Modified $\theta $-Scanning Technique for First/Third-Order Probes for Spherical Near-Field Antenna Measurements

This paper presents a modified thetas-scanning technique for first/third-order probes for spherical near-field antenna measurements. Unlike the traditional thetas-scanning technique, this new scanning technique gives a possibility, due to the cutoff property of the azimuthal spherical modes, to filter out the influence of the undesired third-order azimuthal modes of the probe near the poles of the measurement sphere. Without increasing the measurement time, the technique allows reducing the errors caused by the application of the computationally efficient first-order probe correction technique (incorrectly) to first/third-order probes. The technique is optimal for spherical near-field systems, that employ, for example, an open-ended rectangular (or square) waveguide probe, that closely approximates a first/third-order probe, and apply the well-known first-order probe correction technique. In such systems, compared to the traditional thetas-scanning technique, the modified thetas-scanning technique can be used to significantly reduce the errors caused by the incomplete probe correction.