Accurate and Efficient Computation of Antenna Measurements Via Spherical Wave Expansion

The estimation of measurement uncertainties is mandatory for every high-accuracy antenna measurement. However, a method to analyze the uncertainties of complete 3-D measurements caused by arbitrary test zone field imperfections in a precise and computationally efficient way is still missing. This gap in the uncertainty analysis is closed by simulating a measurement scenario via spherical wave expansion. Thereby, the actual measurement sequence is imitated by using the matrix-vector representation of an antenna measurement. The spherical mode coefficients of the antenna under test held by the vector are mathematically rotated step by step and repeatedly multiplied by the field within the test zone which is represented by the coefficients in the matrix. As the technique is applicable to far-field and near-field data, the evaluation of antenna measurements is considered in general, and the emulation of a measurement process is exemplary carried out for a compact antenna test range. Finally, the numerical results are compared to an implementation of the coupling equation demonstrating the usefulness and efficiency of the proposed algorithm.