Slide 1 Overview of Mixer Measurements Joel Dunsmore Solution 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 Measurements Magnitude Response Phase Response Group Delay Input Match Output Match Isolation Spurious Mixing Products

Slide 4 Mixer Conversion Measurements Conversion 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 power 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 RFRF AM Modulator f mod Swee p LO DUT Measure phase between two demodulated signals Gd = - e (360 * fmod) Phase Detector

Slide 7 Measuring Conversion Phase and Group Delay: FM Technique RFRF Frequency Modulator f mod Swee p LO DUT Measure phase between two demodulated signals Gd = - e (360 * fmod) Phase Detector Demod

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 Technique Described 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 B 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

Slide 13 Measure Mixer+Filter and Open Open

Slide 14 Measure Mixer+Filter and Open

Slide 15 Measure Mixer+Filter and Short (with Open still shown) Short Open

Slide 16 Measure Mixer+Filter and Short

Slide 17 Measure Mixer+Filter and Load (with Open and Short still shown) Short Open Load

Slide 18 Measure Mixer+Filter and Load

Slide 19 From the corrected measurements a 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 easy Phase of mixer S21 is more difficult Complex phase has two roots To choose the proper root: 1. Un-wrap phase 2. Use delay to project DC phase 3. Offset phase by DC phase (assume phase = 0 at DC) 4. Divide phase by 2 5. Re-wrap phase (easy, express in polar form) We call this result T1 which is also equal to T2

Slide 21 If your mixer is reciprocal: Done! If not, you can use the reciprocal cal mixer to calibrate a VNA Set up a VNA with Up/Down converter Step One: Using normal VNA techniques, obtain ERF, ESF, and EDF (all at RF Frequency), and ELF (at IF Frequency) Calibration Planes

Slide 22 Step Two: Measure the uncorrected response of the cal mixer, S21 M1 Place calibration mixer in path, and measure S21 M1 Calculate ETF from the known mixer terms, error terms, and S21 M1

Slide 23 Download cal terms and 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 Trace Mixer with Airline, normalization: Blue Trace

Slide 26 Calibration Mixer Characterization: Amplitude Compared with Power Meter Measurements Mixer Measured as up and down converter, using power meter measurements. Black trace is the average of up/down conversion Mixer Measured as up and down converter, using the new 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-Mixer After Cal Test Path Ref Path or Golden-Mixer Characterization of calibration mixerMixer comparison network analyzer

Slide 30 Comparison Mixer Measurements

Slide 31 Complete Mixer Characterization Int Source Int LO Meas S 11 RF b 0 /a 0 S 21 RFIFb 3 /a R S 12 IFRFb 0 /a R S 22 IF b 3 /a 3

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 mixers For 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 M ixer Definition of Waves

Slide 37 New Rule for Image Mixers a LO a IF b IF a IM b IM S IF* a LO a IF b IF a IM b IM S IF

Slide 38 Take the Conjugate of the Load Simple rules for dealing with moving a reflection from the output of an image mixer to its input

Slide 39 S 21 Characterization With and without an added airline and with and without using the conjugate of the load

Slide 40 S 22 Characterization Shows the proper response when extracted with the conjugate load technique

Slide 41 Image Mixer Summary Common mixer measurement techniques lack the ability to accurately measure phase or delay of mixers A 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