Combatting High Dynamic Range Issues and Extraneous Peaks in Bistatic Passive Radar Exploiting Digital Video Broadcast.

This paper addresses practical issues associated with using the OFDM signal emanating from a Digital Video Broadcast for Terrestrial (DVB-T) Tower as a Signal of Opportunity for Bistatic Passive Radar. In such a system, the signal from the DVB-T Tower is received at the Primary Antenna Array via both a Direct Path (DP) and a Reflected Path (RP) off the target of interest. Complications arise from the DP signal being substantially stronger in power than the RP signal, e.g., by 80 dB, even after the gains achieved through beamforming and other means of mitigation. Often, there is a dedicated Auxiliary Antenna pointed towards the DVB-T Tower to pick up the DP signal. The signal from the Auxiliary Antenna is then subtracted from the Primary Antenna Array. After subtraction, the signal from the Primary Antenna Array is run through a Matched Filter which is based on a Doppler-shifted version of the same DP Signal obtained from the Auxiliary Antenna. There are performance advantages to decoding the OFDMbased DP signal and reconstructing it for both subtraction and matched filtering purposes. Due the large differential in received power, though, even small errors in the reconstructed OFDM signal lead to residual terms in the matched filter output that canmask the RP signal. This paper presents a simple method for mitigating this problem. In addition, simple means are presented for removing the spurious peaks in the autocorrelation of the DVB-T signal due to the cyclic prefix in OFDM.