Mitigation of Load Mismatch Effects Using an Orthogonal Load Modulated Balanced Amplifier

This article presents an orthogonal load-modulated balanced amplifier designed to mitigate the effects of the load mismatch on the power-added efficiency and output power of the amplifier. This is achieved by electronically adjusting the ratio between the two input signals of the power amplifier (PA) (in phase and amplitude) and the reactive termination at the output nominally isolated port. The mode of operation of the PA is described using a theoretical analysis that highlights the role of the different tuning parameters and is confirmed by simulations using a simplified transistor model. The design and characterization under load mismatch of a prototype PA, working in the 1.6-3.2 GHz band are described and the experimental results compared to those of an analogous balanced PA, where it is shown that the orthogonal balanced amplifier is able to increase substantially the mismatch region on which a given target performance is achieved.