Far-Field Estimation Method of Antennas Above Conductive Plane Using a Partially Spherical Near-Field

Abstract

For evaluating the practical performance of land mobile communication antennas via near-field measurement, it is essential to measure the electromagnetic field, including the housing in which the antennas are mounted. When measuring a heavy housing, scattered waves from the supporting turntable for the antenna under test (AUT) disturb the electromagnetic field. A technique for eliminating the influence of scattered waves is required to evaluate the abnormal AUT radiation performance. This paper proposes a method for estimating the far-field when the antenna exists above an infinite conductive plane, using partially spherical near-field measurements that include the turntable. The proposed method estimates the far-field by combining the equivalent source reconstruction and the far-field estimation with the reflection coefficient method. In the proposed method, the equivalent source distribution surrounding an AUT is reconstructed from a partially spherical near-field to remove the effects of the turntable. Through numerical calculations and experiments, this paper shows that the proposed method can estimate the far-field pattern above an infinite conductive plane, with arbitrary electric constants from a partially spherical near-field. The far-field estimation error is less than -20 dB when the upper hemispherical near-field can be obtained.