Method and device for repeating isofrequency signals

摘要

The invention relates to a repeater and a method for re-transmitting single frequency signals, in particular of the type used in single frequency signal repeaters for use in single frequency networks (SFNs) like digital video/audio broadcasting (DVB/DAB) networks. The estimation of echo feedback is derived from the measured power density spectrum with an inclusion of a variable phase shifter (57) in the signal path. Preferably, the phase shifter (57) is controlled by control means (56), which also set the adaptive filter (54) for feedback compensation, such that a signal coupled from the transmitter antenna back to the receiver antenna can substantially be cancelled out. The method according to the invention exhibits quick and stable regulation behaviour and the re-transmitted signal does not suffer from degradation due to added interference. The quality of the signal at the transmitter antenna is improved even if dynamically changing feedback paths from the transmitter to the receiver antenna exist. The transmitter output power can be increased without increasing the risk of system instabilities, such as oscillations.