Fast Far-Field Estimation Method by Compact Single Cut Near-Field Measurements for Electrically Long Antenna Array

This paper proposes a fast far-field estimation method of electrically long antenna in compact measurement space. The presented method estimates a far-field pattern on an orthogonal cut plane from the linear equivalent electric current and circular current distribution. The equivalent electric current data is measured in a reactive near-field region using a small loop probe. In the proposed method, the linear equivalent current distribution is extended by a simple numerical extrapolation formula for improving the accuracy of the estimated far field in the broadside direction. In the horizontal plane, the far-field pattern is calculated from both the circular equivalent electric and the magnetic distribution approximating equivalent magnetic current with equivalent electric current. We confirmed the validity of the proposed method from the numerical simulation and measurements results. The method allows accurate directivity measurement in a small space in about a few minutes.