Antenna arrangement and transponder reader

• US 6,259,413 B1
• Filed: 10/26/1999
• Issued: 07/10/2001
• Est. Priority Date: 02/05/1999
• Status: Expired due to Term

• Current Assignee: Moba Mobile Automation Ag
• Original Assignee: MOBA Mobile Automation GmbH
• Inventors: Schmidt, Andreas, Süb, Matthias
• Primary Examiner(s): Le, Hoanganh
• Assistant Examiner(s): Dinh, Trinh Vo
• Application Number:
  US09/428,138
• Time in Patent Office: 623 Days
• Field of Search: H01/Q 1.112, 343/742, 343/741, 343/866, 343/867, 340/571, 340/572.7, 340/572.3
• US Class Current: 343/742
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: G06K 7/10435 the interrogation device being positioned close to a conveyor belt or the like on which moving record carriers are passing conveying in accordance with bodily destination marks, see B65G47/46, sorting of objects carrying identity markings, see B07C5/34

Abstract

An antenna arrangement, which is preferably incorporated in a transponder reader, comprises a first subloop, which essentially encloses a first area and which has a first and a second end, a second subloop, which essentially encloses a second area and which has a first and a second end, the two first ends of the first and the second subloop being connected together and the two second ends being connected together in such a way that the two subloops together constitute a single winding, and a single feeding device for applying a voltage between the connected first ends and the connected second ends, the first and the second subloop being so positioned relative to each other that the first and the second area are so arranged facing each other that plane areas approximating to the areas are parallel to each other or intersect one another at an acute angle. Since the inductance can be kept as small as possible for such an antenna arrangement, considerably larger pass-through cross-sections can be realized, or larger circuit capacitances can be employed so as to minimize the influence of stray capacitances. In this way stable antenna operation can be achieved in a reliable and economic way even at higher operating frequencies.

Claims

1. A transponder reader comprising:

an antenna arrangement including;

a first subloop, which essentially encloses a first area and which has a first and a second end;

a second subloop, which essentially encloses a second area and which has a first and a second end, where the two first ends of the first and the second subloops are connected together, and where the second ends of the first and the second subloops are connected together, wherein the two subloops together constitute a single closed winding;

a single feeding device for applying a voltage between the connected first ends and the connected second ends, where the first and the second subloops are so positioned relative to each other that the first and the second areas are arranged facing each other and a plane area approximating to the first area and a plane area approximating to the second area are either parallel to each other or intersect at an acute angle;

a read zone formed in proximity to said first subloop and said second subloop, wherein the read zone comprises a volume formed between the first and the second areas which are arranged facing each other;

equipment for transporting an object, to which a transponder is affixed, through the read zone, for reading out the transponder by means of the antenna arrangement.

2. The transponder reader according to claim 1, wherein the read zone features a longitudinal space which extends along a read zone axis, and wherein the first and the second subloops each essentially surrounds the longitudinal space and are spaced apart relative to the read zone axis, wherein the first and the second areas are selected such that the object to which the transponder is affixed can be passed through the first and the second subloops.

3. The transponder reader according to claim 1, wherein the first and the second subloops are arranged to the left and to the right of the read zone respectively, wherein a distance between the first and the second subloops is formed such that an object can be transported between the subloops, and wherein the first and the second areas are selected such that an object cannot be transported through one of the subloops.

4. The transponder reader according to claim 1, wherein, moreover, the transport equipment is arranged so as to move the object through the read zone continuously.

5. The transponder reader according to claim 1, wherein the first and the second area are parallel to each other but intersect a longitudinal read zone at an acute angle.

6. The transponder reader according to claim 1, wherein the first and the second area define an acute angle and intersect a longitudinal read zone at different angles.

7. The transponder reader according to claim 1, wherein the transport equipment is implemented as a flat conveyor belt which has metallic components.

8. The transponder reader according to claim 1, wherein the antenna arrangement is so arranged relative to the transport equipment that the first and the second ends, which are connected to the feeding device, are located as far as possible from the transport equipment so as to minimize leakage currents via stray capacitances.

9. The transponder reader according to claim 1, wherein the first area and the second area of said antenna arrangement are plane areas and where the approximated plane areas are identical to the areas enclosed by the first subloop and the second subloop.

10. The transponder reader according to claim 1, wherein the first and the second subloops of said antenna arrangement are so positioned relative to each other that the current flow direction in the first subloop is in the same sense as the current flow direction in the second subloop.

11. The transponder reader according to claim 1, wherein the first and the second subloops of said antenna arrangement are so positioned relative to each other that a current flow direction in the first subloop is in the opposite sense to a current flow direction in the second subloop.

12. The transponder reader according to claim 11, wherein the first and the second areas are essentially parallel to each other,

wherein the first subloop and the second subloop take the form of nearly complete frames which are only open in that there is a certain separation between the first and the second ends,

wherein the first and the second ends are connected together by means of a first and a second conductor respectively,

wherein the first and the second conductors lie essentially perpendicular to the first and the second areas and, moreover, are crossed over, resulting in opposed current flow directions in the two subloops.

13. The transponder reader according to claim 1, wherein the first and the second subloops of said antenna arrangement essentially enclose areas which are rectangular in shape.

14. The transponder reader according to claim 1, wherein the feeding device of said antenna arrangement has a balun so as to feed the antenna arrangement summetrically.

15. The transponder reader according to claim 1, which also has a turning device for turning the resonant frequency of the antenna arrangement, the tuning device having a tunable capacitive component which as a considerably higher capacitance than stray capacitances between the antenna arrangement and the environment in which the antenna is located.

16. The transponder reader according to claim 1, wherein said antenna arrangement is operable in the frequency range between 12 and 14 Mhz, where the two areas which are essentially enclosed by the two subloops lie between 0.8 and 1.2 m² and where the inductance of the antenna arrangement is much smaller than the inductance of an antenna arrangement with two windings, each of which encloses the same area.

17. A transponder reader according to claim 10,

wherein the antenna arrangement is so arranged relative to the transport equipment that the first and the second ends, which are connected to the feeding device, are located as far as possible from the transport equipment so as to minimize leakage currents via stray capacitances.