Digital Television Repeater Echo Suppression Algorithm And Implementation

Recent years, because of the rapid development and wide application of digital TV, especially the popularization of digital terrestrial television broadcasting, the number of users increases rapidly. The repeater as an effective radio signal transmission and amplification device, have generally used to expand the broadcasting networks and to fill its blind area. Besides, the repeater is widely known as low-input, low operating cost, relatively short construction period and better network quality. So, better results and higher return on investment can be achieved.The feedback oscillation is always the weakness of engineering application of on-channel repeater. The major function of repeater is to amplify the received signal and re-transmit it, so that, the effective signal can be received in blind area. There are two antennas on the repeater--receiving antenna and retransmission antenna, if the isolation between receiving and retransmission antennas is not enough,the coupled signal from retransmission antenna which come into the receiving antenna can easily cause feedback oscillation and make the repeater go into debacle.A practical solution is applied in this paper: (1) The characteristics of the coupling channel is obtained by channel estimation; (2) The estimated echo signal (the mirror echo signal), which subtract from the actual echo at the repeater receiver end, is structured by the digital filter; (3) The filter weights are updated with adaptive algorithm, so that filter output can always tend to echo signal. This solution about echo cancellation is processed in the base-band, have good technical superiority because it can effectively solve inherent problems of the repeater, such as delay, noise, etc. All-digital realization of echo cancellation can easily debug and make overall structure of the repeater more simple, tiny, practical, and can significantly reduce project installation costs, improve equipment stability, versatility and flexibility.In this dissertation, the technology of transmission standard, frame body processing, wave shaping of digital terrestrial television broadcasting is introduced firstly. The key technology and implementation of the solution for feedback oscillation of repeater are comprehensively discussed. Then, characteristics of wireless channel, channel models and channel estimation algorithms are summarized and elaborated. LMS adaptive algorithm is applied to echo cancellation of the repeater, simulation platform is set up to evaluate algorithm performance and floating-point algorithm to fixed-point algorithm is conversed. Finally the FPGA hardware architecture of echo cancellation and the module function are explained, hardware platform is set up to analyze test results.The analysis of the test result verifies that the solution scheme meet the system requirements.