Through‐line method for transmission/reflection estimation of N ‐way multiport power‐combining network

Abstract

A transmission/reflection estimation method based on ‘through‐line’ measurements is proposed for N‐way tree‐shaped power‐combining network, mainly used as an output impedance‐matching network of a multi‐transistor‐cell power amplifier (PA). The method can be applied when all the N branches can be seen identical to each other and are excited uniformly in‐phase, and especially useful when the input impedance of the network has a non‐resistive (reactance) component. In the proposed method, a pair of the N‐way networks is connected directly in a back‐to‐back manner (‘through’ configuration) and with transmission lines in‐between (‘line’ configuration), and their S‐parameters are measured. The transmission/reflection coefficients of single N‐way network can be estimated from the measured ‘through’ and ‘line’ S‐parameters, where in the latter the electromagnetic coupling between the transmission lines should be dealt with carefully to avoid estimation error.