NOISE SUPPRESSION DEVICE FOR FM TRANSMITTER-RECEIVER

摘要

PURPOSE:To attain stable noise suppression by adding a single frequency oscillation circuit oscillated at the center frequency of a frequency discriminator and injecting normally its oscillated output to a reception system to a pre-stage of a frequency discriminator. CONSTITUTION:The oscillator of a single frequency oscillated at the center frequency of a frequency discriminator 6 is added as a noise suppression signal injection circuit 9 to at least the pre-stage of the frequency discriminator 6 in the reception system such as the pre-stage of a filter 3. The injection circuit 9 is used to inject the oscillated output to the reception system of the FM receiver with a slightly larger amplitude than that of the momentary frequency of expected noise thereby obtaining it as a suppression signal. Thus, the noise is suppressed stably and the read error of a start it at the data transmission start from the no signal state and the instability of the receiving state when the input signal reaches the vicinity of the limit of the reception sensitivity are eliminated.