Robust scale invariant detection of coherent narrowband signals in nearly Gaussian noise

A robust test for detection of narrowband coherent signals of unknown amplitude and phase in contaminated Gaussian noise of unknown scale is proposed. The test preserves the structure of the quadrature matched filter. which is the uniformly most powerful (UMP) test for pure Gaussian noise. In the new test, the sample-mean estimators are replaced by robust α- trimmed estimators, with an adaptive threshold derived from noise-reference samples. The resulting detector is shown to be asymptotically CFAR and maximin optimal robust for various signal amplitude models and for arbitrary signal level Monte-Carlo results demonstrate that robustness is maintained even with small sample sizes, and that the proposed test substantially outperforms the robust test that has been derived from the traditional weak signal assumption.