Differential structures such as backplanes and cables are the primary means for transmitting high speed serial data signals. Signal integrity of these systems is determined by the characteristics of the media such as insertion loss, crosstalk, and differential to common mode conversion. Complete measurement of the mixed mode s-parameters is often performed by transforming single-ended s-parameters and assuming that the system is linear. In some cases, linearity cannot be assumed such as where active components are used. This presentation describes how to measure true differential s-parameters which can be measured even in the presence of non-linear elements.

1. True Differential Measurements
Characterization of Balanced Devices and Channels
Dr. Chris Scholz
Product Manager, Vector Network Analyzers Reflectometer 2
Christopher.scholz@rsa.rohde-schwarz.com Meas. Receiver
Ref. Receiver PORT 2
(817) 422 2512
Reflectometer 4
Meas. Receiver
Ref. Receiver PORT 4
Logical
Error PORT 2
corrected Reflectometer 1
Mag Phase Meas. Receiver Balanced
detection DUT
and control Ref. Receiver PORT 1
by software
Logical
PORT 1
Reflectometer 3
Meas. Receiver
Ref. Receiver PORT 3

2. Outline
Reflectometer 2
Meas. Receiver
Ref. Receiver PORT 2
Reflectometer 4
Meas. Receiver
Ref. Receiver
ı Introduction to Signal Integrity
PORT 4
Logical
Error PORT 2
corrected Reflectometer 1
Mag Phase Balanced
 Timing detection Meas. Receiver
DUT
and control Ref. Receiver
 Signal Quality
PORT 1
by software
Logical
ı Balanced Architectures Reflectometer 3
PORT 1
Meas. Receiver
 The need for balanced architectures
Ref. Receiver PORT 3
 Ideal vs. non-ideal devices
ı Measurement Techniques for Balanced Architectures
 Single mode vs. Differential Mode
 Mixed mode S-Parameters Trc18 Sdd21 dB Mag 0.5 dB / Ref -23 dB Ch1 Cal int
Trc21 Sdd21 dB Mag 0.5 dB / Ref -23 dB Ch2 Cal int
2 of 16 (Max)
 TureDifferential vs. Virtual Differential
Sdd21
-20.0
 TruDifferential Vector Network Analyzer -20.5
ı Experimental Examples
-21.0
-21.5
-22.0
-22.5
-23.0
-23.5
-24.0
Ch1 Start -25 dBm — Freq 1 GHz Stop 0 dBm
1/29/2013 Ch2 Start -28 dBm — 2
Freq 1 GHz Stop -3 dBm
3/8/2007, 1:10 PM

3. Introduction – Signal Integrity
ı What is Signal Integrity?
 Signal integrity or SI is a set of measures of the quality of an electrical signal.
 If the PCB or package already exists, the designer can also measure the
impairment presented by the connection using high speed instrumentation
such as a vector network analyzer. For example, IEEE P802.3ap Task Force
uses measured S-parameters as test cases[9] for proposed solutions to the
problem of 10 Gbit/s Ethernet over backplanes.
 (Source: Wikipedia, last accessed 01/29/2013)
ı Two Key Aspects of SI:
Timing Signal Quality
1/29/2013 3

4. Introduction – Signal Integrity
ı Timing
 Jitter
 RJ, DJ, SJ, PJ, DDJ, DCD, ISI, etc.
 interconnect flight time vs bit period
 chip-to-chip vs on-chip
 packaging
1/29/2013 4

5. Introduction - Signal Integrity
ı Signal Quality
Noise = (S+N)-S
 Ringing
10
 Cross talk 8
 Distortion 6
 Ground Bounce 4
amplitude
 Ground Noise 2
 Signal Loss 0
 Power Supply Noise -2
-4
-6
time
1/29/2013 5

6. Introduction – Signal Integrity
ı Reflection Noise
 Caused by impedance mismatch, vias, interconnect discontinuities
ı Crosstalk Noise
 Caused by electromagnetic coupling between traces and vias
ı Power and Ground Noise
 Caused switching noise of the power and ground delivery systems
ı EMC/EMI Susceptibility
1/29/2013 6

7. Balanced Architectures
1/29/2013 7

8. Differential Signaling
Unbalanced Device/Channel Balanced (differential) Device/Channel
c
a
2
1 1 2
b
d
• Signals referring to ground ı Signals with equal amplitude but 180° phase
shift
• Also supports a common-mode (in-phase)
signal
• Virtual ground

9. Balanced devices - Why balanced design?
ı Advantages:
ı High noise immunity
 Minimizes Power and
ground plane noise
 Minimizes EMI
susceptibility
 Minimizes Cross talk
Components with
balanced design: ı Low radiated noise
ı High integration density
• Amplifiers ı Lower power
• Mixers
consumption
• Filters (e.g. SAW filters)
• PCB layout in mobile phones
• LAN adapters, converters, filters
• PC components (HDD control, etc)
• Almost all signals high-speed serial data signals

10. Ideal Balanced Device Characteristics
Gain = 1
Differential-mode signal
Fully balanced
Common-mode signal
(EMI or ground noise)
Gain = 1
Differential-mode signal Balanced to
single ended
Common-mode signal
(EMI or ground noise)
Ideally, balanced devices transmit differential and reject common-mode signals
1/29/2013 10

11. Non-Ideal Balanced Device Characteristics
Differential to common-
ı Non-ideal balanced devices convert modes mode conversion
+
Generates EMI
Susceptible to EMI
Common-mode to
differential conversion
1/29/2013 11

12. Non-Ideal Balanced Device Characteristics
ı Non-ideal balanced devices convert input modes
Differential to common-
mode conversion
Common-mode to
differential conversion
1/29/2013 12

13. Measurement Techniques for Balanced
Devices
1/29/2013 13

14. Parameters to Test for a Balanced Device
ı Performance in pure differential mode
ı Performance in pure common mode
ı Conversion from differential mode to common mode (in both directions)
ı Conversion from common mode to differential mode (in both directions)
1/29/2013 14

15. Balanced Devices Characteristics
ı Real Devices
 Propagation of both common mode and differential mode signals
 Mode conversion due to non-symmetric design
 Susceptability of noise (mainly common mode)
 Detailed insight of differential/common mode response required
ı Description of balanced devices via special type of S-Parameters:
 Mixed-Mode S-Parameters
1/29/2013 15

16. Challenge when measuring balanced devices
ı Network analyzers are unbalanced
ı Classic Network Analyzers are 2-port instruments
ı No balanced calibration standards
ı No standard reference impedance (Z0) for balanced device
ı Characterization of common and differential transmission model
1/29/2013 16

17. Measurement with Physical BalUns
Measurement with differential mode
signals at a balanced device
Unbalanced
network analyzer
DUT
Balun
1/29/2013 17

18. Measurement with Physical Transformers
Measurement with common
Unbalanced mode signals at a balanced
network analyzer device
DUT
1/29/2013 18

19. Balanced Device Characteristics
Balun setup for Mixed-Mode-Characterization
bal DUT bal
unbal unbal
Each 2-port combination between balanced and unbalanced ports is
necessary for complete mixed mode characterization.

20. Balanced Device Characteristics
Physical BalUns: Disadvantages
ı Calibration plane different from desired measurement plane
ı Degradation of measurement accuracy due to poor RF performance
ı Different configurations for different modes necessary (e.g. differential to
common-mode conversion)
ı Limited in frequency range
ı Solution:
 Us ideal (virtual) transformer to characterize mixed mode S-parameters of the
DUT using virtual, ideal transformers
Modal Decomposition Method
Use True Differential Method
1/29/2013 20

21. Basic Architecture: Definition of Differential
Measuremets
Measurement Principle
ı VirDi = Virtual differential Mode
 Characterization of balanced DUT as single ended DUT with mathematical
calculation of mixed-mode S-Parameters form single ended S-Parameters
ı TruDi = True differential Mode
 Stimulation of DUT with true differential and common mode signals with
calculation of mixed-mode S-Parameters from error corrected mixed mode
wave quantities
1/29/2013 21

22. Virtual Differential Measurement
ı Subsequent single ended measurements with post processing using linear
superposition
ı Applicable for all passive devices and active devices operating in their linear
region
ı Large deviations compared to TruDi in large signal operation, especially in
terms of compression curve characteristics
 Nonlinear behavior of the DUT forbids linear superposition
1/29/2013 22

23. True Differential Measurement
ı The DUT is stimulated using a real differential mode or real common mode
signal
ı Better accuracy in small signal operation
ı Accurately measure compression under large signal operation
1/29/2013 23

24. ZVA – True Differential Mode
ı Coherent sources
 Generation of true differential and common mode stimulus signals
 At least one signal output can be adjusted in amplitude and phase with
respect to the other
ı Simultaneous measurement of two reference signals (a waves) and two
measurement signals (b waves)
ı Four-port calibration in the reference plane
 Vector-corrected measurement of a single ended waves or voltages (a and b
waves)
ı Calculation of true differential S-Parameters from vector corrected wave
quantities
1/29/2013 24

25. A True Differential Network Analyzer
Reflectometer 2
Meas. Receiver
Ref. Receiver PORT 2
Reflectometer 4
Meas. Receiver
Ref. Receiver PORT 4
Logical
PORT 2
Error
corrected
Reflectometer 1
Mag Phase Balanced
Meas. Receiver
detection DUT
and control Ref. Receiver
PORT 1
by software
Logical
PORT 1
Reflectometer 3
Meas. Receiver
Ref. Receiver PORT 3
1/29/2013 25

26. True Differential Measurements with R&S Network
Analyzers ZVA and ZVT
1/29/2013 26

27. Sweep modes (R&S®ZVA-K6)
differential mode 180° common mode 0°
Coherent signals of arbitrary phase and amplitude imbalance are possible
 Sweep Modes:
 Frequency
 Phase (Phase of the stimulating signal can be swept from 0° to 180° )
 Magnitude (Variation of the relative magnitude of the differential signals)
 “Classical” calibration techniques sufficient (full two port)
 Investigation of the DUT under real conditions
1/29/2013 27

28. Typical measurements quality parameters
ı Differential and common mode insertion loss
ı Differential and common mode return loss
ı NEXT-Measurements (Near End Crosstalk)
ı FEXT-Measurements (Far End Crosstalk)
ı Amplitude-Imbalance
ı Phase-Imbalance
ı Common-Mode Rejection Ratio (CMRR)
1/29/2013 28

29. True Differential vs. Virtual Differential
TruDi vs. VerDi
1/29/2013 29

30. Modal Decomposition Method Principle
4-port device with Description of virtual
16 measured ideal transformers
unbalanced S-
parameter
Calculated mixed mode
S-parameters
ı Calculation of the mixed mode S-parameters using unbalaced S-Parameters
and virtual transformers
1/29/2013 30

31. Modal Decomposition Method
test fixture
a Port 1 Port 3 a
DUT
DUT
b b
Port 2 Port 4
 a 1   S 11 S 12 S 13 S 14
 b 4
     
 a 2   S 2 1 S 22 S 23 S 24 
 b 3
 a  S S S S  b 
 3   31 32 33 34
  2
 a 4  S 4 1
   S 42 S 43 S 44 
  b 1
 
ı Measure the balanced 2-port device as unbalanced 4-port device with
unbalanced VNA
1/29/2013 31

32. Solution: Modal Decomposition Method
[Z]
[P], [Q]
[Zm]
ı Calculate the mixed mode Zm-parameters of the combination of DUT with
transformers.
1/29/2013 32

33. Port Configurations Mixed Mode DUT
ı Physical single ending ports  logical balanced ports
Port 3 Port 1 Port 4 Port 2 physical ports
DUT logical ports
Port 1 Port 2
ı Different impedances for common-mode and differential-mode
 differential-mode (ideally matched)  100 ( =2*Z0 )
 common-mode (ideally matched)  25 ( = 1/2*Z0 )
1/29/2013 33

34. Modal Decomposition Method
Mixed Mode S-Parameter Matrix
DU Differential-Mode
stimulus
Common-Mode
stimulus
T Port 1 Port 2 Port 1 Port 2
Logical Port 1 Logical Port 2
Differential- Port 1  S dd11 S d d1 2 S dc11 S dc12 
mode
Port 2
S S dd 22 S dc 21 S d c 22 
Response
 dd 21 
Common- Port 1  S cd11 S cd12 S cc1 1 S cc12 
mode
Port 2  
Response
 S cd 21
 S cd 22 S cc 21 S cc 22 
Naming Convention: S mode res., mode stim., port res., port stim.
1/29/2013 34

35. Mixed Mode S-Matrix: DD Quadrant
input reflection reverse transmission
 S dd 11 S dd 12 S dc 11 S dc 12 
 
 S dd 21 S dd 22 S dc 21 S dc 22 
 S cd 11 S cd 12 S cc 11 S cc 12

 
 S cd 21 S cd 22 S cc 21 S cc 22 
forward transmission output reflection
ı Describes fundamental performance in pure differential-mode operation
1/29/2013 35

36. Mixed Mode S-Matrix: CC Quadrant
input reflection reverse transmission
 S dd 11 S dd 12 S dc 11 S dc 12 
 
 S dd 21 S dd 22 S dc 21 S dc 22 
 S cd 11 S cd 12 S cc 11 S cc 12

 
 S cd
 21 S cd 22 S cc 21 S cc 22 

forward transmission output reflection
ı Describes fundamental performance in pure common-mode operation
1/29/2013 36

37. Mixed Mode S-Matrix: DC Quadrant
input reflection reverse transmission
 S dd 11 S dd 12 S dc 11 S dc 12 
 
 S dd 21 S dd 22 S dc 21 S dc 22 
 S cd 11 S cd 12 S cc 11 S cc 12

 
 S cd
 21 S cd 22 S cc 21 S cc 22 

forward transmission output reflection
ı Describes conversion of a common-mode stimulus to a differential-mode
response
ı Terms are ideally equal to zero with perfect symmetry
ı Related to the generation to EMI
1/29/2013 37

38. Mixed Mode S-Matrix: CD Quadrant
input reflection reverse transmission
 S dd 11 S dd 12 S dc 11 S dc 12 
 
 S dd 21 S dd 22 S dc 21 S dc 22 
 S cd 11 S cd 12 S cc 11 S cc 12

 
 S cd
 21 S cd 22 S cc 21 S cc 22 

forward transmission output reflection
ı Describes conversion of a differential-mode stimulus to a common-mode
response
ı Terms are ideally equal to zero with perfect symmetry
ı Related to the susceptibility of EMI
1/29/2013 38

39. 3-Port device
single ended  common / differential-mode
Single-ended differential-mode
common-mode
Port 1 Port 2
(unbalanced) DUT (balanced)
Single Diff.- Com.-
Ended mode mode
Stim. Stim. Stim.
Port 1 Port 2 Port 2
Single-ended
Response
Port 1  Sss11 Ssd12 Ssc12 
S Sdc22 
 ds21 Sdd22
Differential -
Port 2
Mode Response 
common-mode Port 2 Scs 21 Scd 22
 Scc22 

Response
1/29/2013 39

40. Measurement Examples: TrueDi vs.
VirDi
1/29/2013 40

41. Instrument Control of TruDi
1. Apply full n-port calibration,
e.g. with CalUnit
2. Configure balanced
Measurement
3. Switch to True differential
Mode
1/29/2013 41

42. Special Features of TruDi
ı Simultaneous display of VirDi
and TruDi S-Parameters
ı Same “calibration” for VirDi and
TruDi
ı Measurement of error corrected
S-Parameters and wave
quantities
(measure diff/comm power
with diff/comm stimulation)
ı Phase imbalance sweep
 P, f : fixed
  (max) = -180° to +180°
ı Magnitude imbalance sweep
 f : fixed
 P(max) = -10 dB to + 10 dBm
(max)

43. ZVA Coherent Sources
ı Coherence Mode
 allows to set an arbitrary phase
and amplitude between the
R&S®ZVA’s signals sources
ı R&S®ZVA-K6 True Differential
Option
ı Applications:
 Modulators
 Antenna beam forming
ı Realtime measurement
ı In R&S®ZVA67 four individual
phase shifts

44. Example 1: Tunable Active Filter
Trc18 Sdd21 dB Mag 0.5 dB / Ref -23 dB Ch1 Cal int 2 of 16 (Max)
Trc21 Sdd21 dB Mag 0.5 dB / Ref -23 dB Ch2 Cal int
Sdd21
-20.0
-20.5
-21.0
Gain compression
-21.5 true differential
-22.0
-22.5
-23.0
virtual differential
-23.5
-24.0
Ch1 Start -25 dBm — Freq 1 GHz Stop 0 dBm
Ch2 Start -28 dBm — Freq 1 GHz Stop -3 dBm
3/8/2007, 1:10 PM
True differential power axis has been shifted by -3 dB to equalize voltage amplitudes
1/29/2013 44

45. Tunable Active Filter
Trc18 Sdd21 dB Mag 2 dB / Ref -10 dB Ch1 Cal 2 of 16 (Max)
Trc21 Sdd21 dB Mag 2 dB / Ref -10 dB Ch2 Cal int
Sdd21
-2
-4 Trc18 Sdd21 dB Mag 2 dB / Ref -10 dB Ch1 Cal 2 of 16 (Max)
Trc21 Sdd21 dB Mag 2 dB / Ref -10 dB Ch2 Cal int
-6
Sdd21
-8 -2
-10 -4
-12 -6
-14 -8
-16 -10
-18 -12
-14
Ch1 Start 10 MHz — Pwr -20 dBm Stop 2 GHz
Ch2 Start 10 MHz — Pwr -23 dBm Stop -16
2 GHz
3/8/2007, 1:20 PM
-18
Ch1 Start 10 MHz — Pwr -10 dBm Stop 2 GHz
Ch2 Start 10 MHz — Pwr -13 dBm Stop 2 GHz
3/8/2007, 1:19 PM
• No difference between modes at low power (left),
• Higher gain for true mode at high power (right)
1/29/2013 45

46. S-Parameters vs. Input Power
Trc18 Sdd21 dB Mag 5 dB / Ref 0 dB Ca? 1 Trc19 Sdd21 dB Mag 5 dB / Ref 0 dB Cal int 2
Mkr 2
Sdd21
20 Mkr 1 6.96 dBm -4.893 dB Mkr Sdd21
2
20 Mkr 1 6.96 dBm -0.571 dB
Mkr 2 -29.76 dBm 16.145 dB Mkr 2 -29.76 dBm 16.577 dB
10 10
Mkr 1
0 Mkr 1 0
-10 -10
-20 -20
Ch3 Start -30 dBm Freq 1 GHz Stop 11 dBm Ch4 Start -30 dBm Freq 1 GHz Stop 11 dBm
Trc20 Scd21 dB Mag 5 dB / Ref -5 dB Ca? 3 Trc21 Scd21 dB Mag 5 dB / Ref -5 dB Cal int 4
Mkr Scd21
215 •Mkr 1 6.96 dBm -16.735 dB Mkr Scd21
215 Mkr 1 6.96 dBm -12.183 dB
Mkr 2 -29.76 dBm 6.742 dB Mkr 2 -29.76 dBm 7.575 dB
5 5
-5 -5 Mkr 1
Mkr 1
-15 -15
-25 -25
Ch3 Start -30 dBm Freq 1 GHz Stop 11 dBm Ch4 Start -30 dBm Freq 1 GHz Stop 11 dBm
Trc22 Scc21 dB Mag 1 dB / Ref -9 dB Ca? 5 Trc23 Scc21 dB Mag 1 dB / Ref -9 dB Cal int 6
Scc21
-5 Mkr 1 6.96 dBm -6.733 dB Scc21
-5 Mkr 1 6.96 dBm -8.351 dB
Mkr 1
Mkr 2 -29.76 dBm -9.186 dB Mkr 2 -29.76 dBm -8.244 dB
-7 Mkr 2 -7 Mkr 1
Mkr 2
-9 -9
-11 -11
-13 -13
Ch3 Start -30 dBm Freq 1 GHz Stop 11 dBm Ch4 Start -30 dBm Freq 1 GHz Stop 11 dBm
virtual differential mode true differential mode
1/29/2013 46

47. Phase Imbalance Sweep
Trc11 Sdd21 dB Mag 1 dB / Ref -5 dB Cal int 5 of 3 (Max)
Trc12 ac1 dB Mag 10 dB / Ref 0 dBm Cal int
Trc13 ad1 dB Mag 10 dB / Ref 0 dBm Cal int
ad1 Mkr 1 0.000000 ° -2.339 dB
Mkr 1 0.000000 ° -57.751 dBm
10
0 Mkr 1
-10
-20
-30
-40
-50
Mkr 1
-60
-70
Ch7 Phas Imb Start -180° Freq 1 GHz Pwr 0 dBm Stop 180°
1/29/2013 47

48. Phase & Magnitude Imbalance Sweep
Trc1 Sdd21 dB Mag 1 dB / Ref 10 dB Ch1 Cal int 1 of 1 (Max)
Trc2 Sdd21 dB Mag 1 dB / Ref 10 dB Ch2 Cal int
Trc3 bd2 dB Mag 0.5 dB / Ref 3 dBm Ch1 Cal int
Sdd21
15
14
13
12
11
10
9
8
7
Ch1 Ampl Imb Start -10 dB — —Freq 1 GHz Pwr -10 dBm Stop 10 dB
Ch2 Phas Imb Start -180° — Freq 1 GHz Pwr -10 dBm Stop 180°
1/23/2007, 4:54 PM
1/29/2013 48

49. Theoretical Verification
ı Approach:
 A model based analysis
 Analytical calculations using
MATLAB
 Experimental Verification
 Measurements
ı DUT
 The most simple bipolar
differential amplifier

50. Modeling the DUT
ı The two inputs / outputs can be regarded as common / differential inputs and
outputs
Gain of the individual amplifier
Compression and 3rd
order intermodulation
Sdd 21
ı a1 & afb determine the CMRR CMRR 
 ratio between differential mode and common mode voltage gain Scc 21
1/29/2013 50

51. Modeling the DUT
ı Feedback factor afb
1/29/2013 51

52. Modeling the DUT
ı Does not include a shared feed back (CMRR 0)
ı A system of two independent, ideally identical single-ended amplifiers
ı VirDi leads to underestimation!
Input referred 1-dB compression point
1/29/2013 52

53. TruDi « VirDi
ideal differential pair
I current sourced differential pair (CMRR ®∞)
I VirDi leads to overestimation!
1/29/2013 53

54. Experimental Verification: Amplifier Test Circuit
RE = 0  CMRR  0dB
RE = 27W  CMRR 16dB
1/29/2013 54

55. Experimental Verification
1/29/2013 55

56. Experimental Verification: Measurement Results
2,4dB
16dB
1/29/2013 56

57. Experimental Verification: Low CMRR
Trc1 Sdd21 dB Mag 10 dB / Ref 0 dB Ch1 Cal 1 of 1 (Max)
Trc2 Scc21 dB Mag 10 dB / Ref 0 dB Ch2 Cal
Sdd21 • M 1 600.00000 MHz 9.1983 dB
40
M 1 600.00000 MHz 3.8022 dB
30
20
M1
10 M1
0
-10
-20
-30
-40
Ch1 TrD Start 10 MHz — Pwr -25 dBm Stop 2 GHz
Ch2 TrD Start 10 MHz — Pwr -25 dBm Stop 2 GHz
1/29/2013 57

58. Experimental Verification: High CMRR
Trc1 Sdd21 dB Mag 10 dB / Ref 0 dB Ch1 Cal 1 of 1 (Max)
Trc2 Scc21 dB Mag 10 dB / Ref 0 dB Ch2 Cal
Sdd21 • M 1 600.00000 MHz 9.2649 dB
40
M 1 600.00000 MHz -26.255 dB
30
20
M1
10
0
-10
-20 M1
-30
-40
Ch1 TrD Start 10 MHz — Pwr -25 dBm Stop 2 GHz
Ch2 TrD Start 10 MHz — Pwr -25 dBm Stop 2 GHz
8/11/2010 4 39 PM
1/29/2013 58

59. Experimental Verification: Low CMRR
Trc1 Sdd21 dB Mag 2 dB / Ref 4 dB Ch1 Cal int PCai 1 of 1 (Max)
Trc2 Sdd21 dB Mag 2 dB / Ref 4 dB Ch2 Ca? PCai
Trac Stat: Trc1 Sdd21
Sdd21
Cmp In: -4.3 dBm
12 Cmp Out: 3.9 dBm
•Trac Stat: Trc2 Sdd21
10 Cmp In: -4.7 dBm
Cmp
Cmp Out: 3.3 dBm
Cmp
8
6
4
2
0
-2
-4
Ch1 TrD Start -25 dBm — Freq 600 MHz Stop 10 dBm
Ch2 Start -25 dBm — Freq 600 MHz Stop 10 dBm
1/29/2013 59

60. Experimental Verification: High CMRR
Trc1 Sdd21 dB Mag 2 dB / Ref 4 dB Ch1 Cal int PCai 1 of 1 (Max)
Trc2 Sdd21 dB Mag 2 dB / Ref 4 dB Ch2 Ca? PCai
Trac Stat: Trc1 Sdd21
Sdd21
Cmp In: -4.1 dBm
12 Cmp Out: 4.2 dBm
•Trac Stat: Trc2 Sdd21
10 Cmp In: -1.0 dBm
Cmp Cmp Out:
Cmp
7.1 dBm
8
6
4
2
0
-2
-4
Ch1 TrD Start -25 dBm — Freq 600 MHz Stop 10 dBm
Ch2 Start -25 dBm — Freq 600 MHz Stop 10 dBm
1/29/2013 60

61. Summary and Conclusions
1/29/2013 61

62. Summary: TruDi vs. VirDi
ı Passive Devices/Linear operation
 TruDi and VirDi give exactly the same results
ı Active Devices/Non-linear operation
 Significant difference between TruDi and VirDi
 TruDi represents the real operating conditions of a device
ı TruDi Measurements
 Requires two (or more) phase coherent sources
 Ability to scan amplitude and phase independently
 Relative phase stability of VNA sources is crucial for reproducible results
1/29/2013 62

63. Thank you for your Attention
More information
Rohde & Schwarz boot # 701
http://www.rohde-schwarz.com
Chris Scholz
Christopher.scholz@rsa.rohde-schwarz.com
(817) 422 2512

64. Appendix: De/Embedding
1/29/2013 64

65. (De)Embedding - Matching Networks
ı Challenges of Fixtures
 Mask true device behavior
 No well characterized
ı Disadvantages of Physical Matching Networks:
 Poor reproducibility
 Narrow band
 Restricted to low frequencies
 Inflexible (one network for one frequency range)
ı Use of theoretically Embedded Matching Networks:
 Both Embedding and Deembedding
 Highest degree of flexibility to integrate networks
 No frequency restriction
 Possible disadvantages just with active devices
1/29/2013 65

66. Introduction: Embedding
DUT
DUT
+ Test Fixture
+ Matching Networks
Matching Networks
 not present as hardware
 but represented by calculation
Available Networks: network analyzer
1 DUT
• Import of arbitrary S-parameter files
Port 2
Port 1
• Use of predefined matching networks
DUT
DUT
+ Test Fixture

67. Introduction: Deembedding
Response of networks network analyzer
 not corrected by calibration
 corrected by calculation
w/o calibration or deembedding
w/o calibration or deembedding
Reference plane at POR T 1
Reference plane at POR T 2
DUT
Response of test
fixture, strip lines etc.
• Import of S-parameter files
(gained e.g. using a SW design tool)
• Use of predefined networks
Shift of reference plane
by Deembedding
(or alternatively via calibration)

68. (De)Embedding Networks
(single ended DUTs)
Single Ended Port
(De)Embedding
 Import of *.s2p files
ı 8 predefined networks

69. (De)Embedding Networks
(single ended DUTs)
Pre-defined matching networks

70. (De)Embedding Networks
(differential DUTs)
Balanced Port
(De)Embedding
ı Import of *.s4p
files
 12 predefined
networks

71. (De)Embedding Networks
(differential DUTs)
Pre-defined matching networks

72. Appendix 2: Measurement Wizard
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73. Measurement Wizard
Step 1 : Selection of test
configuration

74. Measurement Wizard
Step 2 : Impedance Settings

75. Measurement Wizard
Step 3 : Selection of S-Parameters

76. Measurement Wizard
Step 4 : General Settings

77. Measurement Wizard
Step 5 : Bandwidth and Power
Setting

78. Measurement Wizard
Step 6 : Calibration

79. Measurement Result (1)
Measurement result of SAW Filter

80. Measurement Result (2)
Automatic Amplitude and Phase Imbalance
Measurement