Circularly Polarized Elliptical Microstrip Patch Reflectarray

A double-layered elliptical microstrip patch element is proposed for designing a broadband circularly polarized (CP) reflectarray for the first time. The proposed reflectarray element is composed of two elliptical patches stacked on the top and middle surfaces of two substrates, and reflection phase range is generated by varying the major axes of the elliptical patches. Floquet method is employed for simulating the element, and it is found to be able to generate circular polarization (CP) with a broad reflection phase range of 550 degrees with only two layers. With the use of the element, a CP 11 x 11 full-fledged reflectarray has been designed and fabricated. The reflectarray is fed by a linearly polarized horn. Measurement shows that the proposed CP elliptical microstrip patch reflectarray is able to achieve an antenna gain of 20.38 dBic and a 1-dB gain bandwidth of 11.6%. It also has a broad 3-dB axial ratio bandwidth of 12.47%.