Fully Probe-Corrected Near-Field Far-Field Transformations With Unknown Probe Antennas

According to the electromagnetic uniqueness theorem, the radiation behavior of an antenna under test (AUT) can be recovered from measurements of two tangential components of its radiated fields on an enclosing surface. In practice, measurements conducted in the radiating near-field (NF) of an AUT utilize probe antennas of finite size. Thus, instead of discrete field values, spatially blurred probe signals are acquired. The probe influence can be compensated, and however, this commonly requires precise knowledge about the probe antenna. In this work, the concept of NF far-field transformations (NFFFTs) with full correction of the influence of unknown probe antennas is introduced. Two nonconvex and two convex formulations are presented and their relation to the similar task of phase retrieval is highlighted. Simulation and measurement results illustrate the validity of the concept, shed light on the required complexity of measurement setups, and illustrate the limitations of the approach. Special attention is paid to the case of high practical relevance when AUT and probe are identical.