Determination of the Offset Distance for F-MARS: An Equivalent Source Model Perspective

In many cases, reflections within antenna measurements are the primary factor contributing to the far-field antenna test. The technique named far-field mathematical absorber reflection suppression (F-MARS) has been successfully used to identify and suppress the effects of range multipath effects in antenna testing. While the existing studies have illustrated the effectiveness of the F-MARS technique, the exact value of the offset distance not been elucidated in detail. We present a method to determine the offset distance of F-MARS in this letter. The proposed method incorporates the equivalent source model for vector decomposition of multipath signals, reveals the essence of the separation effect achieved by F-MARS, and deduces an offset distance expression including the interference angle, aperture, and other variables. Numerical simulation and experimental results prove the rationality of the offset distance obtained by the proposed method, and show its guiding significance for F-MARS.

I. Introduction

The direct far-field antenna measurement technique is favored for its ability to obtain far-field antenna pattern data with relative ease and simplicity [1]. Multipath reflections in antenna test environments often contribute significantly to measurement errors within a facility's specified error budget. In particular, direct collimation ranges can be more susceptible to the influence of these undesired elements [2]. In the past, the mathematical absorber reflection suppression (MARS) technique has been employed for an extended duration in the context of spherical [3], [4], [5], cylindrical [6], [7], [8], and planar [9], [10], [11] near-field antenna measurement systems, compact antenna test ranges [12], as well as far-field [1] measurement facilities. The primary purpose of MARS is to detect and mitigate spurious scattering effects. It is a unique measurement and mathematical post-processing technique that only requires minimal detailed information about the antenna under test (AUT), the probe, and the measurement geometry structure [7].