The Development Of High Efficiency Doherty Amplifier

Today the Power Amplifier is widely applied in the Radar, navigation, satellite communication and personal wireless communication systems; it's one of most important equipments in the modern wireless communications. Along with the development of modern modulation technology, in many standards the signal which has high PAR (peak to average ratio) has been accepted such as 802.11(Wireless LAN standards), High Definition Television, 4G, so the higher requirements of amplifier have been required. The amplifier consumes most parts of transmitter's power, but because of its low efficiency it will make the serious waste in the electronic resource and the instability of equipment. So in such application environment, implementing the amplifier which satisfies the requirement of high efficiency is urgent affairs.This paper focus on the design of high efficiency Doherty amplifier. Firstly, a great deal of information on microwave power amplifier has been collected, and the characteristics of different high-efficiency amplifier technologies have been compared. In the new application environment which has been referred, we have done the In-depth theoretic research of the Doherty amplifier. Then combined the Advanced Design System (ADS) software and experienced power amplifier model given by Freescale Company, the design work of amplifier Doherty according to the load-pull theory is completed. Finally the debug of driver amplifier and the Doherty amplifier is done, which has provided valuable practical experience and a clear direction for improving.Secondly, this paper has introduced the amplifier's nonlinear characteristics, analyzed the advantages and disadvantages of different linear technologies, then focus on the research of pre-distortion theory and the usage of pre-distortion module based on polynomial amplifier model. After that, we combined Doherty amplifier with pre-distortion technology, accomplished a design method about high efficiency and high linearity WCDMA power amplifier through the united simulation of MATLAB and ADS, improving energy efficiency, dramatically reducing the cost.