Aspect dependence of time-frequency signatures of a complex target extracted by impulse radar

We study the scattering interaction of a complex-shaped target with electromagnetic pulses of short duration transmitted by an impulse radar. The target is a metallized plastic scale model of an aircraft, in this case a B-52 bomber. The form-function, or radar cross-section (RCS), in the backscattering direction, filtered by the complete system made up of radar and digitizing signal analyzer, is determined from the measured data when the target, located in an anechoic chamber, is illuminated at each one of several different aspect angles. The directions of illumination are the head-on, broadside, and tail-on aspects together with a number of intermediate aspects. Also time-frequency signatures from the target are examined, and we notice in particular that they change in a well behaved manner with the aspect angles throughout the entire angular range from head-on to tail-on. Furthermore, the location of a few prominent features remains constant in wide angular intervals. Our examination of the aspect dependence of the time-frequency signatures suggests that the identification of complex-shaped targets can be based upon a small set of templates for each given target. Such sets of time-frequency signatures could then be used in conjunction with neural networks or other pattern recognizers to achieve the unambiguous classification of targets.