Design Of Multiband Terahertz Filter

Wih the rapid development of communication technology,the limited spectrum resources has become more and more crowded,we pay more and more attention to terahertz spectrum resources?In addition,the development of multiple frequency detection technology has prompted the progress of multiband.Frequency Selective Surfaces(FSS)with high selective characteristic is becoming a hot spot of research.FSS filtering performance is the breakthrough point,the applications of mutiband filter is the demand background,this article analyze the FSS filter working principle and simulate by computer to expand the multiband applications of THz filter.This thesis mainly studied around the miniaturization,multi-band frequency selective surface design and optimization,the main works are listed as follows:(1)In order to choose the right foundamental unit structure,the common patch type like wafer,circle,square ring structure are simulated in the same cycle,respectively for polarization direction,incident angle,the thickness of the substrate,the thickness of the sheet metal,substrate dielectric constant,line length,different structural parameters such as line width are simulated,the simulation results is that circle frequency response is more stable than wafer,and easier to control;In order to obtain the same resonant frequency,the size of the square ring is more compact than the circle ring which meet the miniaturization design trends.So,finally choose the square ring as the foundation unit of the research.(2)In order to satisfy the multiband design requirements,the patch shape square ring regard as basic unit,the nested square ring realize the band-stop filter characteristic of the six bands,and we analyze filtering principle by the simulation of surface current,it is concluded that one ring provide one stopband,and the nested square ring has stability for different incident angle and polarization mode.(3)In order to expand the characteristics of the single ring with one band,we design half square ring and slot filter combined with frequency selective surface itself structurecharacteristics,contrast to single ring structure,the stopband numbers of new structure increased obviously,this change improved the band selection diversity.In addition,the quqntity of structure parameters increase,the center frequency point range of options and flexibility improves greatly.Use the method of equivalent circuit also proved the reliability of the dual stopband.Angle stability is good as well.