EP0689263A1 - Absorber for a device for testing the electromagnetic compatibility of electric and electronic systems - Google Patents
Absorber for a device for testing the electromagnetic compatibility of electric and electronic systems Download PDFInfo
- Publication number
- EP0689263A1 EP0689263A1 EP95109649A EP95109649A EP0689263A1 EP 0689263 A1 EP0689263 A1 EP 0689263A1 EP 95109649 A EP95109649 A EP 95109649A EP 95109649 A EP95109649 A EP 95109649A EP 0689263 A1 EP0689263 A1 EP 0689263A1
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- working medium
- absorber
- absorber according
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- hollow
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- 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
- 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
Definitions
- the determination of the electromagnetic compatibility usually takes place in halls shielded as Faraday cages, which are lined with a large number of absorbers made of or with radiation-absorbing materials and are referred to as absorber halls.
- the absorbers have the task of suppressing reflections of the electromagnetic fields generated in the hall, which can reach very high field strengths if the systems examined are affected by interference, back on the hall walls as far as possible.
- the waves reflected on the walls overlap with the incoming waves to standing waves with strong knots and bellies, which makes the spatial field distribution very inhomogeneous and the results of emission and immunity measurements in a non-manageable, frequency-dependent manner from the arrangement of the test objects and antennas become dependent.
- By suppressing such reflections conditions arise in the hall that are similar to or at least close to those of a free field measurement.
- the energy absorbed by the absorbers is ultimately converted into heat. This can be done in different ways predominantly by generating dielectric losses, by generating eddy current losses and / or according to the principle of destructive interference. In any case, the removal of the heat generated in the absorbers constitutes a considerable problem. It is customary to take the absorber halls out of operation to cool the absorbers, but this can lead to the very long downtimes of the very expensive absorber halls.
- a type of absorber that has long been used extensively in absorber technology is the pyramid absorber made of open-cell polyurethane foam interspersed with graphite and salts.
- This absorber can be used within a wide frequency range and has the advantage of being light in weight.
- heat dissipation is particularly problematic with this type, because the absorbed energy can only reach the surface very slowly due to the low thermal conductivity of the polyurethane and can be dissipated from there.
- Polyurethane foam is also flammable. Although the added salts are said to reduce the flammability, smoldering fires with environmentally harmful emissions have nevertheless occurred in absorber halls with flame-retardant polyurethane absorbers, particularly in the case of high local field strengths. Therefore, expensive, automatically working carbon dioxide extinguishing systems have to be installed in such absorber halls. Furthermore, the material properties are subject to a progressive change, since the constant heating and cooling leads to a gradual embrittlement of the material.
- Pyramid absorbers made of ceramic material are also known, which have the great advantage of non-flammability, but because of their high weight can only be used in special cases.
- Farther Combination absorbers are known which consist of ferrite tiles with attached pyramid absorbers.
- an absorber which consists of a hollow body which has a wall which is permeable to the electromagnetic field and whose cavity contains a liquid working medium which extracts the energy from the electromagnetic field. It is particularly advantageous to design such that the hollow body is designed as a hollow wall body, the cavity wall interior of which is flowed through by the working medium.
- a first group of such liquids are (preferably aqueous) electrolyte solutions, for example saline solutions, in which the penetrating electric field induces a line current, which is converted into heat.
- a second group comprises aqueous or non-aqueous suspensions of ferrite particles, which may be kept in suspension by protective colloids.
- a third group are emulsions of water and liquid polymers (oils), which have a dielectric constant that is different from that of pure water.
- electrolyte solutions with suspended ferrite particles or emulsions from an electrolyte solution and oils or else emulsions from one Electrolyte solution and oils or emulsions from an electrolyte solution and oils with additionally suspended ferrite particles can be combined with one another, for example using electrolyte solutions with suspended ferrite particles or emulsions from an electrolyte solution and oils or else emulsions from one Electrolyte solution and oils or emulsions from an electrolyte solution and oils with additionally suspended ferrite particles.
- a particular advantage of the liquid working medium is that the absorbed energy dissipates very quickly, which, unlike the solid absorber, prevents local overheating even at high field strengths.
- the absorber is designed as a hollow wall body with a working medium flowing through it, there is also the fact that the working medium can be guided outside and passed outside of the absorber hall via a heat exchanger, so that it remains permanently at a constant temperature even under extreme radiation exposure and acts as a cooling liquid to a certain extent . Hall usage can be increased by up to 300% because there is almost no downtime to cool the absorbers.
- Another important advantage is the possibility that the parameters of the working medium can be changed or changed in its composition even during operation of the hall to adapt to changed measuring conditions in the hall. The absorber can therefore be parameterized, which has not yet been possible.
- a hollow body 1 is filled with a liquid working medium.
- the wall 2 of the hollow body consists of a radiation-resistant and radiation-permeable plastic, for example polystyrene, so that the penetrating radiation energy from the working medium located within the cavity 3 for example, a saline solution.
- the hollow body is pyramid-shaped, but can also have a different outer shape and forms one of the absorber bodies which are arranged on the inner wall of an absorber hall.
- a hollow wall body 1 ' is provided which, as shown, can again have a pyramid shape, but does not have to, and forms one of the absorber bodies arranged on the inner wall of an absorber hall.
- the hollow medium interior 4 of this hollow body is flowed through by the working medium in a predetermined layer thickness and is provided with connections 5, via which the working medium can be guided to the outside and returned again.
- a circulation circuit 6 (indicated only schematically) is expediently provided outside the absorber hall, which contains a circulation pump and a heat exchanger in block 7 and supplies all or at least one group of the hollow wall bodies within the hall with the flowing working medium. Valves and connections can also be assigned to block 7 in order to enable a change in the working medium or a change in its composition and to parameterize the absorber (s).
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- Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
- Aerials With Secondary Devices (AREA)
Abstract
Description
Die Ermittlung der elektromagnetischen Verträglichkeit, also beispielsweise der Störeinstrahlfestigkeit, Störabstrahlung oder Strahlungscharakteristik von elektrischen und elektronischen Systemen geschieht üblicherweise in als Faraday-Käfig abgeschirmten Hallen, die innen mit einer Vielzahl von Absorbern aus oder mit strahlungsabsorbierenden Materialien ausgekleidet sind und als Absorberhallen bezeichnet werden. Die Absorber haben dabei die Aufgabe, Reflexionen der in der Halle erzeugten elektromagnetischen Felder, die bei einer Störbeeinflussung der untersuchten Systeme sehr hohen Feldstärken erreichen können, an den Hallenwänden in die Halle zurück so weit wie möglich zu unterdrücken. Die an den Wänden reflektierten Wellen überlagern sich nämlich mit den ankommenden Wellen zu stehenden Wellen mit stark ausgeprägten Knoten und Bäuchen, wodurch die räumliche Feldverteilung sehr stark inhomogen wird und die Ergebnisse von Emissions- und Störfestigkeitsmessungen in nicht überschaubarer, frequenzabhängiger Weise von der Anordnung der Prüfobjekte und Antennen abhängig werden. Durch die Unterdrückung solcher Reflexionen entstehen in der Halle Bedingungen, die denen einer Freifeldmessung gleichen oder zumindest nahekommen.The determination of the electromagnetic compatibility, for example the immunity to interference, radiation or radiation characteristics of electrical and electronic systems, usually takes place in halls shielded as Faraday cages, which are lined with a large number of absorbers made of or with radiation-absorbing materials and are referred to as absorber halls. The absorbers have the task of suppressing reflections of the electromagnetic fields generated in the hall, which can reach very high field strengths if the systems examined are affected by interference, back on the hall walls as far as possible. The waves reflected on the walls overlap with the incoming waves to standing waves with strong knots and bellies, which makes the spatial field distribution very inhomogeneous and the results of emission and immunity measurements in a non-manageable, frequency-dependent manner from the arrangement of the test objects and antennas become dependent. By suppressing such reflections, conditions arise in the hall that are similar to or at least close to those of a free field measurement.
Die von den Absorbern aufgenommene Energie wird letztlich in Wärme umgewandelt. Dies kann auf unterschiedliche Weise geschehen und erfolgt vorwiegend durch Erzeugung von dielektrischen Verlusten, durch Erzeugung von Wirbelstromverlusten und/oder nach dem Prinzip der destruktiven Interferenz. In jedem Fall bildet dabei die Abführung der in den Absorbern erzeugten Wärme ein erhebliches Problem. Üblich ist es, die Absorberhallen zur Abkühlung der Absorber außer Betrieb zu nehmen, was aber unter Umständen zu sehr langen Standzeiten der sehr teuren Absorberhallen führen kann.The energy absorbed by the absorbers is ultimately converted into heat. This can be done in different ways predominantly by generating dielectric losses, by generating eddy current losses and / or according to the principle of destructive interference. In any case, the removal of the heat generated in the absorbers constitutes a considerable problem. It is customary to take the absorber halls out of operation to cool the absorbers, but this can lead to the very long downtimes of the very expensive absorber halls.
Ein seit langem in großem Umfang in der Absorbertechnik eingesetzter-Absorbertyp ist der Pyramidenabsorber aus offenzelligem, mit Graphit und Salzen durchsetzten Polyurethanschaum. Dieser Absorber kann innerhalb eines breiten Frequenzbereichs eingesetzt werden und hat den Vorteil eines geringen Gewichts. Allerdings ist die Wärmeabfuhr bei diesem Typ besonders problematisch, denn die absorbierte Energie kann aufgrund der geringen Wärmeleitfähigkeit des Polyurethans nur sehr langsam an die Oberfläche gelangen und von dort abgeführt werden. Außerdem ist Polyurethanschaum brennbar. Zwar sollen die zugesetzten Salze die Entflammbarkeit verringern, aber es sind trotzdem in Absorberhallen mit schwer entflammbaren Polyurethan-Absorbern insbesondere bei hohen lokalen Feldstärken Schwelbrände mit umweltschädlichen Emissionen aufgetreten. Deshalb müssen teure, automatisch arbeitende Kohlendioxid-Löschanlagen in solchen Absorberhallen installiert werden. Weiterhin unterliegen die Materialeigenschaften einer fortschreitenden Veränderung, da das ständige Erwärmen und Abkühlen zu einer allmählichen Versprödung des Materials führt.A type of absorber that has long been used extensively in absorber technology is the pyramid absorber made of open-cell polyurethane foam interspersed with graphite and salts. This absorber can be used within a wide frequency range and has the advantage of being light in weight. However, heat dissipation is particularly problematic with this type, because the absorbed energy can only reach the surface very slowly due to the low thermal conductivity of the polyurethane and can be dissipated from there. Polyurethane foam is also flammable. Although the added salts are said to reduce the flammability, smoldering fires with environmentally harmful emissions have nevertheless occurred in absorber halls with flame-retardant polyurethane absorbers, particularly in the case of high local field strengths. Therefore, expensive, automatically working carbon dioxide extinguishing systems have to be installed in such absorber halls. Furthermore, the material properties are subject to a progressive change, since the constant heating and cooling leads to a gradual embrittlement of the material.
Weitere bekannte Absorbertypen sind die Ferritabsorber, die als flache Ferritkacheln ausgebildet sind. Diese Typen sind jedoch mechanisch empfindlich, müssen äußerst genau justiert werden, haben ein hohes Gewicht und erfordern damit hohe Investitionskosten. Sie besitzen den Vorteil einer höheren Belastbarkeit für hohe Prüffeldstärken, jedoch ist der wirksame Frequenzbereich schmaler als bei den Pyramidenabsorbern. Problematisch ist außerdem die Temperaturabhängigkeit der magnetischen Suszeptibilität und das allmähliche Verschwinden der Magnetisierung infolge von Ummagnetisierungsverlusten.Other known absorber types are the ferrite absorbers, which are designed as flat ferrite tiles. However, these types are mechanically sensitive, have to be adjusted extremely precisely, are heavy and therefore require high investment costs. They have the advantage of a higher load capacity for high test field strengths, but the effective frequency range is narrower than that of the pyramid absorbers. The temperature dependency of the magnetic susceptibility and the gradual disappearance of the magnetization due to magnetic reversal losses are also problematic.
Es sind auch Pyramidenabsorber aus keramischem Material bekannt, die den großen Vorteil der Nichtentflammbarkeit besitzen, aber wegen ihres hohen Gewichtes nur in Spezialfällen eingesetzt werden können. Weiterhin sind Kombinationsabsorber bekannt, die aus Ferritkacheln mit aufgesetzten Pyramidenabsorbern bestehen.Pyramid absorbers made of ceramic material are also known, which have the great advantage of non-flammability, but because of their high weight can only be used in special cases. Farther Combination absorbers are known which consist of ferrite tiles with attached pyramid absorbers.
Allen diesen Absorbern ist gemeinsam, daß sie durch ihr Material und ihre Form auf den zu absorbierenden Frequenzbereich abgestimmt werden müssen. Dadurch ist es nur mit großem Aufwand möglich, das Abschirmverhalten der Meßumgebung flexibel anzupassen.All these absorbers have in common that their material and their shape have to be tuned to the frequency range to be absorbed. As a result, it is only possible with great effort to flexibly adapt the shielding behavior to the measurement environment.
Es ist die Aufgabe der Erfindung, einen umweltfreundlichen, dauerhaften Absorber zur Verfügung zu stellen, der elektromagnetische Energie innerhalb eines breiten Frequenzbereichs optimal absorbiert, schnell und einfach auf die für den Anwendungsfall erforderlichen Dämpfungseigenschaften eingestellt werden kann und eine gute Wärmeumsetzung ermöglicht, so daß die Brandgefahr beseitigt ist und die durch Abkühlungsphasen der Absorber bedingten Standzeiten der Halle minimiert oder ganz entbehrlich werden.It is the object of the invention to provide an environmentally friendly, permanent absorber which optimally absorbs electromagnetic energy within a wide frequency range, can be quickly and easily adjusted to the damping properties required for the application and allows good heat conversion, so that the risk of fire is eliminated and the downtimes of the hall caused by the cooling phases of the absorbers are minimized or become entirely unnecessary.
Gelöst wird diese Aufgabe durch einen Absorber, der aus einem Hohlkörper besteht, der eine für das elektromagnetische Feld durchlässige Wandung besitzt und dessen Hohlraum ein flüssiges Arbeitsmedium enthält, welches dem elektromagnetischen Feld die Energie entzieht. Besonders vorteilhaft ist dabei eine Ausbildung derart, daß der Hohlkörper als Hohlwandkörper ausgebildet ist, dessen Hohlwand-Innenraum von dem Arbeitsmedium durchströmt ist.This object is achieved by an absorber which consists of a hollow body which has a wall which is permeable to the electromagnetic field and whose cavity contains a liquid working medium which extracts the energy from the electromagnetic field. It is particularly advantageous to design such that the hollow body is designed as a hollow wall body, the cavity wall interior of which is flowed through by the working medium.
Als Arbeitsmedium kommen alle Flüssigkeiten in Betracht, die die einfallende Strahlungsenergie aufnehmen und in Wärme umwandeln können. Eine erste Gruppe solcher Flüssigkeiten sind (vorzugsweise wässrige) Elektrolytlösungen, beispielsweise Kochsalzlösungen, in denen das eindringende elektrische Feld einen Leitungsstrom induziert, der in Wärme umgesetzt wird. Eine zweite Gruppe umfaßt wässrige oder nicht-wässrige Suspensionen von Ferritpartikeln, die ggfs. durch Schutzkolloide in Suspension gehalten werden. Eine dritte Gruppe sind Emulsionen aus Wasser und Flüssigpolymeren (Ölen), die eine von reinem Wasser unterschiedliche Dielektrizitätskonstante besitzen. Natürlich können auch einzelne oder alle dieser Gruppen von Flüssigkeiten miteinander kombiniert werden, also beispielsweise Elektrolytlösungen mit suspendierten Ferritpartikeln eingesetzt werden oder Emulsionen aus einer Elektrolytlösung und Ölen oder aber Emulsionen aus einer Elektrolytlösung und Ölen oder aber Emulsionen aus einer Elektrolytlösung und Ölen mit zusätzlich darin suspendierten Ferritpartikeln. Durch Auswahl der verwendeten Substanzen, ihrer Konzentration und ihrer Kombination lassen sich die für die Strahlungsabsorption erforderlichen Eigenschaften des Arbeitsmediums hinsichtlich Leitfähigkeit, Permeabilität und Permittivität problemlos auf jeden Anwendungsfall abstimmen.All liquids that can absorb the incident radiation energy and convert it into heat can be considered as the working medium. A first group of such liquids are (preferably aqueous) electrolyte solutions, for example saline solutions, in which the penetrating electric field induces a line current, which is converted into heat. A second group comprises aqueous or non-aqueous suspensions of ferrite particles, which may be kept in suspension by protective colloids. A third group are emulsions of water and liquid polymers (oils), which have a dielectric constant that is different from that of pure water. Of course, individual or all of these groups of liquids can also be combined with one another, for example using electrolyte solutions with suspended ferrite particles or emulsions from an electrolyte solution and oils or else emulsions from one Electrolyte solution and oils or emulsions from an electrolyte solution and oils with additionally suspended ferrite particles. By selecting the substances used, their concentration and their combination, the properties of the working medium required for radiation absorption with regard to conductivity, permeability and permittivity can be matched to any application without any problems.
Ein besonderer Vorteil des flüssigen Arbeitsmediums besteht darin, daß die aufgenommene Energie sehr schnell dissipiert, wodurch anders als beim Feststoffabsorber auch bei hohen Feldstärken lokale überhitzungen vermieden werden. Wenn der Absorber als Hohlwandkörper mit durchströmendem Arbeitsmedium ausgebildet ist, kommt noch hinzu, daß das Arbeitsmedium nach außen geführt und außerhalb der Absorberhalle über einen Wärmetauscher geleitet werden kann, so daß es dauerhaft selbst bei extremer Strahlungsbelastung auf einer konstanten Temperatur bleibt und gewissermaßen als Kühlflüssigkeit wirkt. Die Hallennutzung kann dadurch um bis zu 300 % gesteigert werden, weil Standzeiten zur Abkühlung der Absorber weitgehend entfallen. Ein weiterer wesentlicher Vorteil ist die Möglichkeit, daß die Parameter des Arbeitsmediums selbst während des Hallenbetriebs zur Anpassung an geänderte Meßbedingungen in der Halle wechseln oder in seiner Zusammensetzung verändern zu können. Der Absorber ist also, was bislang noch nicht möglich gewesen ist, parametrierbar.A particular advantage of the liquid working medium is that the absorbed energy dissipates very quickly, which, unlike the solid absorber, prevents local overheating even at high field strengths. If the absorber is designed as a hollow wall body with a working medium flowing through it, there is also the fact that the working medium can be guided outside and passed outside of the absorber hall via a heat exchanger, so that it remains permanently at a constant temperature even under extreme radiation exposure and acts as a cooling liquid to a certain extent . Hall usage can be increased by up to 300% because there is almost no downtime to cool the absorbers. Another important advantage is the possibility that the parameters of the working medium can be changed or changed in its composition even during operation of the hall to adapt to changed measuring conditions in the hall. The absorber can therefore be parameterized, which has not yet been possible.
Ausführungsbeispiele werden nachfolgend anhand der Zeichnung näher erläutert. Dabei zeigen
- Fig. 1
- im Querschnitt einen Hohlkörper, der mit einem flüssigen Arbeitsmedium gefüllt ist, und
- Fig. 2
- im Querschnitt einen Hohlwandkörper, der von dem Arbeitsmedium durchströmt und an einen äußeren Kreislauf angeschlossen ist.
- Fig. 1
- in cross section a hollow body which is filled with a liquid working medium, and
- Fig. 2
- in cross section a hollow wall body through which the working medium flows and is connected to an external circuit.
Die Fig. 1 stellt die einfachste Ausführungsform der Erfindung dar. Ein Hohlkörper 1 ist mit flüssigem Arbeitsmedium gefüllt. Die Wandung 2 des Hohlkörpers besteht aus einem strahlungsbeständigen und strahlungsdurchlässigen Kunststoff, beispielsweise Polystyrol, so daß die eindringende Strahlungsenergie von dem innerhalb des Hohlraums 3 befindlichen Arbeitsmedium, beispielsweise einer Kochsalzösung aufgenommen werden kann. Der Hohlkörper ist in der Darstellung der Fig. 1 pyramidenförmig, kann aber auch eine andere Außenform besitzen und bildet einen der Absorberkörper, die an der Innenwand einer Absorberhalle angeordnet sind.1 shows the simplest embodiment of the invention. A
In der bevorzugten Ausführungsform der Erfindung ist ein Hohlwandkörper 1' vorgesehen, der ebenfalls, wie dargestellt, wieder eine Pyramidenform haben kann, aber nicht haben muß und einen der an der Innenwand einer Absorberhalle angeordneten Absorberkörper bildet. Der Hohlwand-Innenraum 4 dieses Hohlkörpers wird in vorbestimmter Schichtdicke von dem Arbeitsmedium durchströmt und ist mit Anschlüssen 5 versehen, über die das Arbeitsmedium nach außen geführt und wieder zurückgeführt werden kann. Zweckmäßig ist dabei außerhalb der Absorberhalle ein (nur schematisch angedeuteter) Umwälz-Kreislauf 6 vorgesehen, der in dem Block 7 eine Umwälzpumpe und einen Wärmetauscher enthält und alle oder zumindest eine Gruppe der Hohlwandkörper innerhalb der Halle mit dem strömenden Arbeitsmedium versorgt. Dem Block 7 können noch Ventile und Anschlüsse zugeordnet sein, um einen Wechsel des Arbeitsmediums oder eine Änderung seiner Zusammensetzung zu ermöglichen und den/die Absorber zu parametrieren.In the preferred embodiment of the invention, a hollow wall body 1 'is provided which, as shown, can again have a pyramid shape, but does not have to, and forms one of the absorber bodies arranged on the inner wall of an absorber hall. The hollow
Claims (8)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19944423332 DE4423332A1 (en) | 1994-06-21 | 1994-06-21 | Absorber for devices for measuring electromagnetic compatibility |
| DE4423332 | 1994-06-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP0689263A1 true EP0689263A1 (en) | 1995-12-27 |
Family
ID=6522165
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP95109649A Withdrawn EP0689263A1 (en) | 1994-06-21 | 1995-06-21 | Absorber for a device for testing the electromagnetic compatibility of electric and electronic systems |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP0689263A1 (en) |
| DE (1) | DE4423332A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR3026894A1 (en) * | 2014-10-07 | 2016-04-08 | Peugeot Citroen Automobiles Sa | DEVICE FOR ADJUSTING ELECTROMAGNETIC LOSSES OF A CAVITY |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3325808A (en) * | 1965-09-07 | 1967-06-13 | North American Aviation Inc | Electromagnetic energy attenuator |
| EP0370421A1 (en) * | 1988-11-22 | 1990-05-30 | Akzo Kashima Limited | Electromagnetic wave absorber |
-
1994
- 1994-06-21 DE DE19944423332 patent/DE4423332A1/en not_active Withdrawn
-
1995
- 1995-06-21 EP EP95109649A patent/EP0689263A1/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3325808A (en) * | 1965-09-07 | 1967-06-13 | North American Aviation Inc | Electromagnetic energy attenuator |
| EP0370421A1 (en) * | 1988-11-22 | 1990-05-30 | Akzo Kashima Limited | Electromagnetic wave absorber |
Non-Patent Citations (1)
| Title |
|---|
| COZZENS ET AL.: "MICROWAVE ABSORBING,OPTICALLY TRANSPARENT MATERIALS", NAVY TECHNICAL DISCLOSURE BULLETIN, vol. 15, no. 1, ARLINGTON US, pages 36 - 41, XP000126607 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR3026894A1 (en) * | 2014-10-07 | 2016-04-08 | Peugeot Citroen Automobiles Sa | DEVICE FOR ADJUSTING ELECTROMAGNETIC LOSSES OF A CAVITY |
Also Published As
| Publication number | Publication date |
|---|---|
| DE4423332A1 (en) | 1996-02-15 |
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