Conjugate gradient method combined with FFT (CG-FFT) is a suitable approach for large scatterers and radiating systems. The uniform sampling scheme, widely used in current applications, requires memory storage and computational complexity which increases very rapidly with the desired accuracy. In this work, to circumvent this difficulty for the case of large structures with localized isolated discontinuities, where higher accuracy (resolution) is required only over some specific parts, a nonuniform sampling scheme is presented.

Proceedings of the IEEE Antennas and Propagation International Symposium. Part 1 (of 2)
Department of Systems and Computer Engineering

Banihashemi, A, & Safavi-Naeini, S. (S.). (1993). CG-FFT method with nonuniform sampling for Pocklington's equation. In AP-S International Symposium (Digest) (IEEE Antennas and Propagation Society) (pp. 76–81).