| CPC G01R 33/0011 (2013.01) [G01R 33/093 (2013.01); G01R 33/096 (2013.01); G01R 33/098 (2013.01)] | 51 Claims |
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1. A self-calibrating magnetic field sensor comprising:
magnetoresistance (MR) circuitry configured to receive an external magnetic field in a first frequency band and a reference magnetic field in a second frequency band, wherein the magnetoresistance circuitry is configured to produce an MR output electrical signal including an external signal based on the external magnetic field and a reference signal based on the reference magnetic field;
a coil driver circuit configured to produce the reference magnetic field and direct it to the magnetoresistance circuitry;
a feedback loop configured to receive the MR output electrical signal from the magnetoresistance circuitry, wherein the feedback loop is configured to filter out the external signal and extract the reference signal, and wherein the feedback loop is further configured to adjust a sensitivity of the magnetoresistance circuitry based on the reference signal; and
a main signal path configured to receive the MR output electrical signal and filter out the reference signal and extract the external signal, wherein the main signal path is configured to produce, based on the external signal, a main signal path output signal indicative of information encoded in the external magnetic field,
wherein the feedback loop comprises a demodulator configured to demodulate the MR output signal at a modulation frequency of the reference magnetic field and produce a corresponding demodulated signal, and
wherein the feedback loop comprises a first sum unit configured to subtract a nominal reference voltage from the demodulated signal and produce a feedback error signal.
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