Ultrawideband Vertically Polarized Omnidirectional Periodic Patch-Inspired Antenna With Low Profile

An ultrawideband periodic patch-inspired antenna with vertically polarized omnidirectional radiation performance and very low profile is proposed. A low-profile periodic patch is initially excited by a driven monopole to radiate vertically polarized omnidirectional waves over a broad frequency band. Then, an annular metal wall, which locates around the driven monopole, is utilized to expand the higher frequency bandwidth. The driven monopole combines with eight short pins to form split ring resonators (SRRs), which is used to generate an additional resonance for widening the lower frequency band. Additionally, a large patch is employed in the center of the periodic patch to further ameliorate the impedance matching within an ultrawide bandwidth. The usage of the characteristic mode analysis (CMA) reveals that the omnidirectional radiation performance is generated by three ideal radiation modes of the periodic patch-inspired antenna. The proposed design achieves an ultrawide bandwidth of 100.9% (1.66–5.04 GHz), good omnidirectivety, and ultralow profile of
$0.055~\lambda _{\mathbf {L}}$
(
$\lambda _{\mathbf {L}}$
represents the in-vacuum wavelength for the lowest frequency of the working band). The excellent characteristics demonstrate that the proposed antenna is suitable for indoor base stations.