Application of Non-Uniform FFT Based on Spherical Mode Expansion

In the spherical near-field measurement, numerous researchers have proposed non-equiangular sampling scheme to address the issue of redundant sampling information. However, conventional spherical near-field measurement processing of uniformly sampled near-field data is accomplished using the Fast Fourier Transform algorithm. In this article, we will apply the Non-uniform Fast Fourier Transform algorithm to process non-equiangular sampled data based on the spherical mode expansion theory. Compared with other non-uniform sampling schemes, the proposed method does not require interpolation before computation, and it also improves computational efficiency. Finally, the proposed approach is validated using a antenna under test which is a horn antenna.