Study On Planar High-order Resonant Mode Complementary Dipole Antenna

High gain characteristic is an important performance for the planar endfire circularly polarized antennas.However,the profile dimensions of the existing high gain planar endfire circularly polarized antennas are larger than 0.1 times wavelength,with complicated configuration and lower front-to-back ratio(FTBR).For example,the gain of the antenna can be increased by using substrate integrated waveguide(SIW)horns and introducing additional dielectric lens with increasing the overall outline size and design complexity of the antenna;although using Yagi antenna and planar bidirectional circular polarization antenna can effectively reduce the profile height of the antenna,the front to back ratio of these antennas is not very high.So it is a challenging task to design a circularly polarized antenna of which the endfire beam is parallel to the plane of the antenna with low profile,simple configuration,high gain,high directivity and enhanced FTBR.This thesis starts from the high-order mode resonant V-shaped complementary dipole antenna and further enhances antenna directivity through helix loading.The main research contents of this thesis includes:1.Using a combination of a planar rectangular microstrip magnetic dipole and an eccentrically fed V-shaped electric dipole,and designing the resonant mode of the electric dipole in the 1.5-wavelength,a high gain circularly polarized antenna with basic structure can be realized.Besides,improve antenna's directivity characteristic by loading an axial-mode helix structure near the oral surfacethe.Finally,the antenna is numerically analyzed by employing Zeland's IE3 D simulation software,and the antenna sample is designed and verified in the 2.45 GHz band.The simulation results are in good agreement with the actual measurement results,which fully proves that the design method is correct and effective.2.Further,using the 1/4 wavelength phase shift line to realize the center feeding of V-shaped dipole,and increasing the number of the helical turns can improve the symmetry of antenna configuration and ulteriorly enhanced gain and front-to-back ratio characteristics.The results of simulation and measurement show that the impedance bandwidth of the antenna is from 2.416 to2.51 GHz,and the 3d B axial ratio bandwidth is form 2.36 to2.68 GHz,and the endfire gain of antenna reaches to 7.1 dbic,and the front-to-back ratio can be enhanced to 14 d B.In other words,the characteristics of low profile,high gain and high front-to-back ratio are achieved through the above research.The above results fully prove that using planar complementary dipole structure which combines high-order resonant mode and helix-loaded is beneficial to the realization of high gain and low profile planar endfire circular polarized antenna.