High-efficiency Power Amplifier Research And Design

With the development of communication technology and 3G technology,the higher requirement in data transfer rate has been substantially proposed. In order to increase the data rates, modern communication systems use non-constant envelope modulation methods (such as BPSK, QPSK and QAM, etc.) to send the signal, which results in the high signal power PAR. However, the demand of linearity of the base station is also raised due to the high signal power PAR. The design of traditional power amplifier utilizes the method of power back-off to obtain a high linearity at the expense of efficiency. In order to ensure the linearity of peak power, power must be more back-off and also less efficient which leads to more waste of energy and heat dissipation of communication equipment and ultimately affects the performance of communication equipment. Therefore, how to design power amplifiers with high efficiency under the condition of high PAR has become a popular topic.In this article, the type of power amplifier devices, the basic indicators and categories are described; a variety of power amplifier efficiency enhancement technology is comparatively analysis; the structure and working principle of Doherty power amplifier; which is currently widely used in the communications equipment, is researched. The performance of Doherty power amplifier is designed and verification and its drawback that practical application appears is improved.This article is mainly the following aspects: First, using the software provided by Agilent's ADS for the simulation and Freescale's LDMOS transistor MRF21010 to design, analysis various factors affecting the performance of the Doherty by the actual simulation results and experimental test results, Secondly, the traditional symmetrical Doherty amplifier in order to overcome the drawback through using Freescale's LDMOS transistor MRF6S20010 to research and design asymmetric Doherty amplifier.Actual measurement shows the performance of the Doherty power amplifier meet the requirements of the design, when the output power of symmetrical Doherty achieves 37dBm, the PAE is 30.1%, IMD3 is -19dBc, when output power of asymmetrical Doherty is 37dBm, the PAE is 31.2%, IMD3 is -30.8dBc.