LPI Performance of an Adaptive Frequency-Hopping System in an HF Interference Environment

| Frequency-hopping is considered to be an eeective method for combating active jamming in military radio systems. To further improve the performance , so-called adaptive frequency-hopping (AFH), which uses an adaptively selected pool of the \best" hopping-frequencies for the communication, has been proposed. In this paper, we examine the low probability of intercept (LPI) performance of such an AFH system on an interference-limited HF channel. The LPI property is evaluated with respect to two diierent hostile detectors; the radiometer and a sub-optimum matched lter detector. It is found that the matched lter detector is a much more serious threat against the AFH system, due to its ability to suppress the strong interfering HF signals in the detection process. Furthermore , the LPI performance proves to be very dependent on whether the interceptor can estimate the pool of hopping-frequencies used by the AFH system or not. If the interceptor cannot perform such an estimation, the AFH signal has a high chance of remaining unde-tected in the dense HF interference environment.