Study On The Design And Applications Of Optical/Radar Dual Band-pass Frequency Selective Surface

High resolution optical detection and full-time working radar detection make optical/radar dual-mode detection technology become the focus of development and advanced technology in the field of precision guidance of aircraft. The design and manufacture of composite guidance window, with functions of stealth and electromagnetic shielding, become one of the core technology of optical/radar dual-mode detection. Currently, electromagnetic shielding techniques for optical guidance window are metallic meshes, ITO, et al. Stealth technology for radar guidance window is frequency selective surface(FSS), et al. Metallic meshes is an excellent optical conductive film. It can shield the electromagnetic wave radar band, because of its micron scale feature size. But it cannot achieve the radar band-pass function. Frequency selective surface is a kind of space filter with a band-pass or band-stop function. It is the best way to solve the difficulty for aircraft observation radome stealth problem. The metal cover rate is too high which will affect its optical properties. Therefore, it is difficult to design a novel artificial microstructure, considering both the high optical transmissivity, high imaging quality, and excellent characteristics of band pass filtering. At present, there are less published literatures in this area at home and abroad.In this paper, we propose a novel structure combined metallic meshes with FSS, and study the design and applications of optical/radar dual band-pass FSS. A search is carried out for the micro structure design method by considering the high optical transmissivity, high imaging quality, and excellent characteristics of band pass filtering. Optimize the micro structure to improve its photoelectric performance. In order to broaden the applications, study the electromagnetic characteristics of optical/radar dual band-pass active FSS. The specific research work includes the following aspects.In order to obtain the excellent characteristics of band pass filter, it should avoid to destruct unit patterns. According to mutual admittance theory, the surface current resonant mode distribution of optical/radar dual band-pass FSS is analyzed and the design constraint conditions are summed up. The microstructure, designed according to the constraint conditions, achieves a high optical transmissivity and excellent characteristics of band pass filtering.There are inherent contradictions in the demands for high spectral transmittance at optical wave band, high transmissivity at millimeter wave band and high electromagnetic shielding efficiency. A scalar diffractive model is built based on Fraunhofer diffractive theory to study the influence of structure parameters, modulation transfer function, stray light on the diffractive properties of optical/radar dual band-pass FSS. Furthermore, annular metallic meshes FSS and iterative metallic meshes are proposed to improve the photoelectric performance.On the basis of the above study, the electromagnetic characteristics of optical/radar dual band-pass active FSS are explored. By embedding lumped elements in microstructure skillfully, the band-pass effect at radar band can be controllable, the optical transparent and radar band pass function are maintained.A series of manufacture tests are carried out to sum up the influence of parameters on optical/radar dual band-pass FSS. The experimental sample achieves high optical transmissivity, high imaging quality, and excellent characteristics of band pass filtering. There is a good agreement between experimental results and simulation results, proving the design method is feasible and precise.