The Effect of Limiting on the Detectability of Partially Time-Coincident Pulse Compression Signals

Analytic approximations are derived to describe the effect of band-pass limiting on the detectability of partially time-coincident pulse compression signals. These are applied to the practical radar case of a fixed threshold decision criterion, which effectively becomes an equivalent variable threshold in any region in which a strong signal controls the limiter action. The suppression and gain control effects of the strong signal cause the detection probability of a weaker signal to deteriorate rapidly as a function of the percentage overlap. A calibrated radar simulator is described. The test equipment operated in either a pulsed CW or a linear FM pulse compression mode. Detection probability curves are presented for different false alarm probabilities in each mode, with and without limiting. Test procedures are described that obtain data in the following areas: 1) The effect of partially time-coincident strong signals on the probability of detection (Pd) of a weaker signal in the pulse compression mode, and 2) The effect of the strong signal on the probability of false alarm (Pfa) in the strong-signal region. The data obtained are in agreement with the analysis, illustrating the degradation of the weaker signal Pd as the overlap factor increased.