Research On Broadband Directional Antenna Based On Resonance-Based Reflector

To solve the problems of large-profile and large area in broadband directional antenna(BDA)application,the conception of Resonance-Based Reflector(RBR)is presented.Because of the characteristics of wide in-phase reflection band and non-periodic structure,it will have great advantages in BDA design with the characteristics of miniaturization and low-profile.In this thesis,the characteristics of RBR are studied,and it is utilized to design a variety of BDAs with excellent performance.The main works and contributions of the dissertation are listed as follow:1?The concept of RBR is analyzed by using transmission line theory and microwave resonator theory,and the impedance and the reflection coefficient formulas of the RBR are deduced,and a kind of ring-shape RBR is designed to verify the correctness of RBR's theory.The working mechanism and electromagnetic characteristics of the RBR are studied at the same time,and it's very helpful to the design of BDA in the later section.Finally,the RBR and AMC are compared,which highlights the advantages of RBR in BDA design.2?The designing of linear polarization BDAs by utilized the ring-shape RBR..Firstly,with the round-end bow-tie antenna as the radiator,two antennas with different performance which are designed by ring-shape RBR with different parameters.The profiles of the antennas are 0.09 ? and 0.1 ?,which prove the controllability of the RBR.In order to solve the problem that the front-to-back ratio(FBR)of the single-layer reflector antenna decreases rapidly as frequency increased,a ring-shaped director is loaded above the antenna.Furthermore,a linear polarization antenna with two opposite uni-directional radiation bands(TUB),which radiate to +z axis at the lower frequency in the operation band and-z axis at the higher frequency,respectively,is designed by using two ring-shaped RBRs.The profile of antenna is only 0.2 ?,and it has excellent directional performance.3?Design of circular polarization BDAs by utilizing the ring-shape RBR.With the Archimedean Spiral Antenna as the radiator,a single-layer ring-shape RBR antenna is designed first with a profile of 0.09 ?.And then,a dual-frequencies reflector is designed by combining the ring-shape RBR and PEC together to enhance the directional performance of the antenna at higher frequency of the operation band significantly.In addition,a circular polarization antenna with TUB is designed by employing the same method with the last section,which is with 0.2 ? profile.Finally,a CPW-fed archimedean spiral slot antenna with a profile of 0.1 ? is designed.And the circular polarization performance isenhanced by loading resistances at the end of the antenna.4?The time domain characteristics of the BRB based UWB antenna are investigated with the group delay,correlation coefficient,pulse width stretch ratio and waveform response of the antenna.Then,an antenna based on RBR in the thesis is taken as an example to evaluate its time domain performance.The results show that the antenna has good performance in time domain,which verify that the RBR has little effect on the time domain characteristics of the UWB antennas.