Research And Design Of Conical Beam Antenna

The maximum radiation direction of a conical beam antenna is on a cone surface that forms a certain inclination angle with the normal direction perpendicular to the antenna aperture plane.Compared with a pencil beam antenna,it has a larger coverage range,and compared with an omnidirectional antenna,it has a higher gain.Therefore,conical beam antennas have great advantages in some special scenarios,such as communication between ground mobile vehicles and satellites,warning systems,and missile fuze systems.There are many structures that can produce conical beams.Based on previous research,this thesis further studies the problems of low gain and difficult control of beam angle for conical beam antennas.The main contributions of this thesis include the following three aspects:1.The analytical solution of the radiation field produced by an open coaxial waveguide operating in the dominant mode TEM is derived.Based on this,a method for designing an antenna with a specific inclined conical beam is proposed.To address the problem of low gain,a dielectric lens is loaded on the aperture plane,and the equation that the dielectric lens surface should satisfy to produce a specific inclined conical beam is derived.The lens not only can control the beam angle of the conical beam but also can enhance the gain to some extent.Finally,a conical beam antenna with an inclination angle of 45° is designed to verify the theory.The simulation results are consistent with the theory,and the gain of the antenna reaches 10.7d Bi.2.A conical beam antenna with high gain is designed based on a circular patch microstrip structure.The structure improves the gain of the antenna by adding a ring of metal through-holes around the circular patch,changing the original field distribution.By introducing a new working mode through an annular slot on the circular patch,the relative impedance bandwidth of the antenna is expanded.An actual antenna is fabricated and tested to verify the design,and the maximum radiation direction is found to be 24° with a gain of 9.4d Bi.3.A ring of six rectangular patches is arranged to generate a conical beam.By changing the placement of the rectangular patches,the radiation gaps are arranged in a radial or circumferential direction,realizing vertically polarized or horizontally polarized conical beams.By chamfering the rectangular patches and adjusting the feeding points,a circularly polarized conical beam is achieved.The results of the physical test show that the maximum radiation direction of the circularly polarized cone beam antenna is 30°,the gain is 6.3d Bi,the main polarization is left-handed circular polarization,and the 3d B axial ratio bandwidth is 3.6%.This article draws on optical theory to design a dielectric lens that can control the cone angle of the beam and enhance its gain,providing a new idea for designing conical beam antennas with high gain at specific angles.This dielectric lens can be used not only in open coaxial waveguides,but also in aperture antennas with circumferential symmetry,such as circular waveguides.The circular patch microstrip structure realizes high gain in a planar structure,which is more easily integrated and processed than a three-dimensional structure.The patch array structure controls the polarization of the conical beam antenna,and adjusting each array element can ensure vertical,horizontal,and circular polarization while producing a conical beam.