Transponder communication station provided with a transmission coil configuration with two transmission coils

• US 6,415,134 B1
• Filed: 12/29/1999
• Issued: 07/02/2002
• Est. Priority Date: 12/30/1998
• Status: Expired due to Term

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Merlin, Erich
• Primary Examiner(s): Chin, Vivian
• Assistant Examiner(s): Lee, John J
• Application Number:
  US09/474,296
• Time in Patent Office: 916 Days
• Field of Search: 455/41, 455/73, 455/106, 455/276.1, 455/101, 455/42, 455/211, 342/42, 342/43, 342/44, 342/51, 342/50, 340/572.5, 340/572.2, 340/572.7
• US Class Current: 455/41.1
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• 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

Abstract

A communication station (1) for contactless communication with at least one transponder is provided with a transmission coil configuration (2) with an active, first transmission coil circuit (21) which includes a first transmission coil (36) and with a passive, second transmission coil circuit (22) which includes a second transmission coil (42), the first transmission coil (36) as well as the second transmission coil (42) being connected to a respective central conductor (38, 50) which is connected, via a third capacitor stage (41, 53), to a connection conductor (33, 48) between two series-connected capacitor stages (31, 32 and 47, 49), the two capacitor stages (31, 32 and 47, 49) constituting capacitor means (30, 43) which are connected parallel to the relevant transmission coil (36, 42).

Claims

1. A communication station for wireless communication with at least one transponder, said communication station comprising:

modulating means for generating a carrier signal at a carrier frequency (f1), which signal upon reception by said transponder is modulated thereby to form a modulated carrier signal having a sideband frequency (f2);

an active first transmission coil circuit (21) having a first transmission coil (36), and a passive second transmission coil circuit (22) having a second transmission coil (42), the first and second transmission coils being inductively coupled so that a current in the first transmission coil induces a 90°

phase shifted current in the second transmission coil; and

first and second capacitor means (30, 43) respectively coupled in parallel with the first and second transmission coils (36, 42), the parallel combination of the second capacitor means and second transmission coil having a resonant frequency substantially corresponding to said carrier frequency (f1);

characterized in that;

the first and second capacitor means (30, 43) each consist of first and second capacitor stages (31, 32 and 47, 49) which are connected in series to a common connection point, which connection point is also connected via a third capacitor stage (41, 53) to the relevant one of the inductively coupled transmission coils (36, 42);

a resonance step-up at the carrier signal frequency (f1) can be achieved in the second transmission coil circuit (22) by adjustment of the capacitances of the first and second capacitor stages thereof (47, 49); and

a resonance step-up at the sideband frequency (f2) can be achieved in the second transmission coil circuit (22) by adjustment of the capacitance of the third capacitor stage (53) thereof.

2. A communication station (1) as claimed in claim 1, characterized in that the first transmission coil circuit (21) and the second transmission coil circuit (22) both include a central conductor (38, 50), a first end (39, 51) of which is connected exactly to the center of the relevant transmission coil (36, 42), and that the first capacitor stage (31, 47) and the second capacitor stage (32, 49) of the first capacitor means (30) as well as of the second capacitor means (43) have equally high capacitance values.

3. A communication station (1) as claimed in claim 1, characterized in that the first capacitor stage (31, 47) and the second capacitor stage (32, 49) of the first capacitor means (30) as well as of the second capacitor means (43) consist of a respective capacitor (54, 55, 56, 57) having a fixed capacitance value and of a respective trimmer capacitor (60, 61, 62, 63) having a variable capacitance value.

4. A communication station (1) as claimed in claim 1, characterized in that the third capacitor stage (41, 53) of the first transmission coil circuit (21) as well as of the second transmission coil circuit (22) consists of a respective capacitor (58, 59) having a fixed capacitance value and of a respective trimmer capacitor (64, 65) having a variable capacitance value.

5. A communication station (1) as claimed in claim 1 characterized in that in the second transmission coil circuit (22) an ohmic resistor (46) is connected between at least one of the first capacitor stage (47) and the second capacitor stage (49) on the one side and the second transmission coil (42) on the other side.

6. A transmission coil assembly for use in a communication station which provides wireless communication with at least one transponder, said communication station including modulating means for generating a carrier signal at a carrier frequency (f1), which signal upon reception by said transponder is modulated thereby to form a modulated carrier signal having a sideband frequency (f2);

said coil assembly comprising;

an active first transmission coil circuit (21) having a first transmission coil (36), and a passive second transmission coil circuit (22) having a second transmission coil (42), the first and second transmission coils being inductively coupled so that a current in the first transmission coil induces a 9020 phase shifted current in the second transmission coil; and

first and second capacitor means (30, 43) respectively coupled in parallel with the first and second transmission coils (36, 42), the parallel combination of the second capacitor means and second transmission coil having a resonant frequency substantially corresponding to said carrier frequency (f1);

characterized in that;

the first and second capacitor means (30, 43) each consist of first and second capacitor stages (31, 32 and 47, 49) which are connected in series to a common connection point, which connection point is also connected via a third capacitor stage (41, 53) to the relevant one of the inductively coupled transmission coils (36, 42);

a resonance step-up at the carrier signal frequency (f1) can be achieved in the second transmission coil circuit (22) by adjustment of the capacitances of the first and second capacitor stages thereof (47, 49); and

a resonance step-up at the sideband frequency (f2) can be achieved in the second transmission coil circuit (22) by adjustment of the capacitance of the third capacitor stage (53) thereof.

7. A transmission coil configuration (2) as claimed in claims 6, characterized in that the first transmission coil circuit (21) and the second transmission coil circuit (22) both include a central conductor (38, 50), a first end (39, 51) of which is connected exactly to the center of the relevant transmission coil (36, 42), and that the first capacitor stage (31, 47) and the second capacitor stage (32, 49) of the first capacitor means (30) as well as of the second capacitor means (43) have equally high capacitance values.

8. A transmission coil configuration (2) as claimed in claim 6, characterized in that the first capacitor stage (31, 47) and the second capacitor stage (32, 49) of the first capacitor means (30) as well as of the second capacitor means (43) consist of a respective capacitor (54, 55, 56, 57) having a fixed capacitance value and of a respective trimmer capacitor (60, 61, 62, 63) having a variable capacitance value.

9. A transmission coil configuration (2) as claimed in claim 6, characterized in that the third capacitor stage (41, 53) of the first transmission coil circuit (21) as well as of the second transmission coil circuit (22) consists of a respective capacitor (58, 59) having a fixed capacitance value and of a respective trimmer capacitor (64, 65) having a variable capacitance value.

10. A transmission coil configuration (2) as claimed in claim 6, characterized in that in the second transmission coil circuit (22) an ohmic resistor (46) is connected between at least one of the first capacitor stage (47) and the second capacitor stage (49) on the one side and the second transmission coil (42) on the other side.