Off-axis magnetic field angle sensors

1. A magnetic field angle sensing system configured to determine a rotational position of a magnetic field source around a rotation axis, comprising:

N sensor devices arranged in a circle concentric to the rotation axis, wherein N>1 and the sensor devices are spaced apart from one another by about (360/N) degrees along the circle, each sensor device comprising:

a magnetic field sensing device having a sensitivity plane comprising at least one reference direction of the magnetic field sensing device, wherein the magnetic field sensing device is sensitive to a magnetic field component in the sensitivity plane and configured to provide a signal related to a (co)sine of an angle between the reference direction and the magnetic field in the sensitivity plane; and

circuitry coupled to the N sensor devices and configured to provide a signal indicative of a rotational position of a magnetic field source around the rotation axis determined by combining the signals from the magnetic field sensing devices of the N sensor devices,

wherein the circuitry is configured to pre-condition and average the signals as part of the combining, and the circuitry is configured to pre-condition the signals by combining integer multiples equivalent to 360 degrees with input data to result in at least one monotonously rising or falling sequence of values in a single clockwise or counter-clockwise direction of angular positions of respective ones of the N sensor devices.

2. The system of claim 1 , wherein the magnetic field source comprises a permanent magnet with a Halbach magnetization.

3. The system of claim 1 , wherein the N sensor devices are arranged on a single die.

4. The system of claim 1 , wherein the magnetic field sensing device comprises a Hall-effect element or a magnetoresistive (MR) element.

5. The system of claim 4 , wherein the magnetic field sensing device comprises a half-bridge circuit comprising two MR elements with different reference directions.

6. The system of claim 1 , wherein the sensitivity planes of the magnetic field sensing devices of each of the N sensor devices are nominally parallel.

7. A magnetic field angle sensing system configured to determine a rotational position of a magnetic field source around a rotation axis, comprising:

N sensor devices arranged in a circle concentric to the rotation axis, wherein N>1 and the sensor devices are spaced apart from one another by about (360/N) degrees along the circle, each sensor device comprising:

a magnetic field sensing device having a sensitivity plane comprising at least one reference direction of the magnetic field sensing device, wherein the magnetic field sensing device is sensitive to a magnetic field component in the sensitivity plane and configured to provide a signal related to a (co)sine of an angle between the reference direction and the magnetic field in the sensitivity plane; and

circuitry coupled to the N sensor devices and configured to provide a signal indicative of a rotational position of a magnetic field source around the rotation axis determined by combining the signals from the magnetic field sensing devices of the N sensor devices,

wherein the circuitry is configured to pre-condition and average the signals as part of the combining, and the circuitry is configured to pre-condition the signals by interpreting the signals of the N sensor devices as coordinates of a complex pointer and rotating the complex pointer into a normalized rotational position that is the same for all N sensor devices.

8. The system of claim 1 , wherein the circuitry is configured to apply a discrete Fourier transform to a set of N signals of the magnetic field sensing devices as part of the combining.

9. A method of determining a rotational position of a magnetic field source around a rotation axis, comprising:

arranging N>1 sensor devices in a circle concentric to the rotation axis such that the sensor devices are spaced apart from one another by about (360/N) degrees along the circle;

sensing, by a magnetic field sensing device of each of the N>1 sensor devices, a (co)sine of an angle between a reference direction of the magnetic field sensing device and the magnetic field in a sensitivity plane of the magnetic field sensing device induced by the magnetic field source, the sensitivity plane comprising at least one reference direction of the magnetic field sensing device;

providing a signal related to the (co)sine of the angle between the reference direction and the magnetic field in the sensitivity plane;

providing a signal indicative of a rotational position of the magnetic field source around the rotation axis by combining the signals from the magnetic field sensing devices of the N>1 sensor devices; and

pre-conditioning and averaging the signals as part of the combining, wherein the pre-conditioning comprises combining integer multiples equivalent to 360 degrees with input data to identify at least one monotonously rising or falling sequence of values in a single clockwise or counter-clockwise direction of angular positions of respective ones of the N sensor devices.

10. The method of claim 9 , further comprising providing the magnetic field source comprising a magnet with a Halbach magnetization.

11. The method of claim 9 , further comprising providing the N>1 sensor devices on a single die.

12. The method of claim 9 , wherein the magnetic field sensing device comprises a Hall-effect element or a magnetoresistive (MR) element.

13. The method of claim 12 , further comprising arranging the magnetic field sensing device in a half-bridge circuit of two MR elements having different reference directions.

14. The method of claim 9 , wherein the sensitivity planes of the magnetic field sensing devices of each of the N>1 sensor devices are nominally parallel.

15. A method of determining a rotational position of a magnetic field source around a rotation axis, comprising:

arranging N>1 sensor devices in a circle concentric to the rotation axis such that the sensor devices are spaced apart from one another by about (360/N) degrees along the circle;

sensing, by a magnetic field sensing device of each of the N>1 sensor devices, a (co)sine of an angle between a reference direction of the magnetic field sensing device and the magnetic field in a sensitivity plane of the magnetic field sensing device induced by the magnetic field source, the sensitivity plane comprising at least one reference direction of the magnetic field sensing device;

providing a signal related to the (co)sine of the angle between the reference direction and the magnetic field in the sensitivity plane;

providing a signal indicative of a rotational position of the magnetic field source around the rotation axis by combining the signals from the magnetic field sensing devices of the N>1 sensor devices; and

pre-conditioning and averaging the signals as part of the combining, wherein the pre-conditioning comprises interpreting the signals of the N sensor devices as coordinates of a complex pointer and rotating the complex pointer into a normalized rotational position that is the same for all N sensor devices.

16. The system of claim 1 , further comprising applying a discrete Fourier transform to a set of N signals of the magnetic field sensing devices as part of the combining.