Research On The Angular Stabilization Of Band-pass Frequency Selective Surface

Typical frequency selective surface is one or two dimensional periodic structure,which is made up of metal patterns on dielectric substrates,and it has significant practical application value in spatial filter field.FSS with a band-pass characteristics has been drawing a lot of attention for its function as a spatial filter.Generally speaking,stable properties under different incident angles with designed resonance frequency,constant bandwidth and low insertion loss are quite important factors for a spatial filter.Therefore,in this paper,the oblique incidence performance of band-pass frequency selective surface is studied,and the main results are as follows:First of all,the second-order band-pass frequency selective surface is studied,two different design methods are analyzed,and the effects of pattern and dielectric parameters on the performance are studied.Then,according to the theory of scan independence,the mechanism of angular stability which can be improved through outer dielectric bonding is analyzed,and an angular stabilized second order band-pass structure working at 14-18 GHz is designed.In addition,the effects of dielectric constant and the substrate thickness on performance of the designed structure are investigated.Furthermore,the patterned dielectric layer which can be obtained from existing commercial products is proposed to adjust the effective permittivity.Then the results are verified and the law is explored by parameter inversion.Finally,in order to further reduce the requirement about the dielectric of the whole structure,an angular stabilized second order band-pass structure working at 8-12 GHz by using capacitance layers is proposed based on the theory of scan independence together with impedance matching principle.The capacitance layer and dielectric layer between band-pass filter and capacitance layer formed an impedance matching network which is consist of transmission line and capacitance.Morever,the effects of transmission line and capacitance layer on its performance is also analyzed by smith chart.A prototype of the proposed structure is fabricated and measured to verify the design successfully.In summary,the oblique incident stability of the band-pass filter with operating band of 14-18 GHz is improved by means of patterned outer dielectric bonding.Furthermore,the oblique incident stability of the band-pass filter having operating band of 8-12 GHz is realized by capacitance layer.