Device and method for reading identifiers of moving objects

Abstract

The invention relates to a device and a method for reading transponders of moving objects, said method allowing multiple objects to be detected simultaneously, namely regardless of the position and the travel direction of the objects. This is achieved in that a device for reading UHF RFID signals emitted from or reflected by at least one transponder (13) of an identifier has at least one UHF RFID reading device (14). Whereas the identifier can be, for example, a vehicle registration plate, it is conceivable that the moving object is a motor vehicle (10). The at least one reading device (14) for reading the transponder (13) can be located next to, above or on a road (11) on which the object moves. The invention is characterized in that the at least one reading device (14) has an antenna in the form of a monopole antenna.

Description

[0001] Device and method for reading characteristics of moving objects

[0002] Description

[0003] The invention relates to a device for reading UHF RFID signals according to the preamble of claim 1. Furthermore, the invention relates to a method for reading UHF RFID signals according to the preamble of claim 19.

[0004] To identify moving objects, such as motor vehicles, it is known that contactless readable transponders are assigned to these objects. These transponders have a data memory on which any data about the object can be stored. In the case of a transponder arranged on a motor vehicle, this data can be, for example, information about the vehicle, the owner, the insurance, the registration or the like. As is known, these transponders can be attached to the motor vehicle or to a windshield in a tag or label. Other embodiments provide for the contactless readable transponder to be integrated into a license plate. The license plate can, for example, be a vehicle license plate that is attached to the vehicle.

[0005] Handheld scanners can be used to read the transponders on a stationary object. The handheld scanners emit UHF (or NFC) RFID signals, which are then detected or reflected by the transponders. The information stored in the data storage device can be read using the signals emitted or reflected by the transponders. Handheld scanners function only to a very limited extent or not at all on moving objects. To read transponders attached to moving objects or moving vehicles, it is common practice to install a reading device with an antenna near a roadway. This reading device can be located in a corresponding device next to or above the roadway. Designs are also known in which the reading device or antenna is integrated into the road surface.It is known that UHF antennas are used to read the RFID signals of the transponders.

[0006] As long as the moving objects or motor vehicles approach the antenna from a specific direction and with a sufficiently large time gap, the transponders can be read with at least a large degree of reliability. However, if the transponders of a large number of vehicles are to be read on a busy, possibly multi-lane, road, and the vehicles are approaching from different directions, as may be the case at an intersection, for example, the existing reading devices reach their technical limits. Reliable reading of the transponders of all vehicles is therefore no longer feasible. This renders such antennas unusable, especially for detecting toll-paying vehicles.

[0007] Based on this, the object of the present invention is to provide a device and a method for reading transponders of moving objects, by means of which several objects can be detected simultaneously, regardless of the position and direction of travel of the objects.

[0008] A device for solving this problem has the features of claim 1. Accordingly, it is provided that a device for reading UHF RFID signals that are emitted or reflected by at least one transponder of a license plate has at least one UHF RFID reading device. While the license plate can be a vehicle license plate, for example, it is conceivable that the moving object is a motor vehicle. This at least one reading device for reading the transponder can be located next to, above, or in a roadway on which the object is moving. The invention is characterized in that the at least one reading device has an antenna that is designed as a monopole antenna. This antenna has an electrically conductive plate element and a first and a second electrically conductive rod element.These rod elements are arranged vertically on the plate element and galvanically separated from the plate element. The device according to the invention is envisaged to be integrated into a road surface or positioned as at least one pillar next to the roadway or attached to a crossbeam above the roadway. This invention makes it possible to read multiple moving transponders simultaneously or with a short time interval. Directed signals are emitted from the antenna, which are detected by the transponders and re-transmitted or reflected. The information detected by the antenna is then evaluated by a control unit. It is irrelevant where the transponder or object is located relative to the antenna.This allows not only transponders moving toward the antenna in the opposite direction of travel of the object to be detected, but also transponders moving away from the antenna in the same direction as the object. This allows the invention to detect not only transponders located at the front of a vehicle, but also those positioned at the rear of the vehicle. Transponders of objects passing the reading device from the side, diagonally, or across the vehicle can also be detected.

[0009] Due to the ability to detect the transponders and thus the moving objects in any position relative to the antenna, the device according to the invention also makes it possible to determine a movement profile of the object or the speed of the object. In particular, due to the high detection rate and the wide detection horizon, the claimed device is particularly well suited for reading a large number of transponders moving around the antenna, as is the case, for example, on a busy road or at an intersection. It is conceivable that several of the devices according to the invention are arranged spaced apart from one another and / or at different positions relative to the roadway, for example to generate redundant data detection or to detect vehicles on multiple roads.By comparing the data recorded at different times, information about traffic flow and traffic development can also be obtained.

[0010] Preferably, a voltage source from a power supply network is assigned to the plate element and the rod elements of the reading device or the antenna. UHF RFID signals can be applied between the plate element and the rod elements via this voltage source. By appropriately controlling the voltage, the reading device's signals can be emitted in different spatial directions. This variable radiation characteristic of the antenna allows for the detection of at least almost all transponders or objects around the reading device.

[0011] In particular, the first rod element and the second rod element are arranged at a distance of one-quarter to three-quarters of the wavelength of the UHF signals. This spacing of the two rod elements achieves both destructive and constructive superposition of the electromagnetic waves emitted by both rod elements. Depending on the amplitude and phase shift of the signals fed into both rod elements, radiation patterns of the antenna can be specifically tailored to the situation.

[0012] A further advantageous embodiment may provide for the first rod element and the second rod element to be arranged at a distance of half a wavelength from each other. This also provides the possibility of generating targeted radiation characteristics of the measuring device by appropriately controlling the rod elements.

[0013] Preferably, the invention can also provide that the feed network is designed such that, with the voltage source between the plate element and the second rod element, UHF RFID signals can be applied, the phases of which are identical to the UHF RFID signals present between the plate element and the first rod element. Likewise, it is conceivable that the feed network is designed such that, with the voltage source between the plate element and the second rod element, UHF RFID signals can be applied, the amplitudes of which are identical to the UHF RFID signals present between the plate element and the first rod element. When the two rod elements are fed with UHF RFID signals of the same phase and amplitude, a radiation pattern is achieved that has two main lobes. These main lobes are shifted significantly downwards (towards the plate element) compared to an elliptical torus of a simple monopole antenna.It proves particularly advantageous that the diameter of the plate element can be less than 0.5 m to achieve the described effect. The directional radiation pattern achieved in this way allows for higher radiated transmission powers. This enables a wider detection range of the reading device, resulting in a more reliable detection rate and a higher detectable object speed.

[0014] A particularly advantageous embodiment can provide that the monopole antenna has a third and a fourth electrically conductive rod element, each arranged perpendicular to the plate element, and that the third rod element and the fourth rod element are arranged at a distance of one-quarter to three-quarters of the wavelength of the UHF signals from one another, and that a connecting line between the first and the second rod element and a connecting line between the third and fourth rod element each intersect halfway along their path, and that both connecting lines are arranged orthogonally to one another. It is conceivable that the third rod element and the fourth rod element are arranged at a distance of half a wavelength of the UHF signals from one another.

[0015] Furthermore, it is conceivable for the feed network to be designed in such a way that, with the voltage source, UHF RFID signals can be applied between the plate element and the third rod element, as well as between the plate element and the fourth rod element, which signals are 180° phase-shifted compared to the UHF RFID signals present between the plate element and the first rod element. Likewise, it is conceivable for the feed network to be designed in such a way that, with the voltage source, UHF RFID signals can be applied between the plate element and the third rod element, as well as between the plate element and the fourth rod element, which signals have the same amplitude as the UHF RFID signals present between the plate element and the first rod element. This arrangement of the rod elements allows UHF RFID transponders to be detected in multiple spatial directions. Depending on requirements, the detection direction can be changed at a high detection rate.

[0016] In particular, it is conceivable that the vertically arranged rod elements are designed as top-loaded monopoles. The rod elements are provided with electrically conductive disc elements with a round, elliptical, square, or rectangular shape at their ends facing away from the plate element. This allows the rod elements to be shortened in length while maintaining the antenna's resonant frequency. For example, a rod element length of 3 cm would then be sufficient. This measure would further flatten the entire antenna arrangement, simplifying integration into the device.

[0017] Another conceivable embodiment may provide for the supply network to be designed such that three of the four rod elements can be short-circuited to the plate element, and that UHF RFID signals can be applied between the plate element and the remaining rod element using the voltage source. The three short-circuited rod elements thus serve as reflectors for the electromagnetic radiation emitted by the remaining rod element. This has the advantage that, for example, for applications on a motorway or expressway with dedicated lanes, the radiation pattern can be directed toward approaching vehicles, thus enabling longer detection zones and thus higher detection speeds.

[0018] Furthermore, the invention can provide for the voltage source to vary the radiation characteristics of the at least one antenna, particularly periodically. This variation allows the device to be used in a situation-dependent and thus highly flexible manner.

[0019] A further embodiment may provide that the plate element has an electrically conductive border on its plate edge pointing in the direction of the rod elements, and that the height of the border extends at least to the height of the ends of the rod elements facing away from the plate element. Furthermore, it may be provided that the feed network and / or the voltage source are integrated in a housing arranged on the side of the plate element facing away from the rod elements. It is also conceivable that the antenna is integrated into the covering such that the side of the plate element facing the rod elements is oriented in the direction of the covering. Preferably, two, three, four or more reading devices are arranged next to and / or above and / or on and / or in the path traveled by the moving object in order to detect a plurality of objects simultaneously.A method for achieving the stated object comprises the measures of claim 19. Accordingly, it is provided that for reading out UHF RFID signals which are emitted by or reflected from at least one transponder of a license plate, in particular a vehicle license plate, of a moving object, the reading is carried out using a device according to at least one of claims 1 to 18. The method according to the invention is characterized in that a radiation characteristic of at least one antenna is varied such that it is oriented in the direction of the moving object. As a result, each transponder of an object can be detected and read out regardless of its position relative to the device. This can be done with a high sampling rate using the method and the device described here.

[0020] The invention preferably provides that, to change the radiation pattern, an electrical voltage is varied between a plate element and at least two rod elements of the antenna. By varying the electrical voltage, the radiated pattern can be radiated in virtually any direction.

[0021] It is preferably conceivable that, by varying the radiation characteristics of the at least one antenna, UHF RFID signals can be read from transponders approaching the antenna and / or from transponders moving away from the antenna. The emitted characteristics of the at least one antenna can be varied such that the UHF RFID signals can be read in a 360° range around the antenna, in particular in a forward, backward, sideways, or diagonal direction.

[0022] A preferred embodiment of the invention is explained in more detail below with reference to the drawing, in which:

[0023] Fig. 1a is a schematic representation of a possible embodiment of the method according to the invention,

[0024] Fig. 1b is a further schematic representation of the method according to Fig. 1a, Fig. 2 is a schematic representation of a further embodiment of the method according to the invention,

[0025] Fig. 3 is a schematic representation of a further embodiment of the method according to the invention,

[0026] Fig. 4 is a schematic representation of a further embodiment of the method according to the invention,

[0027] Fig. 5a is a schematic representation of the device according to the invention,

[0028] Fig. 5b is a representation of a radiation characteristic of the device according to Fig. 5a,

[0029] Fig. 6a is a schematic representation of a further embodiment of the device according to the invention,

[0030] Fig. 6b is a representation of a radiation characteristic of the device according to Fig. 6a,

[0031] Fig. 6c is a representation of a further radiation characteristic of the device according to Fig. 6a, and

[0032] Fig. 7 is a schematic representation of a further embodiment of the device according to the invention,

[0033] The method according to the invention makes it possible to read multiple transponders from moving objects, regardless of their direction of movement. The moving objects can be motor vehicles. The transponders can be located, for example, on or in the license plate of the motor vehicle or in a windshield label. It is also conceivable for the transponders to be located on the vehicle's tires, underneath the vehicle, or at another location on the vehicle. The data stored on the transponders and to be read can be related to a toll system, a parking system, refueling applications, or can be used to identify the vehicle or the vehicle owner. In order to read this data contactlessly, the invention provides a device with a reading unit that is assigned to a roadway on which the motor vehicles are moving. Several conceivable embodiments are illustrated in the figures.However, it should be expressly noted that the invention is not limited to the embodiments presented here. Rather, the scope of protection is intended to encompass further embodiments.

[0034] Fig. 1a shows two motor vehicles 10 moving along a roadway 11 in a direction of travel 12. The motor vehicles 10 each have a transponder 13 at the front and rear. These transponders 13 can, for example, be integrated into a license plate of the motor vehicle 10. Alternatively, it is also conceivable for the transponders 13 to be attached to another location on the motor vehicle 10 or to another component of the motor vehicle 10, such as the wheels.

[0035] In the exemplary embodiment of the method according to the invention shown in Fig. 1a, a reading device 14 for transmitting and receiving UHF RFID signals is integrated into the roadway 11. This reading device 14 has at least one antenna, a control device 30, and a power supply or feed network 31. Because the reading device 14 is integrated into the roadway 11 or into the surface of the roadway 11, it is located in direct proximity to the motor vehicles 10 without obstructing the vehicles 10. As shown highly schematically in Fig. 1a, outgoing signals 15 are emitted by the reading device 14. These outgoing signals 15 can be focused or aligned by the control device 30 such that they are aligned with the detected transponders 13.In this case, both transponders 13 of motor vehicles 10 approaching the reading device 14 and transponders 13 of motor vehicles 10 moving away from the reading device 14 in the direction of travel 12 can be detected. The outgoing signals 15 are either reflected by the transponders 13, or the transponders 13, which can be active or passive RFID chips, emit incoming signals 16 (Fig. 1b). These reflected or incoming signals 16 are detected and evaluated by the laser device 14. The evaluation signals can be used to detect the information stored in the data storage devices of the transponders 13.

[0036] In addition to the embodiment shown in Figs. 1a and 1b, it is also conceivable for the reading device 14 to be arranged in a column 17 next to the roadway 11 (Fig. 2). The transmitting and receiving principle is identical to the previously described embodiment. By positioning the reading device 14 in a column 17, the transmitting and receiving horizon of the reading device 14 can be increased.

[0037] Finally, it is also conceivable for the reading device 14 to be housed in a cross member 18 spanning the roadway 11. This allows both a large transmission and reception horizon of the reading device 14 and the advantageous proximity of the reading device 14 to the motor vehicles 10 to be achieved.

[0038] By means of the method described here and by means of the reading device 14, it is possible to detect not only motor vehicles 10 on one roadway 11, but also on several adjacent roadways 11. As shown schematically in Fig. 4, the outgoing signals 15 can be emitted not only parallel to the roadway 11 in the direction of travel 12, but also perpendicular to it, so that several motor vehicles 10 can also be detected on other roadways 11. This proves to be particularly advantageous on busy roads and in intersection areas. Likewise, the incoming signals (not shown in Fig. 4) from vehicles 10 that are on different roadways 11 can be detected. By continuously detecting signals, the reading device 14 can not only read out information about the motor vehicles 10, but also record their speed.

[0039] Fig. 5a shows a possible embodiment of the reading device 14 for UHF RFID signals or an antenna arrangement. This antenna arrangement is characterized by the fact that two electrically conductive rod elements 20, 21 are arranged perpendicularly on a plate element 19. A key feature of this arrangement is that the two rod elements 20, 21 are spaced apart by half the wavelength of the UHF signals. In the embodiment shown in Fig. 5a, the plate element 19 lies in the xy plane, and the two rod elements 20, 21 are aligned parallel to the z axis.

[0040] A feed network 31 for supplying the reading device 14 with electrical energy is designed such that, with a voltage source, UHF RFID signals can be applied between the plate element 19 and the second rod element 21, the phase and / or amplitude of which are identical to the UHF RFID signals present between the plate element 19 and the first rod element 20. With identical phase and amplitude, the radiation characteristic shown in Fig. 5b results for the reading device 14 shown in Fig. 5a. This radiation characteristic has two main lobes 32, 33 that are shifted in the direction of the plate element 19. This characteristic arises because components of the electric fields in the y-direction of both electromagnetic beams emitted by the rod elements 20, 21 are superimposed constructively and the components of the electric fields in the x-direction are superimposed destructively.

[0041] Fig. 6a shows a further embodiment of the reading device 14 according to the invention. In addition to the first and second rod elements 20, 21, the antenna arrangement has a third and a fourth rod element 22, 23, which are also aligned perpendicular to the plate element 19 and thus parallel to the rod elements 20, 21. These two rod elements 22, 23 are also electrically conductive. The third rod element 22 and the fourth rod element 23 are arranged at a distance of half the wavelength of the UHF signals from one another. A connecting line between the first and second rod elements 20, 21 and a connecting line between the third and fourth rod elements 22, 23 each intersect halfway along their path, with both connecting lines being arranged orthogonally to one another.The four rod elements 20-23 thus form the corners of a square, with the diagonal connecting the opposite corners having a length of half the wavelength of the UHF signals.

[0042] In this exemplary embodiment, the feed network 31 is designed such that, with the voltage source, UHF RFID signals can be applied between the plate element 19 and the third rod element 22, as well as between the plate element 19 and the fourth rod element 23, which signals are 180° out of phase with the UHF RFID signals present between the plate element 19 and the first rod element 20 and / or have the same amplitude. With a phase shift of 180° and the same amplitudes, the radiation pattern shown in Fig. 6b results for the antenna arrangement shown in Fig. 6a. This radiation pattern has four main lobes 34 to 37. The feed network 31 can also be designed such that three of the four rod elements 20-23 can be short-circuited to the plate element 19, and that, with the voltage source, the UHF RFID signals can be applied between the plate element 19 and the remaining rod element.The resulting radiation characteristic of the reading device 14 is shown in Fig. 6c.

[0043] Fig. 7 shows a further embodiment of the reader device 14 according to the invention. The vertically arranged rod elements 20-23 are designed here as top-loaded monopoles. In the illustrated embodiment, the rod elements 20-23 have electrically conductive disc elements 24-27 at their ends facing away from the plate element 19. The disc elements 24-27 shown are round. However, it is also conceivable for the disc elements 24-27 to be elliptical, square, rectangular, or similar.

[0044] Furthermore, the plate element 19 has an electrically conductive border 28 at one plate edge pointing in the direction of the rod elements 20-23. The height of the border 28 extends at least to the height of the ends of the rod elements 20-23 facing away from the plate element 19. However, the border 28 can also extend beyond the ends of the rod elements 20-23 facing away from the plate element 19. The feed network 31 and the voltage source are integrated in a housing arranged on the side of the plate element 19 facing away from the rod elements 20-23. Optionally, the antenna arrangement can be covered with an electrically non-conductive cover 29, so that the rod elements 20-23 are protected from mechanical and chemical influences.

[0045] The antenna arrangement shown here is integrated into the roadway 11 in such a way that the side of the plate element 19 facing the rod elements 20-23 is oriented towards the road surface.

[0046] Furthermore, the invention is not limited to the first rod element 20 and the second rod element 21 being arranged at a distance of half a wavelength of the UHF signals from one another. In further embodiments, the first rod element 20 and the second rod element 21 and / or the third rod element 22 and the fourth rod element 23 are arranged at a distance of one-quarter to three-quarters of a wavelength of the UHF signals from one another.

[0047] *****

[0048] List of reference symbols

[0049] 10 motor vehicle

[0050] 11 Roadway

[0051] 12 Direction of travel

[0052] 13 transponders

[0053] 14 Reading device

[0054] 15 outgoing signal

[0055] 16 incoming signal

[0056] 17th pillar

[0057] 18 T raverse

[0058] 19 plate element

[0059] 20 rod element

[0060] 21 rod element

[0061] 22 rod element

[0062] 23 rod element

[0063] 24 disc element

[0064] 25 disc element

[0065] 26 Disc element

[0066] 27 Disc element

[0067] 28 border

[0068] 29 Cover

[0069] 30 Control device

[0070] 31 Dining Network

[0071] 32 main lobe

[0072] 33 Main lobe

[0073] 34 Main lobe

[0074] 35 Main lobe

[0075] 36 Main lobe

[0076] 37 Main lobe

Claims

Patent claims 1. Device for reading UHF RFID signals emitted or reflected by at least one transponder (13) of a license plate, in particular a vehicle license plate, of a moving object, preferably a motor vehicle (10), comprising at least one UHF RFID reading device (14), wherein the reading device (14) has at least one antenna, and wherein the at least one reading device (14) is integrated next to and / or above and / or on a route traveled by the moving object, preferably a roadway (11), and / or in a surface of the route, in particular in a road surface, characterized in that one antenna of the at least one reading device (14) is designed as a monopole antenna with an electrically conductive plate element (19) and a first and a second electrically conductive rod element (20, 21), wherein the rod elements (20,21) arranged perpendicularly on the plate element (19) and the plate element (19) and the rod elements (20, 21) are galvanically isolated from each other.

2. Device for reading UHF RFID signals according to claim 1, characterized in that a voltage source of a power supply network (31) of the UHF RFID reader (14) is assigned to the plate element (19) and the rod elements (20, 21) in order to apply UHF RFID signals between the plate element (19) and the rod elements (20, 21).

3. Device for reading UHF RFID signals according to claim 1 or 2, characterized in that the first rod element (20) and the second rod element (21) are arranged at a distance of one quarter to one three-quarters of the wavelength of the UHF signals (A / 4 to % A) from each other.

4. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the first rod element (20) and the second rod element (21) are arranged at a distance of half a wavelength of the UHF signals (A / 2) from each other.

5. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the power supply network (31) is designed such that UHF RFID signals can be applied with the voltage source between the plate element (19) and the second rod element (21), the phases of which are identical to the UHF RFID signals applied between the plate element (19) and the first rod element (20).

6. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the power supply network (31) is designed such that UHF RFID signals can be applied with the voltage source between the plate element (19) and the second rod element (21), the amplitudes of which are identical to the UHF RFID signals applied between the plate element (19) and the first rod element (20).

7. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the monopole antenna has a third and a fourth electrically conductive rod element (22, 23) arranged perpendicular to the plate element (19) and that the third rod element (22) and the fourth rod element (23) are arranged at a distance of one quarter to three-quarters of the wavelength of the UHF signals (A / 4 to % A) from each other and that a connecting line between the first and second rod element (20, 21) and a connecting line between the third and fourth rod element (22, 23) each intersect at half their length and that both connecting lines are arranged orthogonally to each other.

8. Device for reading UHF RFID signals according to claim 7, characterized in that the third rod element (22) and the fourth rod element (23) are arranged at a distance of half a wavelength of the UHF signals (A / 2) from each other.

9. Device for reading UHF RFID signals according to claim 7 or 8, characterized in that the power supply network (31) is designed such that UHF RFID signals can be applied to the voltage source between the plate element (19) and the third rod element (22) as well as between the plate element (19) and the fourth rod element (23), which are different from those between the plate element (19) and the first rod element (20) are phase-shifted by 180° in the UHF RFID signals.

10. Device for reading UHF RFID signals according to claims 7, 8 or 9, characterized in that the power supply network (31) is designed such that UHF RFID signals can be applied with the voltage source between the plate element (19) and the third rod element (22) as well as between the plate element (19) and the fourth rod element (23), which have the same amplitude as the UHF RFID signals applied between the plate element (19) and the first rod element (20).

11. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the vertically arranged rod elements (20-23) are designed as top-loaded monopoles.

12. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the rod elements (20-23) have electrically conductive disc elements (24-27) with a round, elliptical, square or rectangular shape at their ends facing away from the plate element (19).

13. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the power supply network (31) is designed such that three of the four rod elements (20-23) can be short-circuited with the plate element (19) and that the voltage source can be used to apply the UHF RFID signals between the plate element (19) and the remaining rod element (20-23).

14. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the voltage source allows the radiation characteristic and / or the radiation direction of the at least one antenna to be varied, in particular periodically.

15. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the plate element (19) is attached to its plate edge has an electrically conductive border (28) pointing in the direction of the rod elements (20-23) and that the height of the border (28) extends at least to the height of the ends of the rod elements (20-23) facing away from the plate element (19).

16. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the power supply network (31) and / or the voltage source are integrated in a housing arranged on the side of the plate element (19) facing away from the rod elements (20-23).

17. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that the antenna is integrated into the surface such that the side of the plate element (19) facing the rod elements (20-23) is aligned in the direction of the surface of the roadway (11).

18. Device for reading UHF RFID signals according to one of the preceding claims, characterized in that two, three, four or more reading devices (14) are arranged next to and / or above and / or on and / or in the path traveled by the moving object in order to detect a plurality of objects simultaneously.

19. Method for reading UHF RFID signals emitted or reflected by at least one transponder (13) of a license plate, in particular a vehicle license plate, of a moving object, preferably a motor vehicle (10), with a device according to at least one of claims 1 to 18, characterized in that a radiation characteristic of at least one antenna is varied such that it is oriented in the direction of the moving object.

20. Method for reading UHF RFID signals according to claim 19, characterized in that an electrical voltage is varied between a plate element (19) and at least two rod elements (20, 21) of the antenna to change the radiation characteristic.

21. Method for reading UHF RFID signals according to claim 19 or 20, characterized in that UHF RFID signals are read by varying the radiation characteristic of the at least one antenna from transponders (13) approaching the antennas and / or from transponders (13) moving away from the antenna.

22. Method for reading UHF RFID signals according to at least one of claims 19 to 21, characterized in that the radiation characteristic of the at least one antenna is varied such that UHF RFID signals are read in a 360° range, in particular in a forward, backward, sideways or diagonal direction, around the antenna. *****

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