Horizontally Polarized Omnidirectional Antenna Using Slotted Rectangular Patch and Defected Ground Structure

An investigation of novel techniques in the designing of a low profile, horizontally polarized omnidirectional (HPO) patch antenna with omnidirectionality in the H-plane using a defected ground structure is presented in this study. The HPO patch antenna is designed by sequentially etching four rectangular and four open diagonal slots symmetrically on the patch and the antenna's ground plane. It creates four quarterwavelength open stubs that produce an in-phase circulating current on both the ground and the patch. Narrow bandwidth is achieved by using the four quarter-wavelength open stubs and by printing sequential slots only on the ground. Another set of four quarter-wavelength shorted stubs is achieved by sequentially etching four rectangular and open diagonal slots on the patch to resonate with another frequency and to increase the bandwidth by merging these two resonance frequencies. Combining these two resonance frequencies covers the applications of 2.39–2.52 GHz WiFi bands. The overall dimension of the proposed antenna structure is 0.32 λ
₀
×0.32 λ
₀
×0.006 λ
₀
with 5.51% bandwidth and moderate gain of 2.2dBi and roundness within 1 dB in the azimuth plane.