Download - Overview of Mixer Measurements
Slide 1
Overview of Mixer Measurements
Joel DunsmoreSolution Architect – Wireless Business Unit
June, 2002
Some additions by Doug Rytting
Slide 2
Agenda
Mixer Characteristics
Traditional Mixer Measurement Techniques
New Concepts in Mixer Characterization
Test Results
Comparison & Complete Mixer Measurements
Image Mixer Appendix
Slide 3
Mixer Characteristics
Conversion MeasurementsMagnitude Response
Phase Response
Group Delay
Input Match
Output Match
Isolation
Spurious Mixing Products
Slide 4
Mixer Conversion MeasurementsConversion gain is the ratio of desired-image power to applied input power
Since the input and output frequencies are not the same, the definition of conversion phase can be confusing. We define the conversion phase as the phase shift of the output, were it synchronously reconverted to the input frequency with an ideal (zero phase shift) converter.
frequency
pow
er
level
Conversion loss
Slide 5
Agenda
Mixer Characteristics
Traditional Mixer Measurement Techniques
New Concepts in Mixer Characterization
Test Results
Comparison & Complete Mixer Measurements
Image Mixer Appendix
Slide 6
Measuring Conversion Phase and Group Delay: AM Technique
RFAM
Modulator
fmod
Sweep
LO
DUT
Measure phase between two demodulated signals
Gd = - e (360 * fmod)
Phase Detector
Slide 7
Measuring Conversion Phase and Group Delay: FM Technique
RFFrequenc
y Modulato
r
fmod
Sweep
LO
DUT
Measure phase between two demodulated signals
Gd = - e (360 * fmod)
Phase Detector
DemodDemod
DemodDemod
Slide 8
Up/Down Conversion with Equal Mixers
Requires Image filter
Requires two matched mixers
Mixers must be reciprocal
Assume that Mixer1 = Mixer2
Must remove filter effects
Must have accessible (or identical) LOs
Slide 9
Three Mixer TechniqueDescribed by Clark, et al, in Microwave Journal, Nov 1996*
Requires 3 mixers, One of which MUST be reciprocal
Requires filtering of images
Does not correct for mismatch between mixers
Must remove filter effects
*US Patent 6,064,694
Mxr A
Mxr A
Mxr B
Mxr B
Mxr C
Mxr C
Slide 10
Agenda
Mixer Characteristics
Traditional Mixer Measurement Techniques
New Concepts in Mixer Characterization
Test Results
Comparison & Complete Mixer Measurements
Image Mixer Appendix
Slide 11
New Concept in Mixer Characterization (Patented)
Requires a Reciprocal Calibration Mixer
Requires an image filter for Calibration Mixer
No other restrictions
Currently supported in the Agilent PNA family
External or Internal LO source
Ref Standards
IF Filter
Slide 12
Mixer Calibration: Only calibrated reflection measurements are
made.
RF signal is reflected off the input of mixer: does not change with load.
IF + signal is converted and then reflected off image filter: does not change with load
IF – signal is converted, passes through the IF- filter reflects off load: Changes With Load
FromVN A
IF-=R F-LO
LO
IF+R F
IF-O ,S,L
O
S
L
Slide 13
Measure Mixer+Filter and Open
Open
Slide 14
Measure Mixer+Filter and Open
R F R eflection
IF+ R eflectionO pen M easurem nt
IF- R eflection*
(S 22*open 2 )
Slide 15
Measure Mixer+Filter and Short(with Open still shown)
Short
Open
Slide 16
Measure Mixer+Filter and Short
R F R eflection
IF+ R eflection
S hort M easurem nt
IF- R eflection*S
(S 22*s2)
Slide 17
Measure Mixer+Filter and Load(with Open and Short still shown)
Short
Open
Load
Slide 18
Measure Mixer+Filter and Load
R F R eflection
IF+ R eflection
Load M easurem ent
Slide 19
From the corrected measurementsa 1-port error model is extracted
By Definition, S11 = EDF, also called D
ESF = Mixer S22, also called M
ERF = Mixer S21 * Mixer S12; Mixer S21 is also called T1 Mixer S12 is also called T2
Error terms include effects of filter and mixer
Slide 20
Calculate T1(mixer S21)Take the square root of ERF (not so easy)
Mag of mixer S21 is easyPhase of mixer S21 is more difficult
Complex phase has two rootsTo choose the proper root:1. Un-wrap phase2. Use delay to project DC phase3. Offset phase by DC phase (assume phase = 0 at DC)4. Divide phase by 25. Re-wrap phase (easy, express in polar form)
We call this result T1 which is also equal to T2
| 21| RFS E
Slide 21
If your mixer is reciprocal: Done!If not, you can use the reciprocal cal mixer to calibrate a
VNASet up a VNA with Up/Down converterStep One: Using normal VNA techniques, obtain ERF, ESF, and EDF (all at RF Frequency), and ELF (at IF Frequency)
CalibrationPlanes
Slide 22
Step Two:Measure the uncorrected response of the cal mixer, S21M1
Place calibration mixer in path, and measure S21M1
Calculate ETF from the known mixer terms, error terms, and S21M1
1( 21 / 1)
(1 1 2 )TF M
LF SF SF LF SF LF
E S T
M E D E E T T E E M D E
Slide 23
Download cal termsand turn on 2-port cal
During calibration ETF is corrected for source match, mixer input match, mixer output match, and load match. Also ERF, ESF, EDF and ELF were calculated at the VNA ports.
ELR, ESR, EDR terms are set to 0 and ETR and ERR are set to 1 since S12 and S22 are not measured.
Provides an input-match-corrected transmission and reflection measurement.
Mixer output-match and reverse-transmission not measured.
Allows real time vector measurements of mixer.
Slide 24
Agenda
Mixer Characteristics
Traditional Mixer Measurement Techniques
New Concepts in Mixer Characterization
Test Results
Comparison & Complete Mixer Measurements
Image Mixer Appendix
Slide 25
Comparison Measurement:Mixer+Airline
Mixer with Airline and vector cal: Gray TraceMixer with Airline, normalization: Blue Trace
Slide 26
Calibration Mixer Characterization: Amplitude Compared with Power Meter Measurements
Mixer Measured as up and downconverter, using power meter measurements. Black trace is the average of up/down conversion
Mixer Measured as up and down converter, using thenew method
Slide 27
Calibration Mixer Characterization:Phase response and Group Delay
Phase Response of Mixer,(Measured as up and down converter)
Group Delay Response of Mixer, (Measured as up and down converter)
Slide 28
Agenda
Mixer Characteristics
Traditional Mixer Measurement Techniques
New Concepts in Mixer Characterization
Test Results
Comparison & Complete Mixer Measurements
Image Mixer Appendix
Slide 29
Comparison Mixer Measurements
Test-MixerAfter Cal
Test Path
Ref Path
orGolden-Mixer
Characterization of calibration mixer Mixer comparison network analyzer
Slide 30
Comparison Mixer Measurements
Slide 31
Complete Mixer Characterization
Int Source
Int LO
a0
b0 b3Port - 1RF
Port - 2IF
a3
a2
a1
b1
b2
Cal orTest-Mixer
aRExt LO
Ext LO
Int LO
Sync Mixer
Int Source
Int
LO
Meas
S11 RF RF b0/a0
S21 RF IF b3/aR
S12 IF RF b0/aR
S22 IF IF b3/a3
Slide 32
Summary
Common mixer measurement techniques lack the ability to accurately measure phase or delay of mixers.
A new technique, based on reflection measurements, resolves this problem, and provides accurate and repeatable measurements of reciprocal mixers for both magnitude and phase response.
Mixers characterized in this way can be used to calibrate test systems, such that non-reciprocal mixers can be measured for phase and absolute delay.
Comparison mixer characterization was described.
Complete mixer characterization approach was proposed.
Slide 33
Agenda
Mixer Characteristics
Traditional Mixer Measurement Techniques
New Concepts in Mixer Characterization
Test Results
Comparison & Complete Mixer Measurements
Image Mixer Appendix
Slide 34
Consider “Hi-side” LO mixersFor image mixers note the frequency sweep reversal,
which implies phase conjugation
Slide 35
Mixer Characterization for an Image Mixer:Very poor result for extracted S22, but only when use
characterized (Ecal) devices (not mechanical standards)
S22 from VNA
S22 from
Mixer char.
Slide 36
Image Mixer Definition of Waves
11 12* **
21 22
IF IFIF IFLO
IF IFIM IMLO
b aS a S
b aa S S
* * *
0
0LOIF IF
LOIM IM
ab a
ab a
Slide 37
New Rule for Image Mixers
aLO
aIF
bIF
aIM
bIM
SIF*
aLO
aIF
bIF
aIM
bIM
SIF
Slide 38
Take the Conjugate of the LoadSimple rules for dealing with moving a reflection from the
output of an image mixer to its input
Slide 39
S21 CharacterizationWith and without an added airline
and with and without using the conjugate of the load
-15
-14
-13
-12
-11
-10
8.4 8.5 8.6 8.7 8.8 8.9 9.0
Using L
*
Using L
Image Frequency (GHz)
Me
asu
red
tra
nsm
issi
on
co
eff
icie
nt
(dB
)
LO
IF+RF
IF- Airline
Re-reflectedsignal
Slide 40
S22 CharacterizationShows the proper response when
extracted with the conjugate load technique
LO
IMIF
PrecisionMatch
Slide 41
Image Mixer SummaryCommon mixer measurement techniques lack the ability to accurately measure phase or delay of mixersA previous technique based on reflection measurements resolves this problem, and provides accurate and repeatable measurements of reciprocal mixers for both magnitude and phase response, but fails to give the correct response for “image” mixers.That technique is modified to account for the phase reversal of image mixers, namely by using the conjugate of the reflection loads.A theory of image mixer conversion parameters has been introduced, which predict and account for the phase-reversal effects.Several measurements verify the new technique, and underlying theory