Slide 1 Overview of Mixer Measurements Joel Dunsmore Solution Architect – Wireless Business Unit June, 2002 Some additions by Doug Rytting

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


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




Test Results



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




Test Results



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




Test Results



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




Test Results



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




Test Results



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

Documents

Slide 1 Overview of Mixer Measurements Joel Dunsmore Solution Architect – Wireless Business Unit June, 2002 Some additions by Doug Rytting