Enhancement of pulse train signals by comb filters

The relative performance of different types of comb filters is investigated in conjunction with signal and noise types similar to those expected in radar applications. The filter types considered are idealized filters with zero transmission stop bands between their pass bands, optimum filters maximizing the peak signal-to-rms-noise ratio, cascaded delay line filters, feedback type filters, and storage tube filters. The pulse train signals consist of rectangular or sin pulses with rectangular or sin pulse envelope shapes. Power spectra of noise considered are rectangular and triangular. With a given number of signal pulses, the performances of the different filters vary from each other only by a few decibels in most cases analyzed. Storage tube filters exhibit lower signal-to-noise power ratios, but higher peak signal-to-rms-noise ratios, than the feedback type filters. Inaccurate delay times of filter delay lines are shown to decrease the peak signal output more than the signal power output and to affect the cascaded delay line filter less than the feedback type filter. Correlation techniques are compared with comb filters. The crosscorrelator exhibits the same peak signal-to-rms-noise ratio as the optimum filter.