TABLE OF CONTENTS The accuracy of probability of detection calculations is detailed in Chapter 13. Meanwhile we note some practical factors which may modify the statistically determined probability. The list is doubtless incomplete and helps confirm the aphorism heading the chapter.
Sidelobes of short-range targets can be a nuisance or navigationally dangerous even when displayed fairly infrequently, with quite low P D. Returns received through sidelobes retain their usual fluctuation characteristics and the radar's pulse to pulse and scan to scan integration systems remains active. The radar threshold and false alarm exponent, F, of course remain as set for main-beam noise and clutter. Note the following.
Passive targets. The scanner gain term applies to transmit and receive legs. If, for example, the scanner main-beam gain is 30 dB and the sidelobes are 27 dB down, effective discrimination against sidelobes is 2 27 = 54 dB. Whether unwanted sidelobe echoes will be displayed is determined by recalculating the radar range equation for echo strength after resetting scanner gain, G, to 30 - 27 = 3 dB and sidelobe P D to, say, 0.1.
Racons. Because of the coding, a racon sidelobe response is unlikely to be mistaken for another racon, but its great length may mask adjacent echoes. Many modern racons include sidelobe suppression circuits which inhibit most or all responses to interrogations which the device calculates to be sidelobes. Not all racons have sidelobe suppression, and an unfortunate...
