Study Of Broadband And Wide Axial-Ratio Beamwidth Circularly Polarized Antenna

With the rapid development of wireless communication technology,circularly polarized(CP)antennas have gained more attentions,because they can combat the multi-path fading and do not require strict alignment between transmitting and receiving antennas.They are widely used in the field such as radar ranging,electronic countermeasures,radio frequency identification are widely used.According to the requirements of scientific research project,the lucubration on broadband and wide axial-ratio(AR)beamwidth antennas have been done.On the basis of grasping relevant theories,a broadband end-fire CP antenna and a omni-directional CP antenna with wide AR beamwidth are designed.1)A novel broadband planar end-fire circularly polarized(CP)antenna is presented.It comprises a diamond-shaped shorted parallel-plate cavity(DSPC)and a planar symmetrical conductor arms(PSCA).The DSPC and PSCA serve as the electric and loop dipole,respectively.By adjusting the aperture of DSPC and bending angle of PSCA,the impedance bandwidth and the axial-ratio(AR)bandwidth are greatly improved.Meanwhile,the end-fire circles are employed to improve the gain of antenna.The overall size of the antenna is 0.98?0×1.05?0×0.055?0(where ?0 refers to the free-space wavelength at center operating frequency).The measured results show that the realized impedance bandwidth for S11?-10 dB is 14.1%(7.63-8.79 GHz)and 3 dB AR bandwidth is 16.4%(7.57-8.92 GHz).The proposed end-fire CP antenna has a small size,low processing cost and broadband performance and so on,which is a good candidate for wireless communication system.2)A low profile omni-directional circularly polarized(CP)antenna with wide axial-ratio(AR)beamwidth in the elevation planes is presented.It consists of an electric monopole and a hexagonal radiator which will generate vertically and horizontally polarized electric field E? and E?,respectively.In order to satisfy CP radiation requires that the double L-shape energy coupling slot(DLECS)and S-shape matched transmission line(SMTL)are introduced.Also,twelve circular shape patches are placed sequentially on the hexagonal radiator for obtaining wide AR beamwidth.The antenna fed by a coaxial probe and the thickness of the antenna is 0.064?0(where ?o refers to the free-space wavelength at center operating frequency).The measured results show that the realized antenna has a impedance bandwidth of 2.1%(5.76-5.88 GHz).In particular,the 3 dB AR beamwidth at 5.8 GHz is extended to 212°(?=0°plane)and 217°(?=90° plane).Stable RHCP omni-directional radiation patterns are obtain over the operating bandwidth with a peak gain of 1.25 dBi.The proposed antenna has the advantages of low profile,compact size,and wide signal coverage.Therefore,it can be a good candidate for wireless communication and energy harvesting systems.