Miniaturized frequency selective surface using the double layered convoluted structures

In this letter, a novel bandpass frequency selective surface (FSS) with miniaturized periodic element is presented. The proposed FSS is printed on one face of a single-layer substrate with a relative permittivity of 2.65. The novel FSS has promising miniaturization characteristics with the unit-cell dimension 0.058λ×0.058λ, where λ represents the free-space wavelength corresponding to the resonant frequency. The FSS exhibits excellent stability under different polarizations and incident angles. Both the simulation and measurement results validate the stable performance of this FSS.

A novel miniaturised frequency selective surface (FSS) unit cell is proposed based on the Hilbert fractal and 2.5-dimensional (2.5-D) metallic loop. For the increase of current path, both sides of substrate are used which are connected together by four vias. The dimension of FSS unit cell is obtained as 0.041λ0 × 0.041λ0 at the frequency of 2.47 GHz. The transmission coefficient is insensitive and independent of angle and polarisation of incident wave. A prototype model of the proposed FSS is fabricated and measured for the proof of concept. It is shown that it achieves better miniaturisation relative to the FSS reported in the literature.

In this paper, the Minkowski fractal is used to design the geometry of a frequency selective surface (FSS) unit cell, which resembles the shapes found in nature. The proposed FSS unit cell has both angular and polarization stabilities of incident wave. For the miniaturization of FSS and decrease of resonance frequency, interdigital capacitances (IDCs) are devised in the FSS structure, which do not eliminate angular and polarization stabilities. The dimensions of the unit cell are 5 mm × 5 mm and miniaturized 0.095λ0×0.095λ0. The resonance frequency is specified as 5.75 GHz with 155 MHz bandwidth. An equivalent circuit is derived for the unit cell to evaluate its frequency responses. The effects of variations of the geometrical dimensions of the FSS unit cell on its performance are studied. A prototype model of proposed FSS is fabricated and measured. The performance of its full-wave computer simulation results and measured data are compared and are shown to be in good agreement.

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 low-profile and miniaturized frequency selective surface (FSS) with dual-polarized bandpass characteristics is proposed in this article. The FSS is a second-order structure with two layers separated by an air spacer, achieving two transmission poles (TPs) and two transmission zeros (TZs) at both sides of the TPs. Using the miniaturized structure, the physical dimension of the element is reduced to 0.09λ × 0.09λ, where λ is the free-space wavelength at the center frequency. Thus, the structure exhibits stable performance with respect to different incident angles. The overall thickness is 0.053λ, which is much thinner than alternative second-order FSSs using the traditional cascading technique. This feature makes it a candidate to be applied in low frequency bands with long wavelengths. In addition, the operating principle of the proposed structure is analyzed by using the equivalent circuit method (ECM) and the surface current distribution is also given. Finally, a prototype is fabricated and measured to validate the simulated results.

Ultrathin and miniaturized frequency selective surface (FSS) with closely located dual bands is proposed in this letter. The proposed FSS comprises parallel patches and meandering lines that construct parallel LC resonators. Then, two independent passbands can be achieved and adjusted by only changing corresponding structure parameters of the element. Through a catercorner arrangement, the structure avoids the effect introduced by the unnecessary inductance. The proposed FSS resonates at 1.59 and 1.96 GHz with a low resonant frequency ratio of 1.23. The proposed FSS provides a low profile of 0.13 mm and a miniaturized unit cell size as compact as 0 . 042λ × 0 . 042λ. A simplified equivalent circuit model is established, which provides good insight into the operation mechanism. Finally, a prototype of the proposed structure is fabricated and measured. All the results present excellent resonant stability with respect to different polarizations and incident angles up to 60°.

In this article, a novel miniaturized frequency selective surface (FSS) is presented, in which each periodic cell consists of a ring slot resonator loaded with four ceramic chip capacitors for reducing the cell size. To eliminate the undesired coupling between unit cells, the unit cell is placed in the substrate integrated waveguide cavity structure. A S‐band bandpass FSS with such structures is designed and fabricated, both simulated and measured results show that the proposed FSS provides high transmission at 2.45 GHz and there is no other frequency resonance up to 15 GHz. Also, it has very good stability to oblique incidence. Furthermore, the dimension of the proposed FSS is miniaturized to 0.083λ0 (λ0 refer to the resonant wavelength). © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3149–3152, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23945

This paper presents the results of our research in the field of frequency selective surface in recent years. Aiming at the traditional passive frequency selective surface (FSS) in this paper, we mainly do two aspects of research work, which is the research of the small frequency selective surface and the research of the ultra wide band frequency selective surface. The center frequency value of the miniaturized FSS is only 2.47GHz, and the relative size of the unit is only 0.0494λ×0.0494λ and. That is to say, the unit size is less than λ/20. Stop band for the double layer structure FSS we proposed is from 11.03 to 13.98 GHz, with a relative bandwidth 23.6%. Pass band for the three dimensional structure FSS we proposed is from 8.1 to 14.6GHz, with a relative bandwidth 57.3%. The miniaturized FSS structure and wide band FSS structure have high practical application value.

In this paper, a band stop all-dielectric metamaterial frequency selective surface (FSS) is designed based on effective medium theory and dielectric resonator theory. The FSS is made of high-permittivity ceramics without using any metallic parts. The stop band FSS is composed of 2D arrays of Jerusalem cross-shaped ceramic resonators. Solid-state sintering method is adopted to prepare the high-permittivity ceramics, which is made of 0.7Ba <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</inf> Sr <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</inf> TiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> –0.3La(Mg <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> Ti <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> )O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> . The permittivity of this ceramics is about 110. The simulation results show that the FSS can achieve a stop band at 6.91–9.25 GHz. The relative effective permittivity, permeability and the normalized impedance of the structure are retrieved, showing that the first resonant is a magnetic resonant and the second resonant is an electric resonant. Due to the magnetic and electric resonant, the impedance matching becomes worse, so the normalized impedance is close to 0 and the stop band forms. The electric fields and magnetic fields of the resonant points are observed to further analysis the FSS. At the first resonant point, the electric field loop is formed, equivalent to a magnetic dipole. At the second resonant point, the magnetic field loop is formed, equivalent to an electric dipole. The magnetic and electric fields are accordance with the retrieved parameters. Since such FSSs are made of high-permittivity ceramics, they have potential engineering application in high-power or high-temperature.

This paper, proposed a frequency selective surface (FSS) with triple band-stop characteristics. The structure demonstrated can be effectively used to shield different scientific and technical applications from unwanted electromagnetic radiation. The compact unit cell consists of a cross-loop surrounded by a dodecagon. The overall dimensions of unit cell are 22 mm × 22 mm. The substrate material is RO-3003 with a dielectric constant (\(\varepsilon_{\text{r}}\)) 3 and thickness 60 mil. The dimensions of each unit cell have computed by the lowest cutoff frequency. This FSS structure is designed for the rejection of three frequency bands, 5.5 GHz, 3.5 GHz and 2.4 GHz, respectively. The proposed FSS structure provides preeminent electromagnetic shielding because of its polarization insensitivity and triple-band absorption.

A convoluted frequency selective surface (FSS) is proposed to provide the unit cell dimension as small as 4.84% of the free space wavelength at resonant frequency. The FSS exhibits high resonant stability for various polarizations and incident angles. Its simple geometry is beneficial for not only easy design but also realizing the single and dual bandpass performances. By introducing an inductance in series connected with the traditional LC parallel resonant circuit, an improved equivalent circuit is established, which can describe the FSS frequency responses more accurately. Furthermore, a set of closed forms related to circuit and dimension parameters are developed. It can serve as the substitute of the full-wave solver to enhance the FSS design efficiency significantly. Finally, a dual bandpass FSS operating at 2.5 and 4.95 GHz was fabricated and measured. The measurement results exhibit satisfactory consistency with the full-wave simulation results.

This paper presents the design of UWB reflector for antenna application by using two layers of a band stop frequency selective surface (FSS). The structures of both FSS are based on the modified square ring resonator. By combination of two FSS structures, they achieve the wide frequency range of 2.9-11.2 GHz. The demonstration of the FSS reflector with UWB slot antenna shows that the radiation efficiency of antenna is improved over the entire UWB spectrum.

In this letter, we propose a novel dual-frequency miniaturized periodic element for creating a dual-band frequency selective surface (FSS) having closely spaced bands of operation. Using this element and its complementary structure, the dual-bandstop and dual-bandpass FSSs can be simultaneously created without extra effort. The mechanism responsible for the two element resonances and the new way to make these resonances closer is revealed. Based on this revelation, the newly proposed element can be simply and quickly designed to be compact in size and to have two resonances closely spaced. Furthermore, the dual-band FSS created using this element demonstrates excellent resonance stability with respect to different polarizations and incidence angles. Both the bandstop and bandpass FSS prototypes are fabricated and examined. Their measured and full-wave simulated results validate the performance. The created element size is about 8% of the free-space wavelength at the first resonant frequency, and the ratio of the second resonant frequency to the first one is only 1.4.

This paper presents the first additively manufactured, single-layer, polarization-insensitive, fluidically switchable band stop frequency selective surface (FSS) for electromagnetic (EM) shielding applications. The unit cell features a meandered square-loop metallic pattern with a fluidic cavity embedded within the substrate via fused deposition modeling. Frequency tuning is realized by controlling the fluidic state of the cavity through an automated pump system. In the absence of water, the structure resonates at 3.5 GHz; introducing distilled water into the cavity lowers the resonance to 2.6 GHz, achieving a 29.5% tuning range. The proposed FSS provides a minimum shielding effectiveness of 30 dB for both cases. An equivalent circuit model is developed to interpret the tuning mechanism, and both simulation and experimental results confirm the effectiveness of the design. The proposed FSS maintains stable performance up to 60 ∘ under both TE and TM polarizations. With its simple, low-profile, single-layered design, this FSS offers strong potential for EM shielding and interference mitigation applications.

In this article, two types of band stop frequency selective surfaces (FSSs) based on infinitely large array of translated crossed dipole and square loop (SL) unit elements are presented and further, compared. The impact of translating the unit elements by half of the periodicity along horizontal and vertical directions is compared. Through full-wave electromagnetic simulation, it is found that the transmission characteristics of FSS array based on conventional unit cell and translated unit cell are almost similar primarily because geometry of FSS array do not get affected by translation of unit cell. Although when compared, the square loop based FSS array exhibits a band stop bandwidth of around 202.14% larger than exhibited by crossed dipole based FSS array.