Design of double-ring unit cells for single-layer microstrip reflectarrays

The reflection characteristics of oblique angles of incidence on single-layer double-ring unit cells for reflectarray antennas have been investigated. The presented results have revealed that the normal incidence can present acceptable approximations for the phasing response for angles up to 30deg degrees. The resonance characteristics of the double-ring elements have also been investigated. A simple method to approximate the reflection phase swing regions with respect to element size has been presented followed by parametric studies. By using the design guide lines presented in this paper, single-layer double-ring structures with an extended phasing range of more than 600deg and a considerably slow slope have been demonstrated.