Radar Spectrum Sharing via Non-repeating Frequency Notched FM Waveforms

Spectrum sensing and transmit waveform frequency notching is a form of cognitive radar that seeks to reduce mutual interference with other spectrum users in the same band. With the reality of increasing radio frequency (RF) spectral congestion, radar systems capable of dynamic spectrum sharing are needed. The cognitive sense-and-notch (SAN) emission strategy has recently been experimentally demonstrated as an effective way in which to reduce the interference a spectrum-sharing radar causes to other in-band users. The case of modifying transmit waveform frequency notch locations when another spectrum user moves in frequency during the radar's coherent processing interval is considered here. The physical radar emission is based on a recent random FM waveform possessing attributes that are inherently robust to sidelobes that otherwise arise for spectral notching. 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. 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.