| Modern wireless communication technology develops rapidly in recent years, Given the limited radio spectrum resources, communication systems need deal with signal which has multiple carriers high peak to average ratio. Therefore, the performance of power amplifier(PA) put forward higher requirements. Operators pay more attention to the efficiency of base station power amplifier. High efficiency means low power consumption, low maintenance cost. Against this background, how to improve the efficiency of the power amplifier has become priority subject in the study of active RF circuit. The Doherty amplifier becomes the focus of current research for its advantages of simple structure, low cost, high efficiency. This paper studies the Doherty structure principle, and designs a Doherty power amplifier for base station. The major achievements are listed as follows:1. This paper introduces in detail the Doherty amplifier structure and operational principles, and deduces the efficiency of the three kinds of working state. It briefly explain the choice principle of the inverted Doherty structure, how to optimize the offset line and impedance transformation line.2. With the help of ADS simulation tools, by utilizing Load-Pull system solve optimal load impedance and source impedance. According to the actual physical size and actual circuit designs the bias network and matching network. The schematic simulation and layout simulation are completed about the driver stage power amplifier, power splitters, and Doherty power amplifier.3. The inverted Doherty power amplifier is designed by utilizing the Freescale's LDMOS MRF8P26080 H, about The main performance of the balanced Class AB PA, the traditional structure Doherty PA and the inverted structure Doherty PA make a comparison. The simulation result shows that the inverted Doherty PA is better than the traditional structure Doherty PA, and has an improvement 23% with power back-off 6dB. From the perspective of software simulation verify the theoretical analysis, and select inverted structure completed design scheme in this paper.4. Eventually, the driver stage PA, power splitters, and the inverted Doherty PA have been fabricated and tested based on the simulated model. The test scheme of power amplifier and the method of optimization circuit are introduced. The test results which in accordance with the trend of simulation results, but is deteriorated. The test error result is analyzed.2.6GHz inverted Doherty power amplifier was designed. The measured results verified Doherty structure PA the excellent performance. The research production of this dissertation has reference values to engineering applications. |
PDF Full Text Request