Hybrid Polarization-Phase Tuning Methodology for Reflectarray Antennas

Abstract

A hybrid polarization-phase tuning methodology is presented for reflectarray antenna designs. First, three representative phasing approaches for reflectarray designs are briefly reviewed, and it is pointed out that when the polarization conversion is considered, these phasing approaches can be combined together to achieve more versatile functionalities and better performance. It is theoretically derived that using the mirror combining approach (MCA), broadband reflectarray elements with polarization conversion can be achieved. Using the rotational combining approach (RCA), both amplitude and phase of the reflected cross-polarization waves can be controlled. Next, a split ring element has been designed as an example to demonstrate the theoretical analysis. By using the MCA, the designed element achieves a linear 360° phase coverage, which suggests its capability of wideband operation. By using the RCA, the designed element achieves continuous amplitude modulation from 0 to 1 and full 360° phase coverage. Finally, a Ka-band reflectarray prototype with broadband behavior is designed, fabricated, and measured. It has achieved high-gain pencil beams pointing at predesigned directions. The measured gain at 20 GHz is 35.6 dBi with the aperture efficiency of 54.4% under linear-polarization (LP) excitation, and the gain is 35.4 dBi with the aperture efficiency of 52% under circular-polarization (CP) excitation. The measured 1 dB gain bandwidth is 18.5% (19-22.7 GHz) and 12.5% (19.3-21.8 GHz) under LP and CP excitation, respectively.