Design of an absorber with high impedance surfaces

Peng, Lin; Li, Ké; Hou, Xinyu

doi:10.1109/isape.2010.5696668

Cited by 3 publications

(2 citation statements)

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“…Introduction: Microwave absorbers based on resistively loaded high impedance surfaces [1] are an attractive option for providing radar cloaking where the main design drivers are weight and thickness. However, the reflectivity bandwidth of this class of absorbers is proportional to the structure thickness [2][3][4][5][6], which is determined by the gap between the frequency selective surface (FSS) and the ground plane. In [2], a −10 dB reflectivity bandwidth of 109% was obtained from a 5 mm-thick metal backed resistively loaded single square loop FSS array.…”

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Compact FSS absorber design using resistively loaded quadruple hexagonal loops for bandwidth enhancement

2015

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The design of a thin microwave absorber which exhibits a −10 dB reflectivity bandwidth of 108% at normal incidence and 16% for simultaneous suppression of TE and TM polarised waves over the angular range 0-45°is presented. The structure consists of a 3 mm-thick metal backed frequency selective surface (FSS) with four resistively loaded hexagonal loop elements in each unit cell. The surface resistivity and width of the loops are carefully chosen to maximise the bandwidth by merging the reflection nulls that are generated by the multi-resonant absorber. Measurement and simulation results are in good agreement over the broad frequency range 7.8-24 GHz.Introduction: Microwave absorbers based on resistively loaded high impedance surfaces [1] are an attractive option for providing radar cloaking where the main design drivers are weight and thickness. However, the reflectivity bandwidth of this class of absorbers is proportional to the structure thickness [2-6], which is determined by the gap between the frequency selective surface (FSS) and the ground plane. In [2], a −10 dB reflectivity bandwidth of 109% was obtained from a 5 mm-thick metal backed resistively loaded single square loop FSS array. This was designed to resonate at the two frequencies where the imaginary component of the FSS impedance is cancelled by the inductance and capacitance presented by the ground plane with gap widths of <λ/4 and >λ/4 at the lower and upper frequencies, respectively. The FSS absorber studied in this Letter is shown to give a similar bandwidth; however, the ground plane spacing is < λ/4 at all frequencies where the reflectivity is below −10 dB. Moreover, because the structure is 40% thinner, the figure of merit (FOM), which is defined as the common (TE/TM) bandwidth divided by the physical thickness normalised to the centre working frequency, is significantly larger, 670 compared with 470 in [2]. For this arrangement, radar backscatter suppression occurs at four frequencies where the complex impedances of the individual hexagonal loops cancel the inductance which is presented by the ground plane. In [3,5,[7][8][9], the simulated backscatter suppression for various resistively loaded thin FSS absorbers based on single and nested square loop elements has been reported, but only for normal or small incidence angle operation. The structure depicted in Fig. 1 which was studied in this Letter, exhibits higher FOM values except for the arrangement reported in [7], where numerical results are presented for an FSS design with different surface resistances for the five individual nested elements in the range 4-1680 Ω/sq. In contrast, our methodology enables the use of the same surface resistance for all four hexagonal loops in the unit cell which significantly simplifies the construction and manufacture of the FSS. Bi-static measured results obtained for an absorber with an FSS that was fabricated by patterning a uniform thickness film of commercially available shielding paint [10] are shown to be in good agreement with numerical predictions...

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Compact FSS absorber design using resistively loaded quadruple hexagonal loops for bandwidth enhancement

2015

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“…Na primeira classe, a distribuição do campo no absorvedor é modificada empregando-se FSS metálicas com uma consequente melhora no desempenho [21][22][23]. Na segunda categoria, perdas são adicionas à FSS com o intuito de dissipar a energia pela superfície e, desse modo, reduzir a espessura [149][150][151]. Este último tipo de absorvedor é semelhante ao absorvedor Salisbury: a ressonância é obtida usando as propriedades de uma superfície de alta impedância, e a absorção ocorre por meio de uma folha resistiva separada [29].…”

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Superfícies seletivas em frequência / FSS

Silva¹

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In this work, the different properties of frequency selective surfaces -FSS are analyzed. Frequency selective surfaces are planar structures with periodic cells and can be classified as a kind of metamaterials. To this end, the working mechanism of these structures has been extensively studied, and a proper method based on the equivalent circuit model in conjunction with fullwave simulations was proposed. The developed tool is useful for a fast preliminary analysis of FSS, which was used to create a database of known elements presented in the literature. Unlike of classical analysis model, the proposed analytical modeling, which is one of the main thesis contributions, uses a simple algorithm for approximate the response of frequency selective surfaces with arbitrary shape, for normal and oblique incidence and for substrates with all thicknesses. In this sense, after the electromagnetic simulation of the structure, it is possible to compute the response of an FSS with different parameters without the time consuming full-wave simulations. The model uses the unique characteristics of High-Impedance Surfaces -HIS, which for certain frequency range, behaves as Perfect Magnetic Conductor -PMC, while outside this band behaves as a Perfect Electric Conductor -PEC, for synthesizing thin planar microwave absorbers.The structures, comprising resistive frequency selective surfaces over a grounded dielectric substrate, are designed aiming different absorption frequency bands and different bandwidths. In the 5.5 GHz frequency range, the aim was to satisfy the specifications of WIMAX, WLAN systems, in view of the IEEE 802.11a standards, as well as radar systems, while signals from other bands can travel across with zero or minimal attenuation. To the highest range, the designed structure provides absorption over 10 GHz to 18 GHz frequency range, and can be applied to the X-and Ku-band.The modeling method for the FSS and the proposed absorbers was physically validated through experimental setups and instrumentation, especially developed for these structures. The ix prototype of the fabricated absorbers are extremely thin and were characterized by using free space and anechoic chamber measurement setups. The designed structures showed excellent performance for measurements ranges, with reflectivity typically below -10 dB over the entire band. The methodology developed in this research can be extended to different frequency bands, bandwidth and applications.

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Angularly Stable Frequency Selective Surface With Miniaturized Unit Cell

Azemi

Ghorbani

Rowe

2015

IEEE Microw. Wireless Compon. Lett.

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A new type of Frequency Selective Surface (FSS) with miniaturized resonator element is proposed. The FSS structure is shown to have a FSS unit cell dimension that is miniaturized to 0.067 . Miniaturization of the FSS unit cell is achieved by coupling two meandered wire resonators separated by single thin substrate layer. The capacitance due to the small separation between the meandered wire elements results in a lowering of the resonant frequency. To demonstrate the validity of the design, the meandered wire resonator FSS was fabricated and tested using a free space measurement facility. The FSS produces a stable angular response up to 80 degrees for TE and TM incident angles.Index Terms-Angular stability, frequency selective surface, FSS, incident angle, meandered wire, miniature resonator.

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Design of an absorber with high impedance surfaces

Cited by 3 publications

References 9 publications

Compact FSS absorber design using resistively loaded quadruple hexagonal loops for bandwidth enhancement

Compact FSS absorber design using resistively loaded quadruple hexagonal loops for bandwidth enhancement

Superfícies seletivas em frequência / FSS

Angularly Stable Frequency Selective Surface With Miniaturized Unit Cell

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