On the effects of clock offset in OFDM-based Passive Bistatic Radar

In Passive Bistatic Radar (PBR) a local communications transmitter is used as an illuminator. A Line Of Sight (LOS) signal is captured to use as a template for radar processing. This may be cleaned via demodulation and remodulation, removing short-delay copies and sensor noise. However differences between the transmitter clock and local clock cause the remodulated signal to be mismatched to the transmitted signal, causing degradation of delay-Doppler processing output. This study presents a model which captures the effect of clock disparity upon remodulated OFDM signals. The model is used in simulation to illustrate the specific effect of clock offsets on PBR by examination of delay-Doppler output. It is shown that modification of the template to account for time-varying clock offsets can restore the delay-Doppler output to be nearly ideal.