EXTERNAL MAGNETIC FIELD ANGLE DETERMINATION

• US 20100321014A1
• Filed: 04/04/2008
• Published: 12/23/2010
• Est. Priority Date: 05/29/2007
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Butzmann, Stefan
• Granted Patent: US 10,209,321 B2
• Time in Patent Office: Days
• US Class Current: 324/252
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01C 17/30 Earth-inductor compasses
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01R 33/09 Magnetoresistive devices
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G01R 33/096 anisotropic magnetoresistance sensors

Abstract

Magnetoresistive sensors are commonly used for angular detection in many automotive applications. According to an exemplary embodiment of the present invention, a sensor is provided in which a first half-bridge has magnetoresistive resistors with barber-pole stripes and in which a second half-bridge has magnetoresistive resistors without barber-pole stripes. One of the resistors without barber-pole stripes is rotated with respect to the other three resistors by 90°. This may provide for an improved angle determination with reduced angular errors due to offset.

Claims

1. A sensor for measuring an angle of an external magnetic field on the basis of a magnetic field modulation, the sensor comprising:

a first half-bridge;

a second half-bridge;

a modulation unit for modulating the magnetic field in two directions;

wherein the first half-bridge has a first and a second magnetoresistive resistor (101, 102) with barber-pole stripes; and

wherein the second half-bridge has a third and a fourth magnetoresistive resistor without barber-pole stripes or with barber-pole stripes having a different orientation with respect to the barber-pole stripes of the first and second magnetoresistive resistors.

2. The sensor of claim 1, wherein the modulation unit comprises:

a first coil for generating a magnetic modulation field in an x-direction;

a second coil for generating the magnetic modulation field in a y-direction; and

an oscillator for exciting the first coil and the second coil in an alternating manner for generation of the magnetic modulation field.

3. The sensor of claim 1,

wherein the first coil and the second coil are both excited in a continuous manner for generation of the magnetic modulation field;

wherein the first coil is excited by a sine signal and wherein the second coil is excited by a cosine signal, such that the external magnetic field is superposed by a rotating magnetic field vector.

4. The sensor of claim 2,

wherein the calculation and control unit is further adapted for deciding, on the basis of measured peak amplitudes, which one of the two half-bridges is used for calculation of the angle of the external magnetic field.

5. The sensor of claim 2, further comprising:

a detector for detecting peak amplitudes which correspond to an output from the two half-bridges; and

a calculation and control unit for calculating the angle of the external magnetic field according to;

α

=arctan(U1pkU2pk),

wherein U1pk and U2pk are the measured peak amplitudes.

6. The sensor of claim 1,

wherein the third magnetoresistive resistor is rotated with respect to the fourth magnetoresistive resistor by an angle of 90 degrees;

and

wherein the first magnetoresistive resistor and the second magnetoresistive resistor are arranged parallel to the third magnetoresistive resistor.

7. The sensor of claim 1,

wherein the first magnetoresistive resistor and the second magnetoresistive resistor are rotated with respect to the third magnetoresistive resistor and the fourth magnetoresistive resistor by an angle of 45 degrees.

8. A method for measuring an angle of an external magnetic field on the basis of a magnetic field modulation, the method comprising the step of:

modulating the magnetic field in two directions by a modulation unit comprising a first half-bridge and a second half-bridge;

wherein the first half-bridge has a first and a second magnetoresistive resistor with barber-pole stripes; and

wherein the second half-bridge has a third and a fourth magnetoresistive resistor without barber-pole stripes.

9. The method of claim 8, further comprising the step of:

alternately generating a magnetic modulation field in an x-direction and in a y-direction.

10. The method of claim 8, further comprising the steps of:

exciting the first coil and the second coil in a continuous manner for generation of the magnetic modulation field;

wherein the first coil is excited by a sine signal and wherein the second coil is excited by a cosine signal, such that the external magnetic field is superposed by a rotating magnetic field vector.

11. A computer-readable medium, in which a computer program for measuring an angle of an external magnetic field on the basis of a magnetic field modulation is stored which, when executed by a processor, causes the processor to carry out the steps of:

modulating the magnetic field in two directions by a modulation unit comprising a first half-bridge and a second half-bridge;

wherein the first half-bridge has a first and a second magnetoresistive resistor with barber-pole stripes; and

wherein the second half-bridge has a third and a fourth magnetoresistive resistor without barber-pole stripes.

12. A program element for measuring an angle of an external magnetic field on the basis of a magnetic field modulation, which, when being executed by a processor, causes the processor to carry out the steps of:

modulating the magnetic field in two directions by a modulation unit comprising a first half-bridge and a second half-bridge;

wherein the first half-bridge has a first and a second magnetoresistive resistor with barber-pole stripes; and

wherein the second half-bridge has a third and a fourth magnetoresistive resistor without barber-pole stripes.