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Doherty and Chireix power amplifier design using an embedding device model
17-Mar-2016 16:00 16:00
Age: 5 yrs




Prof. Patrick ROBLIN - jeudi 17 mars à partir de16h en salle 3103 à l'ESIEE


Abstract:

Amplifiers based on multiple transistors/amplifiers such as the Doherty, are being used to realize amplifiers with high efficiency at high power backoff. Other techniques such as Chireix/Outphasing are also being explored.
These techniques rely on various form of load modulation to maintain the high efficiency over a wide range of power. The Doherty and Chireix theory is usually introduced using ideal memoryless transistor or amplifier models.  Much optimization effort or load-pull search is then taking place to make these amplifying schemes work with real transistors and amplifiers (class B, C, E or F) which exhibit high-frequency memory effects due to the nonlinear transistor capacitances and the linear device and package parasitics.  On the contrary with the model-based embedding PA design technique, the PA  design starts with the intrinsic RF IV characteristics of the transistor.   Resistive parasitics can be included if harmonic injection is not targeted.  The multi-transistor PA is then first designed using the intrinsic IV for each transistor to achieve the desired Doherty (or Chireix) operation.  The intrinsic voltage and current waveforms are then projected to the package planes using the nonlinear embedding device model.  This projection determines in a single simulation the required waveforms at the package reference planes which sustain the desired intrinsic transistor operation.  A loss-less multi-harmonic matching network can then be synthesized to reproject the multi-harmonic complex loads required at the package planes back to the ideal resistive loads required at the Doherty (or Chireix at specific input power levels) combiner.  Practical design examples for both the Doherty and the Chireix amplifier (unpublished) will be presented to show how using this systematic PA design procedure the design is performed without using time-consuming optimizations or load-pull searches.
Current research interested is concerned with the application of this method to wide-band Doherty amplifier design.








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