Devoid Clutter Capture and Filling (DeCCaF) to Compensate for Intra-CPI Spectral Notch Variation

Cognitive spectral notching of FM noise waveforms on transmit has been experimentally shown to be an effective means with which to avoid in-band interference. However, to contend with dynamic interference the transmit notch may be required to move during the coherent processing interval (CPI), which introduces a nonstationarity effect that results in increased residual clutter after cancellation. It was recently shown that optimal mismatched filtering (MMF) can partially mitigate this degradation while maintaining the necessary spectral notch for interference mitigation.Here a new approach to compensate for this nonstationarity is proposed that borrows the missing portion of the clutter (due to notching) from another pulsed response for which the notch is in a different location. By using this borrowed response to fill in the notched clutter, subsequent clutter cancellation largely avoids the nonstationarity effect so that the corresponding residue is reduced. It is shown using measured data that the combination of this clutter filling approach with notched MMFs realizes clutter cancellation performance on par with full-band random waveforms that do not possess spectral notching.