Research On The Application Of Metamaterials To Active Frequency Selective Surfaces

Frequency selective surface(FSS)refers to an infinite array which is arranged periodically by a large number of identical resonant elements in a one-dimension or two-dimension.It essentially corresponds to a spatial filter that can reflect or transmit electromagnetic waves with different frequencies and different polarizations.Active Frequency Selective Surface(AFSS)is a novel kind of FSS that dynamically adjusts the electromagnetic characteristics by loading a series of active devices in the passive FSS,which can effectively solve the defect that the passive FSS cannot adapt to the complicated electromagnetic environment.Metamaterials are artificial composite structures or materials with extraordinary physical properties that are not possessed by natural materials.Due to the extraordinary physical properties,metamaterials can be widely used in civil aviation,military,life,and production,and will bring tremendous changes to the communication,manufacturing,stealth and detection in the future.This paper mainly studies the applications of the metamaterial on active frequency selective surface.Utilizing the unique electromagnetic properties of the metamaterial can effectively enhance the stability of the incident angle and the polarization,and dynamically adjust the transmission characteristics of AFSS.The main research content of this paper includes the following aspects:Firstly,the definitions of metamaterial and FSS are introduced,and their analytical methods are described.Two novel metamaterial elements have been designed.One is an open square ring metamaterial element,the other is a nested triangular ring metamaterial element.Verifying by S-parameter extraction,we can find that they can remain the metamaterial performances in the S and C bands.We also analyze the influences on the electromagnetic performances,due to the structural parameter changes of the metamaterial elements.The frequency selective characteristics of the two novel metamaterials are verified by the three-dimensional electromagnetic simulation software which is based on the finite element algorithm.They can produce a single stopband in the S-band,but they do not possess the stability of the incident angle and the polarization.Therefore,they have some defects.Secondly,a novel FSS based on an open square ring metamaterial element is designed,which can generate a single stopband in the S-band with a maximum angle of 75o for the stability of the incident angle and better stability of the polarization.We analyze the influences on the transmission performances of the FSS,due to the structural parameter changes of the open square ring.An open square ring AFSS is formed by loading varactor diodes between the FSS elements,which can generate a single stopband in the S-band.By changing the capacitance value of the varactor diodes,the electromagnetic transmission characteristics of the open square ring AFSS can be dynamically adjusted under the complicated electromagnetic environment.Finally,a novel FSS based on a nested triangular ring metamaterials element is designed.It can generate a single stopband in the C-band with a maximum angle of 70o for the stability of the incident angle and the polarization.We also analyze the influences on the transmission performances of the FSS,due to the structural parameter changes of the nested triangular ring.By loading the varactor diodes between FSS elements,it can form a nested triangle ring AFSS,which can produce double stopbands in the S and C bands.By changing the capacitance value of the varactor diodes,the electromagnetic transmission characteristics of the nested triangular ring AFSS can also be dynamically adjusted under the complicated electromagnetic environment.