| As the core device of a transmitter in the wireless communication system, RF power amplifier directly determines the performance of the transmitter. Nowadays, RF power amplifier has obtained a wide range of research and application in academia and industry, especially its efficiency and linearity is a hotspot of the study.In this paper a class AB RF power amplifier has been designed according to the requirements of the communication system, the main works are as follows:(1)Introduced the basic knowledge about RF power amplifier including the classification of transistor, the theory of two-port network, the transmission line and the impedance matching techniques, which are the bases of the design of RF circuit;(2)Described the classification of power amplifier, the major design metrics and the key technologies to improve its performance, and then analyzed the output efficiency of linear power amplifier;(3)Demonstrated the process of designing a class AB power amplifier with ADS, and made use of the load-pull technology to design the matching network;(4)Designed the protection circuit including the power and temperature detection, if the power amplifier works abnormally, it will alarm the system and even turns off the power in case of emergency;(5) Designed the PCB and assembled it with the radiator and cabinet, then tested and analyzed the performance of the power amplifier.In this paper we design a class AB power amplifier with cascade structure, and the driver stage and late-stage amplifier consist of MMG3006NT1and MRF5S9070N from Freescale company respectively. With the880MHz operation frequency, the output power and gain of the amplifier reach45dBm and30dB respectively, and the Power-added efficiency is approximately35%. Besides, it can also monitor both the operation temperature and output power with alarm.The PCB is fabricated on the FR4substrate of1mm thickness and the3.5relative permittivity.Finally,the main work has been summarized in the paper. |
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