International Journal of Grid and Distributed Computing Vol. 9, No. 6 (2016), pp.93-102 http://dx.doi.org/10.14257/ijgdc.2016.9.6.10 *Corresponding Author ISSN: 2005-4262 IJGDC Copyright ⓒ 2016 SERSC Design and Simulation of a Reflectarray Antenna using New Cell for Different Beam Angles Iman Aryanian 1 *, Abdolali Abdipour 2 , Gholamreza Moradi 3 1, 2,3Department of Electrical Engineering, Amirkabir University of Technology, Tehran, Iran 1 iman_aryanian@aut.ac.ir, 2 abdipour@aut.ac.ir, 3 ghmoradi@aut.ac.ir Abstract In this paper a new cell is proposed for reflectarray antenna and is used to design the antenna to obtain to maximum gain and efficiency using phase synthesis in a frequency band of 11 GHz up to 11.7 GHz for different beam angles. The proposed cell is a double ring of hexagon which introduces multiple resonances which can provide more than 360 degrees phase variation by changing the loop size. Design method is based on phase-only algorithm where amplitude of the field on the reflectarray surface is forced by the feed. A 1.2 m reflectarray is designed for different beam directions. The results show maximum directivity of 42 dB and maximum efficiency of 73% for the required bandwidth. Focal length is 1.5 m which is set for maximum efficiency. Keywords: loop element; phase-only algorithm; reflectarray antenna 1. Introduction Printed reflectarray has some advantages compared to usual reflectors, three of which- that is, saving volume, simplifying the mechanical design, and applying easily to deployable reflectors are of great importance. A reflectarray antenna is a planar reflector made of microstrip patch arrays illuminated by a feed. The reflection phase from the reflectarray elements are designed so that the reflected energy from the array is collimated to form a main beam in a given direction or to generate a shaped beam in the coverage area. The phase of the reflected field can be changed by varying the size of the resonating patches [1, 2], by a transmission line of proper length connected [3, 4] or aperture-coupled to the patches [5-7], or adding active elements to the antenna [8-11] like MEMs-based structures [12], varactor loaded patches [13, 14], PIN diodes [15-21] or liquid crystal based structures [22]. Square ring, circular ring, dual square rings, dual circular rings [23], multi cross loop [24], and combination of cross and rectangle loop elements [25] are example of ring elements used in previous works. In this paper a new unit cell is proposed and its phase response is obtained. The proposed cell is a double ring of hexagon which introduces multiple resonances with more than 360 degrees phase variation by changing the loop size. Proposed cell is used to design a high gain wideband reflectarray for different beam angles. To synthesis the radiation patterns using reflectarrays, a phase-only synthesis technique is used and the amplitude distribution is imposed by the feed. 2. Reflectarray Design There are some aspects that must be taken into account in design of a reflectarray antenna, like the selection criteria for the phasing elements, the appropriate spacing to provide enough phase range and avoid the appearance of grating lobes and the geometrical definition of the antenna. First step to design a reflectarray is to select a good