Radio receiver with locked loop for automatic frequency control - has muting circuit blocking unwanted audio signals outside tuned region

摘要

The receiver has a frequency locked loop including a VCO with a tuning input, a mixer with an antenna input, a filter, a frequency-to-voltage converter connected to the VCO, and a blocking circuit. The F/V converter is coupled to the VCO via a first amplifier/limiter. The F/V converter is connected to the first amplifier/limiter via alow-pass filter which has a bandwidth greater than the audible frequency range. The F/V converter contains a multiplier one output of which is connected via filter to a second amplifier/limiter. The multiplier is fed by the output of the first amplifier/limiter and a phase-shifted output from the control circuit. The blocking circuit is controlled by a control loop.