A fast algorithm for signature prediction and image formation using the shooting and bouncing ray technique

We present a fast simulation algorithm for generating the range profiles and inverse synthetic aperture radar (ISAR) images of complex targets using the shooting and bouncing ray (SBR) technique. Starting with the time-domain and image-domain ray-tube integration formulas we derived previously, we cast these formulas into a convolution form. The convolution consists of a nonuniformly sampled signal and a closed-form time-domain or image-domain ray spread function. Using a fast scheme proposed by Sullivan (1990), the nonuniformly sampled function is first interpolated onto a uniform grid before the convolution is performed by the fast Fourier transform (FFT) algorithm. Results for several complex targets are presented to demonstrate the tremendous computation time savings and excellent fidelity of the scheme. Using the fast scheme, a speed gain of a factor of 30 is achieved in performing the ray summation as compared to the direct convolution in range profile computation and a factor of 180 in ISAR image formation for a typical aircraft at S-band