Membrane based magnetometer

1. A magnetometer device to measure oscillation frequency, the device comprising:

a feedback loop comprising an amplifier and a voltage bias connected to a first input of a metallic membrane;

a membrane ground connected to a membrane output;

a fixed plate comprising a first fixed plate output connected to a second input of the amplifier,

wherein the fixed plate is physically separated from the metallic membrane but connected to the metallic membrane by a Lorentz force, and where the physical separation differs due to an angle of a magnetic field relative to a direction of a current;

a second fixed plate output sensitive to the Lorentz force; and

a circuit connected to the second fixed plate output to calculate an angle of the magnetic force based upon the Lorentz force,

wherein the feedback loop is configured to:

create a capacitive displacement current;

feed the capacitive displacement current to the amplifier;

amplify, by the amplifier, the capacitive displacement current; and

feed the amplified current as voltage to the metallic membrane.

2. The magnetometer device of claim 1 , wherein the metallic membrane further comprises a continuous sheet of metal.

3. The magnetometer device of claim 1 , wherein the metallic membrane further comprises a continuous metallic winding running in parallel lines from the membrane input to the membrane output.

4. The magnetometer device of claim 3 , wherein the metallic membrane further comprises a dielectric sheet in which the metallic winding is embedded.

5. The magnetometer device of claim 1 , wherein the metallic membrane has an equivalent electrical inductance proportional to the mechanical mass of the metallic membrane, an equivalent electrical capacitance proportional to the mechanical stiffness of the metallic membrane, and an equivalent electrical resistance proportional to the mechanical damping of the metallic membrane.

6. The magnetometer device of claim 1 , wherein the amplifier comprises a current controlled voltage source.

7. The magnetometer device of claim 6 , wherein the current controlled voltage source comprises a gain.

8. The magnetometer device of claim 1 , wherein the fixed plate has the same proportions as the metallic membrane.

9. The magnetometer device of claim 1 , wherein the metallic membrane is freestanding.

10. The magnetometer device of claim 1 , wherein the fixed plate is fixed to a substrate.

11. The magnetometer device of claim 1 , wherein the fixed plate is fixed to a wafer.

12. A magnetometer device to measure the orientation of a device, the magnetometer device comprising:

an oscillator comprising a metallic membrane and a feedback loop;

the feedback loop comprising an amplifier, the feedback loop configured to

drive an alternating electrical current through the metallic membrane;

drive the metallic membrane into an oscillation;

create a capacitive displacement current;

feed the capacitive displacement current to the amplifier;

amplify, by the amplifier, the capacitive displacement current; and

feed the amplified current as voltage to the metallic membrane;

a processor configured to:

measure a shift of oscillation frequency caused by the feedback loop and metallic membrane; and

calculate an angle of an external magnetic field relative to a direction of the current, based upon the shift of oscillation frequency and the current direction.

13. The magnetometer device of claim 12 , wherein the oscillation is close to a mechanical resonance frequency of the metallic membrane.

14. The magnetometer device of claim 12 , further comprising a fixed ground plate, the device further configured to generate a bias voltage between the metallic membrane and the fixed ground plate.

15. The magnetometer device of claim 14 , wherein the fixed ground plate is situated a small distance from the metallic membrane.

16. The magnetometer device of claim 14 , wherein the fixed ground plate has the same proportions as the metallic membrane.

17. The magnetometer device of claim 12 , wherein, in calculating the angle of an external magnetic force, the processor is further configured to cancel oscillation frequency detuning effects.

18. The magnetometer device of claim 17 , the processor further configured to, when cancelling oscillation frequency detuning effects, subtract the oscillation frequency for one or more current directions.

19. The magnetometer device of claim 12 , the processor further configured to filter interference from the oscillation of the metallic membrane.

20. The magnetometer device of claim 19 , the processor further configured to measure the frequency of the oscillator over a sufficient time period.

21. A magnetometer device to measure the orientation of a device, the magnetometer device comprising:

an oscillator comprising a metallic membrane and a feedback loop;

the feedback loop configured to drive an alternating electrical current through the metallic membrane, and to drive the metallic membrane into an oscillation; and

a processor configured to:

measure a shift of oscillation frequency caused by the feedback loop and metallic membrane;

calculate an angle of an external magnetic field relative to a direction of the current, based upon the shift of oscillation frequency and the current direction; and

cancel oscillation frequency detuning effects by subtracting the oscillation frequency for one or more current directions when calculating the angle of the external magnetic field.