| With the rapid development of Beidou Navigation Satellite S ystem and the universal application of GPS system,it's an inevitable trend that Beidou Navigation Satellite System and GPS will boom in the future.As the terminal module to transmit and receive signal in the navigation system,the antenna plays a vital role in the performance of the whole communication system.In order to adapt to the rapid development of the navigation system,the beamwidth,the low elevation gain,the axial ratio and the size of the navigation terminal ante nna need to meet higher requirements.Therefore,the circularly polarized wide-beam antenna has become a research hotspot because of its excellent spatial circular polarization performance.In this paper,we studies and designs several circularly polarized wide-beam antennas.The research of this paper is divided into the following three parts:1?A square dielectric quadrifilar helix antenna is proposed,which has stable and compact structure.The antenna is a short-circuit quadrifilar helical antenna based on dielectric substrate,and it realizes the impedance matching of a low-profile helical antenna by introducing short-circuited and open-circuited branch.At the same time,by means o f adding a parasitic resonant ring,the flow direction of the antenna surface and the distribution of the electric field are changed to improve far-field radiation performance and achieve miniaturization.The improved quadrifilar helical antenna has a bottom diameter reduced to 17 mm and a height reduced to 20 mm.The antenna volume is reduced by 1/4 and the normal gain is improved by 0.8d B.The half-power and 3d B axial ratio beamwidths reach more than 135°,so the antenna has excellent low-elevation performance,and test results show it has good robustness and stability.2?A novel broadband wide-beamwidth circularly polarized antenna with square slot structure is presented.The antenna is composed of four open-ended monopole slot antennas fed by a sequential rotary network,each of which is fed by an L-shaped microstrip line.Compared with the traditional resonant antenna,this antenna has an absolute bandwidths of 600 MHz,which contains the common frequency bands of multiple navigation systems to meet the application requirements of the wideband.The measured results show that the half-power and 3d B axial ratio beamwidths are more than 120° over the common navigation frequency band from 1.1GHz to 1.7GHz,and it has good circular polarization and radiation performance.3?A novel circular polarization wide-beam dual-band discone helical antenna for artillery projectile applications based on polyimide is designed,which has the advantages of light weight,thin structure,small size,high and low temperature resistance,and is easy to conformal with shells.By introducing a logarithmic helical arm,the antenna owns an wider working bandwidth.And the introduction of a short-circuited stub between the two radiating arms enables a good impedance matching.In order to meet the requirement of dual-band circular polarization feeding,a wideband feeding network is designed.It consists of a Wilkinson power divider cascaded wideband phase shifter,which can keep good phase consistency in a wideband.The simulation results show that t he antenna has good gain bandwidth,and the gain bandwidth better than 0d Bi in BD2-B3 frequency band reaches 80 MHz.It has good circular polarization performance in the dual-band and the half-power and 3d B axial ratio beamwidths are all more than 125°.20° elevation gain in the dual-band reach-1.5d Bi and 0d Bi respectively,meanwhile,axial ratio is less than 3.2d B. |
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