Resistive Frequency Selective Surface Research Articles

Dispersion compensation design of high-density stacking RFSS absorbers for wideband applications

Abstract A dispersion compensation design absorber realized by high-density stacking resistive frequency selective surface (RFSS) is proposed for wideband applications. Firstly, the quantitative relationship between the equivalent impedance of RFSS and the permittivity of the effective media is constructed with the help of the transmission matrix method. The dispersion regulation of permittivity is achieved by changing the pattern and the square resistance of RFSS. In terms of absorber design, a uniform absorber with dispersion manipulation is developed as a precursor absorber. The uniform absorber has an absorption performance better than −8.5 dB above 2 GHz at normal incidence. The loss mechanism is analyzed in detail by electric field distribution and surface power loss density distribution, indicating that the uniform design cannot achieve thickness saving when extending to low frequency. Therefore, a dispersion compensation design absorber is proposed to extend −10 dB bandwidth to 1.64–28.8 GHz. Experiment results agree well with the simulation results, validating the analytic methods and design principles.

Notice of Violation of IEEE Publication Principles: A thin broadband microwave absorber with hexagonal resistive frequency selective surface

Notice of Violation of IEEE Publication Principles A Thin Broadband Microwave Absorber with Hexagonal Resistive Frequency Selective Surface by Feifei Li, Chao Meng, Fan-guang Meng, Digang Fan, Ping Chen, and Rui-xin Wu in the IEEE Antennas and Wireless Propagation Letters (Early Access) April 2018 After careful and considered review of the content and authorship of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE’s Publication Principles. This paper contains significant portions of work presented in the paper cited below. The original work was translated and copied without attribution (including appropriate references to the original author(s) and/or paper title) and without permission. Design of a Wide‐band Metamaterial Absorber Based on Resistance Films by Gu Chao, Qu Shao‐Bo, Pei Zhi‐Bin, Xu Zhuo, Lin Bao‐Qin, Zhou Hang, Bai Pen, Gu Wei, Peng Wei‐Dong, and Ma Hua in Acta Physica Sinica, Vol 60, No. 8, August 2011 We realized a thin, broadband absorber based on resistive frequency selective surface (FSS). By introducing a design parameter, p-factor, we successfully designed a microwave absorber, whose reflectivity below -10dB covers 6.4-24.9 GHz. The thickness of the absorber is only 0.087-L at the lowest operating frequency. We show that broadband absorption can be achieved by carefully balancing susceptances of resistive FSS and other parts of the absorber. Furthermore, we find that lossless dielectric slabs with lower dielectric constant are the best choices for broadband absorber. Experimentally, the samples were fabricated by using silk-screen printing technique and their absorbing performance was measured. Experimental results are in good agreement with simulated ones. Our work provides a method to realize broadband absorber in a simple way, which may be used for the absorbers working in THz, infrared or even optical band.

Ultra-wideband thin frequency-selective surface absorber against sheet resistance fluctuation

The design of thin frequency selective surface (FSS) absorber based on resistive film that meets the requirements of broadband, polarization independence, incident angle stability, and strong absorption is a challenging task. Fabrication tolerance of resistive film can result in fluctuations in sheet resistance, which negatively affects the absorber performance. To tackle these problems, this work firstly investigates how sheet resistance fluctuations affect the absorbing performance of resistive film FSS absorber. The analysis of simulated surface current density distribution and impedance reveals that the diversity of current paths provides an effective way to mitigate the influence of sheet resistance fluctuation. This is achieved by enabling flexible variation of surface current in response to sheet resistance fluctuations. Consequently, the variation of input impedance of the FSS absorber due to the fluctuation of sheet resistance is suppressed within a small range. Then, a method of extending bandwidth is proposed by employing the complementary variation of FSS impedance with frequency at different layers. By combining this approach with a miniaturization design, a thin and light FSS absorber is developed that exhibits ultra-wide bandwidth, polarization independence and angle stability while mitigating the effects of sheet resistance perturbation. The proposed FSS absorber achieves a 90% absorption bandwidth from 1.50 GHz to 20.50 GHz, covering Ku, X, C, S bands and part of the L and K bands, with a relative bandwidth reaching 173%. The absorber has a thickness of 0.093<i>λ</i><sub>L</sub> for both transverse electric (TE) polarization and transverse magnetic (TM) polarization, yielding a figure of merit (FoM, the ratio of the theoretical minimum thickness to the actual thickness) of 0.95, indicating that the thickness is close to the theoretical limit. The absorber maintains over 90% absorption rate for TM polarization at an incidence angle of up to 70°, and 80% absorption for TE polarization at 45°. Furthermore, the 90% absorbance bandwidth of the absorber remains at 167.0% when the sheet resistance of any FSS layer fluctuates within a range from 12 to 30 Ω/sq. A prototype of the proposed FSS absorber is fabricated and measured, and the experimental results are in good agreement with the simulation results, thus validating the effectiveness of the proposed method.

2–18 GHz dual‐polarised tightly coupled dipole array with ±75° scanning range

AbstractThe authors proposed an ultrawideband (UWB) dual‐polarised tightly coupled dipole array (TCDA). A split X‐shaped resistive frequency selective surface (FSS) is utilised, which can get more admirable impedance matching. The proposed antenna can achieve active voltage standing wave ratio (VSWR) below 2.9 when scanning up to ±75° and ±60° in the E and H planes from 2 to 18 GHz, respectively. Furthermore, two rectangular patches served as directors are designed, which can provide stronger forward radiation to reduce the loss of resistive FSS for radiation efficiency. As a result, the average radiation efficiency is above 84% and the lowest radiation efficiency is 70%. Moreover, the overall antenna profile is 15 mm (0.1λ at the largest working wavelength). To validate the design method, a 16 × 16 array prototype is fabricated and measured. Good agreement is achieved between the simulations and measurements.

A Switchable A-T-A Rasorber With Polarization Selectivity and High Roll-Off Characteristics

Switchable rasorber has attracted a great deal of interest in recent years due to its in-band shielding ability. In this work, a methodology for designing a switchable rasorber with high roll-off and polarization selection characteristics is proposed. The device can be switched between rasorber, polarization selection and absorber modes, and composes of two resistive layers (a passive and an active resistive layer) and a frequency selective surface (FSS). Transmission zeros (TZs) are introduced in the FSS design to improve the roll-off characteristic of its transmission band. The PIN diodes on the active resistive layer and FSS can be independently controlled in the orthogonal polarizations to realize the polarization selectivity. The simulation results indicate that the device exhibits a 27.5% fractional transmission bandwidth (3.42 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 4.51 GHz) under rasorber mode. In addition, the fractional absorption bandwidth is as large as 142.9% (1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 6 GHz) under absorber mode. A prototype is fabricated and measured to validate the proposed design methodology. This work is promising for designing metamaterials (MMs) with excellent flexibility and high performance.

Tapered Resistive Sheets and FSS Absorber Loading for the Wideband RCS Reduction of the Elliptic Surface at TM Polarization

A wide-band radar cross section (RCS) reduction of the elliptic surface at TM polarization is reported in this communication. The main scattering sources and the corresponding scattering mechanisms of the elliptic surface are accurately identified based on the ISAR imaging technique and the high-frequency approximation theory. The frequency selective surface (FSS) absorber is employed to suppress the specular reflection, and the tapered resistive sheets (TRSs) are used to handle the scattering from the trailing edges. Samples have been fabricated and measured in the anechoic room, both the simulation and measurement results illustrate that 10-dB RCS reduction is achieved within 1.35-4.9 GHz at TM polarization.

Inkjet-printed broadband FSS-based absorber with improved absorption characteristics

Abstract We present the design for a thin planar microwave absorber depicting near unity absorption over a wide bandwidth. The absorber consists of a single layer of resistive frequency selective surface inkjet printed over a paper substrate and suspended over a grounded foam. We have been able to achieve 99.99% absorption of normally incident radiations from 9.7 to 11.74 GHz at an extremely low level of −40 dB absorption bandwidth. The proposed absorber is thin (0.22λ0 at the center frequency), polarization-insensitive, and presents −10, −20, −30, and −40 dB fractional bandwidths as 89.83%, 55.41%, 33.30%, and 19.03%, respectively. It is worth mentioning that the design of an absorber with such steep slopes is highly stringent and requires special attention. Finally, we have experimentally demonstrated the perfect broadband absorption characteristics with a fabricated prototype.

Design of an optically transparent EMW structure with broadband‐absorbing property

AbstractIn this paper, an optically transparent electromagnetic window structure based on frequency selective absorber (FSA) technique is proposed with low‐pass and high broadband absorbing property. The FSA consists of two resistive frequency selective surface layers and a low‐passband layer, which are all designed using square ring structures. To make the whole design transparent, the traditional metal copper and resistors are replaced by indium tin oxide and the dielectric substrate by polyethylene terephthalate. The top and middle layers act as absorbing layers to generate broad absorption bands at high frequencies, while the bottom layer is used to generate low‐pass transmission bands. The simulation results show that the insertion loss is less than 3 dB below 3.6 GHz, while the absorption bandwidth covers 6–18 GHz with an angular stability reaches 45°.

Low-profile broadband microwave absorber based on magnetic coating and artificial electromagnetic structures

In order to realize electromagnetic stealth of large equipment, we propose a low-cost, mass-producible composite microwave absorber in this paper. The developed novel EM absorber comprises a pattern-impregnated honeycomb structure with the absorbent of carbon black (CB), a resistive frequency selective surface (FSS) embedded in polypropylene (PP) foam, and a mixture coating covered on a metal plane whose absorbent is flaky carbonyl iron (FCI). CB particles and FCI particles provide electrical and magnetic losses at the microscopic scale. Moreover, the subwavelength-scale artificial electromagnetic structure achieves broadband matching to free space by adjusting macroscopic geometric parameters. The consistency between measurements and simulations proves that the composite absorber achieves over 90% absorption ratio with a thickness of 8.3 mm from 2.06 to 18 GHz (corresponding to a fractional bandwidth of 158.9%). Additionally, this composite absorber possesses good mechanical property with a maximum uniaxial tensile stress of 67.43 MPa.

Novel radar absorbing material using resistive frequency selective surface based polymer composites for enhanced broadband microwave absorption

In this paper, a novel approach using glass fibre laminate composite (GFLC) with nanoparticle embedded nanofibres and frequency selective surfaces (FSS) for improved electromagnetic (EM) wave absorption has been proposed. For enhanced absorption, the FSS was coated with polyvinylidene fluoride (PVDF) mixed with multi-walled carbon nanotubes (MWCNTs). The coatings were prepared through electrospinning technique. The composite prepared from FSS, PVDF-MWCNT layers and GFLC showed enhanced absorption properties. It was demonstrated that the fabricated composites reduced reflection of electromagnetic waves by the material when compared to metals. An 80% increase in EM absorption (with respect to metal) was observed over a wide frequency range with the novel composite at an overall thickness of only 3 mm. X-ray diffraction (XRD) spectra showed an improvement in the electroactive β-phases in the electrospun PVDF/MWCNTs compared to Plain PVDF. Scanning electron microscopy analysis on various weight percentages of PVDF/MWCNTs revealed the formation of nano fibres with an average diameter of 75–160 nm. In addition, the proposed novel EM wave absorbing composites were of simple configuration and the mechanical properties of the fabricated composites were comparable to that of GFLC. Experimental results indicated that RAS with 0.25 wt % MWCNT/PVDF had 87.5% bandwidth for over 90% absorption from 8.5 to 12 GHz compared to all other configurations. The tailored composite material could be used as excellent radar absorber structures (RAS) and can find tremendous application in the manufacture of stealth aircrafts.

A Rational Design Procedure for Absorbers of Square-Loop-Shaped Resistive Frequency Selective Surface Placed on Glass/Epoxy Laminate

This study proposes a rational optimum design procedure for broadband radar absorbers composed of a square-loop-shaped resistive frequency selective surface (FSS) that are placed on an E-glass fabric/epoxy laminate and grounded by Cu foil covering the X-band (8–12 GHz). A rational optimum design procedure for the broadband absorbing performance was presented based on the analytical and numerical illustration. The effects of the surface resistance of the FSS and dielectric substrate on the design process and performance of the absorber are examined. The resistive FSS was fabricated using screen-printing technology with carbon-type ink as a demonstration. The demonstration samples were developed considering the sectional profile of the circuit lines composing the printed FSS. It revealed that the experimental reflection loss encompassing the frequency range over the entire X-band was repeatable and similar to the simulation result.

Low-frequency broadband multilayer microwave metamaterial absorber based on resistive frequency selective surfaces.

Herein, a low-frequency broadband multilayer metamaterial absorber (MMA) based on resistive frequency selective surfaces (RFSSs) is proposed, which consists of a three-layer RFSS, three-layer polymethacrylimide (PMI) foam substrates, and a copper film. The proposed absorber has the advantages of ultra-broadband absorption with absorptivity more than 90% ranging from 1.91 to 20.78GHz, which covers the entire S, C, X, and Ku bands with the thickness of 0.102λ L (where λ L corresponds to the wavelength of the lowest operating frequency). The absorption performance can keep good stability in a wide angular range for both TE and TM modes. Moreover, a prototype of the proposed MMA is fabricated and experimentally measured to demonstrate its excellent performance. The experimental results show excellent consistency with numerical simulations.

Ultra-wideband dual-polarized tightly coupled dipole array with double layers meta-WAIM

An ultra-wideband dual-polarized tightly coupled dipole array (TCDA) with 10:1 bandwidth is presented. Aimed at solving the ultra-wideband impedance matching problem between the antenna and free space, a novel meta-material wide-angle impedance matching (WAIM) layer is presented. The meta-WAIM utilized a structure of planar double layers with the elliptical split ring on top and the concentric split ring on the bottom, which improves the beam scanning ability over the high-frequency band. The dual-polarized dipoles are arranged as “egg-create” and fed by the integrated double-Y balun. A resistive frequency selective surface (FSS) is loaded between the dipole and ground plane to improve the active VSWR and lower the overall profile, simultaneously. The proposed antenna array can operate over a 10:1 bandwidth (0.2–2 GHz) with an active VSWR < {2.1, 2.7, 4} and average radiation efficiency > {71.6 %, 68.9 %, 60.3 %} for the scan up to {broadside, 45°, 60°}, respectively. The overall antenna profile is 95 mm, which is only 0.063λL evaluated at the lowest operating frequency. A prototype of a 6 × 10 array is simulated, fabricated, and measured. Good agreement is achieved between the simulated and measured results.

Ultra‐wideband metamaterial absorber based on frequency selective resistive film for 5G spectrum

AbstractAn ultra‐wideband metamaterial absorber (MA) is proposed for 5G communication, which features a resistive frequency selective surface printed on a PET (polyethylene terephthalate) layer and a ground layer of resistive film. The proposed MA can provide over 90% absorptivity in the frequency range of 11.2–42.8 GHz. Moreover, it is insensitive to polarization and wide incident angles. The effective medium theory and multi‐reflection interference theory are used to interpret the broadband absorption mechanism. The surface current distribution at three absorption peaks is investigated to further study the physical mechanism behind the wideband absorption. The measured results of the fabricated prototype are in good agreement with the simulation ones, thus verifying the robustness of the design. The presented MA can probably be used in electromagnetic shielding of 5G signals.

A Wideband and Ultra-Thin Metamaterial Absorber Based on Resistive FSS

A wideband, ultra-thin, wide-angle and polarization-insensitive metamaterial absorber with a single-layer resistive frequency selective surface (FSS) is proposed. The simulated results show that the absorption rate of the absorber is greater than 90% in a frequency range of 24.1–42.6 GHz, and the relative absorption bandwidth is up to 55.47%. The thickness of the structure is 1.2 mm, which is 0.088 λ and 0.156 λ for the lowest and highest frequencies, respectively. The power loss density is analyzed to explore the mechanism of the absorption and the resistive film layer is important for the wideband absorption. Meanwhile, a strong absorption for oblique incidence with wide angle and the characteristics of polarization insensitivity are achieved for the proposed design.

A Low Profile, Broadband Circularly Polarized Beam Scanning Array

Based on the idea of tightly coupled dipole array, a low profile, broadband circularly polarized array is designed in this paper. The circularly polarized phased array element consists of dual polarized dipoles with the same phase center and orthogonal arrangement, grounded coupling patches, resistive frequency selective surfaces (RFSS), and a 90° phase shifter network. In order to realize broadband scanning, the effect of RFSS on the input active voltage standing wave ratio and radiation axial ratio (AR) of the element is studied. The results show that the element can operate at 5-11.5GHz, within a ±45° angle scanning range, the AR of each scanning plane is less than 3dB, and the profile height is only 0.33 λ high.

Bandwidth analysis of microwave metamaterial absorber with a resistive frequency selective surface by using an equivalent circuit model

Bandwidth analysis of a resistive frequency selective surfaces (FSS) in microwave metamaterial absorber is very important for bandwidth-targeted design of the FSS pattern. A useful analysis for the case of a thin grounded dielectric substrate was performed a decade ago, however in the cases of thicker dielectric substrates it is not clear how to design the FSS pattern in order to achieve the largest bandwidth. Without the assumption that the grounded dielectric substrate is thin, we investigated relations between the bandwidth and the FSS reactance and revealed explicit expressions of the FSS reactance for the largest bandwidth. Although in full wave simulations for demonstrating the validity of the bandwidth analysis we assumed exemplary the square loop element, the bandwidth analysis is applicable for general FSS element structures. Our findings give design guidance for the FSS patterns of perfect absorbers in order to achieve the largest bandwidth.

Ultra-wideband RCS reduction based on coupling effects between beam diffuse and absorptive structures.

A hybrid design method for broadband radar cross section (RCS) reduction is proposed and successfully demonstrated based on the coupling effects between diffuse and absorptive structures. The reflection energy is distributed into more directions away from the source direction by the one-bit diffuse coding metasurface (CM). The two-layer resistive frequency selective surface (RFSS) is employed in the one-bit CM structure, reducing the amplitude of the co- and cross-polarized reflected waves under circularly polarized wave incidence by converting it into ohmic loss. In addition, the bandwidth of RCS reduction is further broadened through the coupling effects between the metallic patterns and the two-layer RFSS. The coupling effect shows that the absorption rate of the composite structure is significantly improved compared to the only RFSS structure. A lightweight CM loaded with RFSS (the area density is 597 g/m2) was fabricated, analyzed, simulated, and measured. The results show that the proposed mechanism can effectively break the bandwidth constraints of traditional diffusion and absorption methods. Furthermore, the proposed mechanism significantly expands the bandwidth of RCS reduction. The proposed metasurface can achieve a 10 dB RCS reduction in an ultra-wideband from 7.3 to 44.2 GHz with about 143.3% fractional bandwidth. Moreover, the metasurface also has good performances under wide-angle oblique incidences. Under the condition of maintaining lightweight, the design provides an idea for broadening the frequency band.

Flexible and broadband absorbing woven fabric using carbon-based resistive frequency selective surface

In this paper, a flexible and broadband absorbing woven fabric with good mechanical property is proposed. It is composed of two-layer carbon-based resistive patterns printed on plain weave quartz fiber cloth, sandwiched by 3D woven fiber fabric through stitching process. An equivalent circuit model is introduced to guide the broadband absorption design. Both simulation and measured results have verified that such absorber can achieve −10 dB reflection bandwidth ranging from 7.1 to 35.4 GHz with the total thickness of 5.5 mm. The measured tensile strength reaches as high as 112 MPa, exhibiting the excellent mechanical performance compared with the traditional rubber absorbers. In addition, this absorber is also demonstrated to perform well under circumstances of oblique incidence and different polarizations. The above results suggest that our design is promising for the further development of novel flexible absorbers in wearable electronics and communication fields.

Dual-Band Polarization-Independent Absorber Based on Resistive Frequency Selective Surface

In this paper, a three-layered frequency-selective absorber (FSA) that can efficiently absorb electromagnetic waves (EM) in a double-band is proposed. The proposed structure is designed so that signals reflected from the frequency selective ground plane are located at 2.4 and 5.5 GHz (ISM and UNII bands) and absorbed by the front resistive layers. Simulation results show that the proposed absorber not only blocks transmission in the desired bands but absorbs the signals reflected from the conductive layer. Reflective FSS unit cells are composed of double square loops printed on an FR-4 substrate and the resistive layers are formed of OhmegaPly material with a resistivity of 50 ohms per square. Furthermore, the proposed absorber is 0.17λ thick at the lowest frequency of absorption. The experimental results agree with the numerical simulations and show an absorptivity of more than 90% at 2.4 and 5.5 GHz, covering entirely ISM and UNII bands.