Noise suppression circuit for AM radio receiver - has low pass filter before noise gate to reduce blanking out time to minimum

摘要

The noise suppression circuit, for an AM radio receiver, has a gate in the LF signal path opened when noise pulses are detected. The gate is coupled to the output of the mixer via an LP filter. The LP filter cutoff frequency lies just above the IF frequency and it reduces the level of the oscillator signal reaching the gate considerably. The noise pulse therefore reaches the gate without significant spreading which means that the signal is only blanked out by the gate for a relatively short time.