Design of a single layer reflectarray unit cells based on hexagonal ring for wideband operation

In this paper, a microstrip reflectarray unit cell with different configurations of hexagonal element is presented. The aim is to have a large reflection phase range with comparatively linear phase slope as a function of element size to achieve a wider operational bandwidth of a reflectarray antenna. Full-wave EM simulations are used to investigate the phase characteristics and performance of reflectarray unit cells. The simulated results show that a single-resonance hexagonal ring provides an insufficient reflection phase range (<; 360°). It is also shown that multi-resonance hexagonal elements (double hexagonal ring, triple hexagonal ring and hexagonal patch/ring) can provide a reflection phase range exceeding 360°. A centre fed 81-element microstrip reflectarray antenna using one of the proposed structure (double hexagonal ring) is also designed. The simulated results show a constant 3-dB gain bandwidth around the frequency band of 9-12 GHz.