Research On Broadband Antenna Based On The Theory Of Characteristic Mode

The rapid development of modern wireless communication promotes the rapid progress of antenna technology.Among all kinds of antennas,microstrip patch antennas are widely used in a variety of communication fields for the advantages of low profile,easy to manufacture and easy conformality,etc.In the new situation of large-scale commercial use of 5G technology,the high-performance broadband patch antennas covering specific millimeter-wave operating frequency bands has become an urgent need.However,the diversification and complexity of application scenarios bring more and more difficult in the analysis and design of patch antennas.Fortunately,as a powerful tool for solving complex electromagnetic radiation problems and showing unique advantages in the design and application of various high-performance patch antennas,the theory of characteristic mode has therefore received a growing attention in recent years.This thesis utilizes the theory of characteristic mode to study the broadband patch antenna covering the 5G millimeter-wave communication frequency band of 24.25-29.5 GHz.The designed millimeter-wave broadband patch antennas have the advantages,such as miniaturization,low profile,high efficiency and high gain,and are suitable for applications in 5G millimeter-wave communication systems.The details are as follows:Firstly,a broadband patch antenna fed by SIW is proposed.The radiating structure is a split patch consisting of a set of inconsistent-size small patches.After characteristic mode analysis of the patch,the fundamental characteristic mode resonating at higher frequencies of the research band is identified as the working mode.Then,a compact SIW feeding structure is designed for the coupled feeding,and a fundamental cavity mode resonating at lower frequencies is introduced to improve impedance matching significantly,thereby the broadband radiation performance can be achieved.The simulated impedance bandwidth is27.5%(23.5-31.0 GHz)and the realized gain is 6.4-8.9 d Bi.Finally,the manufacture and measurement verified the performance of the simulation.Secondly,a dual-aperture coupled broadband patch antenna is proposed.By characteristic mode analysis,the required working mode is found.Then,according to the modal current distribution characteristics,the microstrip-fed dual-aperture is designed for coupling excitation,and the modal behavior changes in each design stage are gradually and deeply analyzed by utilizing the theory of characteristic mode.Finally,the dominant mode of the patch and the slot mode work together and realize a broadband radiation.The simulated impedance bandwidth of this antenna is 24.2%(23.3-29.7 GHz)with a realized gain of 6.1-8.8 d Bi.Thirdly,single-aperture coupled broadband patch antenna arrays are proposed.The design idea and operating mechanism of the array element are similar to the previous antenna,furthermore,the more miniaturized design of the radiating element is realized.Concretely,the size is only 0.42λ_c×0.42λ_c(λ_c is the wavelength of operating central frequency).Then,two microstrip single-aperture coupling feeding methods are utilized for excitation,and the corresponding binary arrays and quaternary arrays are studied respectively.The simulated results show that these arrays have achieved good broadband radiation performance with a maximum impedance bandwidth of 29.8%and a maximum realized gain of 13.2 d Bi.Finally,the tested results verified the performance of the simulation.