TABLE OF CONTENTS The narrowband superhet receiver has high sensitivity and wide dynamic range. It is not troubled by simultaneous signals. However, it does not cover a broad frequency band, and thus has low probability of intercept in some situations and cannot adequately handle wideband signals (e.g., frequency hop) in others. The IFM provides 100% probability of intercept over broad bands, but it is troubled by time overlapped pulsed signals and CW signals. The receivers described here attempt to overcome these deficiencies.
A straightforward approach to utilizing the properties of a narrowband superhet, while also providing wide frequency coverage, is to use a number of parallel channels, each one tuned to a slightly different RF center frequency. The frequency separation between the channels can be roughly equal to the 3-dB IF bandwidth used. Then, no matter what the carrier frequency, it will be detectable with only a small loss in sensitivity compared to a properly tuned narrowband receiver. Actually, the sensitivity of each channel must be degraded slightly by raising the detection threshold to maintain the same total false alarm rate as a single-channel receiver.
Consider an example in which there are 100 parallel receiver channels. If the tolerable false alarm probability is P FA ,1 in a single channel, the probability of false alarm probability for N independent channels is
If P FA , N is small, such that NP FA , N ? 1, this is approximately
For a single channel,...
