Study On Self-Balanced Planar Magnetic Dipole Antennas With High Front-to-Back Ratio And Wide Beamwidth

Based on the theory of self-balanced feeding,this thesis studies the radiation field of a wide beamwidth self-balanced magnetic dipole antenna and finds the key factor that affects the antenna's back radiation level—the unbalanced current ratio factor(UCRF).Based on this,a wide beamwidth self-balanced antenna with high front-to-back ratio is proposed,then it is extended to the design of wide beamwidth square microstrip patch antenna.The main research contents of this thesis include:1.Based on the principle of self-balanced feeding,it is proved that by changing the UCRF,the back radiation level of the antenna can be steered as desired.The relationship between the antenna's front-to-back ratio and the pattern of the antenna and the UCRF is calculated by using MATLAB simulation software.According to the results,it is fully proved that the design method can improve the front-to-back ratio of the antenna while maintaining a wide beamwidth characteristic.2.In order to verify the effectiveness of this method,a sector magnetic dipole antenna with an operating frequency of 2.45 GHz and a central angle of 180° is designed.Firstly,the initial radius of the sector magnetic dipole is determined according to the cavity model theory.Then,the UCRF can be adjusted by increasing the radius of the bottom surface and changing the shape of the parasitic element.Parameter analyses have been performed to achieve a high front-to-back ratio wide beamwidth performance.Finally,the correctness and effectiveness of the method are further verified by comparing the results of simulation and actual measurement.3.The advanced method is applied to the design of beamwidth broadening of square microstrip patch antenna.Firstly,starting from the square microstrip patch antenna radiation field,it is proved that the half-power beamwidth of the antenna H-plane can be controlled by changing the ratio factor of the unbalanced current on the surface of the parasitic elements.Then,a square microstrip patch antenna with an operating frequency of 2.5 GHz is designed,by changing the size of the parasitic elements to adjust the UCRF.The effect of beamwidth broadening has been achieved.Finally,antenna samples are fabricated to validate the effectiveness and correctness of the design method.