Comparison of vector and Scalar Spherical Harmonics expansions of UWB antenna patterns

Antenna radiation pattern modeling is fundamental in radio channel simulation. In order to have accurate results, the antenna should be described over 4π steradians within the frequency band. For UWB antennas, it represents a large amount of data. Sampling the antenna pattern at the transmitting and receiving sides is computationally costly. Therefore data should be compressed and the spherical harmonics decompositions come up. Two approaches are proposed in this paper: a Vector Spherical Harmonics (VSH) and a Scalar Spherical Harmonics expansions. This paper will presents the first comparison on real data of a set of 17 different UWB antennas measured in a near-field anechoic chamber of both scalar and vector spherical harmonics decompositions. The comparison is based on different criteria: On one hand, the reconstruction error of the antenna radiation pattern and on the other hand the number of significant coefficients.