Impact of PA Mismatching in Chireix-Outphasing System without Stubs

In this paper; new expressions for the Chireix combiner without stubs are derived to study the impact of the combiner mismatching to the efficiency and the linearity of the system. We show analytically that the Chireix outphasing combiner without the shunt reactance is perfectly linear but the instantaneous efficiency degrades when impedance mismatching between the combiner and the PA occurs. We varied the length and the impedance of the lambda/4 transmission line of the Chireix combiner consequently we can see by using ADS software that the system stays linear and the best efficiency exist at length of lambda/4 and impedance of 1.4Z₀. In the other hand, we note that the efficiency is reduced and is at the best equal to that of the hybrid combiner. This work is validated through simulation with ADS software using CDMA and multi-tones and one tone 2 GHz envelope modulated signals.