Class E GaN Power Amplifier Design for WiMAX Base Stations

Abstract

Modern wireless communication systems transmit complex modulated signals with high peak to average ratio in order to deliver high data rates. It demands wide bandwidth and rigorous efficiency performance for power amplifiers. Today’s conventional RF power amplifiers have relatively poor operating efficiency and require more power and area for operation. Therefore, more research on high efficiency power amplifier is crucial to the growth of the wireless industry. Until recent days, WiMAX systems are using technology processes such as Gallium Arsenide (GaAs) and Si LDMOSFET to obtain the performance. Although they are providing the required functional performance, they do not optimize cost and/or size. The primary focus of this thesis is to enhance the efficiency and output power of a compact microwave Power Amplifier suitable for a WiMAX base station. To achieve this goal, this thesis explores the highly efficient switched mode Class E microwave power amplifier using the Gallium Nitride on Silicon Carbide HFET (GaN-on-SiC) technology. The smallest gate length (0.15 µm) device recently released by NRC is used in this design. It provides higher performance at lower cost and area than the alternative Gallium Arsenide (GaAs) technology. Importance is given in designing the bias network of the device. The biasing network has a great impact on efficiency of power amplifiers. Many new techniques of Class E design have been presented to date, but there is not significant improvement related to the biasing network. A highly efficient Class E power amplifier for WiMAX base station transmitter was developed in this thesis for 2.5 GHz application. An improved bias network was introduced for biasing the active device. This successful design shows acceptable simulated performance with a gain of 10.12 dB, an output power of 34.12 dB, and a power added efficiency of 41.7 % at the peak output power.