Investigation of Chireix PA performances by testing one branch variable load amplifier

In this paper, an analytic work is presented showing mathematically an approach where the impedance variation at the input of the Chireix combiner in function of the original phase is studied taking into account reflections between the combiner and the amplifiers. In order to prove that approach, two different experimental works are done. The first is done using one branch amplifier with variable load impedance and the second using LINC amplifier with Chireix combiner without stubs. Indeed, in the experimental work, an advanced load pull implementation tools is used where a computer controlled tuner is connected at the amplifier output in order to produce the desired load impedance. Also, a series power meter, network analyzer and RF sources were used to accomplish these measurements. The output power and the efficiency obtained from both measurements are compared and very good agreement between them is shown.