A multi-band antenna loaded with a windmill-shaped metastructure for WLAN/WiMAX applications

This paper put forward a windmill-shaped left-handed metastructure, which consists of four central-symmetric spiral lines and four metallic sticks. An equivalent circuit of the left-handed unit is modeled based on transmission line theory. Then a multi-band antenna is designed by applying this windmill-shaped unit, just with central-symmetric spiral and cross-bar slits loaded on a rectangular patch. Three operational frequencies of 2.40 GHz, 3.48 GHz and 5.40 GHz for the proposed antenna are obtained with bandwidths in -10 dB of 259 MHz, 55MHz and 912MHz respectively. The surface current distributions and field patterns are analyzed for demonstrating left-handed feature and bandwidth spread.