PA design using Simulation-Based Nonlinear-Embedding: Trust but Verify with NVNA Measurements
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 power amplifiers. Instead of relying on time-consuming multi-harmonic load and source pull simulations, it now possible 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 enables then the practical implementation of waveform engineering. However this approach remains limited by the accuracy of the device model. A new trust and verify approach can then be used in complement to the embedding PA design methodology to verify and optimize the PA design. This is done by fine tuning the large signal operating point (LSOP) using the predicted harmonic and source termination predicted. The PA design can then be completed using the measured optimal current and voltage data obtained at peak and back off. An example using a new optimal class F theory recently reported for realistic transistors will be presented together with its applications to the optimal design of Chireix and Doherty PAs.