A Novel Bandwidth Enhancement Technique for X-Band RF MEMS Actuated Reconfigurable Reflectarray
In this paper, a wideband microstrip antenna for X-band (8.2 GHz--12.4 GHz) applications is introduced. First, simple patch antennas are studied. The resultant design demonstrates better performance than the previously published narrowband microstrip reflectarray antennas. The important features of these elements are simple structure, linear operation, and use of RF MEMS switches for programmable pattern control. Next employing our novel method, this narrowband structure is converted to broadband reflectarray antenna that can cover the whole X band. This novel idea is based on introducing several ground plane slots and controlling their electrical lengths by RF MEMS switches. By means of this method, 952 and 587 degree phase swing is achieved for continuous and discrete slot length variation, respectively. Application of this method along with smaller switches results in phase swing improvement of up to 1616 degree. In all structures a RT duroid (5880) substrate is selected to lower the back radiation. The achieved return loss in all cases is less than 0.32 dB. In comparison with the previous publications, our novel method has more generalization capability and results in single layered broadband reconfigurable microstrip reflectarray antennas with linear phase swing, lower cost, and ease of RF MEMS implementation.