Study And Design Of Dual-band And Omni-directional Circularly Polarized Antenna

With the development of wireless communication technology,circularly polarized antenna is widely used because of its strong anti-interference capability and high polarization matching.The multi-band antenna can make mobile terminals to work in different environment,enhance the reliability of communication and reduce the overall size;omni-directional antenna can effectively reduce the multi-path effect,simplify the receiving system,and improve the receiving efficiency.In this paper,the principle and method of multi-band and omni-directional polarization antenna are studied,and a dual frequency circularly polarized antenna and a omni-directional circularly polarized antenna are designed respectively.The specific contents are as follows:1)A dual-band circularly polarized patch antenna operating in 2.45GHz and 5.04GHz bands is designed.It produces the asymmetric disturbance by introducing four different length rectangular slots around the rectangular patch,and then realizes the circularly polarized radiation;And by changing the length of the rectangular slot to improve the matching between the impedance bandwidth and the axial ratio bandwidth.The antenna is fed by a coaxial feed,and has a size of 0.218?₀×0.211?₀×0.013?₀??₀ is the wavelength of 2.45GHz in free space?.Measured results show that the antenna operates in the range of 2.445-2.476GHz and 5.019-5.058GHz,and the peak gain in two frequency bands are 1.25dBi and 1.34dBi,respectively.2)A omni-directional circularly polarized antenna with wide axial ratio beam in the elevation plane is proposed.The antenna is composed of a vortex radiator,a circular metal ground and two sets of short circuit probes.By adjusting structure of the compound vortex stub|E_?|=|E_?|can be realized.Also,it can be met that the phase of the E_?and E_?is orthogonal by changing the size of sector at the end of stub.The measured results show that the proposed antenna has a-10 dB impedance bandwidth of 3.2%?3.03-3.13GHz?and a 3 dB AR bandwidth of 21.6%?2.5-3.17 GHz?.The 3 dB AR beamwidths at 3.10 GHz are 270°and 274°in the?=0°and?=90°planes,respectively.The axial ratio of the azimuth plane is 0.94-1.46 dB,and the peak gain is 1.44 dBi.A good agreement between the simulated and measurement results is obtained.