An Efficient Antenna Measurements Method in Spherical Near Field Based on Sparse Sampling

A spherical sparse sampling near-field measurements method based on the compressed sensing (CS) approach is proposed in this letter. Since the energy of the spherical wave expansion coefficients (SWECs) of the antenna is concentrated in a limited set of coefficients, sparse optimization sampling becomes a viable choice. To minimize the testing time, nonuniform or adaptive sampling has been extensively explored. However, in practical testing scenarios, these sampling methods fail to guarantee a reduction in the mechanical motion time of the sampling path, making the CS approaches a huge challenge. The proposed uniform undersampling method based on the two-step iterative shrinkage/thresholding (TwIST) algorithm ensures a reduction in sampling time and is suitable for both single-probe and multiprobe sampling systems. A comparison of the near-field to far-field transformation (NFFFT) accuracy between the classical CS methods and the proposed scheme validates its effectiveness. The proposed method achieves a truncation mode number of only one-third of that required by traditional fast Fourier transform (FFT) methods at the same error level. Simulation and measurement results verify the feasibility of this method.