| DAB( Digital Audio Brocadcast ) is a new brocadcast system after amplitude modulation brocadcast and frequency modulation brocadcast.Ensuring maximum possible seamless coverage of DAB terrestrial broadcast services can be technically difficult. The line of sight nature of modern broadcasting imposes the requirement for a large number of transmitters as well as complicated signal distribution systems. In circumstances when traditional solutions for coverage extension cannot be deployed, an on channel repeater may be the only viable alternative.A repeater retransmits a signal on the same frequency as it receives, so that no frequency translation is required as is the case in RF. However, due to short distance induced unwanted multipath coupling between the receiving and transmitter antennas, the device can also receive its own output, thus causing expected signal is buried in the multipath echoes as well as destroying the frequency characteristics of the retransmitted signal. The echo cancellation system proposed in this paper employs adaptive signal processing techniques, and can be used for DAB and other multicarrier transmission system. Moreover, the proposed decoupling system is performance and cost efficient. Thus it is an economical alterative for antenna isolation.The key work of this paper:1,Make a study of the DAB tansmition system and wireless channel;2,Design the signal processing algorithm used in the repeater echo cancellation system, and emulate it;3,Design the hardware platform for this system;4,Implement the signal processing algorithm with FPGA.. |
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