Accelerated Design of High-Efficiency RF Power Amplifiers Using Nonlinear Embedding
It is now well established that PA designers need to control the internal mode of operation of transistors at the current-source (IV) reference-planes to optimize the efficiency of a power amplifier. The typical approach has been to rely on multi-harmonic load and source pull while monitoring the load lines at the current-source reference planes. However given the tremendously huge search space for the load and source multi-harmonic terminations required to find the desired internal waveforms, it is greatly preferable to use a nonlinear embedding device model to obtain in a single simulation the required multi-harmonic voltage and current waveforms at the transistor measurement (package or extrinsic) reference-planes that realizes the desired mode of operation at the current-source reference-planes. Nonlinear embedding device models enable then the practical implementation of waveform engineering. Designers are reporting that the design time is reduced by a factor ten. Furthermore it is possible to implement automatic algorithms for the initial design of complex multi-transistor PA such as Doherty and Chireix PAs. Recently reported examples of such designs for 2-way Doherty and 2-way Chireix power amplifiers will be reviewed to demonstrate how this technique stream lines the design of PAs. New applications of the embedding methodology to the design of 4-way Chireix amplifiers and optimal class F will also be presented.