Planar Polarization Rotation Pattern Manipulation Surfaces with Enhanced Incident Angle Range and Beam Steering Ability

A novel synthesis method of designing polarization rotation pattern manipulation surface (PRPMS) with enhanced performance under oblique incidences and scanning to arbitrary directions is presented in this article. Firstly, the wave conversion process of the structure with incident angle, scan angle, and polarization is theoretically investigated by the proposed equivalent circuit model (ECM), which reveals that the polarization conversion ratio (PCR) is determined by the impedance transforming via the patch. Then, two methods are proposed to achieve a relatively constant relationship of PCR with the incident angle or scan angle, including broadening the beamwidth of the active element patterns and adjusting the feeding positions according to our proposed theory. To reach these goals, four open-ended stubs are loaded on the patch, so as to broaden the 3-dB beamwidth of the patch by reducing the electrical length between two equivalent slots. Taking advantage of the transmission line theory, the desired PCR with different incident angles and scan angles can be easily achieved by only tuning the equivalent feeding positions of the patch. Finally, based on the phased array theory, three PRPMS prototypes are calculated, designed, fabricated, and measured to verify our design concept. Good agreements between these results show that the PRPMS can successfully alter the incident wave to the wanted angle and rotate the polarization while maintaining the PCR over 80%. The results verify that it is possible to use this method in the design of functional surfaces.