Improved inverse class-E matching network for microwave high power amplifiers

This paper presets a 8.5 W GaN inverse class-E power amplifier using an output matching network suitable for high power applications. The presented output matching network overcomes several problems in the original implementation. First a transmission line stub is used directly at the transistor drain to compensate for the drain source capacitance, second the lumped inductor in the original implementation is replaced by a short transmission line, which makes it suitable for high power amplifiers. The designed GaN inverse class-E amplifier achieves a maximum drain efficiency of 77 % with output power of 39 dBm at a drain supply voltage of 35 V. Additionally through varying the supply voltage the presented amplifier gives a drain efficiency greater than 70 % over an 8 dB dynamic range.

I. Introduction

High power amplifiers are essential components in most communication system, since they are the component with the highest power consumption. For this reason efficiency is among one of the most important properties of a power amplifier. The contradicting requirements of high efficiency and linearity are further complicated by the use of varying envelop signals. Due to the demand for high data rates the usage of advanced modulation schemes with varying envelop signals is becoming more and more common. These varying envelop signals have high peak to average ratio which forces the system designer to use traditional linear amplifiers such as class-A and AB in a low efficiency back off mode according to the peak-to-average power ratio (PAPR) of the modulation standard used. As a result the efficiency of the whole transmitter is drastically reduced with increasing the PAPR. Several transmitter systems such as linear amplification with nonlinear components (LINC) and envelop elimination and restoration (EER) offer a solution to the contradicting requirements of efficiency and linearity. At the center of these transmitter structures is a high efficiency power amplifier such as class-E, inverse class-E, class-D, class-F or inverse class-F amplifier.