FM interference and noise-suppression properties of the oscillating limiter

An amplitude limiter with regenerative feedback can, under appropriate conditions, provide an effective tool for suppressing interference from undesired signals, as well as interstation noise. The amount of positive narrow-band feedback that is prescribed for marked improvement in the stronger-signal capture performance causes the limiter to oscillate in the absence of an input signal. Although oscillation results in automatic noise squelch, it also imposes limitations on the frequencies and minimum amplitudes of receivable signals, in the form of a locking frequency range and a locking threshold. The alleviation of these limitations requires careful design of the feedback phase characteristic. The theoretical discussion is followed by a summary of experimental data which brings out several important aspects of oscillating-limiter operation.