Design of a 4-Way Chireix Amplifier using a Nonlinear Embedding Device Model

The inspection of the current and voltage waveforms at the current source reference planes of transistor models provides power amplifier (PA) designers with useful insights for identifying the class of operation of PAs. However when a specific class of operation at the current source reference plane is targeted, time-consuming multi-harmonic load-and source-pull simulations are required. Alternatively if the design is started at the current source reference planes for the targeted class of operation and PA architecture, the load and source multiharmonic terminations at the package reference planes for a given power level for a given can be calculated in a single simulation with the help of an embedding device model. The application of the embedding device model to the design of a 4-way Chireix prototype is explored to facilitate the co-design of the 4 amplifiers and the 4-way Chireix combiner. The 4-way Chireix PA is thus first designed at the current source reference planes. The phase of the excitations driving the 4-way Chireix PA are obtained from the eigenvalues of the impedance matrix of the 4 port loaded Chireix combiner designed. The validity of the intrinsic design is verified with harmonic balance simulations. The efficiency of the 4-way Chireix amplifier at the package reference planes for an ideal circuit implementation is then predicted with the help of the embedding device model and found to degrade by 2-4% compared to the efficiency at the current source reference planes.