Reflectarray antenna design comprised of a single-layer double circular ring element

In this paper a single layer X-band (8-12 GHz) microstrip reflectarray antenna consists of double circular ring element at the centre frequency of 10 GHz is proposed. The reflectarray element is printed on a grounded dielectric substrate layer supported by a thick air layer. The performance of the microstrip reflectarray antenna is investigated by using full-wave EM simulations. The presented design offers a wide linear reflection phase range of more than 525° with a slope of 75°/mm at the frequency of 10 GHz. A centre-fed 81-element reflectarray antenna using the aforementioned structure is also designed. Simulated results show that the 3-dB beamwidth is 9.7° and a gain at 10 GHz is 21.5 dB. The simulated results also show a 1-dB gain bandwidth which is about 20% around a centre frequency of 10 GHz.