Coherent Integration Loss due to Transmit Antenna Scanning Modulation Effect on Passive Bistatic Radar

This paper explored the transmit antenna scanning modulation effect on the signal to noise ratio (SNR) loss in a noncooperative illuminator based bistatic radar. The general expression of normalized filed pattern for widely used antenna was analyzed. The direct-path signal and target echo modulated by the transmit antenna, which is mechanically scanned in azimuth, were described. Mathematical representations for direct-path signal and target echo were proposed with respect to the analytical expression of antenna’s pattern. The SNR loss of the coherent integration via cross-correlation processing was derived. The relationship between SNR loss and SNRs of direct-path channel and target echo channel was evaluated. The simulation result shows that the SNR loss caused by antenna modulation can be ignored if the average SNR in direct path is greater than 15 dB. However, the SNR loss deteriorates rapidly if the visual angle becomes larger. Some suggestions on choosing the IF bandwidth and data selection were presented.