Design Of Dual-Band Frequency Selective Surface

The frequency selective surface(FSS)is a periodic array structure that has been widely used due to its electromagnetic filtering characteristics.In the military field,FSS is often used for the preparation of radar radome,which greatly improves the stealth performance of weaponry.In the field of microwave communications,with the rapid development of multi-frequency communications,FSSs with multiple independent frequency bands are usually used to increase the channel capacity of the communications system and improve work efficiency.In order to meet the actual engineering requirements,FSS needs to have ideal filtering characteristics,showing that the filtering characteristic curve of the structure has a "flat top,steep cut-off" characteristic and remains stable at large incident angles.This paper focuses on the design of FSS structure and designs a dual-band FSS structure with high-angle stability characteristics and “flat top,steep cut-off” characteristics.The main research contents include:Firstly,the basic theory of FSS filtering mechanism,classification characteristics and technical indexes are introduced.Starting from the basic unit FSS,The influence of the structure parameters,dielectric parameters,polarization modes and incident angles of incident electromagnetic waves,and other factors are initially studied for FSS filtering,providing a theoretical basis for the design of the FSS.Then,based on the angle stability of the filter characteristics,the dual-band FSS design method was studied.A dual-band FSS structure design method based on composite element technology and unit meandering technique is proposed.By using this method,a tortuous dual-band FSS structure with high angle stability is designed.The structure achieves a small size of 0.113 ?×0.113? and excellent angle stability,when the incident angle increases,the maximum deviation rate of the resonant frequency is only 0.9%.A dual-band FSS structure design method based on fractal filling curves is proposed.After analyzing the influence of fractal evolution rules and iteration times,a fractal dual-band FSS is designed by a combination of the design concept of tortuous FSS.The miniaturization characteristic of the structure reaches 0.072?×0.072?,and the angle stability is excellent,the resonance frequency deviation rate is less than 1.7%.Finally,the dual-band FSS design method is studied based on the problem of “flat top and steep cut-off” of the filter characteristic curve.Single-screen FSS is generally difficult to achieve "flat top,steep cut-off" features,which usually need to adopt multi-screen FSS cascade method to achieve.A dual-band FSS structure design method based on three-screen cascade is proposed.The formation mechanism of two frequency bands is analyzed by the equivalent circuit method.A dual-band cascade FSS with second order filter characteristics is designed by this method.Compared with the traditional cascade structure,this structure achieves the "flat top,steep cut-off" filter characteristics,and shows good angle stability,the frequency offset rate is less than 5.2%.This paper starts with the stability of the filter characteristics curve and “flat-top,steep cut-off” characteristics of the dual-band FSS structure.It systematically studies from the theoretical analysis of FSS to structural design and simulation optimization,proposes three types of effective structure design method of the dual-band FSS,and the corresponding dual-band FSS structures are designed.The designed structures realize the filter characteristics with high angle stability and "flat top,steep cut-off" characteristics,complete the expected goal,and have certain engineering practical value.It has certain guiding meaning to the related research in the field of dual-band FSS.