Frequency doubling of xMR signals

• US 9,817,085 B2
• Filed: 03/15/2012
• Issued: 11/14/2017
• Est. Priority Date: 03/15/2012
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Zimmer, Juergen
• Primary Examiner(s): Phan, Huy Q
• Assistant Examiner(s): FREDERIKSEN, DAVID B
• Application Number:
  US13/421,008
• Publication Number:
  US 20130241544A1
• Time in Patent Office: 2,070 Days
• Field of Search: 324252, 324166, 324173, 3242072, 32420721, 32420722, 32420725, 324165, 324174
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence
• CPC Class Codes: G01P 3/487 delivered by rotating magnets
• CPC Class Codes: G01P 3/488 delivered by variable reluctance detectors
• CPC Class Codes: G01P 3/489 Digital circuits therefor
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors

Abstract

Embodiments relate to sensors, such as speed sensors and angle sensors, that use a modulated supply voltage to approximately double output signals of the sensors because the sensor element and the supply voltage exhibit the same frequency. In embodiments, the sensor element is an xMR element, and the modulated supply voltage is generated on-chip, such as by another xMR element. Direct frequency doubling of the output signal of the sensor element therefore can be obtained without additional and complex circuitry or signal processing.

Claims

1. A sensor system comprising:

a magnetic field source;

a magnetoresistive sensor configured to provide an output signal related to the magnetic field source, the output signal having a frequency, wherein the sensor comprises a first half-bridge configuration of sensor elements and a second half-bridge configuration of sensor elements forming a first Wheatstone bridge configuration of sensor elements, and a second Wheatstone bridge configuration of sensor elements having a phase arranged between phases of the first and second half-bridge configurations; and

a voltage supply coupled to the sensor to provide a modulated supply voltage having a frequency the same as the frequency of the sensor output signal.

2. The sensor system of claim 1, wherein the modulated supply voltage doubles the frequency of the output signal as compared with an unmodulated supply voltage.

3. The sensor system of claim 1, wherein an output signal of the second Wheatstone bridge configuration of sensor elements is provided to a supply voltage input of the first Wheatstone bridge configuration of sensor elements to provide the modulated supply voltage.

4. The sensor system of claim 3, further comprising an amplifier, wherein the output signal of the second Wheatstone bridge configuration is provided to the supply voltage input of the first Wheatstone bridge configuration of sensor elements via the amplifier.

5. The sensor system of claim 1, wherein the sensor comprises at least one of a giant magnetoresistive sensor element (GMR), a tunneling magnetoresistive sensor element (TMR) or an anisotropic magnetoresistive sensor element (AMR).

6. A sensor system comprising:

a magnetic field source;

a magnetoresistive sensor configured to provide an output signal related to the magnetic field source, the output signal having a frequency; and

a voltage supply coupled to the sensor to provide a modulated supply voltage having a frequency the same as the frequency of the sensor output signal,

wherein the sensor comprises a first Wheatstone bridge configuration of sensor elements, a second Wheatstone bridge configuration of sensor elements, and a third Wheatstone bridge configuration of sensor elements, wherein an output signal of the first bridge configuration is phase-shifted by 90 degrees with respect to an output signal of the second bridge configuration, wherein an output signal of the third bridge configuration has substantially the same phase as one of the output signals of the first or second bridge configurations, and wherein the output signal of the third bridge configuration is provided to a supply voltage input of the first and second bridge configurations to provide the modulated supply voltage.

7. The sensor system of claim 6, further comprising an amplifier, wherein the output signal of the third bridge configuration is provided to the supply voltage input of the first and second bridge configurations via the amplifier.

8. The sensor system of claim 6, further comprising a switch configured to switch the supply voltage input of the first and second bridge configurations between the modulated supply voltage and a constant supply voltage.

9. A method comprising:

providing a sensor having a response to an external magnetic field, the sensor comprising a first half-bridge sensor configuration and a second half-bridge sensor configuration forming a first sensor configuration, and a second sensor configuration having a phase arranged between phases of the first and second half-bridge sensor configurations; and

providing a supply voltage to the sensor having substantially the same frequency as the response of the sensor.

10. The method of claim 9, wherein providing a supply voltage comprises modulating the supply voltage to the first sensor configuration by an output of the second sensor configuration.

11. The method of claim 10, further comprising doubling a frequency of the response of the sensor by the modulating.

12. The method of claim 10, wherein providing the supply voltage comprises amplifying the output of the second sensor configuration.

13. The method of claim 10, wherein the first sensor configuration and the second sensor configuration are first and second Wheatstone bridge sensor configurations, respectively.

14. The method of claim 13, wherein providing a magnetoresistive sensor comprises providing at least one of a giant magnetoresistive sensor (GMR), a tunneling magnetoresistive sensor (TMR) or an anisotropic magnetoresistive sensor (AMR).

15. The method of claim 9, wherein providing a sensor comprises providing a magnetoresistive sensor.

16. A sensor system comprising:

a magnetoresistive sensor comprising a first sensor element configuration and a second sensor element configuration,

wherein in a first mode of operation, the second sensor element configuration is configured to output a modulated output voltage, and further configured to modulate a supply voltage of the first sensor element configuration with a modulation frequency according to the modulated output voltage, and wherein an output signal of the first sensor element configuration has double a frequency of the modulated output voltage output by the second sensor element configuration.

17. The sensor system of claim 16, further comprising a switch configured to select between the first mode of operation and a second mode of operation.

18. The sensor system of claim 17, wherein, when in the second mode of operation, a substantially constant supply voltage is provided to the first sensor element configuration.

19. The sensor system of claim 16, further comprising amplifier circuitry to amplify the output signal of the second sensor element configuration.

20. The sensor system of claim 16, wherein the magnetoresistive sensor comprises at least one of a giant magnetoresistive sensor (GMR), a tunneling magnetoresistive sensor (TMR) or an anisotropic magnetoresistive sensor (AMR).

21. The sensor system of claim 16, wherein in the first mode of operation, the first sensor element configuration provides a halved range of angular uniqueness compared to in the second mode of operation.

22. A sensor system for measuring a parameter of a rotating magnetic field comprising:

a first magnetoresistive (xMR) sensor bridge; and

in a first mode of operation,

a second xMR sensor bridge having an output coupled to an input of the first xMR sensor bridge, wherein the first and second xMR sensor bridges are coupled to each other such that a signal tapped from the first xMR sensor bridge has double a frequency of the rotating magnetic field,

wherein the first and second xMR sensor bridges are coupled to each other such that at least one operating parameter of the first xMR sensor bridge is influenced by the second xMR sensor bridge.

23. The sensor system of claim 22, wherein a change in the frequency of the rotating magnetic field produces a corresponding change in the at least one operating parameter.

24. The sensor system according to claim 22, further comprising a switch configured to switch between the first mode of operation and a second mode of operation.

25. The sensor system according to claim 24, wherein in the second mode of operation, the switch is configured to provide a substantially constant supply voltage to the first sensor element configuration.

26. A sensor system comprising:

a magnetoresistive sensor comprising a first sensor element configuration and a second sensor element configuration,

wherein;

in a first mode of operation, the second sensor element configuration is configured to output a modulated output voltage, and further configured to modulate a supply voltage of the first sensor element configuration with a modulation frequency according to the modulated output voltage,

in a second mode of operation, a substantially constant supply voltage is provided to the first sensor element configuration, and

in the first mode of operation, a substantially doubled angular resolution is provided compared to during the second mode of operation; and

a switch configured to select between the first mode of operation and the second mode of operation.