Miniaturized broadband circularly polarized slot antenna with good gain characteristics

Abstract

A broadband circularly polarized(CP) flower-shaped slot antenna is presented and experimentally studied in this paper. Circular polarization radiation is achieved by a flower-shaped(composed of six ellipses) slot of this antenna. And the irregularly shaped patch with a stub in the center of the slot provides a broad impedance and axial ratio bandwidth. After the prototype is manufactured and tested, it is shown that the measurement results are consistent with the simulation results. The measured results indicate that the proposed antenna has a 3-dB axial ratio bandwidth(ARBW) of 50.7% (from 1.68 to 2.82 GHz) at a CP center frequency of 2.2 GHz, and a wide -10-dB impedance bandwidth(IBW) of 67.0% (from 1.62 to 3.25 GHz). The antenna occupies an overall volume of 0.28λ_l×0.28 λ_l×0.005 λ_l(λ_l is the free-space wavelength at f_l, f_l=1.68 GHz). And the gain values fluctuate slightly within 1.68 to 2.82 GHz, and the variation is less than 0.5 dBic. In particular, the gain at low frequencies is outstanding compared with similar antennas.