Signal limiting apparatus having improved spurious signal performance and methods

摘要

A limiter circuit responds to an input signal which has a plurality of frequencies within a given band. The input signal is split up into two frequency ranges by means of a low pass filter for one range and a high pass filter for a second range. The output of the low pass filter is directed to a first limiter while the output of the high pass filter is directed to a variable notch filter. The outputs from the first limiter and the notch filter are added together to provide a sum signal. The sum signal is applied to a second limiter which performs limiting strictly according to the amplitude. The outputs of the second limiter signal provide the desired signal and a control signal to determine how often the second limiter is limiting. The control signal varies the attenuation of the notch filter. In this manner frequencies, within a selective range and which will be otherwise effected by the spurious frequencies generated during limiting, are reduced.