EP1860733B1 - Absorption element for electromagnetic high-frequency waves - Google Patents

Abstract

The unit has a reflection plate (40) with a curved reflection surface, which has a set of high-frequency radiation focusing sections for producing areas with increased field strength in front of the reflection plate. Dipole-antennas (50a-50b) are adjusted to the frequency of the radiation and arranged at a predetermined distance to the reflection plate, where the antennas comprise two monopoles for receiving the radiation energy and a resistor for converting the radiation energy to another energy form.

Description

The invention relates to an absorption element for electromagnetic high-frequency radiation, in particular for radiation, as used in the RFID (Radio Frequency Identification) area.

RFID is a technology for non-contact automatic identification of objects via radio detection. In this case, data stored on so-called transponders are read without contact and without visual contact. Such transponders can be attached to objects, which are then automatically and quickly identifiable based on the data stored thereon. An RFID reading system stimulates the transponder to transmit the data stored on the transponder by emitting electromagnetic radiation. This technology can be used anywhere where objects must be automatically identified, detected, registered, stored, monitored or transported.

The strength of the fields or the frequencies are determined by national and international regulations. For example, for the UHF range, depending on the country and approval, three to approx. Ten different frequencies are allowed for transmission between transponder and RFID reading system. In certain applications, it is necessary that several such RFID registrations are performed in a comparatively small space. There is no interference between the individual applications as long as different frequencies can be used. However, due to the limited number of available frequencies, it may be the case that for different applications, the same frequency must be used for transmission between the transponder and the RFID reading system, although the radiation fields generated in the applications spatially overlap. This, in turn, may result in the aforementioned disturbances, which ultimately may at least degrade the reliability of the registration, or may jeopardize the simultaneous feasibility of all applications.

A possible solution to this problem may be that the performance of the RFID reading system is adapted to the respective range required. However, this requires an intervention in the electrical circuit of the RFID reading system or requires an increased circuit complexity.

From the publication WO 94/24724 A For example, there is known a radio frequency electromagnetic radiation absorption element comprising a plurality of antenna circuit assemblies adapted to the frequency of the radiation, each having an antenna conductor structure for receiving radiant energy and means for converting the received radiant energy into another form of energy. The Laid-Open Patent US 4,482,897 relates to an antenna having a segmented and curved reflecting surface for generating overlapping antenna beams from different sources.

The invention has the object to improve the generic type absorption element. This object is achieved in a surprisingly simple manner with an absorption element for electromagnetic high-frequency radiation with the features of claim 1.

In this case, the electromagnetic high-frequency radiation absorption element according to the invention has a plurality of antenna circuit arrangements adapted to the frequency of the radiation, each having an antenna conductor structure for receiving radiant energy and a means for converting the absorbed radiant energy into another form of energy. The absorption element according to the invention is characterized in that a reflection device is provided with a curved reflection surface having a plurality of sections focusing on the high-frequency radiation for generating a plurality of regions with increased field strength in front of the reflection device, wherein the reflection surface of the reflection device has a wave structure, in particular a planar wave structure , The reflection surface may have mountains and valleys that run on straight lines. Such a wave structure may be formed as a kind of juxtaposition of a plurality of cylindrical lenses for electromagnetic radiation. With such absorption elements designed according to the invention, the propagation into such areas of space can be avoided, in which radiation of the same frequency for an RFID registration is used so that ultimately a mutual interference of different RFID applications is prevented. Moreover, in a single RFID application by means of such an absorption element according to the invention, it can be prevented that electromagnetic radiation propagates into regions in which this is undesirable.

The invention is based on the idea of preventing the propagation of electromagnetic high-frequency radiation into certain areas of space by providing a device which, on the one hand, reflects the radiation but, moreover, also ensures that the radiation is absorbed, i. is converted into another form of energy, so that no interference by multiply reflected high frequency radiation can occur. High-frequency radiation and thermal radiation are considered as different forms of energy.

In this case, it may be expedient for an antenna circuit arrangement to be arranged in front of the reflection device in a region of increased field strength, so that the radiation is picked up by the antenna circuit arrangement with high efficiency.

Preferably, the means for converting the absorbed radiant energy to generate thermal energy is formed and may, for example, comprise a resistor which is connected to the antenna conductor structure.

In another embodiment, the means for converting the received radiant energy may comprise an electroluminescent emitter such as a light emitting diode connected to the antenna conductor structure.

Both in the generation of thermal energy as well as in the generation of visible photons by the means for Conversion of the received radiation energy, the radiant energy received by the antenna is converted into electrical energy, which in turn is converted into either IR radiation or visible radiation. In the generation of light by the absorption element, the user can visually display the effectiveness of the absorption element according to the invention.

In order to record the electromagnetic radiation particularly effectively, it can be provided that an antenna circuit arrangement is arranged in a region of increased field strength in front of the reflection device such that the antenna conductor structure is aligned with the focused radiation. Expediently, the antenna structure can be adapted to the field strength profile in the areas with increased field strength.

In order to provide an absorption element which operates independently of polarization, it can be provided that the reflection surface of the reflection device comprises mutually adjacent different wave structure regions, wherein the wave troughs or wave peaks of adjacent wave structure regions are arranged perpendicular to one another.

For receiving the electric fields in front of the reflection surface, in particular in the regions with increased field strength, it may be provided to form the antenna conductor structure of the antenna circuit arrangements in the form of a dipole structure. Such a dipoleite structure is particularly well suited to the fields generated by the described wave structure regions of the reflection surface. It may be expedient if the axis of the dipole structure is placed parallel to a wave crest or a wave trough of the wave structure at the reflection surface of the reflection means, i. that the Dipolleiterstruktur is aligned with the wave structure of the reflection surface.

The coupling of the radiation into the antenna conductor structure can be increased if the distance between the antenna conductor structure and the reflection surface is a predetermined distance. It may be expedient if this distance is equal to an odd multiple of half the wavelength of the high-frequency radiation. This ensures that the radiation reflected by the reflection surface of the reflection device is constructively superimposed on the incident radiation at the location of the antenna conductor structure.

It is particularly expedient if antenna circuit arrangements are provided on both sides of the reflection device, so that incident radiation from both sides can be eliminated by the absorption element according to the invention.

It may be expedient if the reflection device comprises a metal sheet or a wire mesh. With such a metal sheet or braid, it is possible in a simple manner to produce advantageous surface structures, in particular the wave structure regions mentioned above, by means of known shaping techniques. To protect the surface structure of the reflection device it can be provided that at least the two main surfaces of the reflection device are each covered by a plate-shaped device. The necessary condition is that the plate-shaped element or the plate-shaped device comprises a material which transmits the radiation to be absorbed and in particular does not have a high degree of reflection for the electromagnetic radiation.

In such cases, in which the reflection device has a wave structure, the covering device can in particular rest directly on the reflection device, so that the wave troughs or mountains are supported on the two covering devices.

When using such covering devices, it may be expedient for the antenna circuit arrangements to be arranged on the surface of the covering device, as a result of which they can be arranged in a particularly simple manner in a location-specific manner, for example via a printing process such as a screen printing process.

The absorption element according to the invention can in principle be produced with any desired dimensions. It may be advantageous if the element is stackable, so that starting from the size of the absorption element arbitrarily large absorption surfaces or walls can be generated. It is expedient if the absorption element according to the invention is designed to be manually transportable in its dimensions or its weight.

Fig. 1

eine Anwendungssituation für ein erfindungsgemäßes Absorptionselement,

Fig. 2a

eine Reflexionseinrichtung im Ausschnitt zur Verwendung in einem erfindungsgemäßen Absorptionselement,

Fig. 2b

eine Antennenschaltungsanordnung zur Verwendung in einem erfindungsgemäßen Absorptionselement,

Fig. 3

ein erfindungsgemäß ausgebildetes Absorptionselement in einer Aufsicht,

Fig. 4

das in Fig. 3 gezeigte Absorptionselement in einer Schnittdarstellung entlang der Linien IV,

Fig. 5

den mit dem Bezugszeichen S gekennzeichneten Ausschnitt von Fig. 4 in einer Detailansicht,

Fig. 6

das in Fig. 3 dargestellt Absorptionselement in einer Schnittdarstellung entlang den Linien VI,

Fig. 7

eine Schnittdarstellung ähnlich der in Fig. 4 gezeigten für eine weitere Ausführungsform eines erfindungsgemäßen Absorptionselements,

Fig. 8a

eine Schnittdarstellung entsprechend der in Fig. 4 gezeigten Schnittansicht für eine weitere Ausführungsform eines erfindungsgemäßen Absorptionselements, und

Fig. 8b

eine Schnittdarstellung entsprechend der in Fig. 6 gezeigten Schnittansicht für die in Fig. 8a gezeigte weitere Ausführungsform eines erfindungsgemäßen Absorptionselements

zeigt.The invention will be explained in the following by describing some embodiments of the absorption element according to the invention with reference to the accompanying drawings, wherein

Fig. 1

an application situation for an inventive absorption element,

Fig. 2a

a reflection device in the cutout for use in an absorption element according to the invention,

Fig. 2b

an antenna circuit arrangement for use in an absorption element according to the invention,

Fig. 3

an inventively designed absorption element in a plan view,

Fig. 4

this in Fig. 3 shown absorption element in a sectional view along the lines IV,

Fig. 5

the marked by the reference S section of Fig. 4 in a detailed view,

Fig. 6

this in Fig. 3 illustrated absorption element in a sectional view along the lines VI,

Fig. 7

a sectional view similar to the one in Fig. 4 shown for a further embodiment of an absorbent element according to the invention,

Fig. 8a

a sectional view corresponding to the in Fig. 4 shown sectional view of another embodiment of an absorbent element according to the invention, and

Fig. 8b

a sectional view corresponding to the in Fig. 6 shown sectional view of the shown in Fig. 8a further embodiment of an absorbent element according to the invention

shows.

In Fig. 1 is an application situation for an inventive Absorption element 1, 2, 3, 4 shown. The figure shows an outer hall wall 30, in which spaced apart two roller doors 31a, 31b are arranged. These gates can be approached, for example, by a truck, such that the loading area is aligned with the gate. With a transport such as a forklift, which moves through the respective gate in the back of the truck, objects can be picked up and introduced through the said gate in the hall. In the situation described, these objects are each provided with a transponder, which is detected by an RFID reading system placed in the area of the door.

In the figure, a transponder 22a, 22b, which in each case comprises a transponder antenna 23a, b, is shown by way of example in each of the gates 31a, 31b. As soon as the respective transponder enters the effective range of the RFID reading device 20a, 20b, which respectively has an RFID antenna 21a, 21b, the respective transponder is detected and registered by the system. If both gates are used at the same time for introduction into the hall of goods marked with a transponder, the electromagnetic fields generated by the data exchange between the RFID reading system 20a and the associated transponder 22a or the RFID reading system 20b and the associated transponder 22b are generated, disturb. Such a disturbance occurs in particular when the RFID recognition systems operate at the same frequencies.

One or more of the absorption elements according to the invention can be used to remedy these disorders. In the figure, four elements 1-4 are shown in the interior of the hall, of which two are stacked on top of each other, such that they extend approximately perpendicular to the hall wall 30 in the hall interior. If, for example, from the antenna 21a of the RFID reading system 20a electromagnetic high-frequency radiation in the direction of the adjacent RFID reading system 20b or whose antenna 21b is radiated, this radiation is reflected and absorbed by the absorption elements 1, 2 arranged as shown, so that this radiation can not lead to erroneous detections. It can be particularly useful as in the FIG. 1 be shown, also on the second gate 31b such absorption elements 3, 4 set up so that all Torerfassungen are decoupled with respect to the gate-specific electromagnetic radiation.

An electromagnetic high frequency radiation absorption element according to the invention in the described embodiment comprises elementary components incorporated in the FIGS. 2a, b are shown. Fig. 2a shows a thin metal sheet 40, which comprises a planar wave structure with wave crests 42 and wave troughs 41, wherein the wave troughs or wave crests each extend on a straight line. The sheet will focus for incident high frequency electromagnetic radiation through the curved sections so that areas of increased field strength are formed in front of the sheet after reflection of the radiation.

At these points of increased field strength, dipole antennas according to the invention are arranged in a manner to be described, see Fig. 2b showing such a dipole antenna 50. It comprises two monopolies 51, 52 as antenna conductor structures, wherein at the base of a matched to the impedance of the dipole loss resistor 53 is arranged, which connects both monopolies 51, 52 to each other electrically. The dipole has an electrical length L corresponding to an odd multiple of λ / 2, where λ is the wavelength of the electromagnetic high frequency radiation. In the example given, the radiation field comprises UHF with a wavelength of 30 cm. The plane wave structure of the reflection plate 40 has the property of cylinder lenses arranged side by side, inasmuch as the in Fig. 2b indicated dipole antenna adapted to the regions of increased field strength generated by the reflective plate 40. In the Fig. 2b specified antenna takes the electromagnetic High frequency field, wherein the absorbed energy is converted by means of the impedance matched resistor 53 into thermal energy.

Fig. 3 shows an inventive absorption element in an overview. The element 1 is of cuboid construction, the main surfaces being provided by two main cover plates 60, 61. The two longitudinal surfaces are formed by the side deck plates 62, 63, while the two end faces are provided by the side deck plates 64, 65. The side surfaces serve as a standing surface, so the in Fig. 3 shown absorption element is also stackable.

Fig. 4 shows that in Fig. 3 shown absorption element 1 in a sectional view along the lines IV-IV. The wave-shaped reflection plate 40 extends between the main cover plates 60, 61 over the entire surface thereof. In each case spaced from a wave trough dipole antennas 50a, 50b are arranged on both sides of the reflective plate 40.

Reference character S denotes a portion of the sectional view which is shown in FIG Fig. 5 shown in detail. As can be seen, the wave structure in the described embodiment is composed of cylinder jacket segments, the radius of the cylinder segments being equal to R. The distance of the antennas, here the antenna 50b, to the trough is A. As out FIG. 4 As can be seen, the distance of all dipole antennas to the respective associated trough is the same in the described embodiment. Depending on the embodiment of the invention, the distance A can be, for example, equal to half the radius of curvature, ie R / 2. M indicates in the drawing the center point for the curvature with the radius R. In order to avoid that incident high-frequency electromagnetic radiation destructively interferes with the radiation reflected by the reflection plate 40 at the location of the dipole antenna, it can be provided that the distance A is set to (n + 1) · ̇ λ / 2, where n is a natural number is.

Fig. 6 shows that in Fig. 1 illustrated absorption element according to the invention in a sectional view along the lines VI-VI, which runs parallel to one of the main cover plates 60 and 61, respectively. As in Fig. 4 2, the front dipole antennas 50a and the rear dipole antennas 50b are offset from each other relative to a plane parallel to the main top plates 60, 61, so that in FIG Fig. 6 only the rear dipole antennas 50b are in the illustrated plane. As shown in the example given, all the antennas 50a, 50b are electrically independent of each other, they each comprise only as described the two matched monopolies, which are connected together at the base via the resistor 53, see Fig. 2 ,

Fig. 7 corresponds to the in Fig. 4 Here, however, the front-side antennas 50b and rear antennas 50a are placed at a different distance to the associated trough, such that they rest against the respective back of the two main cover plates 60, 61. The distance of the respective dipole antenna to the associated trough is in the in Fig. 7 2R shown example, where R corresponds to the radius of curvature of such a wave trough. In such an embodiment of the invention, the arrangement of the antennas is relatively easy to accomplish, for example, the described antenna circuit arrangements can be printed on the back of the plates 60, 61. In this case, the two monopoles can be applied, in particular via a screen-printing process, and subsequently the resistor adapted to the impedance can be glued in with a conductive adhesive.

The embodiments described so far are adapted to the absorption of electromagnetic high-frequency radiation of a predetermined polarization. Since in the reflection of electromagnetic radiation on metallic surfaces a Polarization rotation occurs by 90 °, it may be very advantageous if the absorption element according to the invention for absorbing electromagnetic high frequency radiation of different polarization is formed.

FIGS. 8a and 8b show sections corresponding to those in FIGS FIGS. 4 and 6 shown by such, polarization independent working absorption element. Sections with perpendicular dipole antennas alternate with sections where the dipoles are oriented horizontally, see Figure 8b. In this respect, an absorption element designed in this way captures and absorbs radiation with horizontal as well as radiation with vertical polarization. It is understood that the wave structure of the reflection plate is adapted to the course of the dipole antennas. This means that in the sections where the dipoles are vertical, the wave structure is, for example, as in FIG Fig. 4 indicated, is formed. However, in those sections where the dipoles are horizontal, the wave structure is rotated 90 ° to the wave structure of the previous section, ie wave troughs and wave peaks also run on horizontal lines there, see FIG. 8a.

It should be noted that the invention has been described using antenna circuit arrangements which comprise an antenna dipole, wherein the reflection means is adapted to the geometry of the dipole antennas by means of the described wave structure. In non-illustrated embodiments, other antenna structures may be used, to which then the curvature of the reflection means is adapted.

The absorption element according to the invention can be used in principle for all applications in which electromagnetic interference is to be destroyed.

LIST OF REFERENCE NUMBERS

1

absorbing element

2

absorbing element

3

absorbing element

4

absorbing element

10, 11

rolling gate

20a, b

RFID reader system

21a, b

RFID antenna

22a, b

transponder

23a, b

transponder antenna

30

Hall wall

31a, b

hall door

40

reflection sheet

41

trough

42

Wellenberg

50, 50a, b

dipole antenna

51, 52

straight ladder

53

resistance

60, 61

Main deck plate

62, 63

Side cover plate

64, 65

Side cover plate

S

neckline

L

dipole length

M

Focus

Claims (13)

1. Absorption element (1) for electromagnetic high-frequency radiation, comprising a plurality of antenna circuit arrangements (50a, 50b) adapted to the radiation frequency and each having an antenna wire structure (51, 52) for receiving radiation energy and a having a means (53) for the conversion of received radiation energy into a different form of energy, characterized by a reflection device (40) having a curved reflection surface with a plurality of sections focusing the high-frequency radiation for producing a plurality of zones of an increased field strength before the reflection device, wherein the reflection surface of the reflection device (40) includes a wave structure.
2. Absorption element according to claim 1, characterized in that the means for the conversion of the received radiation energy produced thermal energy and comprises in particular a resistor (53) which is connected to the antenna wire structure (51, 52).
3. Absorption element according to claim 1, characterized in that the means for the conversion of the received radiation energy comprises an electroluminescent radiator such as a light-emitting diode which is connected to the antenna wire structure.
4. Absorption element according to claim 1, 2 or 3, characterized in that an antenna circuit arrangement (50a, 50b) in a zone of an increased field strength before the reflection device (40) is disposed in such a way that that the antenna wire structure is oriented towards the focused radiation.
5. Absorption element according to claim 1, characterized in that the reflection surface comprises adjacent wave structure areas, wherein the wave hollows (41) respectively the wave crests (42) of adjacent wave structure areas are arranged perpendicular to each other.
6. Absorption element according to one of the claims 1 to 5, characterized in that the antenna wire structure (51, 52) presents a dipole structure.
7. Absorption element according to one of the claims 1 to 6, characterized in that the antenna wire structure is arranged with a predetermined distance to the reflection device, particularly with a distance to the reflection device equal to an uneven multiple of half the wave length of the high-frequency radiation.
8. Absorption element according to one of the claims 1 to 7, characterized in that antenna circuit arrangements (51, 52) are provided on both sides of the reflection device (40).
9. Absorption element according to one of the claims 1 to 8, characterized in that the reflection device comprises a metal sheet or a wire mesh.
10. Absorption element according to one of the claims 1 to 9, characterized in that at least one of the two major surfaces of the reflection device is covered by a plate-like covering device (60, 61).
11. Absorption element according to claim 10, characterized in that antenna circuit arrangements (50a, 50b) are mounted to a plate-like element (60,61).
12. Absorption element according claim 11, characterized in that antenna wire structures of the antenna circuit arrangements can be applied to a plate-like element by a printing process such as a screen printing process.
13. Absorption element according to one of the claims 1 to 12, characterized in that the absorption element can be placed by one of its lateral surfaces (62, 63, 64, 65) and stacked.

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