Magnitude calculation in a magnetic field angle tracking system

A method for determining an angle of a magnetic field associated with a rotatable target, comprising:

• generating a first signal indicative of the magnetic field;
• generating a second signal indicative of the magnetic field, wherein the first signal and the second signal are indicative of quadrature components of the magnetic field;
• providing an angle tracking observer having a sine block and a cosine block operatively coupled to form a control loop based in part on a non-orthogonality error term;
• computing the angle of the magnetic field using the angle tracking observer;
• and
• computing a magnitude of the magnetic field using the sine block and the cosine block of the angle tracking observer wherein computing the magnitude of the magnetic field comprises using the following equation:
• Aproposed=x*cos(φ*)+y*sin(φ*+β*)
• where x is the first signal, y is the second signal, φ* is the computed angular position of the target, and β* is the non-orthogonality term.

A magnetic field sensor configured to sense an angle of a magnetic field associated with a rotatable target, comprising:

• a first magnetic field sensing structure configured to generate a first signal indicative of the magnetic field;
• a second magnetic field sensing structure configured to generate a second signal indicative of the magnetic field, wherein the first and second magnetic field sensing structures are configured to detect quadrature components of the magnetic field;
• and
• a controller configured to process the first and second signals to determine an angular position of the target and a magnitude of the magnetic field, the controller comprising:
• an angle tracking observer comprising a sine block and a cosine block operatively coupled to compute the angular position of the target using a control loop based in part on a non-orthogonality error term, wherein the control loop of the angle tracking observer is configured iteratively reduce an error given by:
• error=y*cos(φ*+β*)−x*sin(φ*)
• where x is the first signal, y is the second signal, φ* is the computed angular position of the target, and β* is the non-orthogonality term;
• and
• a magnitude calculator comprising the sine block and the cosine block operatively coupled to compute the magnitude of the magnetic field.