Low-power transmitters can be an important part of a single-frequency network, but the cost of providing a signal to many low-power transmitters by microwave or fiber may be prohibitive. On-channel boosters solve this problem, but it is often difficult to achieve sufficient isolation between the transmit antenna and the receive antenna.
At IBC2007, Axcera demonstrated its solution to this problem—an echo-canceling repeater based on a low-power version of its Innovator LX DVB-T/DVB-H transmitter, introduced at NAB2007. Echo cancellation suppresses the delayed signal received from the output of the repeater, allowing the booster to function with less isolation between the antennas and providing greater system stability.
Axcera said overall insertion delay is as low as six microseconds. The repeater being shown only worked on the DVB-T and DVB-H formats, but the techniques should also be applicable to ATSC repeaters. An ATSC on-channel booster using an echo cancellation system designed at ETRI in South Korea was shown by Hi-Wave at NAB2006.
Axcera said the Innovator transmitter line features a Web browser/SNMP interface and is available at power levels ranging from 5 to 1850 W. Axcera also showed its Innovator HX line of high power solid state transmitters and its 5720 series MMDS transmitter.
From Doug Lung’s RF Report
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