Research And Application Of Reconfigurable Frequency Selective Surfaces

Frequency selective surface is a periodic structure,which exhibits band-pass or band-stop filter characteristics in the spatial electromagnetic environment.In terms of the Passive FSS,its electrical performance can't be changed after it is processed completely,so it can't be adapted to the complicated and changeable electromagnetic environment,but the Active FSS can make up for the shortcomings of the Passive FSS,the filtering characteristics of Active FSS can be controlled by external excitation,which can make it well adaptation to the changes of complex electromagnetic environment,so it has become a studied hot topic for domestic and foreign experts.This thesis briefly introduces the basic theory and related applications of FSS firstly,then utilizing the basic features of FSS to design a Pattern Reconfigurable Antenna loaded PIN diode and a Band Reconfigurable Reflect-array loaded PIN diode.The mainly research content of this thesis is as follows:1.This thesis designs a Pattern Reconfigurable Antenna loaded a PIN diode,which consists of a FSS and a microstrip monopole antenna.Both the monopole antenna and the FSS operate at 2.1GHz,FSS can select the frequence of the electromagnetic wave,so omnidirectional scanning of the beam on the horizontal plane can be achieved by controlling the on and off states of the PIN diode.The scanning step is 30 degrees and the antenna gain is close to 6.9 d B.Compared to a monopole antenna,the antenna radiation gain increases by approximately 4.8 d B,and the 3 d B beam width approaches 120 degrees.Then,on the basis of the previous research,by changing the array structure of the FSS unit,the distance between the feed source and the FSS is changed.and by controlling working states of the PIN diode,the antenna achieved omnidirectional scanning at 2.1GHz,scanning step is close to 15 degrees,the antenna gain is close to 7.4d B,3d B beam width approaches 60 degrees,the beam width of the antenna was reduced.Finally,the actual object was processed.it showed that the measured results were basically consistent with the simulation results,verifying effectiveness of the antenna design.2.In this thesis,on the foundation of discussing the polarization stability and the angle stability of FSS unit,a Band Reconfigurable Reflect-array loaded PIN diode is designed.Phase compensation can be achieved by changing the size of FSS unit,the design of(28)?2251515 reflect-array was finished,it used a pyramidal horn antenna as the feed source.Firstly,the simulation of a standard pyramid horn antenna is performed to obtain the concentration of radiant energy,and then the distance between the horn antenna and the reflect-array is calculated.Secondly the situation of vertical incidence is discussed,simulation results show that when the PIN diode is in the off state,the antenna gain is more than 20 d B in the 9GHz-11.5GHz,when the PIN diode is in the on state,the antenna gain is more than 20 d B in the 7.5GHz-9GHz,thus achieving band reconfigurable function.Owing to the shading effect of the horn antenna,and then on the foundation of the previous research,the distance and tilt angle between the horn antenna and FSS are calculated because of the energy concentration of the horn antenna,and the situation of oblique incidence is discussed,the simulation results show that the gain of the antenna is more than20 d B in the 9.3GHz-10.7GHz,which solves the problem of antenna shielding effect and verifies the effectiveness of the antenna design.The structures designed in this thesis are based on the application of FSS,the Floquet port in the High Frequency Structure Simulator software is used to simulate the periodic structure.And then a Pattern Reconfigurable Antenna and a Band Reconfigurable Reflect-array are realized.It validates the great promising of FSS in reconfigurable antenna applications.