An Effective Method for Accurate Gain Determination in Phaseless Measurement of Limited Planar Sampling Area

It is well known that the truncation effect introduced by the limited sampling area in planar near-field measurements negatively impacts the gain results, becoming more significant as the sampling area decreases. In this paper, the radiation characteristics of the antenna under test (AUT) are equivalently represented by a virtual array through matching the amplitude of the AUT’s planar near-field with that of the superimposed field of the virtual array. Due to the limited planar sampling area, accurate gain and main lobe pattern information are regarded as acceptable, rather than aiming to restore the complete radiation pattern as in traditional equivalent models. Therefore, approximate solutions are considered sufficient, eliminating the need for exact solutions. The proposed method integrates the simplicity of planar sampling with the capability to extend comprehensively to arbitrary sampling shapes, including common shapes such as cylindrical and spherical sampling. Both simulation and experimental results demonstrate the effectiveness and feasibility of the proposed method, significantly reducing the required test area while ensuring the accuracy of gain measurements. This provides a practical solution for phaseless near-field antenna gain measurement.