Accurate Gain Determination in Near-Field Limited Sampling Area Using the Field Extension Method

The use of planar near-field measurements to determine antenna gain is widespread. However, the accuracy of the results is strongly dependent on the size of the sampling area, especially when working in limited test spaces, which affects the precision of the gain measurements. To overcome this limitation, our method uses a virtual array source with adjusted amplitude and phase distributions to extend the sampling field, allowing accurate gain measurements within a small planar near-field and increasing test efficiency. Notably, it remains valid even when the maximum radiation direction is not aligned with the center of the sample plane. Both numerical simulations and experimental data confirm the effectiveness and feasibility of our proposed method, which increases test efficiency and reduces the required sampling area.