Radio receiver with noise suppression amplifier - whose gain can be switched between two levels with hysteresis

摘要

The radio receiver has a chain comprising a BD filter, amplifier , noise rectifier and evaluator, which switches the LF part of the receiver when no carrier is received. An amplifier (5) is located before the BP filter (6) and has its gain controlled by the evaluator (9) such that when noise is detected the gain is increased and when no noise is present it is reduced. The amplifier may have two adjustable gain levels to give hysteresis and thereby prevent the LF part's being switched off by carrier fluctuations when the carrier/noise ratio is acceptable overall.