Compact dual frequency wide band circular patch antenna with U-slot

The radiation properties of a circular patch antenna with u-slot designed on glass epoxy FR-4 substrate are obtained and compared with that of a normal circular patch antenna designed under identical conditions. The modified antenna not only resonates at two different frequencies allotted by IEEE 802.16 working group for lower band (2.495-2.695 GHz) operation for WiMax systems but also presents marked improvement in the bandwidth. The input impedance, return loss and VSWR are measured for simple circular patch antenna and circular patch antenna with u-shaped slot. Reasonably good matching of modified antenna with the feed network is obtained for both the resonance frequencies. The radiation efficiency and directive gain of this antenna are low because the dielectric substrate used for preparation of antenna has loss tangent value.