Non Stationary Bistatic Synthetic Aperture Radar Processing: Assessment of Frequency Domain Processing from Simulated and Real Signals

Bistatic synthetic aperture radar (SAR) imaging from very asymmetric configuration is a promising technique for both military and civilian issues. Indeed, an illuminating radar standing off at a safe distance may be combined with a low cost, possibly unmanned air vehicle using a passive radar receiver operating at closer range. Practical civilian application could be high resolution remote sensing of dangerous disaster areas (fire, chemical or radioactive hazard) with small unmanned aircrafts. Military application could be SAR imaging in the forward direction for a missile guidance without signalling the sensor by its transmitted radiation. However, such configurations are strongly non-stationary in the sense that the transmitter to receiver distance and relative orientation varies. This severely harden the task of frequency domain processing and especially its motion compensation. We tested frequency domain processing and motion compensation for both simulated and real signal for identical asymmetric configurations. The SAR processor may provide self-testing before image synthesis and forecast phase errors in the resulting image depending on terrain elevation features. Error maps provided may be used for illustrating the motion compensation and the frequency domain processing in a didactic way. Opportunistic air-to-air ISAR imaging (of the receiver plane) was successfully experimented, though bistatic imaging was mostly a failure due to local clock jitter. This crucial issue as well as the clock drifting issue will be addressed.