Design And Implementation Of High Speed Digital Modem

With the rapid development of information and communication technology,the requirement for the communication rate becomes higher and higher.It has become more and more difficult for today's communications system to meet the growing demand of communication rate.In a communication system,the rate of modem often determines the transmission rate of the whole system.So the research of high speed data transmission modem has become a hot topic.For a high speed data transmission modem,its processing rate is mostly limited by the clock frequency of its chip.To break through this limit,It's needed to change structure of the modern from the traditional serial structure into a parallel structure.In this paper,we study it in order to give a solution of parallel-structure high speed data transmission modem.In this paper,various aspects of the high speed data transmission modem and its effect on the modem's rate and resources are analyzed.According to this,a series of related aspects such as modulation mode,parallel path number and receiver structure,are selected.They delineate the overall scheme framework,Then,the theory and common algorithms of each step of the modem are studied,especially those parallel implementation algorithms of each step,accordingly,the parallel implementation schemes of each step are given.The modulator section mainly includes parallel differential coding,parallel time domain shaping filter,and mixer-free quadrature up conversion.And the demodulator section mainly includes frequency-domain matching filter,frequency-domain timing phase offset correction,timing frequency offset correction achieved by adding or deleting the sampling point,parallel blind equalization optimized by approximate processing,carrier synchronization which detecting and correcting in polar coordinate system and improved parallel differential coding.These schemes can achieve the corresponding functions with less resource consumption,and their Matlab and Modelsim simulation results also show the efficiency of these schemes.Finally,this paper tests the high-speed parallel modem system on the FPGA development board ML605,and the results show that the performance of the high speed parallel modem is good.