| In this information era of today,Internet has become the center of our work and lives.Especially,the propagation of information on the Internet almost relies on function of the microwave.Antenna,as an important device in the sending and receiving system of microwave,is widely researched by many researchers and applied in many communication occasions.In recent years,the proposal and development of reconfigurable technology,have given a new direction and flexibility in the field of antenna design.On the one hand,except for PIN diode,MENS switch tube and other traditional devices,many researchers implement many special material,such as Graphene,liquid crystal,water and oil material,which are used in the microwave design as well as the reconfigurable field.On the other hand,some new research directions,such as filtering antenna and magnetoelectric dipole,gradually adopt reconfigurable devices,such as PIN diode,to achieve the property of changeable frequency.Nowadays,reconfigurable technology is more and more used in antenna design and microwave equipment in many universities.It also has contributed a lot in communication development.In this thesis,the author has research the appliances and fabrication of liquid crystal in reconfigurable field.What's more,the author has used reconfigurable technology in filtering antenna design to achieve some new properties.This thesis shows the four designs of the author.1、In the chapter 2,firstly,the author has investigated some relative properties of liquid crystal material,and changeable dielectric constant when you connect voltage with this material.Secondly,a new design to package the liquid material in microwave devices has been introduced in this chapter.The phase shifter used liquid crystal,work between12GHz~14.5GHz,with the loss no more than-1.5dB.During the process of the experiments,the author choose three kinds of liquid crystals(LC-BYIPS-P01 of America INSTEC Company,Pentylbenzonitrile of Chinese Ba-Yi Company,MLC-6876-000 of Germany Merck Company)to compare with their loss.2、In the chapter 3,the phase shifter is bended and then used in the slot antenna to make up array.It is used the property of liquid crystal about changing its phase in the phase shifter in order to achieve phase difference between two units near each other and realize the beam scanning.In addition,the author utilizes LTCC technology in this antenna design to reduce the loss of substrate material and improve the integration of model.The beam scanning slot antenna array applied liquid crystal,shows us the working band from14.3GHz to 15.8GHz and a changeable beam scanning from-20°~20°,along with??_rfrom positive to minus under basis voltage.3、In the chapter 4,at the beginning,the author studied the basic knowledge of filtering Yagi antenna and applied stripline in the feed line to enhance the gain of antenna.The stripline low pass filter is integrated with filtering Yagi antena to reach wide out-of-band suppression.This antenna operates from 2.25GHz to 2.55GHz and has a range of gain from5dBi to 8dBi.In out-of-band,it also has a high selective property on the edge of working band,from 2.55GHz(8dBi)to 2.8GHz(-20dBi)and a suppression band from 4GHz~12GHz.4、In the chapter 4,at last,the author shows many theories of filtering structures.On the same size of the original Yagi antenna,various filtering structures(DGS structure,SIR impedance matching structure,parallel coupling line structure and so on)are integrated to expand out-of-band suppression.The reconfigurable frequency filtering Yagi antenna operates from 2.3GHz~3.1GHz(PIN diode is on)and 3.3GHz~3.9GHz(PIN diode is off),with an radiation gain from 4dBi to 7dBi in working band and a suppression from4GHz~18GHz below-10dBi in out-of-band,which is-17dB lower than the maximum working gain. |
