DVB-T passive radar dual polarization measurements in the presence of strong direct signal interference

A dual-polarization passive bistatic radar is used to evaluate the potential benefit of cross-polarized measurements for the suppression of strong direct signal interference in the DVB-T band. The linear array antenna consists of 10 bowtie elements, 5 of which measuring horizontal and 5 vertical polarization. Two small GPS-equipped aircraft were used as targets, flying prescribed patterns. Two antenna locations were used, one in which the broadcasting transmitter was only 20° from the antenna boresight, causing strong direct signal interference, and one in which the antenna was partially shielded from the transmitter. In both polarization channels, reconstruction of the reference signal and reciprocal filtering was used to suppress interference. GPS data from the aircraft was used to find the bistatic range, Doppler, and azimuth location, and the signal to interference pluss noise ratio (SINR) at this location was measured. In addition, the azimuth inferred from GPS was compared with the direction derived from the radar measurements. We find no advantage using cross polarization, even in the case with strong direct signal interference: On average there is no significant difference between co- and crosspolarized SINR, and the co-polarized channel is slightly better predicting the correct azimuth.