Time-Notch Filtering

A method is described for measuring low-level time-truncated signals by using narrow-bandwidth synchronous time-notch filters. These filter systems, intended for use with ordinary narrowband receivers or field intensity meters, provide a means of isolating time-truncated signals of interest from adjacent interfering signals. In addition, the important property of near optimum sensitivity (approaching that of a matched filter) is discussed, and the laboratory results of a low-frequency time-notch filter covering the 500-Hz to 2-MHz range are given.