Analysis of the Feed Absorber Fences in Compact Antenna Test Ranges and their Impact on Quiet Zone Metrics

Author: Vince Rodriguez
Publication: EuCAP 2023
Copyright Owner: IEEE

Compact Antenna Test Ranges (CATR) are one of the workhorses of antenna measurements. They have been recently chosen as the preferred method for testing 5G antenna systems. Ideally, a plane wave is generated at the quiet zone (QZ) by the parabolic reflector. The purity of the plane wave is affected by the pattern of the feed and the termination of the reflector edges. The feed pattern must be broad enough to minimize the amplitude taper across the QZ. However, a broad beam antenna will cause direct illumination of the QZ from the feed, creating an interference ripple on the QZ fields. Recently a paper was presented where a CATR was analyzed using a high order MoM approach. This method provides the field distribution across the QZ, not only from the reflector but also from the source spillover. In this paper the absorber fence that is used to minimize the direct illumination of the QZ from the feed is analyzed. Traditional fences are analyzed for different absorber loadings, from a heavily loaded to lighter loaded absorber. In addition to the analysis of the absorber loading, a differently shaped absorber fence is analyzed. The results show that absorber loading has little effect on the QZ metrics. Shaping the fence is far more important. The specially shaped fence shows that the diffraction is reduced resulting in an improved ripple level and phase variation in the QZ.

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