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(a) FSS with Greek cross apertures (p = 1.25 cm, g = 0.25 cm, w = 0.2 cm). (b) Greek cross patch array, and its (c) equivalent circuit.
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The shielding effectiveness (SE) of a metallic enclosure with double-layer frequency selective surface (DLFSS) has been calculated using a transmission line theory-based analytical formulation. The DLFSS layer placed on the front and back sides of the enclosure consists of a Greek cross aperture array. The equivalent circuit method and an empirical...
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... Greek cross FSS placed at the front and back sides of the enclosure with periodicity p, width of the element w, and gap between the elements g is shown in Fig. 1(a). The equivalent circuit model for the Jerusalem cross patch array developed in [13] is modified to find the impedance of the Greek cross patch array, as shown in Fig. 1(b). For an array of conducting narrow strips, the shunt impedance is either inductive or capacitive, depending on whether the incident wave is polarized parallel or ...
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... Greek cross FSS placed at the front and back sides of the enclosure with periodicity p, width of the element w, and gap between the elements g is shown in Fig. 1(a). The equivalent circuit model for the Jerusalem cross patch array developed in [13] is modified to find the impedance of the Greek cross patch array, as shown in Fig. 1(b). For an array of conducting narrow strips, the shunt impedance is either inductive or capacitive, depending on whether the incident wave is polarized parallel or perpendicular [15]. Assume a vertically polarized wave incident normally on the Greek cross FSS. The Greek cross FSS resonates at a frequency (f r ), when the cross length ...
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... of conducting narrow strips, the shunt impedance is either inductive or capacitive, depending on whether the incident wave is polarized parallel or perpendicular [15]. Assume a vertically polarized wave incident normally on the Greek cross FSS. The Greek cross FSS resonates at a frequency (f r ), when the cross length (p-g) is equal to λ r /2. Fig. 1(c) depicts the equivalent circuit of the Greek cross FSS, where L 1 corresponds to the inductance of the dipole of length (p-g) and width w. C 1 corresponds to the capacitance between the ends of the vertical dipoles. C 2 is the capacitance between the horizontal dipoles spaced (p-w) ...
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... empirical method is developed in this letter to overcome the limitations of the equivalent circuit method discussed above. This empirical method is useful to calculate the impedance of an FSS with any element shape, which does not require insight into the resonant behavior of the FSS. For the Greek cross FSS aperture array shown in Fig. 1(a), an empirical formula has been developed in [14] for FSS element's resonant length (λ r ...
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... DLFSS enclosure was fabricated by using a copper plate of thickness 0.15 mm, where the Greek cross apertures were etched. Fig. 1(a) depicts the details of a single layer FSS and Fig. 2 shows the dimensions of the DLFSS. An EM wave is applied toward the enclosure using a double-ridged horn, as shown in Fig. 3. The field inside the enclosure is measured using a monopole antenna of length 1.77 cm and diameter 2.25 mm inserted on the top plate of the enclosure which ...
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A 2.5 dimensional (2.5D) approach has been used to design a 2.5D miniaturized multifunctional active frequency selective surfaces (2.5D MMAFSSs), in this paper. The unitary element, based on the via-connected metal strips and metallic parallel plates, can be miniaturized to 0.063 lambda0, where lambda0 is the free space wavelength. To achieve the r...
Citations
... Electromagnetic coupling between two half-space regions separated by two slot-perforated parallel doublelayer structures has been reported [12][13][14]. Two-stage enclosures have also been studied for applications requiring EMI shielding to protect the equipment from penetrating electromagnetic fields [15,16]. In addition, some studies have focused on the resonance transmission (or extraordinary transmission) of dual-plate slots [17]. ...
This study investigated the enhancement characteristics of the shielding effectiveness (SE) of a double-layer shielding structure with narrow slots when a plane wave is incident on the slot. Integral equations for aperture magnetic currents in narrow slots were derived and solved by applying Galerkin’s method of moments. The numerical results demonstrate that SE depends on the layer wall spacing for a given frequency. The SE fluctuates with the spacing of the layers, and the fluctuation period is approximately 0.5λ at the resonant frequency. These periodic SE patterns gradually increase in magnitude with increasing layer wall spacing. To enhance the SE against electromagnetic interference at the resonant frequency, two parallel wires were used to minimize the transmission (maximize SE) through the narrow slots. The analysis results show that the SE can be enhanced by connecting the parallel wires to the slots at the resonant frequency. Experimental results are presented to validate the theory.
... It can pass a signal of certain frequencies and reflect others, or vice versa. Among various types, the cross dipole FSS is one of the most popular types of FSS, which is relatively simple to design [10]. By designing an electrode based on cross-dipole FSS with a passband of 10 GHz, the effect of the conductor electrode is minimized and the amount of contact between the X-band signal and plasma is maximized. ...
In this study, a method was experimentally verified for further reducing the radar cross-section (RCS) of a two-dimensional planar target by using a dielectric rim in a dielectric barrier discharge (DBD) plasma generator using a frequency selective surface (FSS) as an electrode. By designing the frequency selective surface such that the passbands of the radar signal match, it is possible to minimize the effect of the conductor electrode, in order to maximize the RCS reduction effect due to the plasma. By designing the FSS to be independent of the polarization, the effect of RCS reduction can be insensitive to the polarization of the incoming wave. Furthermore, by introducing a dielectric rim between the FSS electrode and the target, an additional RCS reduction effect is achieved. By fabricating the proposed plasma generator, an RCS reduction effect of up to 6.4 dB in X-band was experimentally verified.
... Here, F indicates the inductance or capacitance of the strip grating and has been well defined in [38], [39]. e f f is the effective permittivity of the Si O 2 substrate layer. ...
This work offers a new kind of polarization-insensitive, angular stable, tunable fractal frequency selective surface (FSS) based terahertz (THz) absorber. An equivalent circuit model (ECM) of the absorber is developed and impedance is obtained analytically. Further, an ECM-backed artificial neural network (ANN) approach is proposed and used to optimize the absorber to the desired frequency and bandwidth. The minimum mean square error between targeted and observed outputs is only
$1.86\times10$
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. The maximum absorption of 99% is achieved at a central frequency of 1.5 THz. The tunability is accomplished by varying the chemical potential (
$\mu _{c}$
) of the graphene layer introduced in the proposed absorbing structure. The resonance frequency shifts to 1.66 THz from 1.39 THz with a change in
$\mu _{c}$
from 0.3eV to 0.6eV.The dual-band absorption peaks are noticed with fractal FSS based absorber within the operating frequency range of 0.1-4.0 THz. The maximum absorption of 0.99 and 0.98 at the resonant frequency of 1.0 THz and 3.1 THz with fractal FSS, respectively is achieved. Furthermore, the designed absorber works well for both perpendicular and parallel polarizations up to 60
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angle of incidence. Moreover, the effect of structural parameters is also observed on the equivalent inductance and capacitance to understand the physics behind the structure. All the results obtained from ANN are verified with particle swarm optimization (PSO) and Whale optimization (WO) techniques. Good congruence among ANN, PSO, and WO results shows the effectiveness of the aforementioned technique. The possible applications of the proposed tunable absorber are THz imaging, sensing, detection, and stealth.
... However, metal foils block all the transmission regardless of the frequency. Frequency selective surfaces (FSSs) comes as an efficient solution to shield any device at a particular frequency or band [2], [3]. FSSs are periodic patch or aperture backed by a dielectric which has frequency filtering properties [4]. ...
An equivalent circuit model (ECM) backed deep neural network (DNN) is introduced to develop a broadband frequency selective surface (FSS). Shielding effectiveness (SE) and resonant frequency are inputs and shielding structure parameters are the outputs of the DNN. Moreover, three different configurations of DNN are investigated to get a minimum mean square error of 2.99 106 between targeted and observed outputs. The size of FSS is 0.300 0.300 and the total thickness of the shielding structure is only 0.1 mm. The variation in resonance frequency is only 0.08 GHz when the angle of incidence changes from = 00 to 800 for transverse electric (TE) polarization. Furthermore, a fractional bandwidth of 80% is achieved with a resonance at 10 GHz. The broad shielding bandwidth, ultrathin, polarization-insensitivity, wide angular stability attained by using a new, very simple, and miniaturized geometry are a few key features of the proposed structure. The results obtained from DNN are validated using full-wave simulation and by measurement of the fabricated prototype. SE performance concurs well among all demonstrate the effectiveness of the aforementioned technique for electromagnetic interference (EMI) shielding application.
... For better understanding, the equivalent circuit model has been presented in Fig. 4. The unit cell and its equivalent lumped elements have been presented in Figs. 4a-c [36]. Since, the proposed FSS having double metallic layers, the equivalent circuit contains two circuits with similar lumped elements which are cascaded. ...
This paper describes substrate integrated waveguide (SIW) cavity models to control the bandwidth of frequency selective surfaces (FSSs). Two different SIW cavities were presented: one model to reduce (cavity-I) and another model to improve (cavity-II) bandwidth of FSS respectively. The periodic structures were made of SIW cavies and an FSS slot on either side of the dielectric substrate at the centre of the cavity. To prove the concept, a well-known cross slot FSS element has been studied in two different cases and compared their performance. The conformal behaviour of the unit cells has been estimated by considering the practical conformal requirements. The addressed SIW cavities will improve the electromagnetic (EM) performance of conventional FSS without altering its basic shape. The high Q-factor of SIW cavity greatly improves the performance of FSS. A full-wave simulation is used to analyse the response of FSS. The Cavity-I shows 12.61% lesser bandwidth and Cavity-II shows 25.0% higher bandwidth compared to its conventional shape in planar form and 9.1%, 26.17% in the conformal form at a bent radius of 50 mm. Besides, performance parameters were also studied to evaluate the structural dependency on EM performance. Finally, two designed cavity models are fabricated and proved their performance experimentally.
... The design dimensions of cross element are: cell size D x = D y = 16 mm (0.53λ 0 ), length of leg L = 6.25 mm (0.32λ 0 ), and width W = 2.2 mm. The initial frequency response is estimated using the equivalent circuit model (ECM) [35] and validated using full-wave simulation with the help of CST Microwave Studio (MWS) for further optimization, as shown in Fig 3(a). Next, to develop an SIW-based cavity structure, the same cross slots are etched on either side of the substrate without altering its unit cell size. ...
In this paper, a bandpass frequency selective surface (FSS) based on substrate-integrated waveguide (SIW)
technology is presented for airborne radome application. The
proposed FSS element consists of a tapered cross-slot on
either side of the substrate surrounded by metallic vias. The
structure selectively allows the impinging electromagnetic (EM)
wave through it in the specified frequency band. The element
shows very stable frequency response for oblique incidence and
the sharp roll-off performance characteristics at the edges of
operating region in the rejection band. The −10 dB relative
bandwidth (BW) of the element is 12.8% from 9.5 to 10.8 GHz
with a very good insertion loss (IL) of 0.1 dB. Furthermore,
the spectacular advantages of the FSS element based on SIW have
been used for modeling the airborne radome application. The
proposed radome structure is operating at 10 GHz with a relative
10 dB BW of 25.0% (8.20–10.6 GHz) with maximum (IL) better
than 0.1 dB in its passband. The behavior of the FSS radome
has been analyzed at different conformal sectors and thickness
is optimized for optimal performance. The key parameters of
radome such as transmission performance, radiation efficiency,
and radar cross section (RCS) have been studied. Experimental
verifications are carried out to prove the validity of the estimated
results. The results show promising performance of the proposed
FSS based on SIW technology for airborne radome application.
... [3][4][5] To protect sensitive devices from EMI, the traditional method is utilizing a full solid metal enclosure to shield sensitive devices. 6 However, the full solid metal enclosure is both costly and bulky. More important, this metal enclosure is blind and will block the transmission of all the electromagnetic channels. ...
In this article, a novel compact dual‐band frequency selective surface (FSS) with stable response is proposed for GSM shielding. This FSS is designed using 2‐layer cascaded 2.5‐dimension structure of which element is composed of two via‐based modified swastika unit cells. The proposed structure has created two stop bands around frequency 900 and 1800 MHz, respectively, with maximum attenuation value close to 70 dB. Besides, this FSS performs an excellent miniaturization characteristic with overall size of 0.048λ0 × 0.048λ0, where the λ0 represents the free space wavelength of the lower resonance frequency. More important, this FSS exhibits a very stable frequency response up to 80° for TE and TM polarization. To understand the structure better, the design procedure of this FSS is introduced in detail. Since the proposed FSS has an excellent comprehensive performance, this FSS has great potential in shielding GSM signal for small electronic devices. Finally, a prototype of proposed FSS is fabricated and measured. The measurement results prove the validity of simulation results.
... Terahertz wave applications [42,59,79,147,148,195,196,242,243,251,254] Millimeter/sub-millimeter wave applications [26,119,207,243] Radio frequency identification [50,94,122] Wireless communication, shielding applications, EMI/EMC issues, wireless charging pad for portable electronics, polarization transformation [44,68,80,[90][91][92][93]105,115,116,120,121,136,162,166,188,190,199,216,221,225,234,253,268,269] ...
... There is no conflict of interest. [42], circular loop elements [254], four-fold rotational symmetry [251], mesh filter with cross-shaped slots [243], annular mesh element [147,148], graphene patch [242], circular slot [195], annular square shape [147,148], cross shape and wire grid FSS [59], Tunable graphene FSS (GFSS) [79], and LHCPSS based Pierrot cell [196] [234], active annular ring FSS [225], anchor shaped active FSS [269], square loop based switchable FSS [199], multiple-loop element with a meander line [115,116], reconfigurable FSS [68], Varactor based active FSS [268], square type patch FSS [216], square loop [188], Jerusalem cross [44,253], modified Swastika unit cell [166], wire mesh and square loop [105], metallic meander lines impedance loaded with rectangular metal patches [162], mesh coated FSS [80], cross dipole and ring patch elements [221], circular rings [90][91][92][93], truncated patch and grid lines [136], Greek cross FSS [120], Loop FSS [121], phase switching FSS [190], and circular rings [ [3,12,65,76,102,140,143,152,186,206,209,262] Finite element method (FEM) [8,9,14,21,138] Impedance type boundary condition-based model [77] Physical optics method and ray tracing technique [117,118] Monte Carlo method [32] Periodic MOM [71] Finite integration technology (FIT) [138] Algebraic multigrid method [8,9] Transmission line modeling [31] Hurst's method, Prony's method and the discrete Fourier transform (DFT) [81] Characteristic basis function method and spectral rotation approaches [183] ...
This article analyzes a review of recent developments in the field of frequency selective surface (FSS)-based advanced electromagnetic (EM) structures. FSSs have been the subject of intensive investigation for distinct EM applications for more than four decades. An FSS is a type of filter consisting of an array of periodic metallic patches or apertures on a dielectric substrate. The high-pass (inductive FSS) and low-pass (capacitive FSS) filtering operation of FSS results in the exhibition of total transmission and reflection near the resonance wavelength. This paper deals with an overview of different FSS geometries, namely, traditional, active, fractal, three-dimensional and multilayered FSSs. A number of recent practical EM applications of FSS structures like microwave absorbers, radomes, textiles and antennas are discussed. In addition, different types of optimization and fabrication techniques for FSS-based EM structures are incorporated. The FSS-based research directions described in this study may be of interest to the scientific community working in this particular field.
