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Overview of Mixer Measurements

Overview of Mixer Measurements. Joel Dunsmore Solution Architect – Wireless Business Unit June, 2002 Some additions by Doug Rytting. Agenda. Mixer Characteristics Traditional Mixer Measurement Techniques New Concepts in Mixer Characterization Test Results

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Overview of Mixer Measurements

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  1. Overview of Mixer Measurements Joel DunsmoreSolution Architect – Wireless Business UnitJune, 2002 Some additions by Doug Rytting

  2. Agenda • Mixer Characteristics • Traditional Mixer Measurement Techniques • New Concepts in Mixer Characterization • Test Results • Comparison & Complete Mixer Measurements • Image Mixer Appendix

  3. Mixer Characteristics • Conversion Measurements • Magnitude Response • Phase Response • Group Delay • Input Match • Output Match • Isolation • Spurious Mixing Products

  4. Conversion loss power level frequency 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.

  5. Agenda • Mixer Characteristics • Traditional Mixer Measurement Techniques • New Concepts in Mixer Characterization • Test Results • Comparison & Complete Mixer Measurements • Image Mixer Appendix

  6. Gd = - fe ¸ (360 * fmod) LO DUT Measuring Conversion Phase and Group Delay: AM Technique Phase Detector AM Modulator RF Measure phase between two demodulated signals Sweep fmod

  7. Gd = - fe ¸ (360 * fmod) LO DUT Measuring Conversion Phase and Group Delay: FM Technique Phase Detector Demod Frequency Modulator RF Demod Measure phase between two demodulated signals Sweep fmod

  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

  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 Mxr B Mxr A Mxr C Mxr A Mxr B Mxr C *US Patent 6,064,694

  10. Agenda • Mixer Characteristics • Traditional Mixer Measurement Techniques • New Concepts in Mixer Characterization • Test Results • Comparison & Complete Mixer Measurements • Image Mixer Appendix

  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

  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

  13. Measure Mixer+Filter and Open Open

  14. Measure Mixer+Filter and Open

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

  16. Measure Mixer+Filter and Short

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

  18. Measure Mixer+Filter and Load

  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

  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: • Un-wrap phase • Use delay to project DC phase • Offset phase by DC phase (assume phase = 0 at DC) • Divide phase by 2 • Re-wrap phase (easy, express in polar form) • We call this result T1 which is also equal to T2

  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) CalibrationPlanes

  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

  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.

  24. Agenda • Mixer Characteristics • Traditional Mixer Measurement Techniques • New Concepts in Mixer Characterization • Test Results • Comparison & Complete Mixer Measurements • Image Mixer Appendix

  25. Comparison Measurement:Mixer+Airline Mixer with Airline and vector cal: Gray Trace Mixer with Airline, normalization: Blue Trace

  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 the new method

  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)

  28. Agenda • Mixer Characteristics • Traditional Mixer Measurement Techniques • New Concepts in Mixer Characterization • Test Results • Comparison & Complete Mixer Measurements • Image Mixer Appendix

  29. Comparison Mixer Measurements Characterization of calibration mixer Mixer comparison network analyzer Test Path Ref Path or Golden-Mixer Test-Mixer After Cal

  30. Comparison Mixer Measurements

  31. Complete Mixer Characterization

  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.

  33. Agenda • Mixer Characteristics • Traditional Mixer Measurement Techniques • New Concepts in Mixer Characterization • Test Results • Comparison & Complete Mixer Measurements • Image Mixer Appendix

  34. Consider “Hi-side” LO mixersFor image mixers note the frequency sweep reversal,which implies phase conjugation

  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.

  36. Image Mixer Definition of Waves

  37. aIM aIM aIF aIF bIM bIM bIF bIF SIF SIF* aLO aLO New Rule for Image Mixers

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

  39. S21 CharacterizationWith and without an added airlineand with and without using the conjugate of the load

  40. Precision Match IF IM LO S22 CharacterizationShows the proper response whenextracted with the conjugate load technique

  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

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