Research On The Reconfigurable Cone-shaped Beam Antenna And The Cone-shaped Beam Scanning Antenna

By switching the pattern between conical and pencil beam,the conical/pencil beam reconfigurable antenna can be used to detect the lateral and ahead target alternately in fuze applications.The beam is always aimed at the satellite when the carrier moves in the Satcom-on-the-Move system.The conical beam scanning antennas have been widely investigated due to their ability to improve the performance of modern mobile communication systems.The dissertation aims to study a conical/pencil beam reconfigurable antenna at 10 GHz.This antenna focuses on the conical beam antenna with large beam-pointing angle,high efficiency,high gain and the pencil beam antenna with pattern symmetry,low side lobe level.Meanwhile,a conical beam scanning antenna at 12.5 GHz is also introduced to realize low profile,low cost and the performance of fixed-frequency beam scanning.Details are as follows.1.A novel conical/pencil beam reconfigurable antenna is proposed.The design consists of a cylindrical conformal array and a dielectric rod antenna,both of which are switched by a PIN diode SPDT switch.The cylindrical conformal array can produce a conical beam with large beam-pointing angle,small gain ripple and high power capacity.Twelve long-slot leaky wave antenna elements are wrapped around the regular twelve-angular prism in the circumferential direction.The aperture distribution is controlled and the leakage constants are optimized to achieve high radiation efficiency.In addition,the three-dimensional power divider of ?-junction waveguide with inductive posts is used to feed the array.The measured results show that the gain of the cylindrical conformal array is 10.8 dB.The corresponding side lobe level is-11.1 dB.The peak radiation angle is at 65° and the gain ripple is 2.9 dB.The-10 dB impedance bandwidth reaches 4.2%.The tapered dielectric rod antenna which is fed by a simple circular waveguide can produce a pencil beam.A dielectric rod antenna is located in the hollow part of the cylindrical conformal array.The compact structure is easy for integration.The measured results show that the gain of the dielectric rod antenna is 12 dB and the side lobe level is suppressed to-22.7 dB.The reflection coefficient of the overlapped impedance bandwidth between conical beam antenna and pencil beam antenna is less than-18 dB.2.A uniform ferrite-loaded open waveguide structure with the conical beam scanning property is presented.The fixed-frequency beam scanning can be realized by varying the magnetic bias field.The magnetic bias field is applied perpendicularly to the width of the waveguide.Twelve elements are arranged radially around the regular twelve-angular prism to realize small gain ripple and the array is fed by a planar circuit structure to realize low profile.The coupled lines with two shorts are utilized to realize the high characteristic impedance.The measured results show that the conical beam scans from 13° to 31°,the peak gains are from 7.8 dB to 10.1 dB,the corresponding gain ripples are less than 0.4 dB,respectively.The-10 dB impedance bandwidths are from 3.2% to 4.2%.