The Effect of an Intentionally Interfering Signal on the Performance of an Adaptively Matched Filter

This paper shows that, for a power-limited noise jammer, the best jammer strategy for degrading the signal-to-noise (S/N) ratio at the output of a matched filter is for the jammer to transmit a power spectrum proportional to |F(??)| where |F(??)|² is the observed power spectrum of the desired signal. The receiver processing filter is presumed to match adaptively at all times for maximum S/N ratio at its output by considering the spectra of both the desired and jammer signals. If the matched filter is not adaptive, but only maximizes the S/N ratio for a desired signal in white noise, the jammer strategy should be different. In this case, the jammer should transmit a CW signal at a frequency where the power spectrum of the desired signal reaches a peak. For band-limited signals, it is also shown that the best signal design to counter the jammer strategy is to spread the energy spectrum uniformly across the band. Likewise, the jammer strategy for this case is to spread its power spectrum uniformly across the band.