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

A wide stop-band angular stable frequency selective surface (FSS) is presented. This FSS consist of two spiral structures separated by a substrate in the middle. It exhibits a wide stop-band of 20 GHz in the frequency range of V-band. Furthermore it produces a stable angular response upto 80 degree for both TE and TM incidence modes. Since it provides a wide stop-band and good angular stability, it is suitable for millimeter-wave shielding applications.

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.

Fractal geometries have been extensively implemented in the design of multiband antenna and frequency selective surface (FSS). For example, convoluted and Hilbert patch elements were first proposed to reduce the unit cell size of FSS (Parker and El Sheikh, IEE Proc.-H, 138, 19–22, 1991.) A fractal FSS with self-similar Sierpinski dipole array was shown to have two stop bands (J. Romeu and Y. Rahmat-Samii, IEEE Trans., AP-48, 1097–1104, 2000). However, its resonant frequencies are rather sensitive to incident angles and polarizations. Minkowski patch FSS and Sierpinski carpet fractals have been shown to provide two or three stop bands with dual polarization capability (J.P. Gianvittorio, et. al., IEEE Trans., AP-51, 3088–3096, 2003.) Recently miniature band-pass FSS with fractal antenna-filter-antenna arrays was designed and demonstrated with good frequency selectivity (S. Zheng, et. al., IEEE AWPL, 11, 240–243, 2012.) A dual band fractal FSS with a 3:1 reflection to pass band ratio and significantly improved resonant frequency stability was proposed by the author (T.K. Wu, Microwave Optical Tech. Letters, 54, 833–835, 2012).

This work reveals the Design and development of Dual wide band frequency selective surfaces (FSS). Dual-band FSS based on single and multi layers with or without or extra discrete components has been discussed and analyzed. Dual wide band-pass FSSs has been designed and developed by using two metallic layers for the wide targeted pass band frequency bands range of 3.53-5.3 GHz and 3.53-4.21 GHz. In the initial step of Development ultra thin double layer slotted FSS has been used. These generate resonance at 4.0 GHz and 4.8 GHz. Furthermore Hilbert shaped slotted resonator increase pass band width enhancement. Lastly the opposite alignment of similar FSS metallic plate to form the proposed dual layer FSS which exhibit the bandwidth enhancement of the frequency bands.

In 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.

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.

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.

Metasurface has attracted much attentions due to its ability of flexible manipulation of electromagnetic wave. However, the metasurface is limited to the single operating band and poor design generality when it is used for radar cross section (RCS) reduction. In this paper, a stacked metasurface design method has been developed to flexibly achieve dual wide band RCS reduction. Two subarrays with polarization conversion characteristic are firstly designed to operate in two wide bands, respectively. Then a low-pass frequency selective surface (FSS) is developed and sandwiched between two metasurface subarrays to achieve a subarray with the dual-band polarization conversion performance. With the arrangement of the dual-band subarray into a 2×2 array in a rotation way according to the polarization cancellation, the resultant metasurface structure has two −10 dB RCS reduction bands covering 6.6-12.7 GHz and 27.8-38.1 GHz. The designed prototype is fabricated and measured. The simulation and measurement results are given to demonstrate the good dual-band RCS reduction performance.

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, a wideband polarization conversion metasurfaces composed of frequency selective surface (FSS) is proposed. The simulation results indicate that polarization conversion ratio (PCR) is greater than 90% for both x- and y-polarization normally incident electromagnetic (EM) waves and the fractional bandwidth is approximately 96%. In addition, the metasurface is robust under broad-range incident oblique angles. The FSS metasurface processes the merit of wide bandwidth and efficient PCR, which demonstrates a promising future in modern communication systems and new polarization-control devices.

Miniaturized frequency selective surfaces (FSSs) have been intensively investigated because of the space limitation in practical applications, such as wireless communication system working at low frequencies. Loading lumped capacitor is an effective miniaturization method to achieve the unit cell size as compact as λ 0 /15 (λ 0 refers to the resonant wavelength in free space) [1, 2]. But this approach requires bulk components which increase the complexity and cost of fabrication. Also, the tolerance of lumped elements makes it a challenge to maintain a stable resonant performance. Another effective method of reducing the unit cell size is to adopt convoluted elements which perform well in conforming to curved surface [3–5]. This method not only improves the angular stability of the frequency responses, but also moves the operating band away from the grating region which is determined by the periodicity of the array. The convoluted structures can reduce the FSS dimension because of their space filling property [5]. Therefore, their miniaturization potential will be restricted by the element area determined by the periodicity. To address this problem, the double layered convoluted structures, which make use of the element areas on both sides of substrate, are presented in this work to further miniaturize the FSS unit cell. Fig. 1 shows the geometry of the proposed bandpass FSS, which consists of a convoluted square slot loop and a convoluted capacitive element arranged on each side of the substrate. The top layer acts as a parallel LC resonator and the bottom layer acts as a capacitor. The LC resonator and the capacitor are connected in parallel. Therefore, the proposed bandpass FSS operating at 2.5 GHz provides the unit cell dimension as small as λ 0 /23 because of the increased capacitance of the unit cell. On the other hand, a double layered convoluted structure for the bandstop FSS is also proposed as shown in Fig. 2. It is seen that the top and bottom layers are connected by metallic via to construct a closed loop, which results in an increased inductance of the unit cell. Consequently, the element size of the presented bandstop FSS resonating at 2.5 GHz is only λ 0 /22. In addition, all the presented FSSs exhibit good performance of resonance stability with respect to different polarizations and incident angles.

In this paper, a dual-band Frequency Selective Surface (FSS) absorber is presented for Wireless Local Area Network (WLAN) security. The FSS absorber is designed for two frequencies of interest, i.e., 2.45 GHz (lower band) and 5.25 GHz (upper band), respectively. FSS design consists of two layers; first layer consists of conducting square-loop elements while second layer consists of resistive square-loop elements, placed in-front of a conducting FSS layer. The proposed FSS design provides good frequency stability for oblique incidences for perpendicular (TE) and parallel (TM) polarizations. It provides better absorption rate for 2.45 GHz and 5.25 GHz frequency bands and allow the transmission of other microwave frequencies. Also, the proposed FSS design reduces multipath fading of additional WLAN signals which occurred due to the placement of conducting FSS layer. Presented results demonstrate that the proposed FSS design has a stable frequency response for the desired frequency bands for TE and TM polarizations with good absorption rate when the incident wave angle varied from 0<SUP>0</SUP> to 45<SUP>0</SUP>.

A dual-band frequency selective surface (FSS) employing Ti3C2Tx deposited on a polyethylene terephthalate (PET) layer is proposed for Wi-Fi applications. The structure can afford dual-frequency passbands with central frequencies of 2.4 GHz and 5.5 GHz and realize large bandwidths covering 1.7-2.9 GHz and 4.9-6 GHz for -3 dB reference, which are bands of Wi-Fi communication. Featured by the use of 4.3 μm-thick Ti3C2Tx, the FSS reduces the thickness by 16% compared to that using 35 μm thick copper, which renders it preferable for flexible and ultrathin applications. Moreover, the proposed FSS has the advantages of polarization and incident-angle insensitivity as well as the ease of fabrication. The proposed FSS based on Ti3C2Tx MXene for the first time may provide a further step in the development of ultrathin, lightweight and flexible devices for wireless communication, such as filters, absorbers and modulators.

The requirements of frequency-selective surface (FSS) between high transparency in pass band and high reflectance in stop band are contradictory, when they have loaded medium on one side and receive a large range of illumination. In order to solve the contradiction, this paper employs a discrete particle swarm optimization approach (hereafter referred to as a DPSO). In order to seek a balanced FSS with high transparency in pass band and high reflectance in stop band, the periodic intervals and geometrical dimensions of FSS-structures are optimized and designed by using the DPSO method. Simulation and test results indicate that the FSS of super dense Y loop elements in a half-loaded medium structure is presented in this paper: the transparency in pass band and stop band are 80% and 30% respectively. The DPSO method will offer an excellent FSS for the radome which receives a large range of illumination, and on the other hand, it provides a theoretical guidance for the requirements of FSS between high transparency in pass band and high reflectance in stop band.

Single-layer dual-band frequency selective surface for coverage-enhancing applications in millimeter-wave 5G