Undersampled modified algorithm for cylindrical near-field measurement based on cubic spline interpolation

In order to solve the problem of low efficiency of near-field measurement in anechoic chamber, the efficient measurement methods in near-field antenna measurement are studied, and a cylindrical near-field under sampling recovery algorithm is proposed. The high-precision cubic spline interpolation(CSI) algorithm is used to recover the unsampled points, which can reduce the number of sampling points and improve the test speed. In addition, in the process of solving the cylindrical near-field under-sampled recovery CSI, the excellent characteristics of positive definiteness and symmetry of the coefficient matrix are fully utilized, so that the calculation amount of the linear equations is reduced from O(n^3) to O(n), which greatly improves the calculation efficiency of cubic spline interpolation. Finally, the far-field pattern of the antenna is obtained by using the interpolated near-field amplitude and phase combined with the cylindrical near-field to far-field transformation theory. In order to verify the effectiveness of the proposed algorithm, the antenna prototype is tested, and the experimental results are consistent with the theoretical analysis.