Wideband and Low-Profile Omnidirectional Circularly Polarized Patch Antenna

A wideband low-profile omnidirectional circularly polarized (CP) patch antenna is proposed and investigated in this communication. The design utilizes two monopolar modes of a circular patch which connects to a modified ground plane by a set of conductive vias, to achieve wide-band impedance matching. The curved branches introduced at the edge of circular ground plane excite a degenerate mode and create CP fields. To verify the design, a prototype operating at 2.4 GHz-WLAN band has been fabricated and measured. Measured reflection coefficient, axial ratio (AR), radiation pattern, and antenna gain agree well with simulation results. The proposed prototype has a low profile of
$0.024 \lambda _{0}$
, a 10-dB impedance bandwidth of 19.8% and a 3-dB AR bandwidth of 19.3%. To further characterize the design concept, a parametric study of the proposed antenna is carried out using HFSS, and general design guidelines are provided.