Analysis and design of a partitioned circular loop antenna for omni-directional radiation

A novel printed antenna configured with circular loop geometry of approximately one wavelength perimeter is designed for operation at 5.8 GHz with near omni-directional radiation pattern. The loop is partitioned into multiple segments and loaded with capacitive elements at selected locations so as to decrease phase variations in the current flow and thereby increase the radiation efficiency. A total of five capacitors are used to achieve stable current flow, resulting in phase variations of < 12°. The performance of the loop antenna is first analyzed as a transmitter in free space using a method of moments (MoM) solver for thin-wire structures, and then validated using 3-D finite element method (FEM) and MoM solvers. The simulated radiation pattern for the thin-wire model in the plane of the loop is close to omni-directional with directive gain of 1.46 dBi. A printed circuit antenna model is then designed with alternating top- and bottom-layer conductors of annular geometry on a thin substrate, with regions of conductor overlap functioning as physical capacitors. Simulations of the printed antenna demonstrate omni-directional radiation in the azimuthal plane, with peak directive gain of 1.66 dBi, peak directivity of 1.69 dB, radiation efficiency of 0.98, and input impedance close to 50 Ω. Performance measurement data for a fabricated printed circular loop antenna (in process) will be shown during presentation for comparison and validation.