EP0634807B1 - Antenna device - Google Patents

Antenna device Download PDF

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Publication number
EP0634807B1
EP0634807B1 EP94810334A EP94810334A EP0634807B1 EP 0634807 B1 EP0634807 B1 EP 0634807B1 EP 94810334 A EP94810334 A EP 94810334A EP 94810334 A EP94810334 A EP 94810334A EP 0634807 B1 EP0634807 B1 EP 0634807B1
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EP
European Patent Office
Prior art keywords
antenna device
loop
electrically
antenna
partial
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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 - Lifetime
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EP94810334A
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German (de)
French (fr)
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EP0634807A1 (en
Inventor
Philipp Müller
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Actron Entwicklungs AG
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Actron Entwicklungs AG
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2468—Antenna in system and the related signal processing
    • G08B13/2477—Antenna or antenna activator circuit
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2468—Antenna in system and the related signal processing
    • G08B13/2474—Antenna or antenna activator geometry, arrangement or layout
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H01Q7/04—Screened antennas

Definitions

  • the present invention relates to an antenna device for the detection of resonance labels in electronic anti-theft security systems with one between two clamps antenna wire loop guided in one plane, which under Formation of two electrically outer and one electrically middle part loop twisted twice in each case by 180 ° and in which an impedance element is connected.
  • the invention further relates to the use of such Antenna device for the detection of resonance labels with a fixed predetermined resonance frequency.
  • Antenna devices for electronic anti-theft systems are in various designs and Geometries known and also in use. For example reference is made to: US-A-4,251,808, US-A-4,135,183, US-A-4,243,980, US-A-4,751,516, US-A-872,018, US-A-4,260,990, US-A-4,016,553, US-A-4,720,701, EP-A2-0414628, FR-763.681. Reference may also be made to US-A-2,597,518, in which already a receiving antenna with several against each other 180 ° twisted partial loops is described.
  • Fig. 1 an antenna device is shown as it is currently widely used. It shows in series three also partial loops rotated against each other by 180 ° 1, 2 and 3. The twisting of the partial loops against each other serves to wipe out the far field.
  • the Andes Crossing points 5 and 6 provided ohmic resistors 7 and 8 have the task of slightly increasing the antenna characteristics "smear" and thereby avoid detection dead zones.
  • Fig. 2 shows one generated by this antenna device Field intensity distribution at a distance of 30 cm above the xy plane of the three partial loops. According to the three part loops there are three maxima, the field intensity decreases from the first partial loop to the third. This unwanted decrease in intensity is due to the von von loop Loop decreasing amperage.
  • the total inductance the antenna device determines or limits in the rest in addition to the voltage present at the antenna terminals the antenna current. This should be as large as possible. At modern systems have about one at the antenna terminals 12 Voltage of 50 volts available. An increase in Antenna current by increasing this voltage is only with considerable effort possible.
  • the antenna device according to the invention becomes resonant frequency preferably used as in the claim 9 specified.
  • 3a shows an antenna device of a conventional type three partial loops 1, 2, 3 arranged in series, each are rotated against each other by 180 °.
  • the electrically outer Partial loop 3 is geometrical here between the partial loops 1 and 2 arranged.
  • an impedance element 11 is provided at intersection 6 between the second and third partial loops 2, 3, respectively between two connection points 9, 10 at the entrance and exit of the third sub-loop 3.
  • the impedance element 11 is, as shown in FIG. 4, by a Parallel connection of a capacitor C and an ohmic Resistor R formed.
  • the inductance L 3 of the geometrically central partial loop 3 forms a resonant circuit together with the capacitor C of the impedance element 11. At its resonance frequency, this resonant circuit acts as a blocking element.
  • the current I 3 flowing in it or in the geometrically central partial loop is in phase of resonance just 90 ° out of phase with the current I 12 in the other two partial loops 1 and 2.
  • the current I 12 flows through the resistor R and "experiences" otherwise advantageously only the inductors L 1 and L 2 of the first and second partial loops.
  • the impedance of the antenna device according to the invention therefore behaves like one with only two or two and a half partial loops for frequencies in the vicinity of the resonant frequency mentioned, despite the three partial loops.
  • FIG. 5 shows in a diagram corresponding to FIG. 2 the characteristic of the antenna device according to FIG. 3d) in the case of resonance. It is much more uniform than that of FIG. 2. In particular, the undesired drop in intensity from left to right has disappeared. The intensity is also higher overall, because the inductance L 3 of the third partial loop has no limiting effect on the antenna current I 12, which is primarily effective.
  • FIG. 7 shows a representation corresponding to FIG. 3 Another embodiment for an inventive Antenna device (Fig.7d)) and its derivation from a conventional arrangement (Fig. 7a) shown. From Fig. 3 7 differs by the arrangement of the antenna terminals 12. In FIG. 3, these are in the first partial loop 1 and in Fig. 7 arranged in the second sub-loop 2. With regard to the geometrically middle partial loop 3 there is an opposite in the two embodiments Current sense. Otherwise, the two embodiments equivalent to each other. The terminals 12 could also in the area of the middle loop part 3 in one of them passing lines can be arranged.
  • the area of the three partial loops is preferably the same chosen large. However, there could be different ones Areas are provided.
  • the described coordination of Parameters of the antenna device on the resonance frequency of the resonance labels to be detected need not necessarily be exact be. A phase error (compared to the 90 ° phase shift in the case of resonance) up to 30 ° under certain circumstances be tolerated.
  • Fig. 3d and Fig. 7d) is dashed around the three loops 1,2,3 around a single loop so-called Short circuit loop 14 laid.
  • This serves the To improve extinction of the far field (3 to 30 m). she is optimal when the rivers stretch in the span Compensate each other. If so, then it is the current in the outer loop is zero. Unless, then the current arising in the loop acts on the inner one counter and thereby forces extinction. To avoid of unwanted resonances can replace the short circuit a resistor is also used in the outer loop will.
  • All loops of the invention are advantageous Antenna device embedded in a plastic housing, which mechanically stabilizes them.
  • a plastic case has the advantage that it is based on the advantageous characteristic not disadvantageous to the antenna device according to the invention affects. When combined spatially with a broadcast or receiving electronics should do this for the same reason can also be arranged in a plastic housing.
  • the antenna device according to the invention be shielded on one side for the purpose one-sided shielding.
  • the shield would be in a few centimeters (e.g. 4 cm) from the plane of the Arrange antenna wire loops.

Abstract

The antenna device has an antenna wire loop which is intrinsically rotated twice, through 180 DEG in each case, to form two electrically outer partial loops (1, 3) and one electrically central partial loop (2). One of the two electrically outer partial loops (3) is arranged geometrically between the electrically central partial loop (2) and the other electrically outer partial loop (1). An impedance element (11) is connected between two connection points (9, 10) which are arranged at the input and output of the geometrically central partial loop. The antenna device according to the invention has a highly matched characteristic and, if its parameters at the resonant frequency of the labels to be detected are suitably selected, acts like an antenna having only approximately two to two and a half partial loops. <IMAGE>

Description

TECHNISCHES GEBIETTECHNICAL AREA

Die vorliegende Erfindung betrifft eine Antennenvorrichtung zur Detektion von Resonanzetiketten in elektronischen Warendiebstahls-Sicherungsanlagen mit einer zwischen zwei Klemmen in einer Ebene geführten Antennendrahtschlaufe, welche unter Ausbildung von zwei elektrisch äusseren und einer elektrisch mittleren Teilschlaufe zweifach in sich um jeweils 180° verdreht ist und in welche ein Impedanzglied geschaltet ist. Die Erfindung betrifft weiter eine Verwendung einer solchen Antennenvorrichtung zur Detektion von Resonanzetiketten mit einer fest vorgegebenen Resonanzfrequenz.The present invention relates to an antenna device for the detection of resonance labels in electronic anti-theft security systems with one between two clamps antenna wire loop guided in one plane, which under Formation of two electrically outer and one electrically middle part loop twisted twice in each case by 180 ° and in which an impedance element is connected. The The invention further relates to the use of such Antenna device for the detection of resonance labels with a fixed predetermined resonance frequency.

STAND DER TECHNIKSTATE OF THE ART

Antennenvorrichtungen für elektronische Warendiebstahls-Sicherungsanlagen sind in mannigfaltigen Ausführungen und Geometrien bekannt und auch im Einsatz. Beispielsweise kann hierzu verwiesen werden auf: US-A-4,251,808, US-A-4,135,183, US-A-4,243,980, US-A-4,751,516, US-A-872,018, US-A-4,260,990, US-A-4,016,553, US-A-4,720,701, EP-A2-0414628, FR-763.681. Weiter kann verwiesen werden auf die US-A-2,597,518, in der bereits eine Empfangsantenne mit mehreren gegeneinander um 180° verdrehten Teilschlaufen beschrieben ist.Antenna devices for electronic anti-theft systems are in various designs and Geometries known and also in use. For example reference is made to: US-A-4,251,808, US-A-4,135,183, US-A-4,243,980, US-A-4,751,516, US-A-872,018, US-A-4,260,990, US-A-4,016,553, US-A-4,720,701, EP-A2-0414628, FR-763.681. Reference may also be made to US-A-2,597,518, in which already a receiving antenna with several against each other 180 ° twisted partial loops is described.

In Fig. 1 ist eine Antennenvorrichtung dargestellt, wie sie derzeit vielfach verwendet wird. Sie weist in Serie drei ebenfalls um jeweils 180° gegeneinander verdrehte Teilschlaufen 1, 2 und 3 auf. Die Verdrehung der Teilschlaufen gegeneinander dient zur Fernfeldauslöschung. Die an den Kreuzungsunkten 5 und 6 vorgesehenen ohm'schen Widerstände 7 und 8 haben die Aufgabe, die Antennencharakteristik etwas zu "verschmieren" und dadurch Detektions-Totzonen zu vermeiden. Fig. 2 zeigt eine von dieser Antennenvorrichtung erzeugte Feldintensiätsverteilung in einem Abstand von 30 cm über der xy-Ebene der drei Teilschlaufen. Entsprechend den drei Teilschlaufen ergeben sich drei Maxima, wobei die Feldintensität von der ersten Teilschlaufe zur dritten hin abnimmt. Diese unerwünschte Intensitätsabnahme ist durch die von Schlaufe zu Schlaufe abnehmende Stromstärke bedingt. Die Gesamtinduktivtät der Antennenvorrichtung bestimmt bzw. limitiert im übrigen neben der an den Antennenklemmen anliegenden Spannung den Antennenstrom. Dieser sollte möglichst gross sein. Bei modernen Anlagen steht an den Antennenklemmen 12 etwa eine Spannung von 50 Volt zur Verfügung. Eine Erhöhung des Antennenstromes durch Erhöhung dieser Spannung ist nur mit erheblichem Aufwand möglich.In Fig. 1 an antenna device is shown as it is currently widely used. It shows in series three also partial loops rotated against each other by 180 ° 1, 2 and 3. The twisting of the partial loops against each other serves to wipe out the far field. The Andes Crossing points 5 and 6 provided ohmic resistors 7 and 8 have the task of slightly increasing the antenna characteristics "smear" and thereby avoid detection dead zones. Fig. 2 shows one generated by this antenna device Field intensity distribution at a distance of 30 cm above the xy plane of the three partial loops. According to the three part loops there are three maxima, the field intensity decreases from the first partial loop to the third. This unwanted decrease in intensity is due to the von von loop Loop decreasing amperage. The total inductance the antenna device determines or limits in the rest in addition to the voltage present at the antenna terminals the antenna current. This should be as large as possible. At modern systems have about one at the antenna terminals 12 Voltage of 50 volts available. An increase in Antenna current by increasing this voltage is only with considerable effort possible.

DARSTELLUNG DER ERFINDUNGPRESENTATION OF THE INVENTION

Es ist Aufgabe der vorliegenden Erfindung, eine Antennenvorrichtung der eingangs genannten Art so weiterzubilden, dass sie eine ausgeglichenere Charakteristik bei mindestens gleich hoher lokaler Abstrahlleistung aufweist. Diese Aufgabe wird erfindungsgemäss gelöst durch eine Antennenvorrichtung mit den im Patentanpsurch 1 angegebenen Merkmalen.It is an object of the present invention to provide an antenna device of the type mentioned at the beginning, that they have a more balanced characteristic at least has the same high local radiation output. This task is solved according to the invention by an antenna device with the features specified in patent claim 1.

Zur Detektion von Resonanzetiketten mit einer fest vorgegebenen Resonanzfrequenz wird die erfindungsgemäse Antennenvorrichtung vorzugsweise so verwendet, wie im Patentanspruch 9 angegeben. For the detection of resonance labels with a fixed default The antenna device according to the invention becomes resonant frequency preferably used as in the claim 9 specified.

In den abhängigen Ansprüchen sind bevorzugte Ausgestaltungen der Erfindung gekennzeichnet.Preferred embodiments are in the dependent claims characterized the invention.

KURZE ERLÄUTERUNG DER FIGURENBRIEF EXPLANATION OF THE FIGURES

Es zeigen

Fig. 1
wie bereits erwähnt, eine Antennenvorrichtung nach dem Stand der Technik,
Fig. 2
eine Charakteristik dieser Antennenvorrichtung,
Fig. 3
unter a) bis d), wie sich die unter d) dargestellte erfindungsgemässe Antennenvorrichtung aus einer herkömmlichen Antennenvorrichtung schrittweise ableiten lässt,
Fig. 4
ein Ersatzschaltbild der Antennenvorrichtung von Fig. 3d,
Fig. 5
eine Charakteristik der Antennenvorrichtung von Fig. 3d,
Fig. 6
in einem logarithmischen Diagramm Frequenzgänge von in der Antennenvorrichtung gemäss Fig. 3d auftretenden Strömen sowie von deren Phasenwinkeln, und
Fig. 7
eine Darstellung gemäss Fig. 3 betreffend eine andere erfindungsgemässe Antennenvorrichtung.
Show it
Fig. 1
as already mentioned, an antenna device according to the prior art,
Fig. 2
a characteristic of this antenna device,
Fig. 3
under a) to d) how the antenna device according to the invention shown under d) can be derived step by step from a conventional antenna device,
Fig. 4
3 shows an equivalent circuit diagram of the antenna device of FIG. 3d,
Fig. 5
a characteristic of the antenna device of Fig. 3d,
Fig. 6
in a logarithmic diagram, frequency responses of currents occurring in the antenna device according to FIG. 3d and of their phase angles, and
Fig. 7
a representation according to FIG. 3 relating to another antenna device according to the invention.

AUSFÜHRHUNGSBEISPIELEEXAMPLES

Fig. 3a) zeigt eine Antennenvorrichtung herkömmlicher Art mit drei in Serie angeordneten Teilschlaufen 1,2,3, die jeweils um 180° gegeneinander verdreht sind. 3a) shows an antenna device of a conventional type three partial loops 1, 2, 3 arranged in series, each are rotated against each other by 180 °.

Durch Verschieben der drei Teilschlaufen so, wie dies in Fig. 3 unterer b) und c) dargestellt ist, gelangt man von der unter a) dargestellten Anordnung zu der gemäss Fig. 3d), die der erfindungsgemässen entspricht. Die elektrisch äussere Teilschlaufe 3 ist hier geometrisch zwischen den Teilschlaufen 1 und 2 angeordnet. Am Kreuzungspunkt 6 zwischen der zweiten und dritten Teilschlaufe 2,3, respektive zwischen zwei Anschlusspunkten 9,10 eingangs und ausgangs der dritten Teilschlaufe 3, ist ein Impedanzglied 11 vorgesehen. Das Impedanzglied 11 wird, wie Fig. 4 zeigt, durch eine Parallelschaltung eines Kondensators C und eines ohm'schen Widerstandes R gebildet.By moving the three loops as shown in Fig. 3 lower b) and c) is shown, one arrives from the under a) arrangement to that according to Fig. 3d), the corresponds to that of the invention. The electrically outer Partial loop 3 is geometrical here between the partial loops 1 and 2 arranged. At intersection 6 between the second and third partial loops 2, 3, respectively between two connection points 9, 10 at the entrance and exit of the third sub-loop 3, an impedance element 11 is provided. The impedance element 11 is, as shown in FIG. 4, by a Parallel connection of a capacitor C and an ohmic Resistor R formed.

In dem in Fig. 4 dargestellten Ersatzschaltbild der Antennenvorichtung gemäss Fig. 3d) erkennt man, dass die Induktivität L3 der geometrisch mittleren Teilschlaufe 3 zusammen mit dem Kondensator C des Impedanzgliedes 11 einen Schwingkreis bildet. Bei seiner Resonanzfrequenz wirkt dieser Schwingkreis als Sperrglied. Der in ihm, respektive in der geometrisch mittleren Teilschlaufe fliessende Strom I3 ist im Resonanzfall gerade um 90° phasenverschoben gegenüber dem Strom I12 in den beiden anderen Teilschlaufen 1 und 2. Der Strom I12 fliesst dabei über den Widerstand R und "erfährt" ansonsten mit Vorteil nur die Induktivitäten L1 und L2 der ersten und zweiten Teilschlaufe. Die Impedanz der erfindungsgemässen Antennenvorrichtung benimmt sich daher für Frequenzen in der Nähe der genannten Resonanzfrequenz trotz der drei Teilschlaufen wie eine solche mit lediglich zwei oder zweieinhalb Teilschlaufen.In the equivalent circuit diagram of the antenna device according to FIG. 3d) shown in FIG. 4, it can be seen that the inductance L 3 of the geometrically central partial loop 3 forms a resonant circuit together with the capacitor C of the impedance element 11. At its resonance frequency, this resonant circuit acts as a blocking element. The current I 3 flowing in it or in the geometrically central partial loop is in phase of resonance just 90 ° out of phase with the current I 12 in the other two partial loops 1 and 2. The current I 12 flows through the resistor R and "experiences" otherwise advantageously only the inductors L 1 and L 2 of the first and second partial loops. The impedance of the antenna device according to the invention therefore behaves like one with only two or two and a half partial loops for frequencies in the vicinity of the resonant frequency mentioned, despite the three partial loops.

Zur Detektion von Resonanzetiketten mit einer fest vorgegebenen Resonanzfrequenz wird die erfindungsgemasse Antennenvorrichtung vorzugsweise so dimensioniert, dass der erwähnte Resonanzfall gerade bei der vorgegebenen Resonanzfrequenz der Resonanzetiketten auftritt. Dies ist z.B. dann der Fall, wenn die durch den Kondensator C und durch die Induktivität L3 der dritten Teilschlaufe gebildeten Wechselstromwiderstände bei der vorgegebenen Resonanzfrequenz der Etiketten betragemässig gerade gleich dem ohm'schen Widerstand R werden. Es gilt dann auch L = R2C. Bei einer vorgegebenen Resonanzfrequenz von 8,2 MHz und L3 = 1,63 µH ergibt sich für R z.B. ein Wert von 84 Ω und für C ein solcher von 235 pF.For the detection of resonance labels with a fixed predetermined resonance frequency, the antenna device according to the invention is preferably dimensioned such that the mentioned resonance case occurs precisely at the predetermined resonance frequency of the resonance labels. This is the case, for example, when the AC resistances formed by the capacitor C and by the inductance L 3 of the third partial loop become just equal to the ohmic resistance R at the predetermined resonance frequency of the labels. Then L = R 2 C also applies. With a predetermined resonance frequency of 8.2 MHz and L 3 = 1.63 µH, a value of 84 Ω is obtained for R and a value of 235 pF for C, for example.

Fig. 5. zeigt in einem Fig. 2 entsprechenden Diagramm die Charakteristik der Antennenvorrichtung gemäss Fig. 3d) im Resonanzfall. Sie ist sehr viel gleichmässiger als die von Fig. 2. Insbesondere ist der unerwünschte Intensitätsabfall von links nach rechts verschwunden. Die Intensität ist auch insgesamt betragemässig höher, weil die Induktivität L3 der dritten Teilschlaufe sich auf den vor allem wirksamen Antennenstrom I12 nicht begrenzend auswirkt.5 shows in a diagram corresponding to FIG. 2 the characteristic of the antenna device according to FIG. 3d) in the case of resonance. It is much more uniform than that of FIG. 2. In particular, the undesired drop in intensity from left to right has disappeared. The intensity is also higher overall, because the inductance L 3 of the third partial loop has no limiting effect on the antenna current I 12, which is primarily effective.

Fig. 6 zeigt für die gleiche Antennenvorrichtung die Frequenzgänge der Ströme I12 und I3 sowie ihrer Phasenwinkel ϕ12 und ϕ3. Bei ca. 8.2 MHz ist der Strom I3 gegenüber dem Strom I12 gerade um 90° phasenverschoben.6 shows the frequency responses of the currents I 12 and I 3 and their phase angles ϕ 12 and ϕ 3 for the same antenna device. At about 8.2 MHz, the current I 3 is just 90 ° out of phase with the current I 12 .

In Fig. 7 ist in einer Fig. 3 entsprechenden Darstellung ein weiteres Ausführungsbeispiel für eine erfindungsgemässe Antennenvorrichtung (Fig.7d)) sowie ihre Ableitung aus einer herkömmlichen Anordnung (Fig. 7a) dargestellt. Von Fig. 3 unterscheidet sich Fig. 7 durch die Anordnung der Antennenklemmen 12. Bei Fig. 3 sind diese in der ersten Teilschlaufe 1 und bei Fig. 7 in der zweiten Teilschlaufe 2 angeordnet. Bezüglich der geometrisch jeweils mittleren Teilschlaufe 3 ergibt sich bei den beiden Ausführungsformen ein entgegengesetzter Stromlaufsinn. Ansonsten sind die beiden Ausführungsformen zueinander äquivalent. Die Klemmen 12 könnten auch im Bereich der mittleren Teilschlaufe 3 in einer der sie passierenden Leitungen angeordnet werden.FIG. 7 shows a representation corresponding to FIG. 3 Another embodiment for an inventive Antenna device (Fig.7d)) and its derivation from a conventional arrangement (Fig. 7a) shown. From Fig. 3 7 differs by the arrangement of the antenna terminals 12. In FIG. 3, these are in the first partial loop 1 and in Fig. 7 arranged in the second sub-loop 2. With regard to the geometrically middle partial loop 3 there is an opposite in the two embodiments Current sense. Otherwise, the two embodiments equivalent to each other. The terminals 12 could also in the area of the middle loop part 3 in one of them passing lines can be arranged.

Die Fläche der drei Teilschlaufen wird vorzugsweise gleich gross gewählt. Es könnten jedoch auch unterschiedliche Flächen vorgesehen werden. Die beschriebene Abstimmung der Parameter der Antennenvorrichtung auf die Resonanzfrequenz der zu detektierenden Resonanzetiketten muss nicht notwenig exakt sein. So könnte ein Phasenfehler (gegenüber der 90°-Phasenverschiebung im Resonanzfall) bis zu 30° unter Umständen toleriert werden.The area of the three partial loops is preferably the same chosen large. However, there could be different ones Areas are provided. The described coordination of Parameters of the antenna device on the resonance frequency of the resonance labels to be detected need not necessarily be exact be. A phase error (compared to the 90 ° phase shift in the case of resonance) up to 30 ° under certain circumstances be tolerated.

In Fig. 3d) sowie Fig. 7d) ist jeweils strichliert um die drei Teilschlaufen 1,2,3 herum noch eine einschlaufige sog. Kurzschlusschlaufe 14 verlegt. Diese dient dazu, die Auslöschung des Fernfeldes (3 bis 30 m) zu verbessern. Sie ist dann optimal, wenn sich die Flüsse im aufgespannten Gebiet gegenseitig kompensieren. Ist dies der Fall, dann ist der Strom in der äusseren Schleife gleich Null. Wenn nicht, dann wirkt der in der Schleife entstehende Strom dem inneren entgegen und erzwingt dadurch die Auslöschung. Zur Vermeidung von ungewollten Resonanzen kann an Stelle des Kurzschlusses in der äusseren Schleife auch ein Widerstand eingesetzt werden.In Fig. 3d) and Fig. 7d) is dashed around the three loops 1,2,3 around a single loop so-called Short circuit loop 14 laid. This serves the To improve extinction of the far field (3 to 30 m). she is optimal when the rivers stretch in the span Compensate each other. If so, then it is the current in the outer loop is zero. Unless, then the current arising in the loop acts on the inner one counter and thereby forces extinction. To avoid of unwanted resonances can replace the short circuit a resistor is also used in the outer loop will.

Mit Vorteil werden sämtliche Schlaufen der erfindngsgemässen Antennvorrichtung in einem Kunststoffgehäuse eingebettet, welches sie mechanisch stabilisiert. Ein Kunststoffgehäuse hat den Vorteil, dass es sich auf die vorteilhafte Charakteristik der erfindungsgemässen Antennvorrichtung nicht nachteilig auswirkt. Bei räumlicher Kombination mit einer Sende- oder Empfangselektronik sollte diese aus dem gleichen Grund ebenfalls in einem Kunststoffgehäuse angeordnet werden.All loops of the invention are advantageous Antenna device embedded in a plastic housing, which mechanically stabilizes them. A plastic case has the advantage that it is based on the advantageous characteristic not disadvantageous to the antenna device according to the invention affects. When combined spatially with a broadcast or receiving electronics should do this for the same reason can also be arranged in a plastic housing.

Schliesslich kann die erfindungsgemasse Antennenvorrichtung noch einseitig mit einem Abschirmblech versehen werden zwecks einseitiger Abschirmung. Das Abschirmblech wäre dabei in einigen Zentimetern Abstand (z.B. 4 cm) von der Ebene der Antennendrahtschlaufen anzuordnen.Finally, the antenna device according to the invention be shielded on one side for the purpose one-sided shielding. The shield would be in a few centimeters (e.g. 4 cm) from the plane of the Arrange antenna wire loops.

Claims (9)

  1. Antenna device for the detection of resonant tags in electronic product anti-theft systems with an antenna wire loop running in a plane between two terminals (12) and which accompanied by the formation of two electrically outer (1,3) and one electrically central partial loop (2) is twisted twice by in each case 180° and in which is connected an impedance element (11), characterized in that one (3) of the two electrically outer partial loops (1,3) is positioned geometrically between the electrically central partial loop (2) and the other electrically outer partial loop (1) and that the impedance element (11) is connected between two connection points (9,10) arranged at the entrance and exit of the geometrically central partial loop (3) and has in parallel connection a capacitor (C) and an ohmic resistor (R).
  2. Antenna device according to claim 1, characterized in that the two terminals (12) are located in the other electrically outer partial loop (1).
  3. Antenna device according to claim 1,characterized in that the two terminals (12) are arranged in the electrically central partial loop (2).
  4. Antenna device according to one of the claims 1 to 3, characterized in that L=R2C, in which L is the inductance of the geometrically central partial loop (3), R the value of the ohmic resistor and C the capacitance of the capacitor.
  5. Antenna device according to one of the claims 1 to 4, characterized in that the three partial loops (1,2,3) have the same surface area.
  6. Antenna device according to one of the claims 1 to 5, characterized in that a short-circuit loop (14) is placed externally and in the same plane around the antenna wire loop.
  7. Antenna device according to one of the claims 1 to 6, characterized in that a screening plate is provided parallel to the plane of the antenna wire loop and preferably with a spacing of 4 cm.
  8. Antenna device according to one of the claims 1 to 7, characterized in that the antenna wire loop or loops (1,2,3,14) are embedded in a plastic casing.
  9. Use of the antenna device according to one of the claims 1 to 8 for the detection of resonant tags with a predetermined resonant frequency, characterized in that the ohmic resistor (R), the capacitance of the capacitor (C) and the inductance (L3) of the geometrically central partial loop (3) are dimensioned in such a way that the alternating current resistances formed by the capacitor (C) and said inductance (L3) for the given resonant frequency of the resonant tags have the same amount as the ohmic resistor.
EP94810334A 1993-07-13 1994-06-06 Antenna device Expired - Lifetime EP0634807B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH2094/93 1993-07-13
CH209493 1993-07-13

Publications (2)

Publication Number Publication Date
EP0634807A1 EP0634807A1 (en) 1995-01-18
EP0634807B1 true EP0634807B1 (en) 1998-08-12

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP94810334A Expired - Lifetime EP0634807B1 (en) 1993-07-13 1994-06-06 Antenna device

Country Status (6)

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US (1) US5663738A (en)
EP (1) EP0634807B1 (en)
JP (1) JP3606603B2 (en)
AT (1) ATE169776T1 (en)
DE (1) DE59406653D1 (en)
ES (1) ES2122209T3 (en)

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Also Published As

Publication number Publication date
ATE169776T1 (en) 1998-08-15
EP0634807A1 (en) 1995-01-18
ES2122209T3 (en) 1998-12-16
US5663738A (en) 1997-09-02
JPH07154130A (en) 1995-06-16
DE59406653D1 (en) 1998-09-17
JP3606603B2 (en) 2005-01-05

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