The Design And Realization Of PDT Base Station Transmitter Based On Digital Pre Distortion Technology

PDT police digital trunking standard is a new generation of standards with independent intellectual property rights in China,using narrowband communication technology.The traditional narrowband system adopts modular design method,which means each carrier channel is composed of a set of RF front-end and digital baseband processor.There are a large number of modules with high cost in the base station subsystem with large capacity.Using multi carrier transmitter,it will not only reduce the base station volume and cut down the cost,but also improve the efficiency of the whole machine and reduce the complexity of the system design.Because the multi carrier transmission can easily produce band radiation such as intermodulation products,the linearization technology of RF power amplifier has become the focus of system design.As one of the most effective linearization techniques of RF power amplifier,digital pre distortion has the advantages of high stability,good linearity and strong adaptive performance,and is widely used in the wireless communication base station system.This thesis aims to combine digital pre distortion technology to design the PDT base station transmitter which meets the requirements of the system index.The main work is as follows:(1)Analysis of the nonlinear characteristics and nonlinear mathematical model of the RF power amplifier,and the introduction of the mainstream linearization techniques and comparative analysis of digital pre distortion design.(2)Based on the framework of CPU+FPGA,it developed the baseband digital signal processing platform and met the requirements of digital signal processing of the general communication equipment.(3)Using digital intermediate frequency technology IQ orthogonal modulation and demodulation technology,this thesis analyzed the technical indicators,discussed the design schemes and optimized the circuit simulation,and then designedthe RF transmitter which met the requirements of technical indicators of the PDT base station.(4)Based on the above mentioned platform in addition with power amplifier unit,it set up the entire PDT transmitter digital pre-distortion system.The testing results show that the average output power of the power amplifier system is 48 dBm,the power efficiency is 29%,and the linearity IMD is less than-60 dBc,which meet the requirements of the system index.