Patent ID: 9664494
Date: 2017-05-30
CPC Classifications: G01B,G01R

Claim:
1. A magnetic field sensor comprising: a coil driver circuit to generate an AC signal; an AC bias coil coupled to the coil driver circuit to receive the AC signal and to generate an AC bias magnetic field modulated by movement of a ferromagnetic target having a target profile pattern with respect to the AC bias coil; a magnetic field signal generator comprising at least one sensing element to produce, by sensing the modulated AC bias magnetic field, a magnetic field signal indicative of the movement of the ferromagnetic target, the magnetic field signal having a modulated signal portion in a first frequency band based on the sensed modulated AC bias magnetic field and an unwanted signal portion in a second frequency band based on sensing an external magnetic interference; circuitry including a demodulator to perform a demodulation of the magnetic field signal, wherein the magnetic field signal generator and circuitry are provided on a semiconductor die, further comprising a package that includes a lead frame coupled to the semiconductor die and located between the semiconductor die and the AC bias coil, and further includes a mold portion to enclose the semiconductor die, at least a portion of the lead frame and the AC bias coil together; and wherein the demodulation results in the modulated signal portion being shifted from the first frequency band to a third frequency band and the unwanted signal portion being shifted to the first frequency band from the second frequency band.