An omnidirectional circularly polarized patch antenna with bandwidth broadening

In this article, an omnidirectional circularly polarized (CP) patch antenna with bandwidth broadening is proposed. The antenna is composed of a circular patch with four L-shaped slots, a ground plane loaded a metal sleeve and a set of conductive vias. In order to broaden the impedance bandwidth, four parasitic strips are also sequentially rotated around the patch. As a result, it exhibits an omnidirectional CP radiation in the azimuthal plane. To verify the design, a prototype operating at 2.4 GHz industrial, scientific and medical band (ISM band) has been fabricated and measured. Measurement results show that the proposed antenna can achieve a −10 dB impedance bandwidth of 8.2% (ranges from 2.33 to 2.53 GHz) and a 3 dB axial ratio (AR) bandwidth of 9.2% (ranges from 2.29 to 2.51 GHz) in the azimuthal plane. The results indicate that the proposed antenna is a good candidate for 2.4 GHz ISM band applications.