Sensitivity of EW receivers

The operational sensitivity of receivers with high gamma (the ratio of the radio-frequency bandwidth to the video bandwidth) values has been disconcerting owing to the apparent conflict between theoretical calculations and laboratory measurements. For example, calculations have shown that even with false alarm rates as low as 10 to the -10th, a signal-to-noise ratio of about -6 dB can provide a probability of detection value of 90%. Data from actual receiver measurements, however, were at variance with this prediction. It is shown that the apparent conflict between the theoretical predictions and measured quantities is not a conflict at all but a misinterpretation of the theory. The theory and laboratory measurements are shown to agree quite well. Attention is also given to the relationship between the operational sensitivity and the tangential sensitivity. This relationship is important in that tangential sensitivity can be easily calculated for any gamma and it is quite readily measured.