A notch filter method and circuit for GMI magnetic sensor

Abstract

The invention discloses a notch filtering method for GMI magnetic sensors, and a circuit thereof. The notch filtering method comprises steps of performing amplitude phase transforming on input signals and only keeping the amplitude and phase of to-be-filtered interference signals unchanged, and performing differential synthesizing on the signals after amplitude phase transforming and original input signals and then outputting. The notch filtering circuit comprises an amplitude phase transforming module and a differential synthesizing module. The amplitude phase transforming module only keeps the amplitude and the phase of to-be-filtered interference signals unchanged, while the differential synthesizing module performs differential synthesizing on the signals after amplitude phase transforming and the original input signals, and then outputting. The notch filtering method and circuit can effectively filter out power frequency electromagnetic interference signals in the fields such as biological weak current and magnetic detection by using the amplitude phase transforming and differential synthesizing of signals. The method and the circuit can be widely applied to application occasions with high requirement of high notch filtering attenuation times in actual projects and low matching degree of used resistor capacitors, with advantages of high attenuation times and allowing slight mismatching of the resistor capacitors.

Description

technical field [0001] The invention relates to a signal detection technology of a GMI magnetic sensor, in particular to a notch filter method and circuit for the GMI magnetic sensor. Background technique [0002] GMI effect, that is, when the wires or strips of soft magnetic materials (mostly Co-based amorphous and Fe-based nanocrystals) are passed through an alternating current I ac When, the AC voltage U across the material w With the external magnetic field H applied in the longitudinal direction of the wire ex The phenomenon of sensitive change due to the change of the amorphous wire is essentially the sensitive change of the impedance of the amorphous wire itself with the external magnetic field. [0003] The GMI magnetic sensor designed based on the GMI effect contains an induction coil composed of wires or strips of soft magnetic materials (mostly Co-based amorphous and Fe-based nanocrystals). Through the induction coil, the impedance change value of the soft magne...

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Problems solved by technology

[0005] The technical problem to be solved by the present invention: in the case of very serious electromagnetic pollution in the surrounding environment, when the GMI magnetic sensor is used in the detection of the Pitesla biomagnetic field in an unshielded environment, the interference of power frequency and its harmonic signals is particularly serious The problem is to provide a method of synthesizing two-way differential signals to offset the power frequency electromagnetic interference signal, which can be widely used in engineering practice where the attenuation multiple of the trap circuit is required to be high and the matching degree of the resistors and capacitors used is not high. Notch filter method and circuit for GMI magnetic sensor with high multiple and allowing slight mismatch between capacitor and resistor

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