Near-Field to Far-Field Transformation using Near-Field Samples over an Irregular Spherical Surface

In this paper we present a matrix method which takes into account the probe positioning errors in spherical near-field (NF) measurement. The NF irregularities made the determination of the spherical wave expansion (SWE) from the measured data using the Fast Fourier Transformation (FFT) impossible. The irregularities can be randomly distributed but known. The matrix method expresses the linear relation between the measured NF and the corresponding SWE coefficients. The accuracy of the proposed method is numerically studied as a function of the irregularities magnitude and for different noise levels (data Signal to Noise Ratio). Also, experimental results have shown the efficiency of the proposed technique.