Implementing GaN technology in the design of a high efficiency RF power amplifier

Abstract

The output signal of a radio frequency (RF) power amplifier (PA) is referred to as the transmitted signal. The purpose of a RF PA is to amplify/increase the power level of the transmitted signal such that the level of the received signal is at a suitable level above the noise floor to enable detection. RF PA’s implement amplification by converting the DC power applied to the PA into RF output power. Thus, the output signal of the PA is an amplified representation of the input signal. It is practically impossible to convert all the applied DC power into RF output power. Any DC power that is not converted into RF output power is dissipated as heat. This measure of power conversion is defined by two parameters termed the power added efficiency (PAE) and the power conversion efficiency (PE). Although the actual process of amplification is highly non-linear, the output signal of the PA is a linear amplified representation of the input signal. A CubeSat is a miniature satellite in the shape of the cube, with the dimensions of 10 cm x 10 cm x 10 cm. On-board the satellite is a RF communication system which enables communication and data transfer with the satellite. As for any RF communication system and especially satellite communications, a high efficiency PA is required at the final stage of the transmitter due to the limited/restricted available on-board resources. Based on the condition of high efficiency, several PA design methods, techniques and classes of operation were studied. The class E switch-mode PA (zero-voltage switching) satisfies the condition of a high efficiency PA. This thesis presents the design of a class E switch-mode PA using Wolfspeed Cree CGH40010F power active device. Design methods were tested by means of simulation using Agilent Advanced Design Systems (ADS) and results are analysed for correct class-E operation.