On-channel repeaters are able to receive and re-transmit a broadcast signal on the same frequency and thus can facilitate network expansion, particularly in an SFN, and network repair following the introduction of strong adjacentchannel transmissions. For effective operation, systems must incorporate excellent RF design and high-performance signal processing in order to remain stable and re-radiate a clean, decodable signal. This paper describes the operation of on-channel repeaters designed for DAB and DVB-T signals by BBC R, and goes on to outline a number of key techniques, including correlation compensation for controlling unwanted out-of-band products due to part-Nyquist signal occupancy and adaptive null-steering for pre-echo rejection in a DAB SFN. The former is now a field-proven technique whilst the latter is in development and awaiting a full engineering realisation.
Keywords: Active deflector, DAB, DVB-T, on-channel repeater, SFN, transposer, Residual Correlation, Pre-Echoes, Twin-Antenna Reception, steering vector
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