CA2163516C - System for absorbing electromagnetic waves and method of manufacturing this system - Google Patents
System for absorbing electromagnetic waves and method of manufacturing this systemInfo
- Publication number
- CA2163516C CA2163516C CA002163516A CA2163516A CA2163516C CA 2163516 C CA2163516 C CA 2163516C CA 002163516 A CA002163516 A CA 002163516A CA 2163516 A CA2163516 A CA 2163516A CA 2163516 C CA2163516 C CA 2163516C
- Authority
- CA
- Canada
- Prior art keywords
- surface resistance
- layer
- sheet
- carrier
- semi
- 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.)
- Expired - Fee Related
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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
- 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
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0001—Rooms or chambers
- H05K9/0003—Shielded walls, floors, ceilings, e.g. wallpaper, wall panel, electro-conductive plaster, concrete, cement, mortar
Abstract
In order to absorb electromagnetic waves in a measurement chamber, the sidewallsand the ceiling of the chamber are lined with contiguous pyramids (20). The pyramid vertices point into the chamber. The structure element (20) has a frame (22) formed by bars made of an electrically insulating glass fibre material and an outer skin (24). The outer skin is cut out of a surface resistance material web. The surface resistance material web is produced by continuously or almost continuously coating a mechanically flexible support web with an electroconductive layer made of a metallic material.
Description
SYSTEM FOR ABSORBING ELECTROMAGNETIC WAVES
AND METHOD OF MANUFACTURING THIS SYSTEM
The invention relates to a system for the broad band absorption of electromagnetic waves in accordance with the preamble of Claims 1 and 2 and to methods of manufacturing a system for the broad band absorption of electromagnetic waves in accordance with the preamble of Claims 21, 22 and 23.
Such absorption systems are principally used as non-reflective linings of chambers for testing electromagnetic tolerance (EMT).
EP-A 018873 discloses an absorption element for electromagnetic waves which comprises a three dimensional hollow body of rectangular cross-section. The four side walls each have a dielectric substrate and an external surface coating whose specific resistance varies from one end to the other end of the side wall in order to be able to absorb electromagnetic waves with a certain band width.
In another known absorber construction, effective absorption of electromagnetic waves over a predetermined frequency range is supposed to be achieved by increasing the layer thickness and by electromagnetic material parameters designed in dependence on frequency. Such resonance absorbers with large layer thicknesses have a correspondingly large weight and result in relatively high costs and complex static structural features. Their broad band characteristics are not adequate for current EMT test chambers despite the high complexity.
la 2163516 EP-A 0369174 discloses a block-shaped absorption body.
This absorption body includes a sandwich arrangement of carrier material plates, between which thin surface resistance layers are embedded.
A block-shaped absorption body disclosed in WO-A-9105376 includes a sandwich arrangement of thick carrier material layers, between which thin surface resistance layers are embedded. In order to produce an absorption gradient in the direction of the incident waves, the surface resistance layers are coated with different materials or only partially coated with the aid of masks. Such massive absorption elements require a great deal of space and materials.
DE-B 1254720 and BE-A 684834 describe a system in which a plurality of hollow pyramids are arranged on a wall in abutment with one another. The hollow pyramids are coated on their external and internal surfaces with a conductive lacquer. The conductive lacquer layer is either sprayed directly onto the three dimensional carrier body or produced by dipping the three dimensional body.
In the known systems, either the operational characteristics, for instance the band width and the degree of absorption, are inadequate or the manufacture of the absorption system is complex and ex~ensive.
- Translator's note: The words appearing above which are underlined do not appear on the German language replacement page la but have been included above so that a complete translation of the sentence bridging replacement page la and original page 2 is present.
DE-B 1254720 described a system in which a plurality of hollow pyramids are arranged on a wall in abutment with one another. The hollow pyramids are coated on their external and internal surfaces with a conductive lacquer.
The conductive lacquer layer is either sprayed directly onto the three dimensional carrier body or produced by dipping the three dimensional body.
In the known systems, either the operational character-istics, for instance the band width and the degree of absorption, are inadequate or the manufacture of the absorption system is complex and expensive.
It is therefore the object of the invention to combine a high degree of absorption efficiency over a large band width with the advantages of manufacturing in a simple manner which may be automated.
This object is solved in accordance with the invention by the apparatus features of claims 1 or 2 and as regards the method by the features of claims 21,22 or 23.
As a result of the invention it is possible for the first time to absorb a broad band spectrum of electromagnetic radiation with the aid of lightweight and thin surface resistance layer components which may be economically manufactured. The invention is based on the recognition that thin surface resistance sheets have an absorptive effect on electromagnetic radiation with differing wave lengths, even with a uniform distribution of the surface resistance, if they are arranged in a chamber subjected to the, electromagnetic radiation in a predetermined and/or statistical three dimensional geometry. The broad band characteristics are therefore produced by the particular geometrical arrangement of the thin surface resistance layers in the chamber. Both the powder coated or deposited layer of electrically conductive or semi-conductive layer and also the electrically conductive organic layer make a uniform and constant specific surface resistance distribution possible. The absorption characteristics may be adjusted in a reproducible manner.
Since the surface resistance layers are very thin, they advantageously have a low weight and are correspondingly economical to manufacture. The ratio of absorption performance/unit weight of the system is particularly high so that the device in accordance with the invention has an ecological tolerance which has not previously been achieved.
An important aspect of the manufacture of the absorber system in accordance with the invention is that any desired number of absorption elements can be produced from a surface resistance sheet. The carrier sheet or the surface resistance sheet produced after the coating can, for instance, have a breadth of 0.8m and a length of lO,OOOm. The finished surface resistance sheet may be rolled up at the end of the sheet production process into a compact sheet supply. The surface resistance sections required for the geometrical carrier structures are then - cut to size, or stamped out or shaped in some other suitable manner from the roll of material, positioned on the carrier structure and secured. The desired spatial, for instance pyramid-shaped absorber structure is thereby produced. The chamber (in the wall and ceiling regions) subjected to the electromagnetic waves is then lined with such absorber pyramids.
An important embodiment of the invention is characterised 21 635I ~
in that the carrier layer and/or the surface resistance layer is provided with a fire protective layer of electromagnetically inert material, for instance of ceramic, mineral and/or glass-like material.
The surface resistance layer can be a powder coated or deposited metallic or semi-conductor layer. The metallic or semi-conductor materials are preferably selected from the following groups of elements: aluminium, chromium, iron, indium, nickel, antimony, tin, tantalum, titanium and zinc. One or more of these elements are preferably vapour deposited or sputtered onto the carrier sheet, preferably in a vacuum, optionally with the addition of reactive gases, such as oxygen. The vapour deposition method is known per se for the manufacture of aluminium coatings ca.30nm thick on polymer films for foodstuff packaging and can be used in the context of the invention with corresponding advantages.
A polymer film or paper sheet with a thickness <5mm, preferably ~500~m, is sufficient as the carrier layer.
The thickness of the conductive or semi-conductive layer is 5nm - 1000nm, preferably 10nm - 100nm.
In a preferred embodiment the surface resistance layers extend in sections at different angles. This is the case in the wedge-, cone- or pyramid-shaped systems mentioned above. Alternatively, the surface resistance layers can, however, also be arranged, for instance clamped, in a plurality of different planes. The absorption spectrum in the last system referred to above is achieved by the differe~t and preferably parallel absorption planes.
An alternative system, with which principally heavily 2163~16 profiled wall regions can be lined in a broad band absorptive manner, is characterised in a further aspect of the invention in that a three-dimensional absorber structure comprises a receiving container with a filler which is constituted by surface resistance layers in sheet form, preferably bent or creased a number of times.
Heavily profiled wall regions can form at least one side wall of the receiving container. Another side wall of the receiving container can be formed by a simple cover which is scarcely mechanically loaded by the creased surface resistance sheets.
In an alternative embodiment the surface resistance layer can be further processed into bulk absorber material. If - 15 the surface resistance layer is cut up, e.g. into long, narrow strips, a bulk filler is produced for absorber applications which can exhibit the same absorption performance, with a substantially lower material requirement, as conventional absorber materials which are doped with conductive particles instead of the strips.
The arrangement of the narrow strips in the space can be effected not only in ordered structures, e.g. in the manner of a grid, but also statistically distributed, e.g. as in a particulate filler.
The surface resistance layer, e.g. a coated polyethylene film, can also advantageously be further processed by the simple process of thermal shaping and welding. For instance, a thicker absorbent structure may be produced in this manner with chambers and hollow spaces which can be structured in a manner similar to packaging materials of polymer films containing air chambers which were developed for shock-absorbing transport of sensitive products and are known by the name air cushion films.
The positioning and fastening can advantageously be effected particularly simply by pressure differentials, as in an inflatable building, so to speak by "inflating~
the absorber, or by means of a framework, similar to that in tent constructions.
Another embodiment of the invention is characterised in that a plurality of air- or gas-filled hollow body structures are closely jointed together and/or connected together with an outer skin constructed as a surface resistance layer and arranged on at least one wall of the chamber. The closed hollow body structures serving as the absorption elements can have different, for instance statistical, surface shapes.
Other advantageous embodiments of the invention are characterised in the dependent claims.
The invention will be described below in more detail with reference to exemplary embodiments which are schematically illustrated in the drawings, in which:
Fig. 1 is a schematic illustration of a station for producing a surface resistance layer from a carrier sheet with a powder coated metal layer;
Fig. 2A shows a section on a substantially increased scale of a surface resistance layer produced in accordance with Figure l;
Fig. 2B shows a section, also on an enlarged scale, of a surface resistance layer from an organic conductor;
Fig. 3A is a scrap view of an exemplary embodiment of an absorber structure with a pyramidal geometry;
Fig. 3B shows an absorber structure similar to that of Fig. 3A with a carrier structure of different construction; and Fig. 4 is a schematic side view of the interior of a chamber subjected to electromagnetic waves, the side and top walls of which are virtually completely covered with pyramidal absorber structures.
A particularly economical method of manufacturing the active component of the absorption system in accordance with the invention, namely a surface resistance layer 1, will firstly be described with reference to the illustration of Fig. 1. A thin carrier sheet 11 of polymer film or paper of a thickness of 5 - 500~m is withdrawn from a supply roll 2, deflected and moved in the direction of the arrow A into a vapour deposition zone beneath a vapour deposition device 3. Aluminium with oxidative components is applied in the vapour deposition zone in a reactive oxygen atmosphere. An aluminium layer can be vapour coated either in the illustrated manner on one side or on both sides of the carrier sheet 11. In the described exemplary embodiment the A1 layer 12 has a thickness of only ca.12 - 40nm. A
lacquer seal on the resistive layer 12 can be dried in a heating chamber 4. The sheet 1 is thereafter wound up onto a,winding roller 5. The value of the surface resistance can be adjusted by variation of the process parameters to a desired value, for instance 150 Ohms.
An enlarged view of a section of the surface resistance layer 1 is shown in Figure 2A. As may be seen, the carrier layer 11 can also be covered on both sides with thin, conductive or semi-conductive layers 12 and 13 constituting surface resistances. A double sided coating increases the efficiency of the absorption structure produced from the surface resistance layer 1 since the absorbtivity of the structure on both sides of the layer can be matched to the electromagnetic radiation which is present there. A fire protective layer of a non-inflammable or flame resistant, preferably electrically and electromagnetically substantially inert material, e.g. mineral wool, ceramic material and/or glass, can be provided in addition to or as the layer 13.
As is known to the expert, other coating methods, for instance powder coating (sputtering) or continuous screen or roller printing methods, can be used instead of the described vapour deposition process. A layer comprising, for instance, an organic conductor can also be deposited in this manner.
An alternative embodiment of the surface resistance layer is shown schematically in Figure 2B. In this alternative embodiment the surface resistance layer lA comprises a sheet, preferably of plastics material, in which conductive or semi-conductive fine particles 14 are embedded in a distribution which is suitable for absorption purposes. The conductive or semi-conductive particles can also comprise plastics material.
Intrinsically conductive polymers, for instance, can be used.
A schematic sectional view through a pyramidal element 20 of the absorption device in accordance with the invention is shown in Figure 3A. The structural element 20 comprises a rod frame 22 with a square base and four rods of electrically insulating glass fibre material defining the sides of the pyramid and an outer skin 24. The latter is produced from a blank of the sheet material 1 or lA. In an exemplary embodiment which has been made in practice, a surface resistance layer 1 is placed on the rod frame 22 and fixed in position after suitable cutting to size and thermal welding of the film constituting the carrier sheet 11. The pyramid constituting the absorption element 20 had a height of 1.50mm and an open base surface of 0.35 x 0.35m2. As may easily be seen, numerous geometrical structures may be simply made up from a suitable support frame and surface resistance blanks. The apex should be relatively pointed with conical, wedge or pyramid-shaped structures and elements and have an apex angle 26 in the range between 5 and 50, preferably between 8 and 25.
Figure 3B shows a similar absorption element 21 to that (20) of Figure 3A. The single difference is that the outer skin 24 of the pyramid is not supported by a carrier frame 22 but is laminated onto a pyramidal, self-supporting hollow body 23 of a suitable plastics materialor of cardboard. The outer skin 24 can, however, also be constructed as an inflatable component in the manner of an inflatable building in a constructional alternative which is not shown in the drawing. The skin 24 constituting the absorption structure is subjected to a small pressure differential which holds the outer skin 24 in its pyramidal geometry.
Instead of the pyramidal shape illustrated in Figures 3A
2163~16 and 3B, a combined cone-pyramid frustum shape can also be provided. The tip situated closest to the apex is conical and the base plane is of square shape in order to cover a larger absorption surface with corresponding structural elements, without spaces or only with minimal spaces.
A vertical section through an EMT test chamber, whose side wall and ceiling are lined practically gaplessly with pyramidal, abutting absorber structures 20 is shown schematically in Figure 4. An antenna arrangement 31 and the device 32 to be tested are shown in the test chamber 30. As may be seen, the lining of the test chamber 30 with geometrically distributed surface resistances ensures a virtually total, non-reflective absorption of the field energy so that optimum test results are ensured.
Numerous modifications are possible within the scope of the inventive concept. The selection of the materials of the carrier and surface resistances and the geometrical dimensions of the sheets and structures can be matched to the conditions of use. Transparent surface resistance layers are produced, for instance, by the use of indium-tin-oxide.
AND METHOD OF MANUFACTURING THIS SYSTEM
The invention relates to a system for the broad band absorption of electromagnetic waves in accordance with the preamble of Claims 1 and 2 and to methods of manufacturing a system for the broad band absorption of electromagnetic waves in accordance with the preamble of Claims 21, 22 and 23.
Such absorption systems are principally used as non-reflective linings of chambers for testing electromagnetic tolerance (EMT).
EP-A 018873 discloses an absorption element for electromagnetic waves which comprises a three dimensional hollow body of rectangular cross-section. The four side walls each have a dielectric substrate and an external surface coating whose specific resistance varies from one end to the other end of the side wall in order to be able to absorb electromagnetic waves with a certain band width.
In another known absorber construction, effective absorption of electromagnetic waves over a predetermined frequency range is supposed to be achieved by increasing the layer thickness and by electromagnetic material parameters designed in dependence on frequency. Such resonance absorbers with large layer thicknesses have a correspondingly large weight and result in relatively high costs and complex static structural features. Their broad band characteristics are not adequate for current EMT test chambers despite the high complexity.
la 2163516 EP-A 0369174 discloses a block-shaped absorption body.
This absorption body includes a sandwich arrangement of carrier material plates, between which thin surface resistance layers are embedded.
A block-shaped absorption body disclosed in WO-A-9105376 includes a sandwich arrangement of thick carrier material layers, between which thin surface resistance layers are embedded. In order to produce an absorption gradient in the direction of the incident waves, the surface resistance layers are coated with different materials or only partially coated with the aid of masks. Such massive absorption elements require a great deal of space and materials.
DE-B 1254720 and BE-A 684834 describe a system in which a plurality of hollow pyramids are arranged on a wall in abutment with one another. The hollow pyramids are coated on their external and internal surfaces with a conductive lacquer. The conductive lacquer layer is either sprayed directly onto the three dimensional carrier body or produced by dipping the three dimensional body.
In the known systems, either the operational characteristics, for instance the band width and the degree of absorption, are inadequate or the manufacture of the absorption system is complex and ex~ensive.
- Translator's note: The words appearing above which are underlined do not appear on the German language replacement page la but have been included above so that a complete translation of the sentence bridging replacement page la and original page 2 is present.
DE-B 1254720 described a system in which a plurality of hollow pyramids are arranged on a wall in abutment with one another. The hollow pyramids are coated on their external and internal surfaces with a conductive lacquer.
The conductive lacquer layer is either sprayed directly onto the three dimensional carrier body or produced by dipping the three dimensional body.
In the known systems, either the operational character-istics, for instance the band width and the degree of absorption, are inadequate or the manufacture of the absorption system is complex and expensive.
It is therefore the object of the invention to combine a high degree of absorption efficiency over a large band width with the advantages of manufacturing in a simple manner which may be automated.
This object is solved in accordance with the invention by the apparatus features of claims 1 or 2 and as regards the method by the features of claims 21,22 or 23.
As a result of the invention it is possible for the first time to absorb a broad band spectrum of electromagnetic radiation with the aid of lightweight and thin surface resistance layer components which may be economically manufactured. The invention is based on the recognition that thin surface resistance sheets have an absorptive effect on electromagnetic radiation with differing wave lengths, even with a uniform distribution of the surface resistance, if they are arranged in a chamber subjected to the, electromagnetic radiation in a predetermined and/or statistical three dimensional geometry. The broad band characteristics are therefore produced by the particular geometrical arrangement of the thin surface resistance layers in the chamber. Both the powder coated or deposited layer of electrically conductive or semi-conductive layer and also the electrically conductive organic layer make a uniform and constant specific surface resistance distribution possible. The absorption characteristics may be adjusted in a reproducible manner.
Since the surface resistance layers are very thin, they advantageously have a low weight and are correspondingly economical to manufacture. The ratio of absorption performance/unit weight of the system is particularly high so that the device in accordance with the invention has an ecological tolerance which has not previously been achieved.
An important aspect of the manufacture of the absorber system in accordance with the invention is that any desired number of absorption elements can be produced from a surface resistance sheet. The carrier sheet or the surface resistance sheet produced after the coating can, for instance, have a breadth of 0.8m and a length of lO,OOOm. The finished surface resistance sheet may be rolled up at the end of the sheet production process into a compact sheet supply. The surface resistance sections required for the geometrical carrier structures are then - cut to size, or stamped out or shaped in some other suitable manner from the roll of material, positioned on the carrier structure and secured. The desired spatial, for instance pyramid-shaped absorber structure is thereby produced. The chamber (in the wall and ceiling regions) subjected to the electromagnetic waves is then lined with such absorber pyramids.
An important embodiment of the invention is characterised 21 635I ~
in that the carrier layer and/or the surface resistance layer is provided with a fire protective layer of electromagnetically inert material, for instance of ceramic, mineral and/or glass-like material.
The surface resistance layer can be a powder coated or deposited metallic or semi-conductor layer. The metallic or semi-conductor materials are preferably selected from the following groups of elements: aluminium, chromium, iron, indium, nickel, antimony, tin, tantalum, titanium and zinc. One or more of these elements are preferably vapour deposited or sputtered onto the carrier sheet, preferably in a vacuum, optionally with the addition of reactive gases, such as oxygen. The vapour deposition method is known per se for the manufacture of aluminium coatings ca.30nm thick on polymer films for foodstuff packaging and can be used in the context of the invention with corresponding advantages.
A polymer film or paper sheet with a thickness <5mm, preferably ~500~m, is sufficient as the carrier layer.
The thickness of the conductive or semi-conductive layer is 5nm - 1000nm, preferably 10nm - 100nm.
In a preferred embodiment the surface resistance layers extend in sections at different angles. This is the case in the wedge-, cone- or pyramid-shaped systems mentioned above. Alternatively, the surface resistance layers can, however, also be arranged, for instance clamped, in a plurality of different planes. The absorption spectrum in the last system referred to above is achieved by the differe~t and preferably parallel absorption planes.
An alternative system, with which principally heavily 2163~16 profiled wall regions can be lined in a broad band absorptive manner, is characterised in a further aspect of the invention in that a three-dimensional absorber structure comprises a receiving container with a filler which is constituted by surface resistance layers in sheet form, preferably bent or creased a number of times.
Heavily profiled wall regions can form at least one side wall of the receiving container. Another side wall of the receiving container can be formed by a simple cover which is scarcely mechanically loaded by the creased surface resistance sheets.
In an alternative embodiment the surface resistance layer can be further processed into bulk absorber material. If - 15 the surface resistance layer is cut up, e.g. into long, narrow strips, a bulk filler is produced for absorber applications which can exhibit the same absorption performance, with a substantially lower material requirement, as conventional absorber materials which are doped with conductive particles instead of the strips.
The arrangement of the narrow strips in the space can be effected not only in ordered structures, e.g. in the manner of a grid, but also statistically distributed, e.g. as in a particulate filler.
The surface resistance layer, e.g. a coated polyethylene film, can also advantageously be further processed by the simple process of thermal shaping and welding. For instance, a thicker absorbent structure may be produced in this manner with chambers and hollow spaces which can be structured in a manner similar to packaging materials of polymer films containing air chambers which were developed for shock-absorbing transport of sensitive products and are known by the name air cushion films.
The positioning and fastening can advantageously be effected particularly simply by pressure differentials, as in an inflatable building, so to speak by "inflating~
the absorber, or by means of a framework, similar to that in tent constructions.
Another embodiment of the invention is characterised in that a plurality of air- or gas-filled hollow body structures are closely jointed together and/or connected together with an outer skin constructed as a surface resistance layer and arranged on at least one wall of the chamber. The closed hollow body structures serving as the absorption elements can have different, for instance statistical, surface shapes.
Other advantageous embodiments of the invention are characterised in the dependent claims.
The invention will be described below in more detail with reference to exemplary embodiments which are schematically illustrated in the drawings, in which:
Fig. 1 is a schematic illustration of a station for producing a surface resistance layer from a carrier sheet with a powder coated metal layer;
Fig. 2A shows a section on a substantially increased scale of a surface resistance layer produced in accordance with Figure l;
Fig. 2B shows a section, also on an enlarged scale, of a surface resistance layer from an organic conductor;
Fig. 3A is a scrap view of an exemplary embodiment of an absorber structure with a pyramidal geometry;
Fig. 3B shows an absorber structure similar to that of Fig. 3A with a carrier structure of different construction; and Fig. 4 is a schematic side view of the interior of a chamber subjected to electromagnetic waves, the side and top walls of which are virtually completely covered with pyramidal absorber structures.
A particularly economical method of manufacturing the active component of the absorption system in accordance with the invention, namely a surface resistance layer 1, will firstly be described with reference to the illustration of Fig. 1. A thin carrier sheet 11 of polymer film or paper of a thickness of 5 - 500~m is withdrawn from a supply roll 2, deflected and moved in the direction of the arrow A into a vapour deposition zone beneath a vapour deposition device 3. Aluminium with oxidative components is applied in the vapour deposition zone in a reactive oxygen atmosphere. An aluminium layer can be vapour coated either in the illustrated manner on one side or on both sides of the carrier sheet 11. In the described exemplary embodiment the A1 layer 12 has a thickness of only ca.12 - 40nm. A
lacquer seal on the resistive layer 12 can be dried in a heating chamber 4. The sheet 1 is thereafter wound up onto a,winding roller 5. The value of the surface resistance can be adjusted by variation of the process parameters to a desired value, for instance 150 Ohms.
An enlarged view of a section of the surface resistance layer 1 is shown in Figure 2A. As may be seen, the carrier layer 11 can also be covered on both sides with thin, conductive or semi-conductive layers 12 and 13 constituting surface resistances. A double sided coating increases the efficiency of the absorption structure produced from the surface resistance layer 1 since the absorbtivity of the structure on both sides of the layer can be matched to the electromagnetic radiation which is present there. A fire protective layer of a non-inflammable or flame resistant, preferably electrically and electromagnetically substantially inert material, e.g. mineral wool, ceramic material and/or glass, can be provided in addition to or as the layer 13.
As is known to the expert, other coating methods, for instance powder coating (sputtering) or continuous screen or roller printing methods, can be used instead of the described vapour deposition process. A layer comprising, for instance, an organic conductor can also be deposited in this manner.
An alternative embodiment of the surface resistance layer is shown schematically in Figure 2B. In this alternative embodiment the surface resistance layer lA comprises a sheet, preferably of plastics material, in which conductive or semi-conductive fine particles 14 are embedded in a distribution which is suitable for absorption purposes. The conductive or semi-conductive particles can also comprise plastics material.
Intrinsically conductive polymers, for instance, can be used.
A schematic sectional view through a pyramidal element 20 of the absorption device in accordance with the invention is shown in Figure 3A. The structural element 20 comprises a rod frame 22 with a square base and four rods of electrically insulating glass fibre material defining the sides of the pyramid and an outer skin 24. The latter is produced from a blank of the sheet material 1 or lA. In an exemplary embodiment which has been made in practice, a surface resistance layer 1 is placed on the rod frame 22 and fixed in position after suitable cutting to size and thermal welding of the film constituting the carrier sheet 11. The pyramid constituting the absorption element 20 had a height of 1.50mm and an open base surface of 0.35 x 0.35m2. As may easily be seen, numerous geometrical structures may be simply made up from a suitable support frame and surface resistance blanks. The apex should be relatively pointed with conical, wedge or pyramid-shaped structures and elements and have an apex angle 26 in the range between 5 and 50, preferably between 8 and 25.
Figure 3B shows a similar absorption element 21 to that (20) of Figure 3A. The single difference is that the outer skin 24 of the pyramid is not supported by a carrier frame 22 but is laminated onto a pyramidal, self-supporting hollow body 23 of a suitable plastics materialor of cardboard. The outer skin 24 can, however, also be constructed as an inflatable component in the manner of an inflatable building in a constructional alternative which is not shown in the drawing. The skin 24 constituting the absorption structure is subjected to a small pressure differential which holds the outer skin 24 in its pyramidal geometry.
Instead of the pyramidal shape illustrated in Figures 3A
2163~16 and 3B, a combined cone-pyramid frustum shape can also be provided. The tip situated closest to the apex is conical and the base plane is of square shape in order to cover a larger absorption surface with corresponding structural elements, without spaces or only with minimal spaces.
A vertical section through an EMT test chamber, whose side wall and ceiling are lined practically gaplessly with pyramidal, abutting absorber structures 20 is shown schematically in Figure 4. An antenna arrangement 31 and the device 32 to be tested are shown in the test chamber 30. As may be seen, the lining of the test chamber 30 with geometrically distributed surface resistances ensures a virtually total, non-reflective absorption of the field energy so that optimum test results are ensured.
Numerous modifications are possible within the scope of the inventive concept. The selection of the materials of the carrier and surface resistances and the geometrical dimensions of the sheets and structures can be matched to the conditions of use. Transparent surface resistance layers are produced, for instance, by the use of indium-tin-oxide.
Claims (27)
1. System for the broad band absorption of electromagnetic waves, whereby a plurality of thin surface resistance layers (1;1A;24) are arranged three-dimensionally in a chamber (30) subjected to the electromagnetic waves, whereby the surface resistance layer (1) has a carrier layer (11) and at least one layer (12) of electrically conductive or semi-conductive material applied to the carrier layer, characterised in that the carrier layer is constructed as a mechanically flexible layer with a layer thickness less than 5 mm, and that the layer (12) of electrically conductive or semi-conductive material is a continuously or quasi-continuously powder coated or deposited layer with a thickness of 5 nm to 1000 nm and has a uniform and constant surface resistance distribution.
2. System for the broad band absorption of electromagnetic waves, whereby a plurality of mechanically flexible surface resistance layers (1;1A;24) are three-dimensionally arranged in a chamber (30) subjected to the electromagnetic waves, characterised in that the surface resistance layer (1A) is formed from a single layer acting as a carrier with a layer thickness less than 5 mm, comprises an organic conductor and has a uniform and constant surface resistance distribution.
3. System as claimed in claim 1 or 2, characterised in that the surface resistance layers (1;1A) are constituted by electrically conductive particles on and/or in a plastic or paper sheet.
4. System as claimed in claim 3, characterised in that the surface resistance layer (1) comprises a plastic or paper sheet (11) with an electrically conductive or semi-conductive layer (12) applied uniformly to at least one side.
5. System as claimed in one of claims 1 to 4, characterised in that the surface resistance values of the surface resistance layers (1;1A) are between 0.01 Ohm per square metre and 20 kOhm per square metre, preferably between 100 Ohm per square metre and 1kOhm per square metre.
6. System as claimed in claims 1 to 5, characterised in that the surface resistance layer (1) includes a carrier layer of polymer film or paper of a thickness < 5mm, preferably 5 - 5000µm.
7. System as claimed in one of claims 1 to 6, characterised in that the surface resistance layer includes a conductive or a semi-conductive layer of a pure metal, a metal alloy or a semi-conductor with at least one of the elements Al, Cr, Fe, In, Ni, Sb, Sn, Ta, Ti and Zn.
8. System as claimed in Claim 7, characterised in that the conductive or semi-conductive layer (12) has a thickness of 5 nm to 1000 nm, preferably 10 nm - 200 nm.
9. System as claimed in one of Claims 1 to 8, characterised in that at least one of the surface resistance (1; 1A) and carrier layers (11) is provided with at least one closed fire protective layer of a flame-resistant material.
10. System as claimed in Claim 9, characterised in that the fire protective layer comprises an electrically or electromagnetically substantially inert material, e.g.
mineral or ceramic material and/or glass.
mineral or ceramic material and/or glass.
11. System as claimed in one of Claims 1 to 10, characterised in that the surface resistance layers (1, 1A) are disposed in a plurality of different planes.
12. System as claimed in one of Claims 1 to 11, characterised in that the surface resistance layers (1, 1A) are applied to at least one wedge, cone, pyramid or step-shaped carrier (22, 23).
13. System as claimed in Claim 12, characterised in that the carrier comprises a sufficiently shape stable hollow body (23), secured to whose side surfaces are sections of the surface resistance layer (24) cut fittingly to size.
14. System as claimed in Claim 12, characterised in that the carrier comprises a carrier frame (22) which has struts at at least the transition edges between two adjacent planes of surface resistance layers, for instance between two side surfaces of a pyramid.
15. System as claimed in Claim 14, characterised in that the surface resistance layers (1; 1A) comprise flexible material in sheet form and the outer surfaces of the carrier are covered with the sheet material.
16. System as claimed in Claim 11, characterised in that a plurality of sheets with surface resistance layers (1;
1A) are secured in at least partially overlapping relationship in different approximately parallel planes.
1A) are secured in at least partially overlapping relationship in different approximately parallel planes.
17. System as claimed in one of Claims 1 to 10, characterised in that a three-dimensional absorber structure comprises a receiving container with a filler which is constituted by surface resistance layers in sheet form, preferably bent a number of times.
18. System as claimed in Claim 17, characterised in that the surface resistance layer sections in sheet form are disposed in an arbitrary arrangement in the hollow space.
19. System as claimed in one of Claims 1 to 18, characterised in that the side and top walls of the chamber (30) subjected to the electromagnetic waves are substantially completely occupied by three-dimensional, e.g. pyramidal, absorber elements (20, 21).
20. System as claimed in one of Claims 12 to 19, characterised in that the absorber pyramids (20; 21) have acute angled apexes with apex angles in the region between 5 and 50°, preferably 8 to 25°.
21. Method of manufacturing a system for the broad band absorption of electromagnetic waves, whereby a surface resistance sheet (1) is produced by continuously or quasi-continuously coating a mechanically flexible carrier sheet (11) with an electrically conductive layer (12) of a metallic or semi-conductive material; and whereby blanks are formed from the surface resistance sheet (1) for a plurality of two-dimensional surface resistance sections; characterised in that a thin carrier sheet is used, onto which the electrically conductive layer is thinly applied; that the surface resistance sheet is given a substantially uniform and constant surface resistance; that three-dimensional structures (22; 23) are covered with the surface resistance sections in order to form pyramid-, wedge-, cone- or step-shaped absorber elements.
22. Method of manufacturing a system for the broad band absorption of electromagnetic waves, whereby a surface resistance sheet (1) is produced by continuously or quasi-continuously coating a mechanically flexible carrier sheet (11) with an electrically conductive layer (12) of a metallic or semi-conductive material; and whereby blanks are formed from the surface resistance sheet (1) for a plurality of two-dimensional surface resistance sections; characterised in that a thin carrier sheet is used, onto which the electrically conductive layer is thinly applied; that the surface resistance sheet is given a substantially uniform and constant surface resistance; that thereafter a plurality of two-dimensional surface resistance sections are arranged spaced from one another and substantially parallel to one another and fixed in position.
23. Method of manufacturing a system for the broad band absorption of electromagnetic waves, whereby a surface resistance sheet (1) is produced by continuously or quasi-continuously coating a mechanically flexible carrier sheet (11) with an electrically conductive layer (12) of a metallic or semi-conductive material; and, whereby the surface resistance sheet is divided into sections, characterised in that a thin carrier sheet is used, onto which the electrically conductive layer is thinly applied; that the surface resistance sheet is given a substantially uniform and constant surface resistance; and that a plurality of the produced sections is used as filling or additive materials for the manufacture of bulk absorber material.
24. Method as claimed in one of Claims 21 to 23, characterised in that the electrically conductive layer is produced by deposition from the vapour phase in a vacuum or with the addition of reactive gases.
25. Method as claimed in Claims 21 to 23, characterised in that the conductive layer (12) is produced by powder coating in a vacuum or with the addition of reactive gases.
26. Method as claimed in one of Claims 21 to 25, characterised in that the conductive layer (12) is produced with or without a further reactive component from a pure metal, a metal alloy or a semi-conductor with the use of one or more of the elements Al, Cr, Fe, In, Ni, Sb, Sn, Ta, Ti or Zn.
27. Method as claimed in Claim 21, characterised in that mechanically flexible surface resistant sections (24) are formed into a pyramid-, wedge-, cone- or step-shape and positioned in the chamber (30) subjected to the electro-magnetic waves and are thereafter subjected to such a pressure gradient that they are maintained in their desired three-dimensional shape.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4321165.8 | 1993-06-25 | ||
| DE4321165 | 1993-06-25 | ||
| DE4404071A DE4404071C2 (en) | 1993-06-25 | 1994-02-09 | Arrangement for absorbing electromagnetic waves and method for producing this arrangement |
| DEP4404071.7 | 1994-02-09 | ||
| PCT/EP1994/002073 WO1995000983A1 (en) | 1993-06-25 | 1994-06-27 | Arrangement for absorbing electromagnetic waves and process for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2163516A1 CA2163516A1 (en) | 1995-01-05 |
| CA2163516C true CA2163516C (en) | 1999-07-13 |
Family
ID=25927110
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002163516A Expired - Fee Related CA2163516C (en) | 1993-06-25 | 1994-06-27 | System for absorbing electromagnetic waves and method of manufacturing this system |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US5710564A (en) |
| EP (1) | EP0705487B1 (en) |
| JP (1) | JPH08512178A (en) |
| CN (1) | CN1054473C (en) |
| AT (1) | ATE173861T1 (en) |
| AU (1) | AU7124694A (en) |
| CA (1) | CA2163516C (en) |
| DK (1) | DK0705487T3 (en) |
| ES (1) | ES2124894T3 (en) |
| WO (1) | WO1995000983A1 (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1187978A (en) * | 1997-09-09 | 1999-03-30 | Nitto Boseki Co Ltd | Incombustible radio wave absorber |
| NL1010745C2 (en) * | 1998-12-07 | 2000-06-08 | Hollandse Signaalapparaten Bv | Test room. |
| JP4377467B2 (en) | 1999-01-21 | 2009-12-02 | Ｔｄｋ株式会社 | Radio wave absorber assembly member and radio wave absorber using the same |
| WO2001057953A1 (en) * | 2000-02-01 | 2001-08-09 | Science Applications International Corporation | Passive anti-jamming antenna system |
| JP2003229691A (en) * | 2002-01-31 | 2003-08-15 | Riken Corp | Radio wave absorbent |
| JP4346360B2 (en) * | 2002-12-25 | 2009-10-21 | 東レ株式会社 | Sheet material for radio wave absorber and radio wave absorber |
| US7250920B1 (en) | 2004-09-29 | 2007-07-31 | The United States Of America As Represented By The Secrtary Of The Navy | Multi-purpose electromagnetic radiation interface system and method |
| EP1722243A1 (en) * | 2005-05-10 | 2006-11-15 | Fuji Xerox Co., Ltd. | Radio wave absorber for a probe |
| JP2007096269A (en) * | 2005-08-30 | 2007-04-12 | Nisca Corp | Near field electromagnetic wave absorber |
| US7956793B2 (en) * | 2005-12-12 | 2011-06-07 | Icx Technologies, Inc. | Selective reflective and absorptive surfaces and methods for resonantly coupling incident radiation |
| WO2012094498A2 (en) * | 2011-01-07 | 2012-07-12 | The Regents Of The University Of Michigan | Electromagnetic radiation absorbing surfaces for cloaking three-dimensional objects |
| FR3118563B3 (en) * | 2020-12-28 | 2022-12-30 | Emitech | Inflatable anechoic panels |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE540736A (en) * | 1953-03-28 | |||
| DE1934170U (en) * | 1965-07-29 | 1966-03-10 | Siemens Ag | LOW REFLECTION DAMPING BODY FOR ELECTROMAGNETIC WAVES. |
| DE3838749A1 (en) * | 1988-11-15 | 1990-05-17 | Gruenzweig & Hartmann Montage | BROADBAND ABSORBER FOR ELECTROMAGNETIC SHAFTS |
| JPH02142200A (en) * | 1988-11-22 | 1990-05-31 | Akzo Kashima Ltd | Radiowave absorbing body |
| US5125992A (en) * | 1989-10-02 | 1992-06-30 | Brunswick Corp. | Bulk rf absorber apparatus and method of making same |
| DK0425262T3 (en) * | 1989-10-26 | 1995-10-30 | Colebrand Ltd | Absorb |
| FR2666439B1 (en) * | 1990-08-30 | 1994-03-18 | Commissariat A Energie Atomique | ABSORBENT SCREEN BASED ON ELECTRONIC CONDUCTIVE POLYMER. |
| WO1993015530A1 (en) * | 1992-02-04 | 1993-08-05 | Illbruck Gmbh | Absorber of electromagnetic waves |
-
1994
- 1994-06-27 US US08/569,215 patent/US5710564A/en not_active Expired - Fee Related
- 1994-06-27 AU AU71246/94A patent/AU7124694A/en not_active Abandoned
- 1994-06-27 CA CA002163516A patent/CA2163516C/en not_active Expired - Fee Related
- 1994-06-27 CN CN94192565A patent/CN1054473C/en not_active Expired - Lifetime
- 1994-06-27 JP JP7502452A patent/JPH08512178A/en active Pending
- 1994-06-27 WO PCT/EP1994/002073 patent/WO1995000983A1/en active IP Right Grant
- 1994-06-27 EP EP94920464A patent/EP0705487B1/en not_active Expired - Lifetime
- 1994-06-27 DK DK94920464T patent/DK0705487T3/en active
- 1994-06-27 AT AT94920464T patent/ATE173861T1/en not_active IP Right Cessation
- 1994-06-27 ES ES94920464T patent/ES2124894T3/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DK0705487T3 (en) | 1999-08-09 |
| WO1995000983A1 (en) | 1995-01-05 |
| ES2124894T3 (en) | 1999-02-16 |
| CN1126000A (en) | 1996-07-03 |
| CA2163516A1 (en) | 1995-01-05 |
| AU7124694A (en) | 1995-01-17 |
| US5710564A (en) | 1998-01-20 |
| ATE173861T1 (en) | 1998-12-15 |
| EP0705487A1 (en) | 1996-04-10 |
| JPH08512178A (en) | 1996-12-17 |
| CN1054473C (en) | 2000-07-12 |
| EP0705487B1 (en) | 1998-11-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |