DE102009046752A1 - Prefabricated device for eliminating or reducing reflected signals from electromagnetic wave i.e. radar wave, has three dimensional randomly formed grid intermediate layer absorbing partially defused electromagnetic wave to be reflected - Google Patents

Abstract

The device has three dimensional randomly formed grid intermediate layer absorbing partially defused electromagnetic wave i.e. radar wave to be reflected. The grid intermediate layer consists of steel or electrically conductive material, where the layer is designed in various shapes selected from diamond-shape, rectangular shape, polygonal shape and round-mesh shape. A crumple randomly formed grid is arranged within a constructional part, and a reinforcing layer is arranged within a grid structure that is included in a matrix made up of concrete.

Description

Technical area

In high-tech societies, techniques based on electromagnetic waves are becoming increasingly important. In addition to the frequencies in radio and television technology, other wavelength spectra are also increasingly being used, for example in the radio or Wi-Fi area or in radar technology.

In densely populated regions, the reflection of electromagnetic waves on buildings and other structures often causes problems, which can lead to data losses in the signals with serious consequences. Often it becomes necessary, for example, to subsequently repair buildings near the airport or to pay attention to corresponding optimal properties with regard to the reflection behavior already during construction.

In addition, if necessary, there is the requirement to shield indoor areas against electromagnetic waves to protect susceptible devices and facilities or to secure body against localization.

State of the art

In the suppression of buildings size and orientation of the building envelope and the angle of incidence of electromagnetic radiation - in particular the radar near the airport - and the resulting reflection directions are determined. Different methods are used for the problem treatment. Affected façades or partial façades can be structured by geometric measures such as tilting or tilting the surfaces or subdividing the facades into regularly recurring sections with a depth offset (checkerboard pattern). Disadvantage is that these measures have a strong influence on the architecture of the building and thus often affect the overall effect. In addition, it may come with pure reflection of the waves to undesirable reflection effects.

Furthermore, the use of electromagnetically transparent (eg polycarbonate) or absorbing materials based on carbon or ferrite is possible. When using electromagnetically transparent materials in the building envelope, it must be ensured that there are no reflection surfaces in the building as well, otherwise the reflection process would only be shifted. Weather influences can also have a negative effect in the medium term - on electromagnetic-transparent as well as on absorbent materials, which require an additional coating. These materials are thus to be used critically in the facade design. Especially since these materials are inevitable influences on the architectural design of the building. Another disadvantage of these alternative building materials is that the manufacturing costs become more expensive.

In general, there are approaches for various wave ranges to develop absorbers of electromagnetic waves, which can be used as facade elements. In the patent DE 31 31 137 C2 describes a metal fiber concrete with varying fiber lengths and geometries. This fiber concrete is supplemented by a flat steel grid insert whose mesh size can also be changed depending on the acting frequency.

JP 5248013 A represents the inclined position of a steel grid insert within the component for reflection of radio waves.

Among other things DE 698 36 457 are multi-layered structures - with different materials or cavities - known by absorbers.

Object of the invention

The object of the invention is to provide a cost-effective solution for a component which achieves a shielding of the underlying areas or the elimination of reflected noise signals from electromagnetic waves - especially in the frequency range of radar waves - and beyond the facade design is not affected.

Presentation of the invention

The object is solved by the features specified in the characterizing part of claim 1.

For this purpose, the invention provides, if appropriate in a matrix - preferably concrete - to arrange a chaotically shaped grid insert made of metallic material.

The principle of the invention is that the chaotically shaped grid insert - in terms of the reflection of electromagnetic waves - practically consists of many contiguous faces with different orientation. As a result, this leads to a diffuse reflection / scattering, which does not cause unwanted, directed interference signals. Since a matrix does not adversely affect this scattering effect, it can be dispensed with in principle; it only serves the outer shape of the component.

The grid insert can be traced back to a variety in size, shape and orientation chaotically arranged partial surface elements.

The wavelength λ ₀ (free-space wavelength, which is also referred to with lambda ₀ or λ) of the electromagnetic radiation are in front of the dimensions of the partial surface elements: these are for at least 70% of the partial surface elements in a range of between λ _0/10 and λ _0th

The mesh or mesh size of the grid should be between 5 and 30 cm, preferably 10 to 20 cm, for effective radar suppression - with narrower mesh sizes, electromagnetic radiation in a higher frequency range can be diffusely reflected. The depth of the chaotic lattice structure is 3 to 15 cm for radar suppression. In one embodiment good results could be achieved with a depth of 7 cm structure.

It has been shown that chaotically shaped lattice structures are particularly suitable in the range of the frequencies of 1250-1350 MHz which are customary for radar (eg in air traffic control). Preferably, these grid structures extend within a solid component, which is formed, for example, of concrete. The disordered shape, which extends three-dimensionally within the component, is extremely good at diffusely reflecting radar waves. Here, the mesh width, the material thickness and properties as well as the shape of the mesh can be adapted to the external boundary conditions. On the appearance of the component, this has no effect.

In addition to the use of normal concrete, other concretes or materials with suitable suitability as a matrix in the area of the facade are possible because the strength properties result from the requirements of the site and are not required for diffuse reflection. Thus, an additionally installed statically required reinforcement can be installed independently of the crumpled grid insert, as long as this reinforcement is arranged behind the chaotic grid insert, on the side facing away from the radiation. In principle, a combination with steel fiber concrete is also possible to cover extended frequency ranges with regard to the absorption by the component or to increase the static strength. Several layers of such chaotically crenulated lattice structures one behind the other to improve the desired effects are possible. This also allows the use of different grating structures with different material and geometry properties.

The surface design of the components is freely possible from an architectural point of view.

The component can be prefabricated as prefabricated façade element and assembled on site. Likewise, the production in situ is possible, while a corresponding three-dimensionally deformed mesh is introduced into the formwork in the course of conventional reinforced concrete production.

Description of the figures

1 View of a three-dimensionally chaotically shaped lattice structure with irregularly aligned partial surfaces

2 Section through a facade component in the horizontal and vertical directions; with reflection directions of the individual partial surfaces of the chaotically shaped grid mesh insert in a matrix

3 View of three-dimensionally shaped grid structures with different geometrical shapes and chaotically oriented faces

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3131137 C2 [0006]
• JP 5248013 [0007]
• DE 69836457 [0008]

Claims (9)

Device for eliminating or attenuating reflected electromagnetic signals, in particular in the range of radar waves, characterized by the presence of at least one three-dimensionally chaotically shaped grid mesh insert whose effect is to at least partially diffusely reflect and / or partially absorb electromagnetic waves. Apparatus according to claim 1, characterized in that the grid mesh insert consists of steel or another electrically conductive material. Device according to at least one of claims 1 and 2, characterized in that the grid insert has diamond-shaped, rectangular, polygonal or round meshes. Device according to at least one of claims 1 to 3, characterized in that the mesh size for radar waves is about 5 to 30 cm. Device according to at least one of claims 1 to 4, characterized in that the crumpled, chaotically shaped net is arranged arbitrarily within the component and that its lattice structure facing the radiation is arranged in front of the reinforcing steel layers. Device according to at least one of claims 1 to 5, characterized in that the material thickness of the grid is between 1 mm and 15 mm. Device according to at least one of claims 1 to 6, characterized in that the grid structure is located in a matrix. Device according to at least one of claims 1 to 7, characterized in that the matrix consists of concrete. Device according to at least one of claims 1 to 8, characterized in that the device is a prefabricated element.

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