Fast Antenna Far Field Characterization via Sparse Spherical Harmonic Expansion

A procedure is proposed to significantly reduce the amount of time to characterize three dimensional 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 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 three dimensional 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 to standard approaches. These results pave the way to a more efficient use of far field measurement facilities.