Fast analysis of transient scattering in lossy media

The solution of time-domain integral equations pertinent to scattering from perfectly conducting objects residing in unbounded lossy media is considered. The computational cost of classical marching-on-in-time (MOT) schemes for the solution of such equations scales as O(N/sub t//sup 2/N/sub s//sup 2/), where N/sub t/ and N/sub s/ are the number of temporal and spatial unknowns, respectively. A fast Fourier transform (FFT)-based algorithm that reduces the computational complexity to O(N/sub t/N/sub s//sup 2/log/sup 2/N/sub t/) is introduced. When combined with spatial FFT algorithms, the proposed scheme further reduces the complexity of MOT-based integral equation solvers, for example to O(N/sub t/N/sub s/log(N/sub t/N/sub s/)logN/sub t/) if the objects are uniformly meshed. Numerical simulations that demonstrate the accuracy and efficiency of the algorithm are presented.