Design of compact octagonal slotted hexagonal and rectangular shaped monopole antennas for dual/UWB applications

Two CPW-fed compact printed slot antennas for UWB applications are proposed in this paper. In both antennas, the slot in the ground plane is of octagonal shape, while the patch is rectangular in one of the antennas and hexagonal in the other. Thin metallic stubs of different lengths are added to the ground plane and protrude into the slot. These stubs help to improve the impedance matching over a broader bandwidth. The antennas are very compact in size and designed on low-cost FR4 substrate. The measured impedance bandwidths (S-11 < 10 dB) achieved by the rectangular and hexagonal patch antennas are from 3.1 GHz to 5.6 GHz and 3.14 GHz to 5.34 GHz, respectively. The slot antenna with hexagonal patch is further modified to have dual-band characteristics. An L-shaped stub is attached to the ground plane to achieve an additional band from 2.45 GHz to 2.52 GHz for WLAN applications. The radiation patterns of the antennas are dumb-bell shape in the E-plane and omnidirectional in the H-plane. Detailed parametric studies of the antennas have been carried out. The simulated results are found to be in good agreement with the measured results.