REAL TIME FOLIAGE PENETRATION SYNTHETIC APERTURE RADAR

A RADAR OPERATING THROUGH FOLIAGE IS DEGRADED BY FOUR PRINCIPAL EFFECTS: ATTENUATION, REFRACTION, REFLECTION, AND RANDOM DISTRIBUTED RETURNS FROM RESONANT FOREST STRUCTURES. NUMEROUS RADAR DESIGNS HAVE BEEN ATTEMPTED, BUT NONE HAVE RESULTED IN A SATISFACTORY SOLUTION TO THE PROBLEM OF LOCATING TARGETS IN FOLIAGE. THE PROPOSED RADAR SYSTEM CONSISTS OF TWO AIRCRAFT FLYING ROUGHLY PARALLEL PATHS; AT LEAST ONE AIRCRAFT IS TRANSMITTING, BOTH ARE RECEIVING. THIS SYSTEM IS UNIQUE IN AT LEAST TWO MAJOR RESPECTS: (1) THE USE OF LOW ANGLE OF INCIDENCE RADIATION WHICH REDUCES LOSSES DUE TO FOLIAGE, ALLOWS HIGHER FREQUENCIES, AND ALLOWS RANGE RESOLUTION AS A HEIGHT DISCRIMINANT; AND (2) THE USE OF INTERFEROMETER RADAR PRINCIPLES ALLOWS RESOLUTION IN THE CROSS-TRACK COORDINATE. THE RESULTING HEIGHT AND CROSS-TRACK RESOLUTION, IN CONJUNCTION WITH ALONG-TRACK SAR PROCESSING, PRODUCE THREE-DIMENSIONAL RESOLUTION IN POSITION. OTHER FEATURES INCLUDE THE AVAILABILITY OF HEIGHT AND BISTATIC RCS AS TARGET DISCRIMINANTS. IN ADDITION, THE WIDEBAND FREQUENCY SWEEP OF THE PROPOSED WAVEFORM ALLOWS THE FREQUENCY DEPENDENCE OF TARGETS RCS TO BE A DISCRIMINANT.