Numerical investigation of cross polar reduction CATR feed in dual linar polarisation

The polarization purity of an antenna system is an important performance parameter, particularly in dual-polarized systems, where depolarization can prevent operating objectives from being achieved. Accurace polarisation testing, requires a significantly higher polarisation purity of the test system than the test object. The Compact Antenna Test Range (CATR) is widely used for antenna system testing purposes [1]. It provide convenient testing, directly in far-field conditions of antenna systems placed in the Quiet Zone (QZ). Polarization performance is often the main motivation for the CATR implementation based on a more expensive and complex, dual compensated reflector optics rather than a single reflector optics. Improving the QZ cross-polarization performance of the single reflector CATR has been a challenge for the industry for many years. Recently, a feed, based on conjugate matching of the undesired cross-polar QZ fields has been validated sperimentally [2-3]. In this paper, we show by numerical simulation, that the cross-polar discrimination of the QZ can be improved by as much as 10dB with respect to standard feeds on a 1.6:1 bandwidth for dual liner polarization in standard side and edge-feed single reflector CATR.