Antenna Unit With Automatic Tuning

• US 20110148583A1
• Filed: 03/05/2010
• Published: 06/23/2011
• Est. Priority Date: 03/06/2009
• Status: Active Grant

• Current Assignee: N.V. Nederlandsche Apparatenfabrick Nedap
• Original Assignee: N.V. Nederlandsche Apparatenfabrick Nedap
• Inventors: Stekelenburg, Jan Cornelis, Roosenboom, Derk Jan
• Granted Patent: US 9,088,065 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 7/00 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
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance

Abstract

An antenna unit provided with an antenna which comprises at least one turn, wherein the antenna unit is further provided with an electronic circuit which is connected with the antenna, wherein the electronic circuit comprises connection contacts for connecting the antenna unit with a transmitting device, wherein the electronic circuit is arranged to draw energy from a transmission signal which is supplied to the connection contacts and, utilizing this energy, to tune the antenna unit such that this antenna unit has an impedance which has at least substantially no imaginary component in use of the transmission signal concerned.

Claims

1. An antenna unit provided with an antenna which comprises at least one turn, characterized in that the antenna unit is further provided with an electronic circuit which is connected with the antenna, wherein the electronic circuit comprises connection contacts for connecting the antenna unit with a transmitting device, wherein the electronic circuit is arranged to draw the energy which the electronic circuit needs for its operation from a transmission signal which is supplied to the connection contacts and, utilizing this energy, to tune the antenna unit such that this antenna unit has an impedance which has at least substantially no imaginary component in use of the transmission signal concerned.

2. An antenna unit according to any one of the preceding claims, characterized in that the electronic circuit is mechanically attached to the antenna.

3. An antenna unit, according to claim 2, characterized in that the electronic circuit is included in a housing which is mechanically attached to the antenna.

4. An antenna unit according to claim 3, characterized in that the electronic circuit is included in a housing which is arranged through injection molding.

5. An antenna unit according to claim 4, characterized in that the housing also encloses a part of the antenna.

6. An antenna unit according to any one of the preceding claims, characterized in that the electronic circuit is provided with a tuning circuit which forms a tuning capacity which is connected with the antenna, wherein the tuning circuit is arranged to be able to set the magnitude of the tuning capacity.

7. An antenna unit according to claim 6, characterized in that the electronic circuit is arranged to determine and set a magnitude of the tuning capacity, such that this tuning capacity at least substantially compensates the imaginary part of the impedance of the antenna in the use of said transmission signal.

8. An antenna unit according to any one of the preceding claim 6 or 7, characterized in that the electronic circuit is further provided with a supply circuit for taking up the energy from the transmission signal and a measuring and control circuit which comprises said tuning circuit, wherein the electronic circuit is so arranged that the measuring and control circuit for its operation can receive the energy required therefor from the supply circuit and wherein the measuring and control circuit is arranged to measure whether the antenna in combination with the tuning circuit comprises an impedance with an imaginary component and to control the tuning circuit such that any measured imaginary component is reduced.

9. An antenna unit according to claim 8, characterized in that the measuring and control circuit controls the tuning circuit to reduce the measured imaginary component of the impedance when the measured imaginary component is greater than a predetermined value.

10. An antenna unit according to claim 8 or 9, characterized in that the measuring and control circuit is provided with a control circuit, a current circuit for generating a first signal which represents the phase of a current through the antenna, a voltage circuit for generating a second signal which represents the phase of a voltage across the antenna and the tuning circuit and a phase comparator for comparing the first signal and the second signal, wherein the control circuit is arranged for, on the basis of a phase difference signal generated by the phase comparator that represents a phase difference between the first and second signal, controlling the tuning circuit such that said imaginary component is reduced.

11. An antenna unit according to claim 10, characterized in that the electronic circuit is further provided with a terminating switch for modulating the energy supply to the connection contacts of the antenna unit.

12. An antenna unit according to claim 10 or 11, characterized in that the current circuit is part of the supply circuit.

13. An antenna unit according to any one of claims 10-12, characterized in that the electronic circuit is further provided with a transformation selection circuit which is connected by a first side with the connection contacts and which is connected by a second side with the tuning circuit, wherein the ratio between the number of turns on the first side of the transformer and the number of turns on the second side of the transformer is settable, wherein said setting can be carried out, for example, by hand or through a control signal.

14. An antenna unit according to claim 13, characterized in that the voltage circuit is part of the transformation selection circuit.

15. An antenna unit according to any one of the preceding claims 10 to 14, characterized in that the electronic circuit is further provided with a reset unit for resetting the electronic circuit when the energy supply to the antenna unit falls below a predetermined value, wherein as a result of resetting the antenna is re-tuned by the electronic circuit.

16. An antenna unit according to any one of the preceding claims, characterized in that the electronic circuit is arranged for, at the start of the supply of a transmission signal to the antenna unit and/or at predetermined moments when a transmission signal is supplied to the antenna unit, tuning the antenna unit such that this antenna unit has an impedance which has at least substantially no imaginary component in use of the transmission signal concerned.

17. An antenna unit according to any one of the preceding claims, characterized in that the electronic circuit is controllable with a control signal which is supplied to the connection contacts.

18. An antenna unit according to claim 11, characterized in that the terminating switch is controllable by the control circuit for sending data to a reader connected with the connection contacts by closing and opening again the terminating switch in the rhythm of the data to be sent.

19. An antenna unit according to claims 13 and 17, characterized in that said ratio between the turns is settable with the control signal which is supplied to the connection contacts.

20. An antenna unit according to any one of the preceding claims, characterized in that the electronic circuit is arranged for generating an error signal which is supplied to the connection contacts when the tuning cannot be carried out in a predetermined desired manner, wherein said supply of the error signal to the connection contacts may be carried out, for example, through said modulation with the aid of the terminating switch according to claim 11.

21. An antenna unit according to claim 20, characterized in that the error signal is superposed on the transmission signal which is supplied to the connection contacts.

22. An antenna unit according to any one of the preceding claims, characterized in that the antenna unit is arranged for operation in a half-duplex system and for operation in a full-duplex system.

23. An antenna unit according to any one of the preceding claims, characterized in that the electronic circuit is arranged to be activated in response to a command, for carrying out a tuning of the antenna unit.

24. An antenna unit according to claim 23, characterized in that the tuning can be started through an activation signal which is supplied to the electronic circuit, more particularly through an activation signal which is supplied to the connection contacts and/or through a manually operable switch of the antenna unit.

25. An antenna unit according to claim 24, characterized in that the activation signal is formed by the transmission signal, so that the antenna unit carries out the tuning as soon as the transmission signal is supplied to the antenna unit.

26. A system provided with an antenna unit according to any one of the preceding claims and a reader for reading out a responder, wherein the reader is connected with the connection contacts for supplying a transmission signal to the antenna unit for emitting an electromagnetic interrogation field with the antenna unit, wherein a responder when introduced into the interrogation field responds by emitting a reply signal.

27. A system according to claim 26, characterized in that the system is arranged to receive the reply signal from the responder with the antenna unit and to supply same via the connection contacts to the reader.

28. A system according to any one of claim 26 or 27, characterized in that the system is provided with an antenna unit according to any one of claim 17 or 19, wherein the reader is arranged to supply the control signal to the connection contacts.

29. A system according to claim 28, characterized in that the reader is arranged to superpose the control signal on the transmission signal.

30. A system according to any one of claims 26-29, characterized in that the system is provided with an antenna unit according to claim 11, 18 or 20, wherein the reader is arranged to detect the terminating switch being closed.

31. A system according to any one of claims 26-30, characterized in that the system is provided with an antenna unit according to claim 20 or 21, wherein the reader is arranged to receive the error signals.