Circularly polarized reflectarray with microstrip ring elements having variable rotation angles

This paper reports a 0.5-m-diameter right-hand circularly polarized planar reflecting antenna array that uses 437 printed microstrip ring elements of variable rotations to achieve cophasal far-field radiation and wide-band performance at a focal length of 0.35 m. The array is etched on Rogers Duroid 5870 substrate with ε_r= 2.33 and 0.508-mm thickness. At 7.1 GHz, the reflectarray achieves an efficiency of 41.7% with a gain at broadside of 27.6 dB. Sidelobe suppression is greater than 17.3 dB, and the left-hand cross-polarization is 23.2 dB below the desired right-hand component. The best efficiency of 45.7% and the maximum gain of 28.2 dB occur at 7.3 GHz.