg
Ref 21.50 dB
Ref -115.7 deg
-4.50 dB m
1.00 dB
Use transmission setup
with a power sweep
● Disp
lay phase of S21
● A M - PM = 0.
86 deg/dB
●
2
1
2
1
Start -10.00 dB m
Start -10.00 dB m
Network Analyzer Basics
C W 900.000 MHz
C W 900.000 MHz
1
Stop 0.00 dBm
Stop 0.00 dBm
Copyright
2000
Agenda
●
W hat measurements do we make?
Network analyzer hardware
Error models and calibration
Example measurements
●
Appendix
●
●
●
●
●
●
Network Analyzer Basics
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!
Copyright
2000
Time-Domain Reflectometry (TDR)
●
W hat is TDR?
time-domain reflectometry
analyze impedance versus time
distinguish between inductive and
capacitive transitions
With gating:
analyze transitions
inductive
analyzer standards
transition
■
■
■
●
■
impedance
■
Zo
time
capacitive
transition
Network Analyzer Basics
non-Zo transmission line
Copyright
2000
TDR Basics Using a Network Analyzer
start with broadband frequency sweep (often requires microwave VN
● use inverse-Four
ier transform to compute time-domain
● resolut
ion inversely proportionate to frequency span
●
Time Do main
Frequency Do main
F
C H1 S 22
-1
Cor
50 mU/ REF 0 U
20 GHz
f
t
∫ F(t)*dt
Re
6 GHz
t
Integrate
1/s*F(s)
0
TDR
F
t
Network Analyzer Basics
-1
f
C H1 START 0 s
ST OP 1.5 ns
Copyright
2000
Time-Domain Gating
TDR and gating can remove undesired reflections (a form of
error correction)
● Only usefu
lfor broadband devices (a load or thru for example)
● Def
ine gate to only include D UT
C H1 S11& M log MA G
5 dB/
REF 0 dB
● Use two-por
t calibration
●
PR m
Cor
C H1 M E M Re
PR m
Cor
2
20 mU/ REF 0 U
1: -45.113 dB 0.947
G Hz
2: -15.78 dB 6.000
G Hz
Gate
1: 48.729 mU 638 ps
RISE TIME
29.994 ps
8.992 m m
2: 24.961 mU 668 ps
1
3: -10.891 mU 721 ps
2
3
Thru in time domain
C H1 START 0 s
Network Analyzer Basics
ST OP 1.5 ns
1
Thru in frequency
domain, with and
without gating
START .050 000 000 GHz
ST OP 20.050 000 000 GHz
Copyright
2000
Ten Steps for Performing TDR
1. Set up desired frequency range (need wide span for good
spatial resolution)
2. Under SYSTEM, transform menu, press "set freq low
pass"
3. Perform one- or two-port calibration
4. Select S11 measurement *
5. Turn on transform (low pass step) *
6. Set format to real *
7. Adjust transform window to trade off rise time with ringing
and overshoot *
8. Adjust start and stop times if desired
9. For gating:
● set s
tart and stop frequencies for gate
● tu
rn gating on *
● adjust gate shape to t
rade offresolution with ripple *
10. To display gated response in frequency domain
* If● us
ing
channe
lso
(even
if coupga
led)
,these
must be set
tu
rntwo
trans
form
ff (leave
ting
on)parameters
*
independent
r second
channel itude *
● changely
fofo
rmat
to log-magn
Network Analyzer Basics
Copyright
2000
Time-Domain Transmission
RF Input
RF Output
C H1
Main Wave
Leakage
S21 log MA G
Surface
W ave
Triple
Travel
C H1
S21
log MAG
10 dB/ REF 0 dB
15 dB/ REF 0 dB
Cor
Cor
RF
Leakage
Triple
Travel
Gate off
Gate on
Network Analyzer Basics
ST OP 6 us
START -1 us
Copyright
2000
Time-Domain Filter Tuning
•
•
Deterministic method used
fortuning cavity-resonator
filters
Traditionalfrequencydomain tuning is very
difficult:
lots oftraining needed
may take 20 to 90
minutes to tune a
single filter
Need VNA with fast sweep
speeds and fast timedomain processing
■
■
•
Network Analyzer Basics
Copyright
2000
Filter Reflection in Time Do main
•
•
•
Network Analyzer Basics
Set analyzer’s center frequency
= center frequency ofthe filter
Measure S11 or S22 in the time
domain
Nullsin the time-domain response
correspond to individual resonators
in filter
Copyright
2000
Tuning Resonator #3
•
•
•
•
Network Analyzer Basics
Easier to identify mistuned
resonator
in time-domain:
null #3 is missing
Hard to tell which resonatoris
mistuned from frequencydomain response
Adjust resonators by minimizing
null
Adjust coupling apertures using
the peaks in-between
the dips
Copyright
2000
Frequency-Translating Devices
Medium-dynamic range
measurements (35 dB)
High-dynamic range measurements
(100 dB)
FRE Q OFFS
O N off
8753ES
8753ES
LO
MENU
Ref In
1
2
Filter
DO WN
C O NVE RTER
Ref out
UP
C O NVE RTER
Attenuator
Attenuator
Ref in
RF > LO
Reference
mixer
RF < LO
Start: 900 MHz
Stop: 650 MHz
Start: 100 MHz
Stop: 350 MHz
Fixed LO: 1 GHz
LO power: 13 dBm
VIE W
M EASU RE
Filter
Attenuator
RETU R N
CH1 CONV MEAS
log MAG 10 dB/
REF 10 dB
D UT
Attenuator
Attenuat
or
Powe
r
splitt
er
ES G-D4000A
START 640.000 000 MHz
Network Analyzer Basics
STOP 660.000 000 MHz
Copyright
2000
High-Power Amplifiers
Prea mp
8753ES
Source
Ref In
Prea mp
UT
ADUT
R
B
A
A UT
+43 dBm max input (20 watts!)
8720ES Option 085
85118A High-Power
Amplifier Test System
Network Analyzer Basics
Copyright
2000
High-Dynamic Range
Measurements
C H1 M E M
C H2 M E M
LO G
LO G
15 dB/ REF 3 dB
15 dB/ REF 3 dB
•
•
PR m
Cor
Avg
10
PR m
Standard 8753ES
Cor
Avg
10
•
8753ES Special Option H16
C H1
C H2
Network Analyzer Basics
START 775.000 000 M Hz
START 775.000 000 M Hz
ST OP 1000.000 000 M Hz
ST OP 1000.000 000 M Hz
Copyright
2000
Multiport Device Test
8753 H39
CH1
CH2
S 21
S 12
log MAG
log MAG
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
1
Hld
PASS
1
880.435 000 MHz
PRm
Cor
2
PASS
Hld
CH1 START 775.000 000 MHz
CH2 START 775.000 000 MHz
Network Analyzer Basics
STOP 925.000 000 MHz
STOP 925.000 000 MHz
Multiport analyzers and test sets:
● improve throughput by reducing the
number of connections to D UTs with
more than two ports
● al
low simultaneous viewing oftwo
paths
(good for tuning duplexers)
● inc
lude mechanical or solid-state
switches, 50 or 75 ohms
● degrade raw per
formance so
calibration is a must (use two-port
cals whenever possible)
● Agi
lent offers a variety of standard
and custom multiport analyzers and
test sets
Copyright
2000
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
Fixture
D UT
Once an hour:
automatically perform a
•
•
•
•
•
For use with 8712E family
SelfCal using internal
standards to remove
systematic errors in the
50 Ω: 3 MHz to 2.2 GHz, 4, 8, or 12 ports
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
Network Analyzer Basics
Copyright
2000
Test Set Cal Eliminates
Redundant Connections of
Calibration Standards
Through Connections
Reflection Connections
12-port
12-port
8-port
8-port
4-port
4-port
0
100
Network Analyzer Basics
200
300
400
0
25
■
Test Set Cal
■
Traditional VN A Calibration
50
75
Copyright
2000
In-Fixture Measurements
Measure ment problem: coaxial
calibration plane is not the same as the
in-fixture measurement plane
Measurement
plane
Calibration
plane
Fixture
ED
ES
ET
Error correction with coaxial calibration
D UT
●
●
●
Network Analyzer Basics
Loss
Phase shift
Mismatch
Copyright
2000
Characterizing CrystalResonators/Filters
Ch1
Z: R
phase
40 / REF
0
1: 15.621 U
E5100A/B Network Analyzer
31.998 984 925 MHz
Min
Cor
1
START 31.995 MHz
SE G START
STOP
POINTS
ST OP 32.058 MHz
PO W E R
IFB W
1 31.995 MHz
32.008 MHz
200
0 dB m
200Hz
> 2 32.052 MHz
32.058 MHz
200
0 dB m
200Hz
EN D
Exa mple of crystal resonator
measurement
Network Analyzer Basics
Copyright
2000
Balanced-Device Measurements
•
ATN-4000 series (4-port test set + software)
measure tough singled-ended devices like couplers
• measure ful
ly-balanced or single-ended-to-balanced DUTs
ize mode conversions (e.g. com mon-to-differential)
• character
ional accuracy
• incorporates 4-port error correction for except
• works with 8753ES and 8720ES analyzers
• more info at ww w.atnm icrowave.co m
•
σα
Channel Partner
Network Analyzer Basics
Copyright
2000
Traditional Scalar Analyzer
Incident
Transmitted
D UT
Reflected
SOURCE
SIGN AL
SEP A R ATION
processor/display
INCIDENT (R)
REFLECTED
(A)
TRA NS MITTED
(B)
R E C EIVER / DETECT O R
source
P R O C ESS O R / DISPLAY
Example: 8757D/E
● requi
res external detectors, couplers, bridges, splitters
● good forlow-cost microwave scalar appl
ications
RF
R
A
B
RF
Detector
R
Detector
Detector
Bridge
Reflection
D UT
D UT
Termination
Trans mission
Network Analyzer Basics
Copyright
2000
A
B
Directional Coupler Directivity
Coupling Factor (fwd) x Loss
Directivity =
(through arm)
Isolation (rev)
Directivity (dB) = Isolation (dB) - Coupling Factor
(dB) - Loss (dB)
50 dB
Exa mples:
20 dB
Test
port
50 dB
Directivity = 50 dB - 20 dB = 30 dB
30 dB
Test
port
Directivity = 50 dB - 30 dB - 10 dB = 10 dB
10 dB
60 dB
20 dB
Test
port
Directivity = 60 dB - 20 dB - 10 dB = 30 dB
10 dB
Network Analyzer Basics
Copyright
2000
One Method of Measuring Coupler Directivity
1.0 (0 dB) (reference)
Coupler
35 tdB
Direc
ivit(
y.018)
Source
short
.018 (35 dB) (normalized)
Directivity = 35 dB - 0 dB
= 35 dB
Source
Network Analyzer Basics
load
Assume perfect
load (no
reflection)
Copyright
2000
Directional Bridge
50 Ω
50 Ω
Detector
●
●
●
50 Ω
Test Port
●
Network Analyzer Basics
50-ohm load at test port
balances
the bridge -- detector reads
zero
Non-50-ohm load imbalances
bridge
Measuring magnitude and
phase ofimbalance gives
complex impedance
"Directivity"is difference
between maximu m and
minimu m balance
Copyright
2000
Incident
NA Hardware: Front
Ends, Mixers Versus
Sa mplers
Transmitted
D UT
Reflected
SOURCE
SIGN AL
SEP A R ATION
INCIDENT (R)
REFLECTED
(A)
TRA NS MITTED
(B)
R E C EIVER / DETECT O R
P R O C ESS O R / DISPLAY
Sa mpler-based front end
AD C / DSP
S
AD C / DSP
Mixer-based front end
Harmonic
generator
f
frequency "comb"
Itis cheaper and easier to make
broadband front ends using
sa mplers instead of mixers
Network Analyzer Basics
Copyright
2000
Three Versus Four-Receiver Analyzers
Source
Source
Transfer switch
Transfer switch
R1
R
A
A
B
B
R2
Port 1
Port 2
3 receivers
●
●
●
more economical
TRL*, LR M* cals only
includes:
8753ES
8720ES (standard)
■
■
Network Analyzer Basics
Port 2
Port 1
4 receivers
●
●
●
more expensive
true TRL, LRM cals
includes:
8720ES (option 400)
8510C
■
■
Copyright
2000
W hy Are Four Receivers Better Than Three?
TRL
TRL*
8720ES Option 400 adds
fourth sa mpler, allowing full
TRL calibration
●
TRL*
assumes the source and load match of a test port are equal
(port sym metry between forward and reverse measurements)
thisis 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*
W hat about coaxial applications?
S OLT is usually the preferred calibration method
coaxial TRL can be more accurate than SOLT, but not commonly used
■
■
●
■
■
●
●
■
■
Network Analyzer Basics
Copyright
2000
Challenge Quiz
1. Can filters cause distortion in co m m unications 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
2. Which statem ent about trans mission lines is false?
A. Usefulfor efficient transmission of RF power
B. Requires termination in characteristicimpedance forlow VSW R
C. Envelope voltage of RF signalisindependent of position along line
D. Used when wavelength of signalis small compared to length ofline
E. Can be realized in a variety offorms such as coaxial, waveguide, microstri
3. Which statem ent 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
Network Analyzer Basics
Copyright
2000
Challenge Quiz (continued)
4. Maximu m dyna mic range with narrowband detection is defined as:
A. Maximum receiverinput power minus the stopband of the device under te
B. Maximum receiverinput 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 maximu m source output power
E. Maximum source output power minus the receiver's noise floor
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
6. Calibration(s) can remove which of the following types of measure ment
A. Systematic and drift
B. Systematic and random
C. Random and drift
D. Repeatability and systematic
E. Repeatability and drift
Network Analyzer Basics
Copyright
2000
Challenge Quiz (continued)
7. Which statem ent about TRL calibration is false?
A. Is a type oftwo-port error correction
B. Uses easily fabricated and characterized standards
C. Most com monly used in noncoaxial environments
D. Is not available on the 8720ES family of microwave
network analyzers
E. Has a specialversion for three-sampler network
analyzers
8. For which co mponent is ithardest to get accurate
trans mission and reflection measure ments 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 oflack of broadband detectors
E. Attenuators because source match cannot be corrected
9. Power sweeps are good for which measurements?
A. Gain compression
Network Analyzer Basics
B. AM to PM conversion
C. Saturated output power
Copyright
2000
Answers to Challenge Quiz
1. E
2. C
3. A
4. B
5. C
6. A
7. D
8. B
9. E
Network Analyzer Basics
Copyright
2000