EP0409343A1

EP0409343A1 - Vehicle identification system

Info

Publication number: EP0409343A1
Application number: EP90201931A
Authority: EP
Inventors: Willem Hendrik Jacob Venema; Jan Saeys
Original assignee: Nederlandsche Apparatenfabriek NEDAP NV
Current assignee: Nederlandsche Apparatenfabriek NEDAP NV
Priority date: 1989-07-17
Filing date: 1990-07-16
Publication date: 1991-01-23
Also published as: CA2021223A1; NL8901836A

Abstract

An electromagnetic detection and identification system for identifying vehicles or their occupants. An interrogation field is generated by a transmitter/receiver through an antenna coil. The vehicles are provided with an opening surrounded by at least one frame and a responder is arranged on or in each vehicle in the vicinity of said frame.

Description

This invention relates to an electromagnetic detection and identification system for identifying vehicles or their occupants by means of an interrogation field generated by a transmitter/receiver through an antenna coil.
Electromagnetic detection and identification systems for identifying human beings, animals and goods, including various systems of the present applicants, are well-known. Such identification systems can be used, for example, for permitting or refusing access to premises, for feeding animals, and for monitoring and supervising logistic processes.
One example of an electromagnetic detection and identification system is described in Netherlands patent specification 176404. Such systems operate as follows. An electromagnetic A.C. field is generated by a transmitter/receiver. Identification labels, also referred to as responders, are provided with an electronic circuit including at least a resonant circuit and a coding device. If the responder is moved into an electromagnetic A.C. field generated by the transmitter/receiver (the interrogation field), the resonant circuit will start resonating. By means of the resonant circuit, the responder circuit is capable of withdrawing electrical energy from the field. This energy is used, after rectification, to provide the coding device with supply power. The coding device then generates a code which through the same coil and the same electromagnetic field can be identified by the transmitter/receiver. Taking into account the maximum permissible field strength in the various countries, such identification systems can achieve a detection distance of about 90 cm. The drawback of the prior systems is that, for a number of uses, this distance is insufficient. Under certain conditions, detection is even downright impossible. In the case, for example, of persons seated in (metallic) vehicles, such as motorcars, detection is basically impossible, as the metal construction virtually is a perfect electromagnetic screen (Faraday cage). Furthermore, if identification is possible after all, the detection distance would be insufficient for the system to function properly in practice for the identification of vehicles.
It is an object of the present invention to overcome the drawbacks outlined above, and, in general, to provide an electromagnetic identification system for vehicles, such as motorcars, which operates reliably.
For this purpose, according to the present invention, a system of the above-described kind is characterized in that the vehicles are provided with an opening surrounded by at least one frame and that, in operation, a responder is arranged in the vicinity of said frame.
The transmitter/receiver generates an electromagnetic A.C. field. The field lines generated induce a current along the metallic parts surrounding vehicle openings, such as windows When a responder with a resonant circuit is applied in the vicinity of a vehicle post, the current induced, which is concentrated in the post, will in turn generate an electromagnetic field in the resonant circuit. Owing to the existence of a second field, the electromagnetic field of the transmitter/receiver will be concentrated.
In accordance with a further elaboration of the present invention, the form of the electromagnetic field of the transmitter/receiver is influenced by using a metallic floor plate, which is positioned in or on the roadway to extend partly under a vehicle in the longitudinal direction. The floor plate will cause a portion of the magnetic field lines of the electromagnetic field generated by the transmitter/receiver to be concentrated in the direction of the vehicle. Owing to the above features of the present invention, the responder is capable of drawing more electrical power from the more concentrated electromagnetic field to generate a code, which can be detected, via the same electromagnetic field, by the transmitter/receiver. Owing to the more concentrated electromagnetic field, a larger detection distance can be bridged than the conventional 90 cm.
Some embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings. In said drawings,

Fig. 1 diagrammatically shows a system according to the present invention for the identification of motorcars;
Fig. 2 shows a side-elevational view according to the arrow II of Fig. 1; and
Fig. 3 diagrammatically shows a detail of Fig. 2.

Fig. 1 shows a transmitting antenna 1 with a vehicle 2, in this case a passenger car. The field lines 3 of transmitting antenna 1 extend towards vehicle 2. Vehicle 2 is within an electromagnetic field generated through the transmitting antenna by a transmitter/receiver 10. As a consequence, an electrical current is generated in the metallic parts which surround openings, such as windows and doorways, of vehicle 2. Owing to the presence of the openings, a concentration of these induced currents is brought about. Furthermore, a metallic floor plate 9 may be provided, which promotes that the field formed by antenna 1 is concentrated in the direction of vehicle 2.
Fig. 2 shows a practical arrangement. Antenna 1 is arranged next to the vehicle and is dimensioned to match the dimension of the vehicles to be identified. For example, for passenger cars the antenna coil may be 4 m long and 1 m high. As a result of the electromagnetic field generated, a current is induced around window 4 in door 5. A floor plate 9 is again provided to bring about a concentration effect with regard to the electromagnetic field. The (A.C.) current i induced around window opening 4 by the interrogation field generates in turn an electromagnetic A.C. field, which can serve as an interrogation field for a responder. A responder placed within the field generated by the current i around a window post 6 is shown schematically at 7 in Fig. 2. All this is shown in more detail in Fig. 3.
Fig. 3 shows a responder 7 in the vicinity of post 6. The current i in post 6 generates an electromagnetic A.C. field 8. As the responder 7 is in the vicinity of the post, the resonant circuit of the responder is coupled electromagnetically with the electromagnetic field of the current through the post. When responder 7 is positioned so as to achieve maximum coupling for this application, the intake of electrical energy will be relatively high. When used with vehicles, the responder 7 is preferably arranged in one of the corners of the window or doorway. In fact, the field is concentrated in the vicinity of the corner of a window or doorway, at least in the interior zone of the angle. In Fig. 3, responder 7 is shown to be positioned in the vicinity of the front bottom corner of the window opening of a passenger car 2. Alternatively, however, the responder may be positioned in the vicinity of any of the other corners.
A final feature of importance to the present invention is that the transmitting antenna should be positioned so that the current flows optimally through the vehicle posts. To this effect, the antenna is preferably disposed in a vertical plane to extend substantially parallel to the side of the vehicles to be identified.
It is noted that, in view of the above, various modifications will readily occur to those skilled in the art. Thus, if the system is designed to identify vehicles, a responder will be fixed to the vehicle. If, however, the system is intended for the identification of passengers, the vehicle could be provided with a holder disposed, in the manner described, in the field of an induction current, and adapted to receive a card-shaped or other responder in a predetermined position.
These and similar modifications are considered to fall within the scope of the present invention.

Claims

1. An electromagnetic detection and identification system for identifying vehicles or their occupants by means of an interrogation field generated by a transmitter/receiver through an antenna coil, characterized in that the vehicles are provided with an opening surrounded by at least one frame and that, in operation, a responder is arranged in the vicinity of said frame.

2. An electromagnetic detection and identification system as claimed in claim 1, characterized in that the responder is fixed.

3. A system as claimed in claim 1, characterized by a holder arranged in the vicinity of the frame, said holder being adapted to receive a responder of a pre-determined shape in a pre-determined position.

4. A system as claimed in any of the preceding claims, characterized in that the responder is arranged in the vicinity of a corner of the opening.

5. A system as claimed in any of the preceding claims, characterized in that the opening is a window or doorway of the vehicle.

6. A system as claimed in any of the preceding claims, characterized in that the antenna is an elongate antenna coil extending horizontally in a substantially vertical plane approximately parallel to the side face of the vehicles.

7. A system as claimed in claim 6, characterized by a metal plate disposed in or on the roadway under the field generated by the antenna coil to extend partly under a vehicle provided with a responder.

8. A method of identifying vehicles or their occupants by means of an electromagnetic detection and identification system, characterized in that an electromagnetic interrogation field is formed substantially transversely to the side of the vehicle, and that a responder is placed in the vicinity of a post of the vehicle extending along a doorway or window of the vehicle.