Angularly Stable Frequency Selective Surface Research Articles

A Novel Ultra-Miniaturized Angularly Stable Frequency Selective Surface for L-Band Shielding Applications

This paper presents a novel ultraminiaturized frequency selective surface (FSS) for L-band electromagnetic shielding applications. A basic square loop incorporated with folded arms in the top layer constructs the single-layer FSS design. Band-stop characteristics for the entire L-band operating frequency ranging from 1 GHz to 2 GHz are offered by the proposed design. An ultraminiaturized profile of 0.028λο × 0.028λο is achieved by the designed FSS, where λο corresponds to the lowest operating frequency, achieving at least 32.1% miniaturization when compared to the state-of-the-art FSS designs in the literature. Polarization insensitivity with a peak shielding effectiveness of 45.4 dB is manifested by the rotational symmetry of the proposed design. The proposed FSS exhibits excellent angular stability performance up to 80° with a frequency deviation of less than 1%. The equivalent circuit model helps to understand the working principle of the proposed FSS. The experimental results of the designed FSS prototype agree well with the simulation results. Hence, the proposed spatial filter is a suitable candidate for enhancing security in wireless communication at the carrier frequencies of GPS systems.

Optically transparent and angularly stable broad‐stopband frequency selective surface for millimeter wave electromagnetic interference mitigation

AbstractAn optically transparent and angularly stable frequency selective surface (FSS) with a broad stopband is introduced for addressing millimeter wave (mmW) electromagnetic interference. The unique FSS unit cell pattern incorporates a cross patch with Y‐shaped branches, effectively broadening the bandwidth and enhancing the angular stability. Utilizing transparent conductive indium tin oxide deposited on both sides of a glass substrate enables the FSS to reflect and absorb electromagnetic waves. Consequently, the proposed FSS exhibits an exceptionally wide stopband ranging from 18.7 to 40.2 GHz, featuring an insertion loss of 14 dB and maintaining stable angular response up to 60° for both transverse electric and transverse magnetic polarizations. Moreover, an equivalent circuit model is developed to characterize the stopband behavior of the FSS. Finally, measurements conducted on a physical prototype of the proposed FSS validate its effectiveness, showing good agreement with the simulation results.

Miniaturized dual stop band frequency selective surface with broadband linear co to cross polarization conversion ability

This work presents a miniaturized angularly stable frequency selective surface (FSS) on a single layer substrate. Unit cell comprises of convoluted circular rings connected cross dipole and linear arrow headed dipole printed on both sides of the substrate. A closely spaced dual stop band resonances are obtained at 10 and 14.3 GHz with frequency ratio of 1.43. FSS shows a − 10 dB stopband bandwidth (BW) from 7.32 to 11.05 GHz (40.61%) and 12.68 to 15.97 GHz (22.97%) with >30 dB stop band rejection at center frequencies. FSS poses the features of stable performance under change in polarization and angularly stable response up to 60° incident angle. Later the proposed FSS is printed on grounded thick dielectric substrate and it shows broadband reflection type co to cross polarization conversion from 7.2 to 17.32 GHz (82.54%) with polarization conversion ratio >80% and oblique angle stability up to 35°. To the best of authors' knowledge, this is the first time in literature a single unit cell geometry with two different properties, spatial filtering on transmission and polarization conversion on reflection have been designed and analyzed in details. A finite array with size 25 × 25 of the proposed FSS is fabricated and the measured filter response shows a good agreement with simulated performance at normal and oblique incidences. The proposed FSS is used as a reflector of a dual band monopole antenna and the simulation results shows gain improvement of 5.51 and 3.8 dB at the two stopband frequencies.

A Tri-band Angularly Stable Frequency Selective Surface with Controllable Resonances for EM Shielding

AbstractIn the paper, a tri-band angularly stable frequency selective surface (FSS) with controllable resonances for electromagnetic shielding is proposed. Different from traditional single-layer structure, the FSS proposed is based on cascaded structure that creates three adjustable blocking bands around frequency 5.93 GHz, 7.33 GHz and 9.17 GHz, respectively. The designed FSS has a low profile with thickness of λ0/100, where the λ0 represents wavelength of the first band-stop resonance frequency. Besides, the proposed FSS exhibits stable frequency response up to 70° with respect to different polarizations. Therefore, this FSS is flexible and can be used in electromagnetic shielding field where needs conformal screen. To investigate and understand the operating mechanism better, a equivalent circuit model (ECM) is deduced and given in the Section 2, the calculated results match the full-wave EM simulation results perfectly. Finally, a prototype of this FSS is fabricated and measured, the measurement results are in accordance with the simulation results.

Reducing the RCS of a MIMO antenna using an angularly stable FSS

A systematic design procedure for reducing the radar cross section (RCS) of a multiple-input multiple-output (MIMO) antenna is presented in this paper. The RCS reduction was achieved at 11.3 GHz, which was out-of-band compared to the antenna's working frequency of 2.18 GHz. The design flow started with developing an isolation-enhancement network for the MIMO antenna that did not disturb the RCS reduction process. An incident- and polarization-angle-insensitive frequency-selective surface (FSS) was next designed. The conventional ground plane of the MIMO antenna was replaced by an FSS array. The designed FSS was introduced in such a way that the antenna's characteristics and isolation among the antenna ports were preserved by achieving the RCS reduction of an antenna at the bandpass frequency of the FSS. The proposed FSS was angularly stable, and hence an almost constant RCS reduction was found for most of the incident angles. The final proposed low-RCS MIMO antenna was fabricated and measured to validate the simulation results.

A 2.5-D Angularly Stable Frequency Selective Surface Using Via-Based Structure for 5G EMI Shielding

A novel broadband bandpass frequency-selective surface (FSS) designed for fifth generation (5G) EMI shielding is proposed in this paper. This new design employs the vertical vias into the 2-D periodic arrays, and such a single 2.5-D periodic layer of via-based structure is demonstrated to produce a highly stable angular response up to 60° for both TE and TM polarizations. By cascading two layers of such 2.5-D periodic arrays, the proposed FSS is able to obtain a broad passband as well as the wide out-of-band rejection. Moreover, it has a quite sharp band edge between the passband and the specified stopband. A corresponding equivalent circuit model (ECM) is further developed for better analysis of the operating principle. Finally, a prototype working at the center frequency of around 28 GHz is fabricated and measured. The main novelty of this paper is introducing the 2.5-D concept into designing a wideband FSS, and further reduce the unit size as well as improve the angular stability. Favorable agreement is achieved among the 3-D full-wave simulation, ECM and measurement. All these results demonstrate that the proposed FSS is a good candidate for 5G EMI shielding.

Compact angularly stable frequency selective surface using hexagonal fractal configurations

AbstractA compact bandstop frequency selective surface (FSS) using fractal structure is proposed. This flexuous design elongates the cell perimeter of the ring‐shaped FSS, which means the cell size gets smaller at the same resonance frequency. Furthermore, the unit cells adopt regular hexagon and the array employs equilateral triangle form. Because of its symmetric configuration, good frequency stability has been achieved for both horizontal and vertical polarizations at different oblique angles. For the stable bandstop character, this FSS can be used for protecting the staff of S‐band radars against electromagnetic radiation, while the 900/1800/1900 MHz mobile bands and the 5.2/5.8 GHz wireless local area network signals are not affected. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2541–2544, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24676