Design And Laser Precision Machining Technologies For Frequency Selective Surface Radome

Frequency selective surface(FSS)is a monolayer or multilayer planar structure with the arrangement of periodic two-dimensional passive resonant units.FSS have certain frequency selective characteristics for electromagnetic wave and light wave.The electric stator structures of FSS are formed by etching the two-dimensional periodic aperture location or unit of paste metal strips on the metal film,thus rendering the frequency selective characteristics of band pass(cork-pore)or band-stop(patch)for electromagnetic wave.The FSS radome,which can effectively reduce the radar cross section(RCS)of the aerospace vehicles,has important significance for the stealth aircrafts and naval vessels.In this thesis,the design,simulation and the high efficiency laser precision machining technology of the FSS structure of radome(plane,regular surface and complex surface types)are discussed in detail.Firstly,the main factors affecting the design of plane FSSs and their simulation model are discussed;the geometry parameters and the plane wave incident angle“theta” that affected the electromagnetic filtering characteristics are studied.The characterization parameters of surface electric field distribution and near-field energy distribution are obtained by adopting the time domain finite integration method to carry on simulation calculation.Secondly,the engineering practical bending cover method is used for the design and simulation of flattenable regular surface FSS radome.Using the improved time domain finite integral algorithm and simulation model,the transmission characteristic curve and RCS reduction of the circle slot type cylinder and cone conformal FSS are analyzed.As to the non-flattenable freeform surface FSS radome design,a novel method of on-line modeling,layout and processing integration procedure is proposed for the conformal periodic pattern layout on complex surface,and the instance simulation is realized based on CATIA software.Full-wave simulation analysis of Y slot type FSS conformal freeform surface radome on complex surface is carried out by seting up a phased array antenna,and the good results of broadband penetration rate and the aiming error show that the modeling and layout design of FSS on complex curved surface radome is a feasible engineeringmethod.Finally,the principle of parallel projective galvo scanning(PPGS)laser precision machining technology is introduced,and the plane,cylinder and cone FSS radome are fabricated by the PPGS laser precision machining equipment that independently developed by the group team.The micro etching boundary contour and SEM microstructure investigation are discussed,and the transmission characteristic curves of the samples are tested.Results show that the technology of PPGS laser precision machining can be compatible with the processing of the FSS radome with plane,regular and freeform surface shape,which proved that it is a feasible technical solution for the high efficiency and multi-scale processing of large complex FSS radome.