Dual Polarized Wideband Feed with Cross-Polarization Reduction and Compensation Proprieties for Compact Antenna Test Range
Measurement applications in a Compact Antenna Test Range (CATR) often require low cross-polarization or high polarization purity of the Quiet Zone (QZ). This requirement is often the main motivation for choosing the more complex and thus expensive compensated dual reflector system as opposed to the simpler and cheaper single reflector system. In this paper, a novel, wide-bandwidth, conjugate matched feeding concept is presented. The concept aims at the cancellation of the geometrical optics cross-polar component in the QZ of standard single reflector CATR. The concept is valid for both side and diagonal fed configurations in dual simultaneous polarizations. The conjugate matched feeding concept, is described in detail and the cross-polarization cancellation properties of the proposed wide-bandwidth feed system is discussed. The concept is initially verified and the solution consolidated using numerical simulation of the reflector and full wave simulation of the feed system. The achievable wide-band cross-polar discrimination of 40dB in the QZ is confirmed on an operational bandwidth of 1:1.5. The conjugate matched feeding concept is then validated by a reduced hardware demonstrator and measurements. The target crosspolar discrimination of 40dB is confirmed by QZ probing of a standard single reflector CATR system.