Quad-Polarization Reconfigurable Reflectarray With Independent Beam-Scanning and Polarization Switching Capabilities

A quad-polarization reconfigurable reflectarray (RA) antenna, which can work in horizontal polarization (HP), vertical polarization (VP), left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP) modes with simultaneous large-angle beam-scanning capability, is designed and experimentally verified. Under the traditional view at the element level, at least 2-bit phases are required because a 90° phase shift step is needed for conversion from linear polarization (LP) to circular polarization (CP). In this work, we found that the extra phase shifts (90°/
$- 90^{\circ })$
can be achieved by changing the global reference phase of the 0/1 coding arrangement in the spatially fed architecture, while 1-bit phase resolution is used in the element level. As verification, a square patch with four slots loaded with two positive-intrinsic–negative (PIN) diodes is exploited as an RA element with 1-bit phase independent control of dual-LP. Then, the RA aperture contains 16
$\times16$
elements, where 512 PIN diodes are integrated to control each state independently by a field-programmable gate array (FPGA), excited by a linearly polarized horn is developed and fabricated. Besides, the superposition of the aperture field approach is used to optimize the CP radiation performance, especially the axial ratio (AR). The measured results of the prototype demonstrate the simultaneous multipolarization reconfigurable and the beam-steering capability, where scanning beams are up to 60° in horizontal and vertical planes. The proposed low-lost design is believed to be a promising candidate for mobile communication and cognitive radar applications.