COIL AND DEVICE FOR WIRELESS SIGNAL TRANSMISSION, AND METHOD FOR PRODUCING SUCH A COIL

Abstract

The invention relates to a coil in the form of a transmitting and/or receiving coil of a device for wireless signal transmission by means of electromagnetic waves, wherein the coil has an impedance matching circuit for adapting the connection impedance of the coil to an input impedance of a signal transmitting and/or receiving device of the device for wireless signal transmission to be connected to the coil, wherein the impedance matching circuit is formed entirety or at least partially by at least partially overlapping conductor tracks of the coil. The invention also relates to a device for wireless signal transmission by means of electromagnetic waves, comprising a signal transmitting and/or receiving device and a coil connected to the signal transmitting and/or receiving device. The invention further relates to a method for producing such a coil.)

Claims

1. A transmission and/or reception coil of a device for wireless signal transmission or for wireless signal reception, comprising: an impedance matching circuit for matching connection impedance of the coil to an input impedance of a signal transmission and/or reception device wherein the impedance matching circuit is formed entirely or at least in part by at least partially overlapping conductor runs of the coil.

2. The coil as claimed in claim 1, further comprising: connection lines which are used to connect the coil to the signal transmission and/or reception device, wherein the connection lines are connected to the conductor runs of the coil outside of an area of overlap of the conductor runs of the coil.

3. The coil as claimed in claim 2 wherein the area of overlap extends over an angular range that is not a multiple of 360 degrees.

4. The coil as claimed in claim 1 wherein the conductor runs have, at least partially or completely, a flattened cross-sectional shape.

5. The coil as claimed in claim 1 wherein the conductor runs are formed, at least partially or completely, from flexible circuit board material.

6. The coil as claimed in claim 1 wherein the coil is configured as an air-cored coil.

7. A device for wireless signal transmission or for wireless signal reception, comprising: a signal transmission and/or reception device; and a coil connected to the signal transmission and/or reception device; and a decoupling circuit and a connecting line configured to couple the device to the coil.

8. The device as claimed in claim 7, wherein the coil comprises an impedance matching circuit for completely or partially matching connection impedance of the coil to an input impedance of the signal transmission and/or reception device, wherein the impedance matching circuit is formed entirely or at least in part by at least partially overlapping conductor runs of the coil.

9. The device as claimed in claim 7 wherein the decoupling circuit has a filter circuit.

10. The device as claimed in claim 7 wherein the decoupling circuit is designed as an active decoupling circuit, by way of which the coil is operated outside of an intrinsic resonance during operation as a transmission coil.

11. The device as claimed in claim 10 wherein the active decoupling circuit has a diode.

12. The device as claimed in claim 7 wherein the decoupling circuit and the connecting line has an electrical length of (2.Math.n-1).Math.λ/4, wherein n is a natural number and lambda (λ) is the wavelength.

13. A method for producing a coil as claimed in claim 1 wherein the area of overlap is changed through lengthening or shortening until the connection impedance of the coil reaches a predefined impedance value.

Description

[0025] The invention will be explained in more detail below on the basis of exemplary embodiments using drawings.

[0026] In the figures:

[0027] FIG. 1 shows a device for wireless signal transmission and

[0028] FIG. 2 shows a coil and

[0029] FIG. 3 shows a coil with an active decoupling circuit and

[0030] FIG. 4 shows a further embodiment of a coil and

[0031] FIG. 5 shows the individual conductor runs of the coil according to FIG. 4 and

[0032] FIG. 6 shows a cross section through the conductor runs of the coil according to FIG. 4 and

[0033] FIG. 7 shows a coil with an active decoupling circuit in a further embodiment.

[0034] FIG. 1 illustrates a device 1 for wireless signal transmission by way of electromagnetic waves. The device 1 has a signal transmission and/or reception device 2, which has an input impedance ZE. A coil 3 having conductor runs 4 is also illustrated as part of the device 1. The conductor runs 4 of the coil 3 are connected to connection lines 5 of the coil 3. The coil 3 is able to be connected, via the connection lines 5, to the connections, having the input impedance ZE, of the signal transmission and/or reception device 2. In the illustrated example, the coil 3 has a connection impedance ZS. The aim is then to match the connection impedance ZS to the input impedance ZE.

[0035] To this end, the coil 3 may be provided with an impedance matching circuit 6, for example a matching network formed from capacitors, as shown in FIG. 2. The impedance matching circuit 6 may for example have a tuning capacitor CT connected in parallel with the coil 3 and a matching capacitor CM connected in series with the coil 3. The tuning capacitor CT, with the inductance of the conductor runs 4, forms a resonant circuit. The real part of the impedance ZS may be set to the desired impedance value of for example 50 ohms using the tuning capacitor CT. The remaining imaginary part may be compensated with the matching capacitor CM, such that the complex input impedance ZS then has the desired value of for example 50 ohms.

[0036] FIG. 3 shows the use of a coil 3 of the type described above in connection with an active decoupling circuit 9, 10, 11, 12. The coil 3 is connected to this decoupling circuit via its connection lines 5 and an impedance-matched connecting line 8. In the present example, it is assumed that the matching capacitor CM is still present on the coil side.

[0037] The decoupling circuit has a first capacitor 9 that is connected to the connecting line 8 and is grounded. An inductor 10 is connected thereto in series. A further capacitor 11, in parallel with a diode 12, is arranged downstream of the inductor 10, wherein the further capacitor 11 and the diode 12 are grounded. The capacitors 9, 11 form a filter circuit with the inductor 10. The common connection of the components 10, 11, 12 is connected to a preamplifier 13, which may be connected to the signal transmission and/or reception device 2. By virtue of this decoupling circuit 9, 10, 11, 12, the resonant behavior of the coil 3, that is to say the intrinsic resonant circuit of the coil, is able to be decoupled when using said coil in a transmission process by suppressing the current in the coil through an impedance transformation.

[0038] FIG. 7 illustrates a further embodiment of such a decoupling circuit, via which the coil 3 is connected to a preamplifier 13. In contrast to the embodiment in FIG. 3, a further capacitor 16 is connected in series at the output of the decoupling circuit, that is to say downstream of the parallel circuit consisting of the diode 12 and the capacitor 11. The diode 12 is thus connected to the preamplifier 13 via the capacitor 16. This additional capacitor 16 allows independent tuning of the states that arise in the two switching states of the diode 12.

[0039] The described impedance matching circuit 6 may be formed completely or at least partially by at least partially overlapping conductor runs 4 of the coil 3, this being illustrated by way of example in FIG. 4. It is assumed that a lower layer 4b of the conductor runs in an area of overlap 7 overlaps an upper layer 4a of the conductor runs in an angular range a. As may be seen, the area of overlap 7 extends over an angular range a that is not a multiple of 360 degrees. By way of example, the angular range a may be in the range from 90 degrees to 270 degrees.

[0040] The conductor runs 4a, 4b are connected to conductors of the connection line 5 via respective connection points 15. The conductor runs 4a, 4b may be designed for example as conductor tracks on a circuit board 14, for example a flexible circuit board.

[0041] This may accordingly be a circuit board 14 coated on both sides with conductive material, one conductor run 4a being formed on one side of the circuit board and the other conductor run 4b being formed on the opposite side of the circuit board 14.

[0042] FIG. 5 illustrates the appearance of the individual conductor runs 4a, 4b when they are not illustrated in overlapping form. The conductor runs 4a, 4b may for example have something like a sickle shape.

[0043] FIG. 6 shows a cross section through the arrangement according to FIG. 4 in the area of overlap 7. It may be seen that the conductor runs 4a, 4b have a comparatively large width B in relation to their height H, for example a width B at least five times greater than height H. It may also be seen from FIG. 4 that the inside diameter of the coil 3, characterized by 2ri, is significantly greater than the width B of the conductor runs 4a, 4b, for example at least ten times greater than the width B.