Research On Broadband Technology Of Microstrip Antenna And Crossed Dipole Antenna

In recent years,with the rapid development of wireless communication technology,there are more and more wireless communication devices working in different frequency bands.In order to realize the interconnection and communication between various devices,antennas for wireless communication devices are required to work in multiple frequency bands at the same time.Broadband antenna technology has become a research focus.In this thesis,the broadband technology of microstrip antenna and cross-dipole antenna is studied as follows:1.This thesis introduces the research background and significance of broadband antenna technology,and then investigates and summarizes the development and research status of microstrip antenna and crossed dipole antenna broadband technology.The relationships between antenna electrical indexes and bandwidth,the radiation principle of microstrip antenna and cross-dipole antenna are analyzed,and theoretical basis for broadband antenna design are provided.2.The broadband technology of microstrip antenna is studied.In this thesis,a double-layer microstrip antenna with ring structure is designed.The impedance bandwidth for VSWR<2of 76%and the 3dB gain bandwidth of 65.7%are obtained.Firstly,a broadband microstrip antenna is designed based on coupling feed technology.Secondly,by adding metal patches upon the microstrip patches,the problem of radiation pattern distortion in high frequency is solved,and the gain bandwidth of the antenna is expanded.Thirdly,the gain bandwidth of the antenna is further expanded by loading a metal ring structure between the two layers of patches.Finally,the antenna is fabricated and tested.The results of the measurements and simulations are in good agreement,which verifies the feasibility of the design.3.The broadband crossed dipole antenna is studied.In this thesis,a dual-polarized broadband crossed dipole antenna with square-ring aperture structure is designed.The antenna achieves operating bandwidth of 67.8%for port 1 from 1.96 to 3.97GHz and 68.7%for port 2 from 1.94 to 3.97GHz.The isolation of the two ports is better than 20 dB in the whole bandwidth.In this thesis,three square-ring aperture structures are loaded at the end of each dipole arm of the cross-dipole antenna,which changes the current amplitude distribution of the radiation patch at high frequency,which solves the problem of radiation pattern distortion,and realizes the radiation pattern stabilization.In addition,the loaded structure can reduce the current path at the end of the dipole arm and reasonably change the position of resonance points.So the impedance bandwidth of the antenna is extended.Through the design of Marchand Balun feeding structure,the differential feeding of crossed dipole antenna is realized,and then the antenna is manufactured and measured.The test results verify the validity of the design method.4.The broadband dual-polarized patch antenna is studied.In this thesis,a low profile broadband dual-polarized patch antenna is designed.The overall profile of the antenna is0.1 ?₀,and the operating bandwidth of the antenna is 3.04 GHz-5 GHz.The impedance bandwidth of the antenna is effectively expanded by using the method of coupling feeds in the same layer and adding parasitic patches.The forward gain of the antenna is improved by adding a middle layer patch under the radiation patch.By loading a short-circuit column between the radiation patch and the floor,the front-to-back ratio of the antenna at high frequency is increased by 2.8dB.Finally,through the design of planar broadband balun,the differential feeding of the antenna is realized,and the antenna is manufactured and measured.The test results verify the correctness of the design method.