An antenna for generating omnidirectional circularly polarized radiation

摘要

An antenna, suitable for generating omnidirectional circularly polarised radiation, comprises a planar ground electrode 110 sandwiched between two planar radiating electrodes 115 and where a dielectric medium 120 is interposed between each of the said electrodes. Each of the radiating electrodes 115 includes a perturbation 130 and a feed 140 which is arranged to couple, in-phase signals, to each radiating element 115. The three electrodes 110, 115 are in a spatial arrangement such that, when the radiation electrodes are excited, their respective electric fields electrically couple together to generate an omnidirectional radiation pattern. The footprint of the ground electrode 110 may be 10% to 80% larger than that of the resonant electrodes 115. The electrodes may, for example, be square, rectangular and/or circular shaped. Circular radiating electrodes may be concentric. The perturbation associated with the resonant electrodes may be stubs or other phase perturbation means such as truncated corners or slot voids or any suitable geometric formation. The feed may include a tapered electrode located in a slot. The antenna may be used in global positioning systems, RFID, vehicle communications, tolling and wireless communication systems.