A novel miniature circularly polarized antenna with beamwidth improvement

Abstract

A novel miniature circularly polarized (CP) microstrip antenna with beamwidth improvement is proposed. The approaches employed in this design to improve the beamwidth performance are to utilize four vertical conductive walls around the radiation patch and to locate four metal isosceles triangle patches at the top of the radiation patch. Four slots are etched along the diagonals of radiation patch with the ground plane folded to achieve the miniaturization of the antenna by extending the current path. In addition, by introducing an electromagnetic coupling feed and a compact broadband phase shifting network, the proposed antenna can achieve a wide impedance bandwidth for VSWR ≤ 1.5 ranging from 1.1 to 1.8 GHz (about 48%) and a 3-dB AR bandwidth from 1.1 to 1.7 GHz. Moreover, the 3-dB beamwidth is over 100° in this operating frequency range. In this way, the antenna size is reduced to 0.42 λ ₀ × 0.42 λ ₀ × 0.16 λ ₀, whereλ ₀ is the wavelength at the center frequency in the free space.