EP0439337A2 - Absorbeur d'ondes à large bande - Google Patents

Absorbeur d'ondes à large bande Download PDF

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Publication number
EP0439337A2
EP0439337A2 EP91300505A EP91300505A EP0439337A2 EP 0439337 A2 EP0439337 A2 EP 0439337A2 EP 91300505 A EP91300505 A EP 91300505A EP 91300505 A EP91300505 A EP 91300505A EP 0439337 A2 EP0439337 A2 EP 0439337A2
Authority
EP
European Patent Office
Prior art keywords
wave absorber
wave
radio
structure according
magnetic material
Prior art date
Legal status (The legal status 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 status listed.)
Granted
Application number
EP91300505A
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German (de)
English (en)
Other versions
EP0439337A3 (en
EP0439337B1 (fr
Inventor
Yoshiyuki Naito
Michiharu Takahashi
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Individual
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Individual
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Publication date
Priority claimed from JP2023818A external-priority patent/JPH03228398A/ja
Priority claimed from JP2150690A external-priority patent/JPH077886B2/ja
Priority claimed from JP2162403A external-priority patent/JP2509369B2/ja
Application filed by Individual filed Critical Individual
Publication of EP0439337A2 publication Critical patent/EP0439337A2/fr
Publication of EP0439337A3 publication Critical patent/EP0439337A3/en
Application granted granted Critical
Publication of EP0439337B1 publication Critical patent/EP0439337B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H01Q17/008—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems with a particular shape

Definitions

  • the present invention relates to a wave absorber constructed using a ferrite magnetic material, and, in particular, to a broad-band wave absorber in which ferrite blocks are arranged at a specific spacing on a conductive plate.
  • the construction of the wave absorber that has become a conventional standard is such that ferrite tiles (plates) are arranged on a conductive plate, as shown in Fig. 17.
  • An object of the present invention is to provide a novel wave absorber having an improved characteristic of handwidth.
  • the present invention was designed while taking the above points into consideration, with the aim of providing a broadband wave absorber that has a much broader bandwidth than a conventional absorber, that can be used in the VHF, UHF, and microwave bands, and that has excellent characteristics such that it can not only be used as an absorber with respect to waves polarized in the horizontal and vertical directions, it can also be used as a wave absorber for unidirectional-polarization use.
  • the present invention provides a broad-band wave absorber wherein beams formed of a ferrite magnetic material are placed at an optimal spacing and are aligned in a lattice form in longitudinal and lateral directions on a conductive plate.
  • a magnetic material of a specific thickness t m is formed into cylindrical blocks of a height d (where d ⁇ t m ) wherein an end surface thereof is polygonal, and the cylindrical blocks are provided with a radio-wave reflecting surface arranged in such a manner that this surface is perpendicular to the axial direction of the blocks, and the end surface of the blocks is approximately perpendicular to a direction from which radio waves are incident.
  • the ferrite magnetic material could also be formed into rectangular prisms of thickness 2t m , height d, and length in the longitudinal direction thereof L, with the prisms aligned at a spacing b on a radio-wave reflecting surface, the direction of the height dimension of the prisms being approximately parallel to a radio-wave incidence direction, and the surfaces thereof of the dimensions 2t m and L being perpendicular to the radio-wave incidence direction, forming a plane parallel to a magnetic field direction of incident radio waves and the dimension L, wherein the following relationships hold:
  • the wave absorber of the present invention has the characteristic that the equivalent surface with the large surface area is aligned parallel to the direction of incident radio waves, and the resultant electromagnetic characteristics are dramatically different.
  • the conventional wave absorber has tiles aligned with L-d surfaces thereof perpendicular to the direction of incident radio waves, but the wave absorber of the present invention, on the other hand, achieves a much broader bandwidth by having- tiles aligned with the L-t surfaces thereof perpendicular to the direction of incident radio waves.
  • the present invention can provide a broadband wave absorber able to absorb radio waves over a wide frequency range, by reducing -wave reflection and by increasing absorption by TM wave.
  • FIG. 1(a) shows the essential details of an embodiment of the wave absorber of the present invention that uses horizontally and vertically polarized waves.
  • Fig. 1(b) shows a wave absorber similar to that of Fig. 1(a), but in which the vertically aligned magnetic frames are removed and a conductive plate that is in contact with the radio-wave reflecting surface is inserted into the thickness of each lateral frame, and
  • Fig. 1(c) shows a further example in which the conductive plates are omitted from within the ferrite frames.
  • the wave absorber of the present invention is configured of a stack of a large number of identical units of the same construction shown in Fig. 1.
  • Each unit consists of ferrite plates 3 formed in a box shape on a conductive plate 2 that forms a radio-wave reflecting surface, the thickness of the ferrite plates 3 being 2t m , the spacing therebetween being b, and the height thereof being d; and the units are aligned on the conductive plate 2 in such a manner as to form a lattice. Since all of these units act in exactly the same manner, analysis thereof can be conducted by considering a single unit.
  • Fig. 2(a) shows a single-cell model used in such analysis.
  • the symmetry of the overall structure means that it is possible to assume that a metal plate can be inserted into the central portion of each ferrite plate, parallel thereto, without affecting in any way the magnetic field thereof. Therefore, the analysis below uses the model shown in Fig. 2(b).
  • ⁇ r l + ⁇ K l x f l / (f l + jf) ⁇ where f is frequency MHz and (l + k l ) is the initial relative permeability under DC conditions.
  • fl [MHz] corresponds to the frequency at which the imaginary part of the relative permeability becomes a maximum.
  • a value S is the product of kl and fl (i.e., kl x fl), is the quality of ferrite magnetic materials. Of the various compositions of ferrite is 10,000 MHz or less.
  • This analysis is based on the use of ferrite whose value of kl is 1000 and fl is 6 MHz.
  • curve A shows the absorption frequency characteristics for a single-layer absorber.
  • the absorption characteristic B for a wave absorber for which the above dimensions were selected is shown superimposed on the characteristic A of the conventional single-layer absorber.
  • the reflectivity that is a characteristic of a wave absorber must be less than or equal to a permissible reflection coefficient. This analysis concerns evaluation at a frequency bandwidth that is 1% of the power level, i.e., at -20 dB or less.
  • the absorber of the present invention has three parameters: the thickness 2t m of the ferrite plates, the spacing b between the ferrite plates, and the height d of the ferrite plates.
  • Another parameter is (b - 2t m )/b, the proportion of the metal plate occupied by the empty portions between ferrite plates, hereinafter called the vacancy ratio.
  • Fig. 4 shows absorption frequency characteristics obtained by varying the height of the ferrite plates while keeping the thickness thereof constant at 8 mm and the spacing therebetween constant at 20 mm. It is clear from the curves of Fig. 4 that when the height d of the ferrite plates becomes less than 20 mm, the characteristic at higher frequencies becomes better, but, in contrast, the characteristic at lower frequencies worsens. Therefore, in this case, it is considered that the best characteristic occurs when the height d is 20 mm.
  • Fig. 5 shows absorption frequency characteristics obtained by varying the thickness of the ferrite plates
  • Fig. 6 shows absorption frequency characteristics obtained by varying the spacing therebetween.
  • Fig. 7 shows absorption frequency characteristics obtained by keeping the thickness of the ferrite plates fixed at 20 mm, but varying both b and 2t m in such a manner that the vacancy ratio (b - 2t m )/b was constant at 60%.
  • Fig. 8 shows the characteristics obtained by using the above optimal structure at which the product S is fixed at 6000 MHz, but kl and fl [MHz] are varied.
  • the bandwidth broadens.
  • the frequency at which the curve starts to fall below -20 dB is determined by K l
  • the frequency at which the curve starts to rise above -20 dB is determined by the configuration of the absorber.
  • Fig. 9 shows the absorption frequency characteristics obtained when the product S was 8000 MHz.
  • the wave absorber shown in Figs. 10(a) and (b) has an annular configuration of an inner diameter of 12 mm, a thickness of 1.5 mm, and a length of 5 mm. This absorber is aligned with a coaxial internal conductor in front in the axial direction f a short-circuiting plate of a circular, coaxial conductive tube. Measurements of the absorption frequency characteristics with respect to variations in length of this wave absorber are shown in Fig. 10(c).
  • FIG. 1 Another alternative to the plate-shaped ferrite magnetic bodies of Fig. 1 is a circular or polygonal prismatic form, as shown in Fig. 11.
  • pyramid type wave absorber as shown in Fig. 12 and that operates at frequencies above the upper limit of the wave absorber of the present invention, either to the front or between parallel flat of the present invention enables compounding to further broaden the band.
  • Fig. 14 is effective for horizontal and/or vertical polarized waves.
  • Fig. 15 shows another embodiment of the present invention, in which the shape of the end surfaces of the ferrite magnetic body is formed into a cylindrical shape so that it forms a perpendicular unit.
  • This perpendicular unit uses ferrite having a thickness t m so that one side is a, and so that the other side is b.
  • This perpendicular unit is formed as a cylindrical block with a height d.
  • Fig. 16 shows one portion of a wave absorber of a required area and in which the cylindrical blocks of Fig. 15 are overlapped in the direction of the one side a, and in the direction of the other side b.
  • the magnetic material used in the present invention can be ferrite of NiZn, MgZn or MnZn or the like, and moreover, can be materials, such as ferrite powder is mixed with glass, ceramic, rubber, plastic, carbon, paper, or fiber, etc.

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  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
  • Aerials With Secondary Devices (AREA)
EP91300505A 1990-01-25 1991-01-23 Absorbeur d'ondes à large bande Expired - Lifetime EP0439337B1 (fr)

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
JP15798/90 1990-01-25
JP1579890 1990-01-25
JP2023818A JPH03228398A (ja) 1990-02-02 1990-02-02 フェライト電波吸収体
JP23818/90 1990-02-02
JP150690/90 1990-06-08
JP2150690A JPH077886B2 (ja) 1990-01-25 1990-06-08 ブロック形磁性体を用いた電波吸収体
JP2162403A JP2509369B2 (ja) 1990-06-20 1990-06-20 広帯域電波吸収装置
JP162403/90 1990-06-20

Publications (3)

Publication Number Publication Date
EP0439337A2 true EP0439337A2 (fr) 1991-07-31
EP0439337A3 EP0439337A3 (en) 1991-11-06
EP0439337B1 EP0439337B1 (fr) 1995-04-05

Family

ID=27456451

Family Applications (1)

Application Number Title Priority Date Filing Date
EP91300505A Expired - Lifetime EP0439337B1 (fr) 1990-01-25 1991-01-23 Absorbeur d'ondes à large bande

Country Status (3)

Country Link
EP (1) EP0439337B1 (fr)
KR (1) KR0130755B1 (fr)
DE (1) DE69108577T2 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996000992A1 (fr) * 1994-06-28 1996-01-11 Gec-Marconi Limited Dispositifs d'absorption d'energie
EP0694987A1 (fr) * 1994-07-25 1996-01-31 Michiharu Takahashi Absorbeur à large bande pour ondes radioélectriques
EP0724309A1 (fr) * 1995-01-24 1996-07-31 Mitsubishi Cable Industries, Ltd. Absorbeur d'ondes
WO2000041270A1 (fr) * 1999-01-04 2000-07-13 Marconi Caswell Limited Structure dotee de proprietes magnetiques
WO2003032438A1 (fr) * 2001-10-08 2003-04-17 Marconi Uk Intellectual Property Ltd Structures possedant des proprietes magnetiques
CN107809006A (zh) * 2017-10-22 2018-03-16 南京理工大学 基于透明导电薄膜的透明超宽带微波吸波器

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1838345A (zh) * 2005-03-22 2006-09-27 株式会社东芝 天线装置及用于制造天线装置的方法
EA017646B1 (ru) 2007-07-09 2013-02-28 Клеаруотер Холдингс, Лтд. Электромагнитное устройство модульной конструкции с изолированными съёмными обмотками и самоудерживающимися инерционными магнитными подшипниками
KR101944959B1 (ko) * 2017-10-12 2019-02-01 국방과학연구소 전파흡수체를 이용하여 제작된 스텔스 구조물

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB776158A (en) * 1953-03-28 1957-06-05 Werner Genest Ges Fur Isolieru Improvements in or relating to absorbers for radio waves
GB1170420A (en) * 1966-12-30 1969-11-12 Eltro Gmbh Improvements in or relating to a Spatial Absorber for Electromagnetic Waves
US4118704A (en) * 1976-04-07 1978-10-03 Tdk Electronics Co., Ltd. Electromagnetic wave-absorbing wall

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB776158A (en) * 1953-03-28 1957-06-05 Werner Genest Ges Fur Isolieru Improvements in or relating to absorbers for radio waves
GB1170420A (en) * 1966-12-30 1969-11-12 Eltro Gmbh Improvements in or relating to a Spatial Absorber for Electromagnetic Waves
US4118704A (en) * 1976-04-07 1978-10-03 Tdk Electronics Co., Ltd. Electromagnetic wave-absorbing wall

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IEEE TRANSACTIONS ON BROADCASTING. vol. 25, no. 4, December 1979, NEW YORK US pages 143 - 146; TAKIZAWA: 'REDUCTION OF GHOST SIGNAL BY USE OF MAGNETIC ABSORBING MATERIAL ON WALLS ' *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996000992A1 (fr) * 1994-06-28 1996-01-11 Gec-Marconi Limited Dispositifs d'absorption d'energie
EP0694987A1 (fr) * 1994-07-25 1996-01-31 Michiharu Takahashi Absorbeur à large bande pour ondes radioélectriques
US5617096A (en) * 1994-07-25 1997-04-01 Takahashi; Michiharu Broad-band radio wave absorber
EP0724309A1 (fr) * 1995-01-24 1996-07-31 Mitsubishi Cable Industries, Ltd. Absorbeur d'ondes
WO2000041270A1 (fr) * 1999-01-04 2000-07-13 Marconi Caswell Limited Structure dotee de proprietes magnetiques
US6608811B1 (en) 1999-01-04 2003-08-19 Marconi Caswell Limited Structure with magnetic properties
AU767300B2 (en) * 1999-01-04 2003-11-06 Marconi Caswell Limited Structure with magnetic properties
WO2003032438A1 (fr) * 2001-10-08 2003-04-17 Marconi Uk Intellectual Property Ltd Structures possedant des proprietes magnetiques
GB2396969A (en) * 2001-10-08 2004-07-07 Marconi Uk Intellectual Prop Structures with magnetic properties
CN107809006A (zh) * 2017-10-22 2018-03-16 南京理工大学 基于透明导电薄膜的透明超宽带微波吸波器

Also Published As

Publication number Publication date
DE69108577D1 (de) 1995-05-11
EP0439337A3 (en) 1991-11-06
DE69108577T2 (de) 1996-01-11
KR0130755B1 (ko) 1998-04-14
EP0439337B1 (fr) 1995-04-05

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