Evaluation of Phase Responses of Double Ring Elements for Reflectarray by Simulation and Measurement

This paper presents design and performance analysis of three proposed shapes for use as microstrip patch elements for reflectarray antenna. The elements are formed of patches of variable size. The comparison focuses on effect of the elements shapes and boundaries on the performance of reflection phase represented by; range, slope and magnitude. Variation of the responses with frequency is also investigated to examine the frequency response of the proposed elements. Three shapes in the form of double-rings inspired by the Koch fractal are investigated. The elements are of single layer configuration printed on composite substrate of FR4 and foam. The bandwidths of the elements were estimated from the phase responses. The analyses were performed using the CST Microwave Studio software package. Experimental validations are given using measurements by vector network analyzer VNA, and employing the X-band waveguide simulator. The elements showed improved bandwidth.