Study On Miniaturization And Tunability Of Frequency Selective Surfaces

With the development of science and technology,the application of Frequency Selective Surface is more extensive.In this paper,Frequency Selective Surface with Miniaturized Elements and Active Frequency Selective Surface are studied in the direction of optimizing the Frequency Selection Surface.Compared with the traditional Frequency Selective Surface,Frequency Selective Surface with Miniaturized Elements has a smaller unit size,which breaks the limitation that the unit size of traditional Frequency Selective Surface is consistent with the resonant wavelength,and can work in a wider frequency band with better Angle stability.In some special environments,including non-plane wave irradiated areas and small bending parts,it has higher application advantages.The performance of the Active Frequency Selective Surface can be changed.Compared with the single fixed performance of the traditional Frequency Selective Surface,the Active Frequency Selective Surface can flexibly change the performance according to different application scenarios and has more powerful functions.The main research work of this paper includes the following three parts:1.Based on the coupling mechanism of the inductive surface and the capacitive surface,a broadband structure with high transparency is designed.The structure is composed of an s-shaped metal grid on an inductive surface,a square metal patch on a capacitive surface and a dielectric layer in the middle.There is a very wide transmission band near the resonant frequency.The simulation transmission band covers 7.50-22.34GHz,and the relative bandwidth reaches 99%.The experimental transmission band covers 9.03-23.12GHz,and the relative bandwidth reaches 88%.Through theoretical analysis,the equivalent circuit of the structure is obtained,and the working principle of the structure is intuitively understood.At the same time,the structure is not sensitive to polarization and has good angular stability.2.Based on the concept of optically controlled Active Frequency Selective Surface,a kind of Frequency Selective Surface of optically controlled elements directly loaded into the periodic element structure is studied.At present,the research in this field is mainly about the loading of light-controlled materials,and there is almost no design of light-controlled devices.Here we have designed a kind of Frequency Selective Surface with adjustable center frequency of stopband directly loaded with photosensitive resistor.In the simulation,the loaded photosensitive resistor is equivalent to a variable resistor.However,the experimental results show that the performance of the photosensitive resistor at microwave frequency is more complex,and it is necessary to further study the microwave characteristics of the optically-controlled device in order to directly load the optically-controlled device.3.Based on the concept of optically controlled Active Frequency Selective Surface,the adjustable Frequency Selective Surface controlled by optically controlled element is studied.Using photodiode to control varactor diode and using photodiode diode to control PIN diode respectively,a kind of Frequency Selection Surface which achieves adjustable absorption and a kind of Frequency Selection Surface which realizes the switch between reflection and absorption are designed.Using equivalent circuit method,we analyze its simulation performance respectively.The experimental results show that the optically-controlled method is feasible when the optically-controlled element is used as the external power supply.However,the optically-controlled element is only suitable for the components with small power requirements.The optically-controlled element can only control the varactor diode,but it cannot be used to control the PIN diode.