Fundamental experiment of a polarization-rotating reflector of Van Atta array design for polarimetric calibration

Polarization-rotating reflectors are important as a reference target for polarimetric calibration of a synthetic aperture radar. A polarization-rotating retrodirective reflector of Van Atta array design has already been proposed by one of the authors. This paper describes the result of an experimental verification of the proposed polarization-rotating retrodirective reflector. The experimental system consists of two subarrays each composed of 2 × 2 dual-polarized elements for horizontal and vertical polarizations working at 2.4-GHz frequency band. In the experiment, two subarrays are arranged side by side, and the respective orthogonal polarization ports of the subarrays are connected with lines of the same electrical length to form a one-dimensional polarization-rotating Van Atta array. To increase the radar cross section, amplifiers are inserted into the lines. The reflection pattern of the reflector is measured in a radio anechoic chamber by rotating the reflector around the axis perpendicular to the array normal direction. From the experiment, a wider angular response of the proposed reflector in the horizontal direction, which is provided by the retrodirective characteristics of the Van Atta array, than the conventional array reflector of the same element number as the proposed reflector is verified in addition to its polarization-rotating capability introduced by the dual-polarized antenna elements.