The object of the invention relates to an antenna unit for product protection apparatuses, which has a carrying body assembled from an enclosing piece and a covering piece partially surrounding the enclosing piece, where the covering piece has two stem pieces and a bridging piece located between the connecting ends of the individual stem pieces and connecting them together, there is an angle of inclination of 70 to 110° between the individual stem pieces and the bridging piece, in addition it has a signal transmission element made from a conductive material and located at least partly in the enclosing piece of the carrying body and a signal management part-unit electrically connected to the signal transmission element, the signal transmission element has at least a single loop-like shape with at least two sections at an angle to each other different to 0°.

Today product protection systems are used in numerous places to prevent theft from shops. The essence of these is that passive signalling elements are placed on the products to be protected that are capable of communicating with the transceiver antenna installed in the vicinity of the entrance and exit of the shop. Depending on the result of the exchange of information between the antenna and the signalling element the signal management partunit of the antenna may send a signal to a central system, which may produce an alarm signal in the case that a product gets in the vicinity of the entrance or the exit which has not yet been paid for.

There are numerous expectations of the antennas forming a part of the product protection systems and located in the vicinity of the entrance and/or the exit of the shop. One such expectation is that it should be sufficiently sensitive to receive the signal returned by the signalling element, but remote interference signals arriving from outside the shop, for example, should not influence the appropriate operation of the antenna. The other such expectation is that the antenna unit itself should have small dimensions in the interest of it not obstructing the traffic at the entrance or at the exit. The third important requirement is that the antenna be aesthetic and also be resistant to any vandalism attempts. Numerous solutions have been elaborated to date to satisfy these requirements. Such antenna units may also be seen in patent specification registration number DE 3844848 and registration number CA 2938362.

Patent specification with registration number E 3844848 presents an antenna unit where two upper and two lower antenna loops are located in the same plane, in the case of the two upper and the two lower antenna the one is inside the other in a figure of eight, and the antenna sections close to each other are positioned inclined at an angle of approximately 20° to the vertical plane. The antenna is supported by an accommodation body made of plastic and provided with seats, the accommodation body is delimited by planar facade panels, and the edges of these are surrounded by an extruded bumper frame, the task of which is to connect together the facade panels delimiting the accommodation body. Neither the facade panels nor the extruded bumper frame take part in the operation of the antenna. The purpose of the given antenna structure, i.e. the loop arrangement is to reduce the magnitude of the antenna blind cone appearing horizontally and to improve the efficiency of detection.

The disadvantage of the solution, however, is that due to the planar arrangement it is unable to effectively overcome the interference created during the “communication” between the antenna and the goods protection label, so its operation reliability is insufficient.

An additional disadvantage is that the material and structure of the structure supporting the antenna does not facilitate appropriate reduction of the interference arriving from remote space, and, therefore, from this point of view operation reliability is not satisfactory either.

The essence of the constructions presented in patent specification registration number CA 2938362 is that the antenna is supplemented with metal structural elements for shielding the electronic part-units located in the lower part of the antenna structure.

The disadvantage of this design is that it significantly increases the physical dimensions of the antenna structure, and so it becomes difficult to position these so that they do not bother the customers so much. However, the disadvantage of the known solutions is that antenna units with large dimensions are created in the interest of achieving suitable sensitivity to closer signals and lack of sensitivity to remote interference, which obstruct the movements of the customers. While if the emphasis is placed on preferable dimensions, and the antennas are located more distant from the routes where customers walk, then the sensitivity of the antenna to the signalling element becomes worse due to the greater distance and so the level of antitheft efficiency will not be satisfactory.

An additional disadvantage in the case of the known solutions is that the antenna unit must have a support element that supports the antenna loop, which means a further increase in its size, and so it becomes even more difficult to find the optimal installation location for the antenna units along the routes where the customers walk.

Our objective with the structure according to the invention was to overcome the disadvantages of the known versions and to create an antenna unit that has significant sensitivity for detecting the signalling elements moving in the nearby space even in spite of the unconventionally small size, and that, due to its structural arrangement, is more resistant to any sabotage, and that may be produced in a simple way at a favourable cost.

The recognition that led to the solution according to the invention was that if the receiver and transmitter loops constituting the antenna are created in an unconventional way, and if the windings constituting the loops and the individual transmitter and receiver loops are arranged with respect to each other in a novel way, and if the created loops are fitted into a uniquely formed, novel carrying body, where the controlled shielding of the antenna loops is also solved, then we obtain lower inductance loops that result in better tuning, therefore in addition to reducing the size of the antenna unit the near-field sensitivity of the antenna increases, while the far-field interference sensitivity drops, furthermore its stability will also be greater, and so the task may be solved.

In accordance with the set objective the antenna unit for product protection apparatuses according to the invention, - which has a carrying body assembled from an enclosing piece and a covering piece partially surrounding the enclosing piece, where the covering piece has two stem pieces and a bridging piece located between the connecting ends of the individual stem pieces and connecting them together, there is an angle of inclination of 70 to 110° between the individual stem pieces and the bridging piece, in addition it has a signal transmission element made from a conductive material and located at least partly in the enclosing piece of the carrying body and a signal management part-unit electrically connected to the signal transmission element, the signal transmission element has at least a single loop-like shape with at least two sections at an angle to each other that is not equal to 0°, - is set up in such a way that the covering piece is made from a material that conducts electricity and there is a free opening between the free ends of the individual stem pieces opposite to the connecting ends, and in this way the covering piece forms a U-shape, and the free opening between the free ends of the stem pieces of the covering piece is more distant from the base supporting the antenna unit, while the bridging piece is closer to the base.

A further feature of the antenna unit according to the invention may be that the signal transmission element has a loop positioned in a single support plane made from metal wire formed from straight and/or curved sections.

In the case of a different version of the antenna unit the signal transmission element has two or more loop groups positioned in a single support plane created from loops formed from straight and/or curved sections connected to each other.

In the case of yet another different embodiment of the invention the signal transmission element has two or more loops made from metal wire formed from straight and/or curved sections made from windings connected to each other, where the first winding is located in the first support plane, while the other winding is located in the second support plane, the first support plane and the second support plane are positioned parallel to each other.

In the case of another different embodiment of the antenna unit the signal transmission element has two loops connected to each other made from metal wire and formed from straight and/or curved sections, where the support plane of the first loop and the support plane of the second loop have different positions. In the case of an additional embodiment of the invention the signal transmission element has two or more loop groups made from metal wire positioned in a single support plane created from loops formed from straight and/or curved sections, and two or more loop groups also made from metal wire positioned in another support plane created from loops formed from straight and/or curved sections, where the first support plane of the first loop group and the second support plane of the second loop group have different positions.

From the point of view of the invention it may be preferable if the covering piece is folded from metal plate, and optionally holes are arranged in the metal plate constituting the covering piece.

In the case of another embodiment of the antenna unit the enclosing piece is made from an insulating material. The material of the signal transmission element is metal wire.

The antenna unit according to the invention has numerous preferable characteristics. The most important of these is that due to the structure of the antenna loops and the arrangement of the windings the inductance of the antenna will be lower, and so the ability to tune it will be improved, as a result of which the near field sensitivity will be greater.

A further advantage is that due to the unique form of the carrying body far-field interference is significantly reduced, which improves the reliability of the antenna unit and the detection of the response of the active signal transmission elements moving in the near field. As a result of this the number of products that thieves intend to steal may be significantly reduced as a result of the successful alarms.

An advantage that also originates from the above is that due to the near-field sensitivity improving because of the unique structure the antenna unit may also be located more distant from access routes, which makes customers feel more comfortable, and this may also have a preferable effect on their desire to make purchases.

It is also an advantage that the dimensions of the antenna unit may be reduced, which further improves the positioning options of the antenna unit, and, in addition, a more aesthetic shape may be implemented due to the smaller size. Another feature that may be listed among the advantages is that as a consequence of the carrying body consisting of two structural units, not only is the resilience and its defence against sabotage improved, but the carrying body may be manufactured in a simpler way at a lower cost.

In the following the antenna unit according to the invention is described in more detail in connection with embodiments with reference to figures, wherein

Figure 1 shows a side view of a possible version of the antenna unit in partial crosssection,

Figure 2 shows the half view - half cross-section taken on the stepped intersection plane taken along the line II,

Figure 3 shows a view of a version of the signal transmission element according to the invention,

Figure 4 shows a view of a different version of the signal transmission element according to the invention,

Figure 5 shows a view of yet another version of the signal transmission element according to the invention,

Figure 6 shows a view of another embodiment of the signal transmission element according to the invention.

Figures 1 and 2 depict a possible version of the antenna unit 1 according to the invention. It may be observed that the antenna unit 1 consists of a base 2, a carrying body 10 positioned on that, and, in the case of the given embodiment, a signal management partunit 30 built into the base 2, and a signal transmission element 20 embedded into the carrying body 10. The enclosing piece 11 and the covering piece 12 partially covering the external surface 1 la of the enclosing piece 11 and supporting it form a part of the carrying body 10. The signal transmission element 20 is built into the inside of the enclosing piece 11. The signal transmission element 20 itself is a curved, loop-like structural element made from a metal that has at least one section 20a and at least one section 20b that are at an angle a to each other that is not equal to 0°. The sections 20a and the sections 20b may be straight or curved. In the case of straight sections 20a and sections 20b the angle a may be preferably a right angle.

The sections 20a and sections 20b located next to each other together constitute a loop 21, which is a metal strand, e.g. metal wire running in a plane or in space. After this the loop 21 of the signal transmission element 20 connects to, in a way known of in itself, to the signal management part-unit 30 installed into the base 2.

It should be noted here, however, that the metal wire, and so the loop 21 may be made using a metal material being applied to a substrate using metal vapour deposition or even by printing using metal foil.

It must also be mentioned that one loop 21 may consist of a single winding, but a loop 21 may also have several windings. In such a case the individual windings may also be located next to each other. In this way the first winding is in support plane S 1 while the other is in the parallel support plane S2. Naturally there is a metal connection between the support plane SI and the support plane S2, between the individual windings of the loop 21. This, among other things, is illustrated in figure 2, in which the first winding of the loop 21 is to be found in support plane SI while the other is to be found in support plane S2, and support plane SI and support plane S2 are located parallel to each other.

Figure 1 also illustrates that the covering piece 12 of the carrying body 10 is essentially is a U-shape bent from metal consisting of the stem piece 12a, the stem piece 12c and the bridging piece 12b located between the connecting end 12d of the first stem piece 12a and the connecting end 12e of the second stem piece 12c. The angle of inclination 0 between the stem piece 12a and the bridging piece 12b, and the stem piece 12c and the bridging piece 12b here is a right angle. It is not compulsory but it is preferable to select the angle of inclination 0 to be between 70 and 110°. Because of the metal material the first stem piece 12a, the bridging piece 12b and the second stem piece 12c are in an electrically conducting connection with each other. There is no connection between the free end 12f of the first stem piece 12a and the free end 12g of the second stem piece 12c, here the free opening 12h is created. The covering piece 12 is positioned as compared to the base 2 so that the bridging piece 12b is secured to the base 2, while the free opening 12h is positioned upwards, opposite to the base 2.

Both figure 1 and figure 2 well illustrate that the plate of the stem piece 12a and the stem piece 12c encloses the enclosing piece 11 in such a way that base plane Al of the stem, piece 12a and the support plane SI, as well as the base plane A2 of the stem piece 12c and the support plane S2 are at right angles to each other. This is important in the interest of reducing remote interference. But it must also be mentioned that the angle y between the base plane Al and the base plane A2, and the support plane SI and, optionally, the support plane S2 does not have to be a right angle, however it is essential that it be not equal to 0°.

In figure 2 it may also be seen that the covering piece 12 has openings 13. This, in the case of the production of the appropriate pattern, has, on the one part, aesthetic value, and, on the other part, reduces the weight of the covering piece 12. Thirdly, it also has a preferable influence on the effectiveness of the antenna unit 1.

Here it must also be mentioned that the enclosing piece 11 may also be made of several pieces. Its essence is that it at least partially, but preferably completely covers the signal transmission element 20. Preferably material of the enclosing piece 11 is an insulating material.

Moving over now to figure 3, a signal transmission element 20 may be observed in it, in the case of which its section 20a and its section 20b are at an angle of 90° to each other, and the loop 21 assembled from them forms a shape with a rectangular perimeter consisting of a single winding, which is located in the support plane SI.

Figure 4 depicts a different embodiment of the signal transmission element 20 of the antenna unit 1. It may be observed that here two loops 21 are linked together, and in this way the signal transmission element 20 constitutes a loop group 22 in which two loops 21 may be found that are produced from two rectangular perimeter pieces. Here this forms a figure of eight-like simple transmitter loop. Figure 5 presents a signal transmission element 20 version in which the first loop 21 and the second loop 23 are positioned so that they are rotated in space as compared to each other. The loop 21 may be found in support plane SI while the loop 23 may be found in the support plane S2, which preferably positioned are at an acute angle 8 to each other.

Figure 6 shows yet another version of the signal transmission element 20. Here the loop group 22 consisting of two loops 21 “threaded” next to each other is located in support plane SI, while the loop group 24 formed from the loops 23 is located in support plane S2. Here the support plane SI and the support plane S2 are at an acute angle 8 to each other.

Naturally the enclosing piece 11 of the carrying body 10 is formed in such a way that in all cases it is able to accommodate the planar or even spatial signal transmission element 20 with the established angle and consisting of one winding or several windings, and is able to protect it from physical impacts. While the U-shape of the covering piece 12 constitutes the rigid frame of the carrying body 10, which supports the enclosing piece 11 and the signal transmission element 20 located in it.

The operation of the antenna unit 1 according to the invention is essentially the same as that of the conventionally used antenna units. Periodically the signal management part-unit 30 sends out energy packets into the nearby space at a tuned frequency. If there is a product protection label in the given area that has not yet been deactivated by the cashier or if it has not been removed from the product, in other words the product has not been paid for, then the energy packet activates the RLC circuit of the product protection label, which emits a signal into the nearby space. This signal is received by the signal transmission element 20 embedded into the enclosing piece 11 of the carrying body 10 of the antenna unit 1. The signal received by the signal transmission element 20 passes to the signal management part-unit 30, which evaluates the received signal and sets off the alarm, which warns of an attempt to steal the product passing at that moment through the given nearby space.

The antenna unit according to the invention may be used to good effect in all places where the installation of a smaller sized, but higher efficiency and more reliably operating product protection device is desired in the accessways where customers walk in a sales outlet. List of references antenna unit base 0 carrying body 11 enclosing piece 11a external surface

12 covering piece 12a stem piece (one) 12b bridging piece 12c stem piece (other) 12d connecting end 12e connecting end 12f free end

12g free end 12h free opening

13 opening 0 signal transmission element 20a section

20b section

21 loop

22 loop group

23 loop

24 loop group

30 signal management part-unit

Al base plane

A2 base plane (other

SI support plane (one)

S2 support plane (other) a angle angle of inclination y angle

8 angle