Design And Preparation Of Frequency Selective Surface Based On Ceramic

With the rapid development of electromagnetic stealth technology in the field of defense,frequency selective surface(FSS)radome has gradually become the key technology and got much more attention by people.The FSS radome not only plays the roles of bearer, insulation and so on,but also has an effect of filtering on electromagnetic waves,thus effectively reduces the radar cross section(RCS) of aircraft and achieves electromagnetic stealth.With the increasing speed of the aircraft flight,traditional organic material is not suitable for the harsh environments and high temperature generated by hypervelocity during the flight any more.The ceramic which have better permeability properties and higher mechanical strength and adapt to high temperature and thermal shock has become the most popular radome material.How to fabricate the ceramic-based FSS radome successfully has become a bottleneck of stealth technology.In this paper,the relevant research work of ceramic-based FSS which based on the previous has been done.On the one hand,the basic principles of frequency selective surface and its application in the radome was studied and the method of optimization of the traditional multi-screen frequency selective surface was summarized.And Successfully designed a variety of X-band band-pass multi-screen frequency selective surface.On the other hand the quartz ceramic which doped Li2O-K2O-Al2O3 was adopted as the raw materials.And we got use of high temperature co-fired ceramics(HTCC) to explore the preparation of multi-screen tablet of ceramic-based flat FSS.The article solved some technical problems and got the relevant process parameters.Firstly, the properties of quartz ceramic which doped Li2O-K2O-Al2O3 were studied, and the dielectric properties, mechanical properties and thermal properties of the doped silica ceramic were tested and analyzed.Experimental tests proved that the dielectric constant could be down to 4.37,the minimum dielectric loss could reach 0.0038(14GHz),and at the room temperature flexural strength can reach up to 163 MPa,thus the doped ceramic has successfully overcome the poor mechanical strength of traditional quartz ceramics.The ceramic have a very dense structure,and some anti-rain-erosion and sand-erosion capacity were expected. The material has the potential to be one of the radome material and can be compatible with the crafts of HTCC.Secondly, this article summarized the basic theory of FSS, classification and its various applications, and designed a variety of X-band multi-screen FSS successfully. In this paper,the structure of multi-screen FSS based on traditional cross of Jerusalem was improved by taking measures such as using of the closed ring structure, loading minor metals, using fractal structure.the FSS simulation emphasized on bandwidth, polarization stability, the stability of the angle of incidence and band rejection performance.The simulation results showed that the Jerusalem Cross unit which loaded with a cyclic structure allows smaller FSS cell size and can improve its incident angle stability, eliminate band waveform distortion and enhance the performance of band rejection;The unit of FSS which loaded minor metals can effectively reduce the size of the FSS units and enhance the stability of incidence angle;The FSS Using new structure of the antenna-filter-antenna can achieve steep filtering,while the FSS has a much lower section, which were not possessed by conventional FSS;The FSS using higher-order fractal structures tends to have a better stability of incidence angle and much better band rejection.Thirdly,the quartz ceramic doped Li2O-K2O-Al2O3 was selected as the raw material in this paper,And the high-temperature co-fired ceramics(HTCC) was firstly used to fabricate flat multilayer FSS.And the preliminary exploration of the process was done.Successfully the film-rolling, printing, isostatic, latex and other process problems were resolved.Experiments show that, due to the large amount of alkali metal oxides in the ceramic powder,traditional mature adhesive PVA for film-rolling process is not suitable for the quartz ceramic doped Li2O-K2O-Al2O3.Herein and polyvinyl acetate were used as the binder instead.The smooth rolling diaphragm tended to have some flexibility,And the appropriate row of plastic sintering system was finally worked out.Finally, the article discussed the problems which often encountered in the process, and analyzed the possible causes.