The auxiliary envelope tracking RF power amplifier system

Abstract

The advancement of the mobile communication industry increases the need for RF power amplifier (RFPA) to be more efficient and linear. The communication network that is shifting towards smaller micro-cell or nano-cell network has also motivated the design of the RF power amplifier to be simple, compact and cost efficient. In this research work, a novel technique for efficiency and linearity improvement of the RFPA is presented. A simplistic approach in the technique called ‘Auxiliary Envelope Tracking' (AET) system has promoted the design for small and straightforward AET tracking generator, a key component in the system. The use of low cost components in the AET tracking generator has made the technique commercially attractive. The AET technique proposes a separation in generating DC and AC components of the AET signal that biases the drain of the RFPA. The separation eases the generation of the signals resulting in low power consumption that leads to efficiency improvement. The investigation of the gain characteristic of gallium nitride (GaN) RFPA has shown an important RFPA attribute where the gain varied substantially as the drain voltage increases. By using the AET technique, the gain characteristic is harnessed to get linearity improvement. In order to validate the technique, AET measurement systems for two-carrier and WCDMA signals were developed and experimented. A special Class AB RFPA is designed and implemented to use dedicatedly for this investigation. In two-carrier signal measurement, a tracking generator is developed that consists of an envelope amplifier (EA) and a diplexer. The RFPA and the tracking generator are then combined to be an integrated AET block. In order to accommodate the high peak-toaverage ratio (PAR) and high bandwidth WCDMA signal, a broadband RF transformer was designed as part of the AET tracking generator to replace the diplexer. The two-carrier and WCDMA signals measurement results have proven that the AET technique is a valid technique for efficiency and linearity improvement. The improvements were achieved with simple, compact and cost-effective implementation.EThOS - Electronic Theses Online ServiceGBUnited Kingdo