Bandwidth enhancement of electrically large shaped-beam reflectarray by modifying the shape and phase distribution of reflective surface

In this paper the bandwidth performance of a reflectarray antenna to obtain fixed shaped-beam radiation pattern is studied. In order to achieve this purpose two parameters including the curvature of reflective surface and the phase distribution of reflective surface in the whole frequency band are simultaneously manipulated. Phase synthesis procedure is used to analyze the reflectarray. The particle swarm optimization is also used for obtaining the shaped-beam radiation pattern in the whole frequency band. It is shown that the bandwidth of a large reflectarray is considerably enhanced by decreasing the path length difference between phase center of the feed antenna and each point of the reflective surface. To verify this purpose, a shaped-beam reflectarray with concave reflective surface has been designed and simulated in the X-band with the commercial full-wave electromagnetic software, CST Microwave Studio and results to about 17% bandwidth for the stable cosecant square radiation pattern and pencil beam radiation pattern in E and H planes respectively.