Magnetic-field sensor with a back-bias magnet
An embodiment of a magnetic-field sensor includes a magnetic-field sensor arrangement and a magnetic body which has, for example, a non-convex cross-sectional area with regard to a cross-sectional plane running through the magnetic body, the magnetic body having an inhomogeneous magnetization.
1. A magnetic-field sensor comprising:
a magnetic-field sensor arrangement; and
a back-bias magnet, wherein a structure of the back-bias magnet comprises an inhomogeneous magnetization.
2. The magnetic-field sensor as claimed in claim 1 , wherein the back-bias magnet is moldable as unitary member and of cuboidal shape, circular shape, elliptical, or frustum shape.
3. The magnetic-field sensor as claimed in claim 2 , wherein the back-bias magnet comprises materials selected from the group consisting of ferrites, aluminum-nickel-cobalt (AlNiCo), samarium-cobalt (SmCo) and neodymium-iron-boron (NdFeB).
4. The magnetic-field sensor as claimed in claim 1 , wherein the inhomogeneous magnetization of the back-bias magnet is symmetrical to a first symmetry line within at least one cross-section of the back-bias magnet.
5. The magnetic-field sensor as claimed in claim 4 , wherein the first symmetry line is a symmetry line of a substantially mirror-symmetrical inhomogeneous magnetization within the at least one cross-section of the back-bias magnet.
6. The magnetic-field sensor as claimed in claim 4 , wherein the first symmetry line within the at least one cross-section of the back-bias magnet is a symmetry line of higher order, rotational symmetry, or ellipsoidal symmetry.
7. The magnetic-field sensor as claimed in claim 4 , wherein the inhomogeneous magnetization is further symmetrical to the first symmetry line within a further cross-section of the back-bias magnet, the further cross-section intersecting the cross-section at the first symmetry line.
8. The magnetic-field sensor as claimed in claim 1 , wherein the inhomogeneous magnetization of the back-bias magnet causes a magnetic flux density outside the back-bias magnet.
9. The magnetic-field sensor as claimed in claim 3 , wherein magnetic flux caused by the inhomogeneous magnetization is substantially not confined to an inside of the back-bias magnet.
10. The magnetic-field sensor as claimed in claim 1 , wherein the back-bias magnet comprises the inhomogeneous magnetization in at least 50% of a volume of the back-bias magnet.
11. The magnetic-field sensor as claimed in claim 4 ,
wherein the at least one cross-section is spanned by a first direction and a second direction, the first and second direction not being parallel, and
wherein when walking along the second direction for a given coordinate value for the first direction, an angle between the second direction and a local direction of magnetization varies at least over a portion of a walking path, the walking path being different from the first symmetry line.
12. The magnetic-field sensor as claimed in claim 11 , wherein the angle varies monotonically when walking along the walking path.
13. The magnetic-field sensor as claimed in claim 11 , wherein the angle varies non-monotonically when walking along the walking path, if the walking path runs perpendicular to the first symmetry line.
14. The magnetic-field sensor as claimed in claim 1 , wherein the magnetic-field sensor arrangement comprises a first magnetic-field sensor element and a second magnetic-field sensor element, the first magnetic-field sensor element being arranged, with respect to the back-bias magnet, such that the first magnetic-field sensor element is exposed, with regard to a predetermined spatial direction, to a magnetic flux density caused by the back-bias magnet and being within a first flux density range, and the second magnetic-field sensor element being arranged, with respect to the back-bias magnet, such that the second magnetic-field sensor element is exposed, with regard to the predetermined spatial direction, to a magnetic flux density caused by the back-bias magnet and being within a second flux density range.
15. The magnetic-field sensor as claimed in claim 14 , wherein the first flux density range and the second flux density range enable operation of the first and second magnetic-field sensor elements.
16. The magnetic-field sensor as claimed in claim 14 , wherein the first and second flux density ranges only comprise values smaller than or equal to 20 mT in magnitude.
17. The magnetic-field sensor as claimed in claim 14 , wherein the first flux density range comprises flux densities of opposite sign to the second flux density range.
18. The magnetic-field sensor as claimed in claim 15 , wherein the first and second magnetic-field sensor elements are magneto-resistive sensor elements.
19. The magnetic-field sensor as claimed in claim 15 , wherein the first and second magnetic-field sensor elements are arranged on a substrate, and wherein the predetermined spatial direction is substantially parallel to a main surface of the substrate.
20. The magnetic-field sensor as claimed in claim 1 , wherein the back-bias magnet is annular or comprises an annular section.