Research On High Performance Polarization Reconfigurable Antenna And Pattern Reconfigurable Antenna

With the rapid development of communication technology,higher and higher requirements for the wireless communication antennas have been proposed.Although the traditional antennas have the stable performance,they are difficult to meet the needs of many different occasions at the same time for their fixed function.Relied on the good flexibility and adaptability,reconfigurable antennas have attracted considerable interests of many scholars and become a hot spot in the field of antenna research.The reconfigurable antenna can change the radiation current distribution of the antenna by means of electrical or mechanical adjustment,so that the antenna has a reconfigurable capability in one or more properties such as the operating frequency,polarization,or pattern.The reconfigurable antenna can not only improve the anti-interference ability of the wireless communication system,but also increase the communication capacity and the coverage area of the system.It is worth to be applied in practice.With the deepening of research on reconfigurable antennas,methods in implementing the antenna's reconfigurable function have been more and more professional.Besides the research on the implementation methods,the study on how to improve or expand the other radiation performances of the reconfigurable antenna also has practical significance,such as improving the antenna's cross polarized performance,achieving dual-polarized radiation and so on.Towards this research direction,to maximize the flexibility and practicability of the reconfigurable antenna will make the reconfigurable antenna more practical.In order to develop a reconfigurable antenna with much more excellent performance,several theoretical methods have been utilized in this thesis.These methods include the theory of characteristic modes,the microstrip patch antenna theory and the Yagi antenna theory.Totally,two reconfigurable antennas are proposed in this thesis.One is the polarization reconfigurable antenna with low cross polarization.The other one is a dualpolarized pattern reconfigurable antenna.The main contents of this article can be summarized as follows:1.At first,this article briefly introduces the research background of the reconfigurable antenna and the latest study no matter at home or aboard.Secondly,the implementation method and design difficulties of reconfigurable antenna are discussed.Finally,by summarizing the current research status in the field of reconfigurable antenna research and combining practical application requirements,the research goals of developing polarized reconfigurable antennas and pattern reconfigurable antennas with more excellent performance are proposed.2.A polarization reconfigurable antenna with low cross polarization is designed.This antenna operates at the frequency band from 2.4 to 2.5 GHz.By means of a reconfigurable feeding network,the polarization of this antenna can be switched among vertical polarization,horizontal polarization,left-hand circular polarization and right-hand circular polarization.The entire design process of the antenna is analyzed and guided by the characteristic mode theory.By elaborately designing the feeding structure,we can selectively stimulate the characteristic modes that meet the design requirements and suppress the interference modes that do not conform to the design requirements.In addition,a method about effectively suppressing the cross polarization is presented and applied to the antenna design,so that the cross polarization of this polarization reconfigurable antenna is lower than-30 d B.3.Based on the microstrip antenna theory and the Yagi antenna theory,a dualpolarized pattern reconfigurable antenna with an operating frequency of 2.4 GHz is designed.This antenna is based on a microstrip Yagi patch antenna.By embedding a loop shaped slot in the parasitic patch and adding varactors,the electrical size of the parasitic patch can be tuned,further achieving beam scanning at two main radiation planes.In addition,the TM01 and TM10 are respectively excited by two 50? coaxial probes to realized dual-polarized radiation(vertical polarization or horizontal polarization).