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60 GHz mixed signal active load pull for millimeter wave devices characterization


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Master thesis presentation held on 16-05-2012. In this work a prototipe for a mm-wave mixed signal active load pull working in the frequency range from 50 to 65 GHz is presented. Further work has been accomplished on the topic, and a final version of the measurement setup has been presented at 81st and 83rd ARFTG conferences.

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60 GHz mixed signal active load pull for millimeter wave devices characterization

  1. 1. Università degli studi di Napoli Federico II FACOLTÀ DI INGEGNERIA CORSO DI LAUREA SPECIALISTICA IN INGEGNERIA ELETTRONICA 60 GHz mixed signal active load pull for millimeter wave devices characterization RELATORE CANDIDATO Prof. Niccolò Rinaldi Luca Galatro Matr. 884/372 CORRELATORE Prof. Marco Spirito
  2. 2. The Load-Pull Technique  Load pull is the measurement technique where the load impedance is varied as the performances of the DUT are measured  The purpose is to determine the ideal matching network impedances when the device is driven into large signal operations  Useful for determining the DUT operating characteristics and design parameters for a given drive level and termination.
  3. 3. Passive Load-Pull Power Meter Power Meter Signal Generator Tuner Tuner DUT Reference planes •Passive Networks to synthesize the desired loading condition •Allows medium and high power measurements Drawbacks •Slow (Mechanical Tuning) •Limitations on high Gamma values Tuners must be placed as close as possible to the DUT!
  4. 4. Active Load-Pull  Synthesizes the reflection coefficient at the output reference plane by means of an auxiliary signal injected into the DUT output  No costraints on the reflection coefficient magnitude  Fast active tuning  Closed Loop and Open Loop
  5. 5. Active Load-Pull – Closed Loop LOS S ϕ b2 a2 ϕ LOSS Closed Loop • Amplified and phase shifted version of b2 used as a2 • Independent control for amplitude and phase of the load reflectance Fast tuning • Feedback topology Instability • High linearity amplifiers
  6. 6. Active Load-Pull – Open Loop LOS S ϕ b2 a2 ϕ LOSS Open Loop • The source signal is splitted, the two resulting signals are amplified and phase shifted to obtain a1 and a2 • Need for iterative approximations • No feedback – No instability •No need of linear
  7. 7. Issues  Electrical Delay  Physical Impedance far from the DUT  Electrical length brings rapid phase variations vs. frequency  Dynamic Range  When working with harmonics and high linearity devices, a wide dynamic range is needed to correctely measure all the harmonics
  8. 8. Mixed Signal Active Load-Pull Digital A/DDigital AWG Digital AWG I signal Q signal Q signal I signal RF RF To RF To LO RF source LO source LO LO L O LO a1 b1 a2 b2 aREF • Low frequency and wideband generation and acquisition •Upconversion with IQ mixers – modulated signals can be used •No phase variations due to electrical delays in the signal paths • Low frequency acquisition allows to reduce costs and to improve the flexibility (low frequency signal manipulation is possible)
  9. 9. Project Outline  Realization of a fully synchronized signal generator module for the I and Q signals generation using FPGA based modules  Design of a 60 GHz Mixed Signal Active Load Pull system  Realization of a VNA interface for signal acquisition  Modification of an existent load-pull software for the project specifications  Realization of a prototype
  10. 10. Signal Generation  All the injected signals have to be locked in phase exhibiting no phase drift among each other Synchronization RF source sharing I and Q signals synchronization
  11. 11. Signal Generation NI Flex-RIO Modules FPGA Module Adapter Module (Digital and Analog I/O) LabVIEW FPGA Custom controls and measurement hardware without any prior knowledge about Hardware Description Language
  12. 12. System Architecture Digital AWG Digital AWG I signal Q signal Q signal I signal RF RF To RF RF source a1b1a2b2 x3 VNA PA PAHPA DUT Reference planes • Mixed signal generation • VNA acquisition • x3 multiplication in the LO loop – lower frequency generation • Attenuators to exploit mixer’s dynamic range • HPA in the output loop to maximize the system’s dynamic range • Waveguide Structure
  13. 13. System Design
  14. 14. System Design
  15. 15. System Design
  16. 16. System Design
  17. 17. VNA Acquisition  VNA acquisition to take advantage of the internal IF downconversion mixers so to cut down the costs  GPIB controllable  Need for a special software interface  Real Time measurements not allowed  Low IF bandwidth control
  18. 18. Gamma convergence routine •Any desired reflection coeffient behavior vs. frequency can be created by iteratively adjusting amplitude and phase of the injected waveform independently at each frequency component of interest. • Optimization by means of subsequent iterations • Injection and acquisition in the time domain • I and Q definition, error checking and optimization in the frequency domain
  19. 19. The Prototype • Hybrid waveguide- coaxial setup •Signal acquisition performed using VNA
  20. 20. The Prototype •First waveguide stage: Multiplication – Signal splitting – IQ upconversion – Attenuation for IQ voltage swing maximization
  21. 21. The Prototype •Second waveguide stage: Signal amplification – Reflectometer for a and b waves coupling
  22. 22. The Prototype •Third waveguide stage: DUT connection
  23. 23. Measurement Results • Millitech AMP 15-02100 amplifier Frequency range 50 to 66 GHz Nominal Gain 22 dB P1dB at 15 dBm • 41 loading condition • Input power sweep from -15 dBm to -7dBm • Measurements @ 54-57-60 GHz
  24. 24. Measurement Results @ 60 GHz @ 54 GHz @ 57 GHz
  25. 25. Conclusions  Design of 60 GHz Mixed Signal Active Load- Pull  Large Signal Measurements for mm-wave devices  High dynamic range  No phase variations  Relatively fast  High ruggedness  Prototype realization and design  Proved software functionality, stability and ruggedness
  26. 26. Future Works  Realization of the full waveguide structure  On wafer measurements  Multitone and Modulated signals measurements  Introduction of external IF mixers and low frequency acquisition  On board signal processing, exploiting Flex- RIO modules capabilities