Frequency-Selective Limiting

In the usual microwave limiter the presence of a large signal above a certain threshold power level produces a change in gain or attenuation of the device so that the output power level of this signal remains approximately constant as the input level is varied. This characteristic is desirable in many applications to provide crystal burnout protection in a receiver, act as a power leveler, etc. When more than one signal is present, however, such a limiter will have the undesirable property of increasing the attenuation of a small signal which is also within the passband of the limiter. Thus, while a receiver may be protected from permanent damage by such a limiter, it would be rendered inoperative whenever a strong signal is present.