| The radio frequency power amplifier is the research hotspot as the most important device of the wireless communication base station for a long period.It can consume less electric energy and increase the service life because of the high efficiency,so the working efficiency becomes one of the most important indexes of the power amplifier as the highest power consumption device in base station.Among several mainly efficiency improving technologies,the Doherty power amplifier has simpler structure and higher working efficiency,so it becomes very popular in radio circuit industry.In this thesis,the L band symmetry and asymmetry Doherty power amplifier applied to mobile communication base station are designed according to the theory of the Doherty power amplifier.The main contents are as follows.First,the design indexes of the L band Doherty power amplifier and driver stage power amplifier are formulated according to the application requirements after introducing the fundamental principles.After that,the transistors of the Doherty power amplifier and driver stage power amplifier are decided.Secondly,the driver stage power amplifier and the Doherty power amplifier are designed in ADS,including the quiescent operating point,the bias network,the matching network,the small-signal analysis,the big-signal analysis and the printed circuit board(PCB)simulation.What's more,it involves the power divider design and the compensating line design of the Doherty power amplifier.Finally,the measurement and debugging are accomplished after designing the driver stage power amplifier and Doherty power amplifier.After testing,the saturated output power of the Doherty amplifier is about 45.20 dBm,the biggest power added efficiency is 38.40%.The efficiency is bigger than 30.00% when the power back-off is 5.10 dB.Besides,the measurement results of the driver stage power amplifier are similar with the simulation results by comparing.Nevertheless,the working indexes of the Doherty power amplifier are worse than simulation results.These problems are analyzed and the probable solutions are put forward.Whtat's more,the asymmetry Doherty structure of higher efficiency are proposed after the L band symmetry Doherty power amplifier is designed and measured.What's more,the two kinds of structure are compared at last. |
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