Frequency selective surface based on metallic mesh can realize the physical properties of both high infrared transmittance and millimeter-wave band-pass filter. In order to improve the optical transmittance, reduce surface resistance and suppress the effect of high order diffraction energy on the imaging quality of the optical system, a new design of frequency selective surface based on hybrid period metallic mesh is obtained. In this paper, the diffraction intensity distribution and surface current of frequency selective surface are analyzed based on metallic mesh. Simulation and experimental results show that frequency selective surface based on hybrid period metallic mesh realizes a stable millimeter-wave band-pass filter property, at the same time, it obtains 5% increase of infrared transmittance and 4 Ω reduce of surface resistance. New design of frequency selective surface based on hybrid period metallic mesh effectively suppresses the effect of high order diffraction energy on the imaging quality of the optical system.
Frequency selective radome is one of the most important applications of frequency selective surface (FSS). In order to obtain better stealth performance, a novel element FSS, based on a regular slot element FSS, is presented in this paper. The novel element consists of a slot element in the center and at least two slot strips placed on the periodic boundary. We call such FSS the “hybrid-element type FSS” because it exhibits characteristics of both slot type and patch type FSS. Simulation and optimization work is carried out by using a period moment method and a discrete particle swarm optimization method based on the application requirements of a missile radome. Simulation results show that the hybrid-element type FSS has much steeper transition section between pass-band and stop-band, and much lower transmittance in stop-band when compared with the corresponding slot type FSS. The new FSS also has much lower insertion loss in pass-band, much thinner thickness, much simple structure and fabrication process when compared with the ordinary two-layer FSS. Equivalent sample plate is fabricated using printed circuit method and tested using the free space method. Good fit between simulation and testing results verify the accuracy and feasibility of this novel FSS design. The hybrid-element type FSS is especially suitable for the stealth radome when woking frequencies of both sides are very close. It provides a simple and feasible approach for developing frequency selective radome.
We propose a miniaturized-element frequency selective surface (MEFSS) by using the coupling mechanisms between capacitive surface and inductive surface, so the uint cell size will not be restricted by wavelength. In order to improve resonance stability performance with respect to different polarizations and incidence angles, according to the traditional FSS Y element, we create periodic elements of capacitive surface and inductive surface with Y shape and Y element array is in the form of equilateral triangle, The grid array and the effects of the parameteristics of Y loop element on the frequency response characteristics of MEFSS are calculated using the modal matching method. With filming technology and lithography, the corresponding capacitive surface and inductive surface between polyimide are produced and a prototype MEFFSS using freedom space method is examined. Both simulated and measured results obtained show that the MEFFSS constructed by using equilateral triangle Y element array has much better f0 resonance stability performance with respect to different polarizations and 60 incidence angles, and the -3 dB bandwidth reaches up to 7.6 GHz. We present a theoretical and experimental reference of MEFSS for the applications in large-angle incidence curved streamlined radome.
In order to meet the multi-band and integration requirements of the communication apparatus, the coupling and resonance mechanism can be exploited to design a frequency selective surface (FSS), with two pass-bands at Ku-band and Ka-band, which is composed of three metallic layers and fabricated on a flat substrate equivalent to a solid wall radome or an A-sandwiched radome. According to the physical structure of the FSS, an equivalent circuit model is established to analyze the filtering mechanism, and the transmission characteristics of the radomes with FSS are obtained by using a full-wave analysis software. The first pass-band at Ku-band with miniaturization property can be achieved by coupling the electric and magnetic field of the three surfaces, while the second pass-band at Ka-band can be achieved by the resonance of the square loop slots embedded in the capacitive surfaces. The transmissions of the solid wall radome and A-sandwiched radome with FSS are 89% and 94.7% at Ku-band, and 88.2% and 93.7% at Ka-band, respectively. When the incident angle is varied from normal to 60°, the frequency response characteristics of the two pass-bands are stable. Finally, the experimental results of the prototype with a solid substrate measured in free-space environment are in good agreement with the simulated values. The proposed radome structure with FSS, which is based on the coupling and resonance mechanism, can achieve two stable pass-bands at Ku-/Ka-band. This may provide some theoretical and experimental assistance for the study of the multi-band and wide band spacing FSS.
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