WO2016209181A1 - Absorbeur radar - Google Patents

Absorbeur radar Download PDF

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Publication number
WO2016209181A1
WO2016209181A1 PCT/TR2016/000079 TR2016000079W WO2016209181A1 WO 2016209181 A1 WO2016209181 A1 WO 2016209181A1 TR 2016000079 W TR2016000079 W TR 2016000079W WO 2016209181 A1 WO2016209181 A1 WO 2016209181A1
Authority
WO
WIPO (PCT)
Prior art keywords
radar
layer
radar absorber
absorbers
layers
Prior art date
Application number
PCT/TR2016/000079
Other languages
English (en)
Inventor
Egemen YILDIRIM
Mehmet Erim INAL
Oguz DOGAN
Original Assignee
Aselsan Elektronik Sanayi Ve Ticaret Anonim Sirketi
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aselsan Elektronik Sanayi Ve Ticaret Anonim Sirketi filed Critical Aselsan Elektronik Sanayi Ve Ticaret Anonim Sirketi
Publication of WO2016209181A1 publication Critical patent/WO2016209181A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
    • H01Q15/0026—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective said selective devices having a stacked geometry or having multiple layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/006—Selective devices having photonic band gap materials or materials of which the material properties are frequency dependent, e.g. perforated substrates, high-impedance surfaces

Definitions

  • the present invention relates to a multi-layered radar absorbing structure for absorbing radar signals.
  • a radar absorbing structure/material is a structure that reflects incident electromagnetic wave, as low as possible, over operating frequencies and converts a large part of the electromagnetic energy into heat so as to absorb it.
  • Radar absorbers may be used in air, land and sea platforms wherein a small radar cross-section is of critical importance. By using radar absorbers on an outer surface of said platforms, radar signals reaching the surface of the platform are highly absorbed and the target detection range of the radar systems may be considerably reduced. In order to reduce the radar trace of the platforms where they are used with respect to various radar systems, radar absorbers must operate over a broad bandwidth (e.g. absorb signals over a broad range of frequencies). In addition, radar absorbers should be very light in order not to apply additional weight to the platform where they are used, which is of great importance especially for air platforms.
  • Radar absorbing structures/materials are such structures that absorb incident electromagnetic energy and reflect a very small part thereof.
  • the main principle is to keep the input impedance of the structure as close as possible to the intrinsic impedance value of the electromagnetic wave in air by combining materials and/or lossy surfaces having different magnetic and electrical features, so as to absorb incident wave without a substantial reflection.
  • radar absorbers are mainly divided into four groups based on their structures. Said groups are classified as gradual- transition absorbers, resonant absorbers, magnetic absorbers, and circuit analog absorbers. In the gradual- transition absorbers, the impedance transition is achieved using geometrical shaping or gradual transition in electrical features of the material.
  • absorbers with geometrical shaping there exists no change in the electrical feature of the material through the structure, and homogenous materials are shaped geometrically in order to prevent reflection.
  • the length of such absorbers is kept long up to several wavelengths at the lower limit of the operating frequency. This results in a heavy, large and fragile structure of such absorbers.
  • said gradual- transition absorbers with geometrical shaping are not suitable for outdoor applications. They are especially preferred in EMI/EMC test fields and antenna measurement chambers.
  • An impedance transition between the impedance value of an electromagnetic wave in air and the short- circuit value of 0 ohm may also be accomplished by imposing a gradual transition in the electrical features of the material used.
  • Absorbers that are obtained by gradual feeding of a lossy filler into a lossless or low loss base material (with a concentration increasing from the surface to the base) constitute another field of application of such gradual- transition absorbers . With a gradual increase in the concentration of the filler, a gradually-changing impedance value is obtained so that broadband impedance conversion is achieved. It is not easy to manufacture such absorbers, and also high thickness values are required for broadband characteristics.
  • absorbance principle of resonant absorbers relies on accumulation of multiple reflections created in the structure such that they dampen each other.
  • these structures should also include a highly conductive layer at the lowermost layer.
  • this conductive layer has a high effect on the performance of the structure. Since the resonant absorbers are thinner than the gradual- transition absorbers, the amplitude of the sign reflected from the conductive layer is relatively large and its role in the total reflection coefficient is high.
  • the electromagnetic wave incident on the resonant structures experiences a first reflection on the surface of the structure and penetrates thereto.
  • the wave passing through the structure is reflected from the lowermost conductive plate in single-layer structures whereas in multi-layer structures, it is reflected from each surface where electrical discontinuity is available.
  • electrical features of the layers used in the structure and cross-layer distance it is aimed at having an equivalent reflection on the surface of the structure as small as possible.
  • the Salisbury screens, Dallenbach layers and Jaumann type absorbers are typical resonant absorbers. In resonant absorbers, broadband characteristics and a high damping rate may be obtained only by using a plurality of layers. In this case, since the distance between the successive layers is one quarter-wavelength, the total thickness of the structure is greatly increased.
  • Magnetic absorbers are formed by combining a layer or layers having a magnetic constant different from 1. Along with the dielectric constant, the fact that magnetic constant is controllable provides for design flexibility, and structures with no need for a high thickness may be provided with acceptable absorbance characteristics. Artificial materials with magnetic features are obtained by scattering particles of iron and ferrite into dielectric materials. Therefore, such absorbers may be thin, but they are also very heavy. Furthermore, such absorbers are usually preferred in low frequency applications since the magnetic features of the materials used are effective at low frequencies. Magnetic constants of ferrites are rapidly reduced as the frequency increases, but electrical constants remain unchanged to a considerable extent. Thus, electrical losses take place at high frequency regions.
  • CA RAS Circuit -Analog Radar Absorbing Structures
  • FSS Frequency Selective Surface
  • the lossy surfaces may be modeled using an equivalent capacitor, coil and resistance so that equivalent circuit techniques may be used in the design of the absorbing structure. Therefore, such absorbers are called as circuit analog radar absorbing structures.
  • circuit analog radar absorbers In conventional circuit analog radar absorbers, the distance between the successive lossy FSS layers is equal to a quarter-wavelength. Broadband characteristic structures may be obtained only by increasing the number of the layers, which results in very thick structures as it is in the resonant absorbers.
  • the number of the layers in the radar absorber should be very high in order to achieve the desired bandwidth.
  • the prior art radar absorbers are quite heavy, and accordingly, they are not preferred in air and sea platforms, in particular, where weight is of critical importance.
  • a radar absorber which absorbs radar signals.
  • Said radar absorber comprises at least one base layer with a high conductivity; at least two spacing layers located on the said base layer, in the form of a glass fabric, each having thereon at least one frequency selective surface; and at least one filler layer interposed between said spacing layers.
  • the frequency selective surfaces are designed based on the desired bandwidth, they are applied on a spacing layer made of glass fabric by means of a printing method.
  • a filler layer made of different materials is disposed between the spacing layers.
  • the radar absorber operates over the desired frequency range, and thanks to the low density fillers used, its weight is kept very low.
  • the frequency selective surface is coated on the spacing layer by a printing method, the radar absorber is produced in an easy manner.
  • An object of the present invention is to provide a radar absorber having a high bandwidth (3,4 octaves; 1 decade).
  • Another object of the present invention is to provide a radar absorber having a low weight (0.9 g/cm 3 ). Another object of the present invention is to provide a thin ( ⁇ /20) radar absorber.
  • Another object of the present invention is to provide a radar absorber suitable for use in different platforms.
  • Another object of the present invention is to provide a radar absorber which is easy-to- manufacture, durable and reliable. Still another object of the present invention is to provide a radar absorber having superior absorbance features (>15 db across the band, >20 dB on particular frequency points).
  • Figure 1 is a side sectional view of the radar absorber.
  • Figures 2a-2e are exemplary views of the different patterns of frequency selective surfaces provided in the radar absorber.
  • Radar absorbers constitute one of the primary techniques used to reduce the radar traces of air, land and sea platforms.
  • the radar absorbing structures/materials used for such purposes are applied on outer surfaces of the platforms, and they absorb incident electromagnetic wave at a high level, and reflect part of it that has a very low energy back to the energy source.
  • the number of the layers and thus the total thickness thereof should be high. Therefore, in case high density materials are used, radar absorbers having a high bandwidth become quite heavy.
  • the radar absorbers having a high weight cannot be utilized in those platforms where weight has a critical importance. Therefore, with the present invention, there is provided a radar absorber which is quite light though its bandwidth is high.
  • the radar absorber (R) according to the present invention, as illustrated in figures 1-2, comprises at least one base layer (1 ) which is preferably fixed to a surface (i.e. an air platform); at least two spacing layers (2) located on the said base layer (1 ), in the form of a glass fabric, each having thereon at least one lossy frequency selective surface (3); and at least one filler layer (4) interposed between said spacing layers.
  • the lossy frequency selective surfaces (3) as illustrated in figure 2 are designed based on the desired bandwidth, and they are applied on the spacing layer (2) made of glass fabric preferably by means of a printing method.
  • the pattern of the frequency selective surface (3) on each spacing layer (2) may be different, or the pattern of the frequency selective surface (3) on at least two spacing layers (2) may be the same.
  • said base layer (1 ) is in the form of a carbon fabric (carbon fiber woven fabric). With the high conductivity value of the base layer (1), the radar absorber (R) is prevented from being affected by electrical features of the surface of the platform where it is used.
  • the layers of the lossy frequency selective surface (3) are obtained by applying a radar- absorbing paint on a fiber-reinforced plastic or thin base material in accordance with periodic patterns. Between the successive layers of lossy frequency selective surface (3), different fillers (4) may be used. In structures with a plurality of filler layers (4), the structure of the filler layers (4) may be the same, or different structures may be employed for different filler layers (4). These materials are:
  • thermoset resin fabric containing at least one magnetic/dielectric loss filler.
  • said radar absorber (R) comprises at least one outer layer (5) that is located at the top surface thereof and protects the underlying layers from external effects.
  • Said outer layer (5) preferably contains glass fiber woven thermoset resin fabric.
  • the radar absorber (R) is used on a platform, said outer layer (5) is the outermost surface surrounding the platform. Since the outer layer (5) is made from a robust material such as glass fiber woven thermoset resin fabric, the radar absorber (R) may be used for a long period of time with low maintenance cost and without experiencing any performance loss under harsh environmental conditions.
  • the radar absorber (R) comprises a base layer (1 ) located at the undermost side and made of carbon fabric; five spacing layers (2) made of a glass fabric, each having thereon one frequency selective surface (3); a filler layer (4) interposed between the spacing layers (2) and made of a closed cell structured foam; and an outer layer (5) located at the uppermost side and made of glass fiber woven thermoset resin fabric. After the said layers are assembled, they are cured at different temperature values and under pressure and/or vacuum. In this way, the radar absorber (R) is formed as a composite structure. In this embodiment, the absorption rate of the radar absorber (R) over a broadband is higher than 15 dB, and at spot frequencies it is higher than 20 dB. The weight of the radar absorber (R) is 0.9 g per cubic centimeter. With this production method, the invention may be used as a structural material for different platforms (land, air, sea, submarine, etc.) and with different geometric shapes.
  • the electromagnetic wave incident on the structure experiences a first reflection on the outer surface of the structure.
  • Said electromagnetic wave that has lost a small part of its energy due to said reflection penetrates into the structure.
  • a new reflecting component is generated within the structure at each point having discontinuity.
  • Said reflection points are those surfaces where lossy frequency surface (3) layers are located. Reflective characteristics of these layers are closely related with the geometric patterns of the surfaces and the surface resistance values. Therefore, the layers with different reflective and conductive characteristics may be obtained by adjusting the geometric patterns and surface resistance values.
  • the absorbance performance of the structure is defined by the structural properties of the lossy frequency selective surface (3) layers and the distance between said layers. With these parameters, high broadband absorbance performances may be obtained with low reflection values. Moreover, with the invention, an absorbance performance having very low reflection values ( ⁇ -25 dB) may be obtained at specific frequency points, along with the reactive impedance induced flexibility of the patterned FSS layers. Another significant aspect of the invention is that it is not necessary to use resonating surfaces in selecting lossy FSS as it is the case in conventional circuit analog radar absorbing structures. The distance between the layers may be greatly reduced by using capacitive or inductive characteristic surfaces, whereby very thin absorbing structures may be designed.
  • the radar absorber (R) In the radar absorber (R) according to the present invention, after the lossy frequency selective surfaces (3) are designed based on the desired bandwidth, it is obtained by applying a lossy material on the spacing layer (2) made of glass fabric by means of a printing method, in accordance with the desired geometrical form.
  • the filler layer (4) made of different materials is disposed between the spacing layers (2). In this manner, the radar absorber (R) operates at the desired frequency range and it is made light-weight. Furthermore, since the frequency selective surface (3) is coated on the spacing layer (2) by a printing method, the radar absorber is produced in an easy and repeatable manner.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Aerials With Secondary Devices (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)

Abstract

Selon la présente invention, un absorbeur radar à large bande et à faible poids (R) absorbe des signaux radar. Ledit absorbeur radar (R) comprend au moins une couche de base (1) ; au moins deux couches d'espacement (2) situées sur ladite couche de base (1), sous la forme d'un tissu de verre, chacune ayant sur cette dernière au moins une surface sélective de fréquence (3) ; et au moins une couche de remplissage (4) interposée entre lesdites couches d'espacement.
PCT/TR2016/000079 2015-06-22 2016-06-03 Absorbeur radar WO2016209181A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
TR201507628 2015-06-22
TR2015/07628 2015-06-22

Publications (1)

Publication Number Publication Date
WO2016209181A1 true WO2016209181A1 (fr) 2016-12-29

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107257033A (zh) * 2017-07-18 2017-10-17 东南大学 基于高阻抗表面实现的多频带吸波器
CN107565218A (zh) * 2017-08-23 2018-01-09 重庆邮电大学 基于fss多层反射调制板的uhf雷达频谱搬移方法
CN109599679A (zh) * 2018-10-25 2019-04-09 西安理工大学 一种应用于超宽带天线的超宽带频率选择表面结构
CN110048240A (zh) * 2019-04-23 2019-07-23 电子科技大学 一种高阻带抑制度低雷达散射截面积透射阵列天线
CN110416742A (zh) * 2019-07-26 2019-11-05 中国人民解放军军事科学院国防科技创新研究院 一种轻薄宽频吸波超材料的设计
WO2021141647A1 (fr) * 2020-01-06 2021-07-15 Raytheon Company Absorbeur radiofréquence (rf) accordable et dissipateur de chaleur thermique
US11924963B2 (en) 2022-02-03 2024-03-05 Raytheon Company Printed-circuit isolation barrier for co-site interference mitigation

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993023893A1 (fr) * 1992-05-15 1993-11-25 Chomerics, Inc. Structure electromagnetique absorbant l'energie
EP2096711A1 (fr) * 2005-10-21 2009-09-02 Nitta Corporation Corps de tôle permettant d améliorer la communication, dispositif d antenne muni d un tel corps de tôle et appareil de transmission d informations électroniques

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993023893A1 (fr) * 1992-05-15 1993-11-25 Chomerics, Inc. Structure electromagnetique absorbant l'energie
EP2096711A1 (fr) * 2005-10-21 2009-09-02 Nitta Corporation Corps de tôle permettant d améliorer la communication, dispositif d antenne muni d un tel corps de tôle et appareil de transmission d informations électroniques

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107257033A (zh) * 2017-07-18 2017-10-17 东南大学 基于高阻抗表面实现的多频带吸波器
CN107565218A (zh) * 2017-08-23 2018-01-09 重庆邮电大学 基于fss多层反射调制板的uhf雷达频谱搬移方法
CN109599679A (zh) * 2018-10-25 2019-04-09 西安理工大学 一种应用于超宽带天线的超宽带频率选择表面结构
CN110048240A (zh) * 2019-04-23 2019-07-23 电子科技大学 一种高阻带抑制度低雷达散射截面积透射阵列天线
CN110416742A (zh) * 2019-07-26 2019-11-05 中国人民解放军军事科学院国防科技创新研究院 一种轻薄宽频吸波超材料的设计
CN110416742B (zh) * 2019-07-26 2020-12-08 中国人民解放军军事科学院国防科技创新研究院 一种轻薄宽频吸波超材料
WO2021141647A1 (fr) * 2020-01-06 2021-07-15 Raytheon Company Absorbeur radiofréquence (rf) accordable et dissipateur de chaleur thermique
US11784416B2 (en) 2020-01-06 2023-10-10 Raytheon Company Tunable radio frequency (RF) absorber and thermal heat spreader
US11924963B2 (en) 2022-02-03 2024-03-05 Raytheon Company Printed-circuit isolation barrier for co-site interference mitigation

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