Adaptive FSK/PSK radar with applications to low probability of intercept noncooperative target recognition

Adaptive FSK/PSK is a spectrally agile pulse compression radar signaling scheme that learns target-specific information over time and integrates that information into the design of its radar signal processor in real-time. This use of target-specific information into the real-time transmitter signal design process enhances the return from the target, thus improving the performance of the radar system in both additive noise environments (jamming) and ground clutter limited environments (low altitude targets). Since FSK/PSK signaling is a pseudorandom pulse compression scheme with a large time-bandwidth product, it has inherent low probability of intercept characteristics. Additionally, adaptive FSK/PSK signaling is able to learn target-specific information which can be used to identify the target using existing target identification techniques.; In this study, the cross-ambiguity function of a general FSK/PSK waveform is derived and analyzed in a probabilistic manner. The results of this probabilistic analysis are used to develop a design methodology that allows the signal to be matched to an arbitrary target. It is shown that both the signal to clutter ratio and signal to noise ratio of a matched FSK/PSK radar are superior to those of a conventional signaling radar that utilizes no target-specific information. Since the target-specific information is not known a priori, an iterative design algorithm based on gradient descent is developed. This iterative real-time design technique allows the matched FSK/PSK signal to be designed over time. A parametric study of the iterative design algorithm is also performed in order to determine the effect of additive noise, random target range drift, and random target angular motion on the technique.; The fundamental concepts discussed in this study are applicable to many active sensor problems other than radar. These applications include: sonar for underwater mine detection, ultrasound diagnostics in medicine, flaw detection in composite structures, and laser radar. Additionally, the signaling scheme could be used to improve the performance of spread spectrum communication links through fading channels.