DSI Suppression with Adaptive Beamforming in DVB-T Passive Radar Measurements

Adaptive beamforming (ABF) for maximizing the signal to interference plus noise ratio (SINR) is applied to acquisitions made by a passive bistatic radar (PBR) exposed to strong direct signal interference (DSI). The DVB-T transmitter was located approximately 20° from boresight. ABF is applied after the formation of range Doppler maps where the formation was based on reconstruction of the reference signal and reciprocal filtering. Acquisition was done both with a linear array antenna of 11 horizontally polarized bowtie elements, and with two co-located linear arrays of 5 bowtie elements each, one horizontally polarized and the other vertically polarized. A small GPS equipped aircraft was used as target. The aircraft GPS data was used to find the bistatic range and Doppler, and the SINR was measured at this target location for half an hour. The Distortionless (DL) ABF obtains notably improved SINR compared to the conventional beamformer for the antennas co-polarized with the transmitter, on average 4.5dB for 11-elements and 2dB for 5-elements. Less than 1 dB improvement was achieved for the 5-element cross-polarized antenna. Stationary interference allowed for defining the DL beamformer by the same spatial covariance matrix with no updates throughout an acquisition of half an hour without deteriorating the beamformer response notably.