Fast Antenna Far-Field Characterization via Sparse Spherical Harmonic Expansion

A procedure is proposed to significantly reduce the amount of time to characterize 3-D antenna far-field patterns. The measured far field is expanded into spherical harmonics, and a sparse recovery algorithm is used to recover the spherical wave coefficients giving access to the field radiated by the antenna everywhere. A small number of measurement points are required, since the relevant information of the most antenna patterns is concentrated in only a few spherical wave coefficients. Sampling strategies enabling fast spherical scans are discussed, which makes the approach both efficient and easy to implement in existing far-field measurement facilities. Simulations are first provided to show the potentialities of this compressive sensing-based approach. The proposed strategy is then applied to characterize 3-D far-field patterns radiated by several antennas operating in different frequency bands measured in far field in direct line of sight configuration and in a compact antenna test range. Experimental results show that a saving in the number of measurement points up to 70% can be achieved compared with standard approaches. These results pave the way to a more efficient use of far-field measurement facilities.