Pruned NUFFT-3 for far-field calculations

We deal with an approach based on Non-Uniform FFTs (NUFFTs) of type-3 and on a pruned FFT to efficiently computing the far-field radiated/scattered by volumetric sources/objects. The approach consists of three steps: 1) representation of “non-uniformly sampled” Fourier exponentials by a finite number of “uniformly sampled” ones, with such number controlling the accuracy; 2) “pruned” FFT; 3) interpolation, again with controlled accuracy, of the “uniformly sampled” exponentials onto the “non-uniformly sampled” ones corresponding to the relevant observation directions. The computational performance of the approach is sketched.