A reflectarray design with gapped ring elements and reduced cross-polarization for polarimetric radar

Dual polarimetric weather radar provides better interpretation of the type of precipitation and more accurate information of precipitation fall rates. Since the precipitation detection in dual polarimetric measurements relies on complete isolation of orthogonal components of the fields, a low cross-polar radiation is desirable. Reflectarray is a good antenna candidate for dual-polar weather detection, due to its low cross-polar radiation performance. In this paper, a reflectarray with gapped double-ring elements was designed to suppress the cross-polar level at and around broadside. In this design, gaps are cut on the double-ring elements to change the directions of the surface currents, so the cross-polar radiation components will cancel each other along the broadside direction, and thus a low cross-polar level can be achieved. Both simulation and measurements were carried out on the design, and a cross-polar level of -44 dB at broadside and less than -33 dB for all azimuth ranges (-90° <; θ <; 90°) is achieved in measurements.