A 3-D Plane Wave Spectrum Filtering-Assisted Near-Field Measurement Using Scanning Optic-Induced Plasma Scattering Technology

Near-field measurement is an effective approach for evaluating antenna performance. Multiple reflection interference between the probe and the antenna under test (AUT) is a common error source in near-field measurement. The recently introduced scanning optic-induced plasma scattering (SOPS) technology exhibits significant susceptibility to interference, which adversely impacts its measurement precision. The SOPS technique enables the efficient acquisition of near-field distribution data across a sequence of multiple planes. In this communication, we take advantage of this high efficiency and propose a 3-D plane wave spectrum filtering-assisted near-field measurement method. The measured near-field data at different distances were first decomposed through plane wave expansion theory. Then, based on different behaviors between the original wave and the reflected waves at various distances, multiple reflected wave components were filtered out in the spatial spectrum along the distance dimension to suppress the multiple reflection interference between the AUT and the silicon wafer. A typical Ka-band antenna was simulated and measured using the proposed method. The filtered near-field distribution and far-field pattern agree well with the simulation results. The 3-D plane wave spectrum filtering-assisted SOPS technology enables near-field measurements to be completed within a few minutes. The proposed method is particularly valuable for measuring high-frequency antennas with a large aperture, and it presents an effective solution to deal with multiple reflections associated with near-field measurement.