Analytical Design Methodology of Outphasing Amplification Systems Using a New Simplified Chireix Combiner Model

An analytical design methodology of outphasing amplification systems is proposed using new simplified analytical expressions for the instantaneous efficiency and the input/output voltages of Chireix outphasing combiners. These expressions are derived first for ideal voltage sources with nonzero internal impedance and later for ideal Class-B amplifiers where dc current variation is incorporated. They take into account the impedance mismatch between the amplifiers and the lossless combining structure and account explicitly for the all of the combiner's electrical parameters. We show that the maximum achievable instantaneous combining efficiency can be controlled in position and in value through the judicious choice of the combiner's stub length and transmission-line characteristic impedance. We further show that, when this choice is combined with the amplified signal's distribution, the average combining efficiency can be precisely controlled and easily maximized. Various validations of the proposed expressions are performed by comparison with experimental and simulation results for various combiners as well as for a complete linear amplification with nonlinear components amplifier. Excellent agreement between simulations and measurements is obtained in all cases considered.