Jamming wave rejecting device

A jamming wave rejecting device comprising a narrow-band rejection filter which is inserted in series in a received signal path and the rejection frequency of which is varied by a control signal;

• first and second band-pass filters which are connected to the input and output sides of the narrow-band rejection filter, respectively, and the pass center frequencies of which are substantially equal to the rejection frequency of the narrow-band rejection filter and are controlled by the abovesaid control signal and which have substantially the same filter characteristic;
• a phase comparator for detecting the phase difference between the outputs from the first and second band-pass filters;
• a level comparator for detecting the difference between the output levels of the abovesaid first and second band-pass filters;
• a variable control signal generator for generating a control signal which automatically varies to sequentially change the rejection frequency of the abovesaid narrow-band rejection filter;
• and a change-over switch which is controlled by the output from the abovesaid level comparator to supply to a control terminal of each of the narrow-band rejection filter and the first and second band-pass filters with the output from the abovesaid variable control signal generator when the abovesaid level difference is less than a predetermined value and the output from the phase comparator when the abovesaid level difference is larger than the predetermined value.