Fast Antenna Testing With a Reconfigurable Near-Field Leaky-Wave Probe

This paper presents a novel, compact, and fast antenna characterization method using a spatially dispersive, reconfigurable leaky-wave antenna (LWA) probe. In the proposed setup, the antenna under test (AUT) and the LWA are placed face-to-face in the radiative near-field region, and the voltage transmission coefficient between them is measured for various electronically controlled LWA configurations, referred to as interrogation modes. Each mode corresponds to a unique near-field plane-wave spectrum defined over a fictitious interrogation plane. An approximate transmission model is developed based on the spectral overlap of the tangential electric fields of the LWA and AUT in this plane. When the LWA’s field distributions are known a priori, the measurement process becomes a spectral-domain sensing problem. To ensure accurate reconstruction, a set of orthogonal interrogation modes with sharp main beams and low sidelobes–steered over the angular range -75∘ to 75∘–is synthesized by optimizing the LWA’s tunable varactors. The AUT’s one-dimensional tangential electric field distribution is reconstructed using Tikhonov regularization, followed by a near-field to far-field transformation to obtain its radiation pattern. The proposed approach eliminates the need for mechanical scanning in this one-dimensional configuration, significantly reducing measurement time. Simulation and experimental validation with various AUTs–including waveguides, horns, and patch arrays–demonstrate accurate far-field reconstruction, particularly for narrow-beam antennas and observation angles up to 60∘. This electronically reconfigurable setup offers a practical solution for fast, high-throughput antenna testing in modern RF and microwave systems.