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Journal ArticleDOI

Design of a Lightweight Magnetic Radar Absorber Embedded With Resistive FSS

TL;DR: In this article, a 5-mm-thick magnetic radar absorber with weak wave-absorbing performance is obtained on the basis of polyurethane foam filled with flake ferrous microwave absorbent.
Abstract: In this letter, the design of a lightweight magnetic radar absorber (RA) having broadband bandwidth in frequency range of 1-18 GHz is demonstrated. A 5-mm-thick magnetic RA with weak wave-absorbing performance is obtained on the basis of polyurethane foam filled with flake ferrous microwave absorbent. The use of frequency selective surfaces (FSSs) results in a significant increase of the absorbing intensity and operating bandwidth of the RA. By selecting the unit dimensions and modulating the location and square resistance of FSS, a maximal operating bandwidth with the reflectivity below -10 dB can be obtained. Experimental results are presented and compared to numerical simulations, and they demonstrated that the RA embedded with lossy FSS has a super broad bandwidth of 3.19-18 GHz with the reflectivity below - 10 dB for the double-layer case. The density of the absorber is only 0.62 g/cm3 , which is far more less than that of the conventional magnetic coating radar absorbing materials (RAMs).
Citations
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Journal ArticleDOI
TL;DR: In this paper, a frequency-selective surface (FSS) with high in-band transmission at high frequency and wideband absorption at low frequency is presented. But the PLC structure is not considered.
Abstract: This communication presents a novel frequency-selective surface (FSS) with high in-band transmission at high frequency and wideband absorption at low frequency. It consists of a resistive sheet and a metallic bandpass FSS separated by a foam spacer. The resistive element is realized by inserting a strip-type parallel $LC$ (PLC) structure into the center of a lumped-resistor-loaded metallic dipole. The PLC resonates at the passband of the bandpass FSS and exhibits an infinite impedance, which splits the resistive dipole into two short sections per the surface current; this setup allows for high in-band transmission at high frequency. Below the resonance frequency, the PLC becomes finite inductive and the entire FSS performs as an absorber with the metallic FSS as a ground plane. The surface current distribution on the resistive element can be controlled at various frequencies via the PLC structure. The wideband absorption and high in-band transmission of the proposed design are verified by both numerical simulation and experimental measurements. The potential extension to polarization-insensitive designs is also discussed.

224 citations

Journal ArticleDOI
01 Jan 2019-Carbon
TL;DR: In this paper, a flexible broadband microwave absorber with self-recoverability was fabricated by self-assembling graphene sheets into polypropylene 3D framework, which has a full-band absorption (more than 90%) in the working ranges of microwave communication and detection in military radars.

176 citations

Journal ArticleDOI
TL;DR: In this article, the authors report on the design, fabrication, measurement, and analysis of a tunable low-frequency and broadband radar absorber applied in the frequency range of 1-12 GHz.
Abstract: In this letter, we report on the design, fabrication, measurement, and analysis of a tunable low-frequency and broadband radar absorber applied in the frequency range of 1–12 GHz. Numerical simulations indicate that absorbers based on the resistor-loaded frequency selective surface (FSS) can be resistively tuned to give a broadband absorption of exceeding $-\hbox{10 dB}$ between 1 and 12 GHz. Moreover, superior absorbing performance can be achieved by introducing capacitance paralleled with resistance. Measurement results show that the radar absorber, by way of configuration with active FSS (AFSS) controlled by p-i-n diodes, can be tuned to provide a continuously variable reflectivity level of less than $-\hbox{10 dB}$ from 2 to 11.3 GHz with varied bias voltages. Furthermore, experimental results have good agreement with simulations.

111 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed a low-profile broadband absorber consisting of two layers: a lossy layer with four rotationally symmetric bent metallic strips embedded with two chip-resistors, which is modified from a doubly fed dipole antenna, and a metallic ground separated from the lossy layers by an air spacer, and the measured absorption band with a fractional bandwidth of 127.9% is achieved for at least 10dB reflectivity reduction under the normal incidence.
Abstract: This article proposes a new method to realize a low-profile broadband absorber. The unit cell of the proposed absorber consists of two layers: a lossy layer with four rotationally symmetric bent metallic strips embedded with two chip-resistors, which is modified from a doubly fed dipole antenna, and a metallic ground separated from the lossy layer by an air spacer. Three resonant modes of the metallic strip embedded with two chip-resistors are generated, and the current in the strip passes through the chip-resistors under different modes and it is finally consumed, resulting in energy dissipation. As a result, an ultrawideband absorber is realized. The designed absorber is fabricated and measured, and the measured absorption band with a fractional bandwidth of 127.9% is achieved for at least 10-dB reflectivity reduction under the normal incidence. In addition, the thickness of the designed absorber is only $0.08\lambda _{L}$ , where $\lambda _{L}$ is the wavelength at the lowest operating frequency.

76 citations

Journal ArticleDOI
TL;DR: In this article, a frequency selective surface (FSS)-based novel hybrid nanocomposite absorber for enhanced electromagnetic absorption is presented, which consists of an FSS pattern printed over a dielectric substrate backed by aluminum foil.
Abstract: This paper presents the design, fabrication, and electromagnetic testing of a frequency selective surface (FSS)-based novel hybrid nanocomposite absorber for enhanced electromagnetic absorption. The proposed hybrid absorber consists of an FSS pattern printed over a dielectric substrate backed by aluminum foil, which is integrated together with a customized dielectric nanocomposite sheet. The dielectric sheet comprises the conducting carbon black (CB) nanopowders embedded into the epoxy matrix. The fabricated nanocomposite sheet is first characterized for the effective complex permittivity using the free-space measurement technique, and the measured electromagnetic properties are then used for the design of a hybrid absorber. The proposed hybrid absorber having overall thickness of 2.6 mm shows enhanced −10-dB absorption bandwidth of 3.5 GHz, which is much higher than that of the FSS and CB nanocomposite samples measured individually. The proposed work provides an effective way to combine the absorption properties of FSS with that of a customized dielectric absorber sheet in order to design an efficient hybrid absorber having reduced thickness with enhanced absorption bandwidth for stealth technology and various strategic applications.

63 citations

References
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Book
26 Apr 2000
TL;DR: In this article, the authors present a comparison of band-pass and Dichroic filter designs for one and two-dimensional periodic structures, and present an overview of the current state-of-the-art.
Abstract: General Overview. Element Types: A Comparison. Evaluating Periodic Structures: An Overview. Spectral Expansion of One- and Two-Dimensional Periodic Structures. Dipole Arrays in a Stratified Medium. Slot Arrays in a Stratified Medium. Band-Pass Filter Designs: The Hybrid Radome. Band-Stop and Dichroic Filter Designs. Jaumann and Circuit Analog Absorbers. Power Handling of Periodic Surfaces. Concluding Remarks and Future Trends. Appendices. References. Index.

3,896 citations

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the reflection and transmission coefficients calculated from transfer matrix simulations on finite lengths of electromagnetic metamaterials, to determine the effective permittivity and permeability.
Abstract: We analyze the reflection and transmission coefficients calculated from transfer matrix simulations on finite lengths of electromagnetic metamaterials, to determine the effective permittivity ~«! and permeability ~m! .W e perform this analysis on structures composed of periodic arrangements of wires, split ring resonators ~SRRs!, and both wires and SRRs. We find the recovered frequency-dependent« and m are entirely consistent with analytic expressions predicted by effective medium arguments. Of particular relevance are that a wire medium exhibits a frequency region in which the real part of « is negative, and SRRs produce a frequency region in which the real part of m is negative. In the combination structure, at frequencies where both the recovered real parts of « and m are simultaneously negative, the real part of the index of refraction is also found to be unambiguously negative.

2,689 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of the surface resistance of the FSS and dielectric substrate characteristics on the input impedance of the absorber is discussed by means of a circuital model.
Abstract: High-impedance surfaces (HIS) comprising lossy frequency selective surfaces (FSS) are employed to design thin electromagnetic absorbers. The structure, despite its typical resonant behavior, is able to perform a very wideband absorption in a reduced thickness. Losses in the frequency selective surface are introduced by printing the periodic pattern through resistive inks and hence avoiding the typical soldering of a large number of lumped resistors. The effect of the surface resistance of the FSS and dielectric substrate characteristics on the input impedance of the absorber is discussed by means of a circuital model. It is shown that the optimum value of surface resistance is affected both by substrate parameters (thickness and permittivity) and by FSS element shape. The equivalent circuit model is then used to introduce the working principles of the narrowband and the wideband absorbing structure and to derive the best-suited element for wideband absorption.

612 citations

Journal ArticleDOI
Abstract: Analytic properties of the reflection coefficient of a multilayer metal-backed slab are considered. The result is a new form of the dispersion relationship, which characterizes the integral of the reflectance over wavelength in terms of the total thickness and averaged static permeability of the slab. The relation may be transformed to an inequality, which produces the least thickness to bandwidth ratio achievable for a physically realizable radar absorber. The particular cases of broad-band and narrow-band absorbers are discussed. The least thickness of a 10-dB broad-band dielectric radar absorber is shown to be 1/17 of the largest operating wavelength. The discussion also involves the results of a numerical study.

608 citations

Journal ArticleDOI
TL;DR: In this article, the absorbing properties of FSS absorber with cross-shaped resistive patches were studied by finite element method and the calculated results indicate that lattice type, element spacing, cross dipole size, patch sheet resistance and thickness of dielectric substrate all can affect the absorbing performance of the FSS absorbing material.

115 citations