Simple circularly polarized planar monopole inverted T-shaped antenna

This article presents a novel planar monopole antenna with circular polarization. The 3-dB axial ratio (AR) is achieved by: shifting a vertical monopole to the left edge of the substrate in conjunction with a laterally inverted L-shaped ground plane. When viewed from the top, the antenna resembles an uneven T-shaped structure rotated at 90 degrees. Measurement results show that; a 3-dB AR bandwidth is achieved from 3.1 to 6.2 GHz (66.7% fractional bandwidth) and an S-11 <= -10 dB bandwidth is realized from 2.5 to 6.5 GHz (88.9% fractional bandwidth). The proposed antenna is compact with an area of 20 mm(2), produces stable radiation patterns, and its simple to design and fabricate without using parasitic elements or introducing slots on the antenna.