Tone detection of non-uniformly undersampled signals with frequency excision

We address the problem of detecting and locating narrowband tones in an undersampled signal. It is known that uniformly undersampled signals exhibit frequency aliasing, whereby the frequency location is impossible. To alleviate aliasing, non-uniform sampling can be used. This, however, generates a high level of frequency leakage that prevents detection of weaker signals. We introduce a novel iterative frequency excision technique that allows to detect tones below the original noise floor due to leakage. Up to 20dB of leakage reduction has been achieved with this method.