Papers by Keyword: Frequency Selective Surface

Abstract: In order to get the low transmission rate in both mid infrared atmospheric window and far infrared atmospheric window, an infrared frequency selective surface composed of two layers based on hexagonal ring structure was designed. Simulation analysis using CST electromagnetic software shown that the frequency selective surface had two stopbands in both 3μm~5μm and 8μm~15μm regions, of which the average transmittance is lower than 2.5%. Therefore, this frequency selective surface realized two stopbands in infrared wavebands; This paper analyzed the filtering mechanism of the frequency selective surface based on the effective medium theory. In the end, this paper researched the effect of electromagnetic wave polarization mode, incident angle and dielectric layer thickness on the transmission properties of the frequency selective surface. The results revealed that the transmission of frequency selective surface is insensitive to polarization mode and incident angle, while the dielectric layer thickness is an important factor to the transmittance of frequency selective surface.

Abstract: A double screen infrared frequency selective surface (FSS) with dual transmission stopbands was proposed and numerically investigated. Simulation results show that the infrared transmittance of the structure is lower than 10% in mid-infrared band (3~5 μm) and far-infrared band (8 ~14 μm).This structure is polarization insensitive to the incident electromagnetic waves. For a wide range of incident angles from 0° to 60°, the infrared transmittance of the structure is still lower than 25% in the band of interest. Compared with black body, the radiation ratio of structure is lower in the MWIR and LWIR ranges. The structure provide the potential applications for infrared stealth.

Abstract: With the advancement in telecommunication in indoor environment, the use of wireless technology for information systems has drastically increased. The intensive use of indoor wireless devices in 2.4GHz and 5.8GHz ISM bands causes mutual interference in neighboring networks which degrades the system performance. Secure personal communication within such wireless networks is also another important problem. A band-stop frequency selective surface (operating in the WLAN frequency band) which is attached to the walls of buildings can provide a solution for these interference and security problems. In this work, a new band-stop hybrid frequency selective surface element consisting of two circular looped type geometries is introduced which is capable of attenuating the incoming 2.4GHz and 5.8GHz ISM signals minimum 13dB for all polarizations and incident angles varies from 0⁰ to 45⁰. Besides, a periodic cell size (p=26,5mmm) which is almost one fifth of the first resonance wavelength is obtained.

Abstract: Frequency selective surface (FSS) is a two-dimensional periodic structure. It exhibits total reflection and transmission in the neighborhood of the element resonances. As it performs as a filter, FSS is widely used in the fields of microwave and optics. In this paper, the finite element method is used to analysis frequency selective surface and study on the feasibility of Ansoft HFSS software for frequency selective surface simulation. Hexagonal element of frequency selective surface is as an example to explore the simulation method and the process of Ansoft HFSS. Through the comparison of the simulation curves and the measured curves of hexagonal element frequency selective surface film by photoetching technology, the simulation method of Ansoft HFSS software for frequency selective surface is correct. At the same time, this paper further verified the reliability of the simulation through the example of the ring and the cross unit structure.

Abstract: An ultra-wideband (UWB) circularly polarized complex spiral antenna with low radar cross section (RCS) is proposed in this paper. By replacing the metal reflect board of the antenna with a novel UWB frequency selective surface (FSS), the RCS of the spiral antenna is significantly reduced in a wide frequency range, while the radiation performances of the spiral antenna are maintained. The proposed antenna operates over the frequency band between 2GHz to 6.5GHz under the condition of axial ratio<3dB and |S₁₁| < - 10dB. Simulation and measurement results demonstrate the validation of broadband spiral antenna RCS reduction by using the novel UWB FSS.

Abstract: The combination element frequency selective surface (FSS) with regular triangle patches and circular aperture elements in activated carbon fiber (ACF) felts were designed. The effects of the structure parameters and periodic arrangement of regular triangle patches on ACF felt composites were investigated. As the regular triangle patches were embedded into circular apertures, the combination element ACF felt screen (ACFFS) composites presented fluctuant absorbing characteristics and showed double-band frequency response characteristic including band pass and band stop. When the regular triangle edge length (L) increased, the effective absorption frequency (the reflection loss below-10 dB) shifted to low frequency, and the effective bandwidth increased without reducing the maximum absorption value. When the regular triangle patches (L = 30 mm) were in staggered rows, the effective absorption frequency drifted by 3.1 GHz, and the effective bandwidth was enhanced from 4.3 GHz to 11.0 GHz. Although the regular triangle patches are not central symmetry, it is proved that the absorption properties can be improved obviously by both horizontal polarization and vertical polarization.

Abstract: A new scheme that FSS applies in chipless RFID tag is proposed. The bandpass cross-slot FSS cell is used in the chipless RFID tag based on the spectrum signature as the resonator. The chipless RFID tag successfully performs 6 bit in 3-9GHz, the test result of S12 is-11.9~-14.3dB. The whole tag could be completely printed and the cost could be quite low. The size of the whole tag is 24.5*9cm².

Abstract: In this work, a kind of conductive polymer-silver paste was used to fabricate carbon fabric composite frequency selective surfaces (FSS) with four-legged slot elements. Screen printing and 3D engraving process were carried out to coat the conductive polymer-silver paste onto the carbon fabric preform and sculpt composite panels into composite FSSs, respectively. Free space and finite element methods were carried out to measure and calculate the electromagnetic transmission characteristics of the composite FSS, respectively. The calculated results are in good agreement with the experimental data. The cascaded effect in double-layered FSS were investigated by finite element method and design of experiment technique (DOE).

Abstract: In this work, the hybrid fabrics of carbon and quartz fibers as filters were adopted in PMI core sandwich structures for low-observable radomes. The advantages of fabric composite frequency selective surfaces (FCFSSs) are easily fabricated by braiding and shaped into curved surfaces. This paper mainly studied the electromagnetic (EM) transmission characteristics of the low-observable radome wall with composite FSS by 3-dimensional electromagnetic analysis software. First of all, the accuracy of the simulation model composed of up and down composite face sheets, a layer of composite FSS and PMI core was validated by comparing with experimental results. Then, the studies on electromagnetic transmission characteristics of the sandwich structure with composite FSS and the sensitivity analysis about the thickness and permittivity of face sheets and PMI core were carried out. The results show that the sandwich structure with single layer composite FSS can realize the function of frequency selection, limit the reflection at the resonance frequency and decrease the sensitivity of EM transmission loss about the thickness of sandwich structures.

Abstract: The three common frequency selective surface (FSS) structure, i.e. ring, crosses and Y-aperture which have the same center frequencies are designed, then the three FSS structures are placed at absorbing materials to form complex absorbing structures which are simulated by means of spectral domain approach. Therefore, the effects of different FSS on the characteristics of absorbing materials are studied and the influence laws are given. This research offers reference to element selection for the application of common FSS to absorbing materials.