Research On Reconfigurable Antenna Based On Frequency Selective Surface

Frequency selective surface(FSS)belongs tometal strips on the dielectric substrate or the specific structure of the slot arranged in order.FSS has been widely studied during the last decades.To date,FSS has been widely used in different applications,such as mobile communications,satellite communications,space filter,polarizer and absorber,due to its simplicity of processing and loaded antenna,FSS can be also widely used in reconfigurable antenna.For instance,it can realize frequency reconfigurable antenna,pattern reconfigurable antenna,and polarization reconfigurable antenna.Besides,FSS has wide application prospect in the reflectarray.With many advantages,such profile,low cost,low loss,small volume and high gain,it can overcome the drawbacks of parabolic antenna and phased array antenna.We first give a brief introduction to the basic principle of FSS and its related applications,and then we design three types of X band based antenna,including a reconfigurable antenna based on FSS,a petal type microstrip reflectarray antenna based on FSS,and a loading capacitance diode of a frequency reconfigurable antenna.More detail of our study is described as follows:Firstly,this thesis presents an X-band polarization reconfigurable antenna based on FSS,which works at 10 GHz and is composed of FSS polarizer and a 2?2 microstrip array antenna.The FSS contains an angle between the polarizer and microstrip antenna array,through the angle between the FSS structure and microstrip array antenna,and then changing the angle(e.g.0 degrees,45 degrees,90 degrees,135 degrees)can realize the switch of antenna polarization.To be specific,antenna can switch among the linear polarization,left-hand circular polarization and right-hand circular polarization.To validate the effectiveness of the proposed design,the circular polarizer and 2?2 microstrip array antenna in the radius of 30 mm dielectric substrate is fabricated and measured,which is fixed by the nylon screws.We have performed extensive tests in microwave anechoic chamber.The results show that good axial ratio can be achieved.Specifically,the antenna polarization exhibits linear polarization at the angle of 0 degree and 90 degree,while the antenna polarization exhibits circular polarization at the angel of 45 degree and 135 degree with the axial ratio lower than 3d B.The obtained results show that the polarization reconfigurable antenna performs well,and the axial ratio also satisfies the design of circular polarization.Secondly,an X-band microstrip reflectarray antenna based on FSS is designed.The cell structure of reflection array is composed of cross flowertype unit.To achieve the desired phase shift for the cell structure,we can change the size of cell structure.By analyzing the phase compensation of the array elements and the phase compensation of each cell in the array,we design two types of array with size 9?9(28)81 and15?15(28)225,respectively.In this thesis,the design process of the array and the influence of the array size on the microstrip array are discussed in detail.As microstrip reflectarray takes horn antenna and Vivaldi antenna as feed source,which is a feed forward way,we simulate various arrays on the Ansoft HFSS.The results show that the gain of antenna has been greatly improved,and realize the beam focusing function.Lastly,based on the microstrip reflectarray,an X-band microstrip reflectarray antenna based on FSS is designed.The unit structure of the reflective array is composed of a rectangular ring,the inner ring with a circular groove.The two rings are connected by a capacitor,and the middle part are four PIN diodes.By controlling the states of four PIN diodes,the reflectarray element can work at two states of 9GHz and 12.22 GHz.Then,the Vivaldi antenna is used as the feed,and form the microstrip array of size 99?.In the HFSS simulation,the results show that under the two working conditions,the microstrip antenna is resonant at the 9GHz and 12.22 GHz,and it can realize the frequency reconstruction.The structure of this thesis is based on the application of FSS.In simulation,we use floquet port of simulation software to simulate periodic structure.Furthermore,we realize the reconfigurable polarization and frequency reconfigurable based on FSS.The results validate great application prospect of reconfigurable antenna.