On the Use of Metal-Only Polarization Rotation Elements for Reflectarray Designs

A reflectarray antenna employing metal-only polarization rotation elements is proposed in this letter. The element is composed of double metallic layers separated by an air gap and rotates the reflection wave polarization orthogonally with respect to that of the incidence wave. By tuning the structural dimension, a pair of elements with 90° phase difference are obtained. These two elements together with their mirroring images can be employed as a 2-bit phase shifter with 0°, 90°, 180°, and 270° phase shift from 9 to 10.8 GHz. For proof-of-concept, a metal-only reflectarray containing 225 unit-cells is developed and tested. According to experimental results, the 1 dB and 3 dB gain bandwidth of the metal-only reflectarray are 19% and 38% respectively while the peak aperture efficiency is 34%. These encouraging features demonstrate that reflectarrays can be successfully designed with metal-only polarization rotation elements and present a good potential for space applications.