Radar Scattering and Target Imaging Obtained Using Ramp-Response Techniques

The response from targets illuminated by a transient plane wave the time dependence of which takes the form of a ramp function has been used to generate signatures for conductive and penetrable targets. Modified geometrical profile functions of various targets are used to generate their ramp response, which in turn is used to evaluate their scattered fields as a function of frequency. In early time, the ramp response is proportional to the physical cross-sectional area of the target (as a function of time or distance as the wave propagates over the target). Thus, the ramp response can be generated from the target´s geometry. This is then Fourier transformed to obtain the spectrum of the ramp response. To obtain the spectrum of the impulse response, this result is simply multiplied by (jomega)², where omega is the angular frequency. These simple steps can be readily performed by anyone with an electrical engineering background to obtain the backscattered fields to a reasonable approximation. These same fundamentals can also be used to approximate a target´s image from the measured ramp response. This has been done for axial incidence of rotationally symmetric targets. It can be extended to non-rotationally symmetric targets using an iterative process.