Augmentation of Class-E PA reliability under load mismatch conditions

Class-E PAs present significant efficiency advantages over other PA topologies, but are sensitive to load mismatch. Extreme cases of load mismatch can lead to reliability issues. In this work, a system for automatically compensating for load variations in Class E PAs, to increase reliability aspects, was developed. This work extends current research work by Ali Ghahremani. A proof of concept demonstrator was built, using class-E PA chips that were previously designed in the SHERPAS research project. To confirm the theory, a measurement setup was developed where load mismatch was reliably set using a PC-controlled antenna tuner setup. A PC-connected oscilloscope, with an active differential probe, was be used to sense the peak drain voltage of the PA. The obtained information was be processed by PC software (e.g. MATLAB) to predict the amount of additional switch parallel capacitance required to compensate the PA to operate under the present load mismatch. A PC-controlled microcontroller allows capacitors aboard the Class E PA integrated circuit to be switched in or out, providing improved load matching. The results show increased safe area on the Smith chart as well as improved efficiency, providing strong confidence in the validity of the theoretical work by Ali Ghahremani.