Research On Broadband And Wide Beamwidth Antenna

With the development of radar,communication and electronic reconnaissance systems,the demand for broadband and wide beamwidth antennas is on the increase.Based on microstrip antennas and dipoles,which are the commonly used base station antennas,this thesis studies the methods to widen their bandwidth and beamwidth,at the same time,several antennas are fabricated and measured,including the microstrip fed by L-probe,the dipole with transitional structure and reflector,and the printed dipole loaded with parasitic dipoles.The main work is displayed as follows:Firstly,the research backgrounds and significance of antennas with broadband and wide beamwidth are introduced.Besides,the current situations of microstrip antennas and dipole antennas is summarized,and it is beneficial to lay the foundation of this thesis.Secondly,the principle,analytical and design methods of microstrip are introduced,and its feasibility is validated by a rectangular microstrip antenna.In order to make the bandwidth wider,a microstrip fed by stripline is designed and manufactured,and the test illustrates that the bandwidth can be broadened by using stripline,but the beamwidth of horizontal plane does not change a lot.Under this circumstance,a microstrip fed by L-probe is designed,which realizes a broadband and wide beamwidth,moreover,the measurement is in agreement with the simulation.Besides,an improved multi-layer microstrip antenna fed by L-probe is proposed,and it can enhance the gain and beamwidth feature.Thirdly,the basic theory of dipoles is introduced,and a conventional dipole is designed on its basis,which shows that a wide bandwidth can be achieved by increasing the radius of the dipole.To make the band wider,the dipole with a transitional structure is raised.On this basis,the effect from the geometry and size of ground is studied,and a dipole with unidirectional radiation pattern and wide beamwidth is designed.Fourthly,a printed dipole antenna is designed,which make the planarization come into reality.To widen its bandwidth,two parasitic dipoles are added.In addition,the simulation and measurement are carried out,and they are in agreement with each other.Fifthly,to improve the gain,a 1?4 printed dipole array is designed based on the theory of antenna array,and its characteristics are analyzed by simulation and measurement.The result shows that gain can be enhanced by arraying.