The effect of bandpass limiting on a signal in wideband noise

The authors present a way to find the change in signal-to-noise-density ratio when a constant amplitude signal embedded in wideband noise passes through a bandpass limiter. This ratio is a more accurate predictor of demodulation or detection performance than the commonly used signal-to-noise-power ratio of the limiter output if signal processing includes narrowband elements such as matched filters. The noise bandwidth out of the bandpass limit is at least as wide as the input noise bandwidth, and subsequent signal processing will remove much of the output noise before a decision is made. The present result is given in the form of an infinite series for the limiter output noise power spectrum density at the signal frequency. This can be combined with a known expression for output signal power to find the change in signal-to-noise-density ratio