Magnetoresistive relaxation oscillator type magnetometer

1 . A magnetoresistive relaxation oscillator type magnetometer, comprising: a capacitor, a charging resistor, a discharging resistor, a charge-discharge transfer switch, a high-voltage source terminal, a grounding terminal and a signal output terminal, the charging resistor consisting of at least one charging magnetoresistance unit, and the discharging resistor consisting of at least one discharging magnetoresistance unit; wherein

a first end of the capacitor is connected to the grounding terminal, a second end of the capacitor is respectively connected to the charging resistor, the discharging resistor and the signal output terminal via the charge-discharge transfer switch, and the charge-discharge transfer switch is further connected to the high-voltage source terminal;

in a charging stage, the charge-discharge transfer switch is switched to the high-voltage source terminal, and the high-voltage source terminal charges the capacitor via the charging resistor; while in a discharging stage, the charge-discharge transfer switch is switched to the grounding terminal, so that the capacitor discharges to the grounding terminal via the discharging resistor; and

when an external magnetic field causes resistance change in the charging resistor and the discharging resistor, charge-discharge time of the capacitor is changed, a pulse signal output by the signal output terminal contains one or more harmonic waves of the charging resistor or the discharging resistor, and a signal processing circuit measures the pulse signal to measure the external magnetic field.

2 . The magnetoresistive relaxation oscillator type magnetometer according to claim 1 , wherein the charging magnetoresistance unit and the discharging magnetoresistance unit are anisotropic magnetoresistance units, giant magnetoresistance units or tunnel magnetoresistance units.

3 . The magnetoresistive relaxation oscillator type magnetometer according to claim 1 , wherein the charge-discharge transfer switch is a metal-oxide semiconductor field effect transistor MOSFET, wherein the second end of the capacitor and a second end of the charging resistor are both connected to a gate of the MOSFET, the discharging resistor is located between a drain of the MOSFET and the grounding terminal, and the high-voltage source terminal is respectively connected to a first end of the charging resistor and a source of the MOSFET; or

the charge-discharge transfer switch is a triode, wherein the second end of the capacitor and the second end of the charging resistor are both connected to a base of the triode, the discharging resistor is located between an emitter of the triode and the grounding terminal, and the high-voltage source terminal is respectively connected to the first end of the charging resistor and a collector of the triode.

4 . The magnetoresistive relaxation oscillator type magnetometer according to claim 3 , wherein the charging resistor and the discharging resistor are opposite in magnetic field sensitive direction and same in sensitivity, and are same in resistance when no external magnetic field is applied and form a push-pull type magnetoresistor.

5 . The magnetoresistive relaxation oscillator type magnetometer according to claim 3 , wherein the charging resistor is a magnetic field sensitive magnetoresistance unit.

6 . The magnetoresistive relaxation oscillator type magnetometer according to claim 1 , wherein the charge-discharge transfer switch is a triode bidirectional switch, comprising an on end, an off end and a connecting end, wherein the high-voltage source end is connected with the on end via the charging resistor, the grounding terminal is connected with the off end via the discharging resistor, and the second end of the capacitor is connected with the connecting end; and

in a charging stage, the on end is conducted to the connecting end, and in a discharging stage, the off end is conducted to the connecting end.

7 . The magnetoresistive relaxation oscillator type magnetometer according to claim 1 , wherein the charge-discharge transfer switch is a triode bidirectional switch, comprising an on end, an off end and a connecting end, wherein the charging resistor and the discharging resistor are the same one common resistor, the second end of the capacitor and the common resistor are connected in series to form an RC series, the RC series is connected with the connecting end, the high-voltage source terminal is connected with the on end, and the grounding terminal is connected with the off end; and;

in a charging stage, the on end is conducted to the connecting end, and in a discharging stage, the off end is conducted to the connecting end.

8 . The magnetoresistive relaxation oscillator type magnetometer according to claim 7 , wherein the signal output terminal is connected to an F-V converter, the F-V converter converts the pulse signal into a voltage signal, and then the voltage signal is converted by a V-1/V converter into a voltage signal directly proportional to the external magnetic field.

9 . The magnetoresistive relaxation oscillator type magnetometer according to claim 1 , wherein the charge-discharge transfer switch is a triode bidirectional switch, comprising an on end, an off end and a connecting end, wherein the charging resistor is connected in series with a diode with a charging direction turned on to form an RD charging series, the discharging resistor is connected in series with a diode with a discharging direction turned on to form an RD discharging series, the RD charging series and the RD discharging series are connected in parallel to form an RD series, the second end of the capacitor and the RD series are connected in series to form an RC series, the RC series is connected with the connecting end, the high-voltage source terminal is connected with the on end, and the grounding terminal is connected with the off end; and

in a charging stage, the on end is conducted to the connecting end, and in a discharging stage, the off end is conducted to the connecting end.

10 . The magnetoresistive relaxation oscillator type magnetometer according to claim 1 , further comprising: a low-voltage source terminal; wherein

the charge-discharge transfer switch is a trigger, an input terminal and an output terminal of the trigger are respectively the high-voltage source terminal or the low-voltage source terminal, the charging resistor and the discharging resistor are the same one common resistor, the second end of the capacitor is connected to the input terminal of the trigger, two ends of the common resistor are respectively connected to the input terminal and the output terminal of the trigger, and the signal output terminal is located at the output terminal or the input terminal of the trigger.

11 . The magnetoresistive relaxation oscillator type magnetometer according to claim 1 , further comprising: a low-voltage source terminal; wherein

the charge-discharge transfer switch is a trigger, an input terminal and an output terminal of the trigger are respectively the high-voltage source terminal or the low-voltage source terminal, the charging resistor is connected in series with a diode with a charging direction turned on to form an RD charging series, the discharging resistor is connected in series with a diode with a discharging direction turned on to form an RD discharging series, the second end of the capacitor is connected to the input terminal of the trigger, the RD charging series and the RD discharging series are connected in parallel, and two ends of the parallel connected RD charging series and RD discharging series are respectively connected to the input terminal and the output terminal of the trigger, and the signal output terminal is located at the output terminal or the input terminal of the trigger.

12 . The magnetoresistive relaxation oscillator type magnetometer according to claim 1 , wherein the signal output terminal is connected to an RC low-pass filter, a first end of a first capacitor in the RC low-pass filter is connected to the grounding terminal, a first resistor in the RC low-pass filter is located between the signal output terminal and a second end of the first capacitor, two ends of the first capacitor output a direct current and a first harmonic wave, and the signal processing circuit converts signals across the first capacitor to obtain a charging duration and a discharging duration value.

13 . The magnetoresistive relaxation oscillator type magnetometer according to claim 1 , wherein the signal output terminal is connected to an analog-digital converter, the pulse signal is converted by the analog-digital converter, a converted signal is then processed and output by a microcontroller, and the signal processing circuit directly measures the signal output by the microprocessor to obtain a charging duration and a discharging duration.