Radar cross section enhancement using phase conjugated impulse signals.

摘要

Apparatus (10) and methods (50) for enhancing the radar cross section of a target (12). The present invention is an impulse radar system (10) that implements a method (30) that comprises the following steps. A pilot impulse radar pulse (11) is transmined (51) at a target. The pilot pulse comprises a plurality of individual pulses having respective distinct frequencies generated by the impulse radar system (10). A return impulse radar pulse (11a) from the target is received (52) by the impulse radar system and provides information indicative of target scattering centers. The return pulse is used as a calibration signal for generating (53) a phase conjugate impulse radar pulse (11b). The phase conjugate impulse radar pulse is then transmitted (54) at the target. Processing (55) a target return signal derived from the transmitted phase conjugate impulse radar pulse enhances the radar cross section of the target (12) because the waveform of the transmitted phase conjugate impulse radar pulse is matched to the characteristics of the target (12). The present invention is adapted to detect low radar cross section targets (12) without encountering the problems and frequency restrictions with conventional radar systems. In a second embodiment of the present invention, when a progressive phase variation is applied to the transmit pulses, the radar cross section contributed by backward travelling wave is made to add in phase in the received direction by processing the received target return pulses while adaptively adjusting the phase sequence of the transmitted pulses. When the appropriate phase sequence is achieved which is such that the transmitted pulses match the scattering centers on the target, then an enhanced return signal is received. <IMAGE>