.20 W Linear Pre-distortion Power Amplifier

The third generation mobile communication (3G) has already integrated with people's life in European, which is also just been around the corner in China. The third generation mobile communication system which could support massive different kinds of services, and provide person-to-person communication service to anybody, in any place, any time needs good network architecture support. The trunk amplifier and the repeater are very important in optimizing the network. As the key part of the trunk amplifier and repeater, power amplifier plays an important role in these systems. Its performance has greatly affects on the system. The information transmission technology of modern communication system is developing rapidly in the direction of multi-carrier,multi-level,broad band and high Peak-Average- Ratio(PAR).New broad band digital transmission techniques(such as OFDM, WCDMA)and high spectrum efficiency modulation techniques (such as QPSK)are extensive used. These high efficient multi-carrier & multi-channel digital modulation transmission techniques, which are based on non-constant envelope,request high linearity of radio frequency power amplifiers(RF RAs).When signal is amplified by RF PAs,intermodulation distortion is generated,which results in spectral regrowth,then leads to adjacent channel interference. In modern wireless communication system,adjacent channel interference has got stringent restrictions, so it is challenge to designing PA used in modern communication systems.The main job of this project is developing a 20W high linear power amplifier which could be used in the trunk amplifier and repeater that working on WCDMA communication system. In this paper, we first introduced the parameters which may affect the Linearity of power amplifier when used in the enlargement of WCDMA downlink signal as well as the linearity parameter. The response of nonlinear radio frequency power amplifier also discussed as well as the principle of Linearization technology such as back off, feedback, predistortion and so on. The summary to the memory effect is made in this paper with referring to the domestic and foreign literature. With the help of these analyses and summarize, finally we choose the analog predistortion as the Linearization method of this design. Through the strict predistortion module project concept demonstration, the predistortion component choice and the careful debugging, we finished the design of the predistorter, the driver and the main power amplifier which working on 2110MHz-2170MHz.The predistortion system also finished finally with simply structure, low cost which the linearity of power amplifying is improved.