Design Of A Modified Broadband Doherty Power Amplifier Based On Asymmetric Structure

In recent years,with the development of wireless communication technology,2G,3G and 4G coexistence of multi-mode communication system,which requires the power amplifier used in wireless communication system can cover multiple communication band,therefore,the broadband power amplifier has attracted much attention;at the same time,the transmission rate of high demand information leads to the high spectral efficiency of modulation and transmission standard widely used,and the modulation generally have higher peak to average power ratio(PAPR),in order to improve the average efficiency of the power amplifier to reduce energy consumption,the power amplifier can be guaranteed linearity,achieve high efficiency in large power back-off.Therefore,the research of high efficiency broadband Doherty power amplifier has become a hot spot of research at home and abroad.The main work and innovation of this paper are as follows:(1)a modified Post-Matching structure based on stepped transmission line is proposed.The simulation results show that the drain efficiency in the edge band is increased by 7%-10%compared with the traditional Post-Matching structure.(2)The way to increase the power back-off of Doherty power amplifier is compared and analyzed.The influence of asymmetric drain voltage,asymmetrical input power and asymmetrical drain voltage +asymmetric input power on the performance of Doherty power amplifier is simulated and analyzed in three ways.(3)Using the modified Post-matching structure based on stepped transmission line and the asymmetric drain voltage + asymmetric input power mode,a modified broadband Doherty power amplifier with 1.7GHz-2.7GHz working frequency is designed and implemented.The simulation and test results show that the output power of the power amplifier is larger than 43.5dBm,the saturation drain efficiency is more than 60%,the drain efficiency is greater than 55%in the 6dB power back-off;the drain efficiency is greater than 50%in the 7-8dB power back-off,after digital pre-distortion,the power amplifier meets the linear requirement of the system.