System Of Adaptive Echo Filter Based On FPGA

In the long-distance communications and digital co-channel repeater, because the transmitting antenna and receiving antenna, the physical location relationship between the refraction and reflection with the ground, the receiver will receive a strong multi-path echoes, seriously affect the signal quality of communication. The echo is a multiple output signal attenuation through the channel attenuation and returned to the input received signal with frequency interference, conventional duplexers or filters can filter out the interference signal band work, work in the same frequency band Difficult to filter out signal interference. Thus, Need a special filter system to filter out echo echo interference. This system began to be widespread concern by people.This article first echo filter system works analyzed the characteristics of echo signal for the selected finite length Adaptive Filter. Adaptive algorithm based on the accuracy, convergence speed, stability and other indicators selected LMS algorithm, and the traditional LMS algorithm is modified to improve the accuracy of the system. Based on this basic model of the system and its simulation analysis, simulation to determine the design weights and step values. FPGA as the core, then the echo filter system was established to explain the signal's frequency and speed of processing both inside and outside the FPGA. Mainly rely on the AD5512 and an external FPGA DA9779, rely mainly on programming generated within each module. Finally, the composition of the experimental equipment, commissioning of the principles and methods are described, and built a debug module, the echo filter system for online debugging. Adjustment of system parameters, by entering the OFDM signal simulation and actual operation, the results show that the echo filter system can filter out the echo interference, improve the quality of communication.