LOOSELY-COUPLED OSCILLATOR

• US 20090051445A1
• Filed: 08/22/2007
• Published: 02/26/2009
• Est. Priority Date: 08/22/2007
• Status: Active Grant

• Current Assignee: St. Jude Medical Luxembourg Holdings Ii S.A.R.L.
• Original Assignee: CardioMEMS Incorporated
• Inventors: Ellis, Michael G.
• Granted Patent: US 7,667,547 B2
• Time in Patent Office: Days
• US Class Current: 331/65
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: A61B 5/03 Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs A61B5/205 takes precedence
• CPC Class Codes: A61B 5/07 Endoradiosondes
• CPC Class Codes: G01D 5/12 using electric or magnetic means G01D5/06 takes precedence

Abstract

Aspects and embodiments of the present invention provide a loosely-coupled oscillator including a sensor circuit and an electronic device that are not physically connected. In some embodiments, the electronic device includes an amplifier stage and a feedback network and the sensor circuit includes one or more LC circuits. When electromagnetically connected, the sensor circuit and electronic device form an oscillator that is adapted to output an oscillation signal. The resonant frequency of the sensor circuit can be obtained based on the oscillation signal. The sensor circuit may be implanted into an object and the resonant frequency of the sensor circuit can be used to determine characteristics of the object.

Claims

1. An oscillator comprising:

a sensor circuit comprising an inductor and a capacitor, the sensor circuit being adapted to resonate at a resonant frequency;

an electronic device physically disconnected from the sensor circuit, the electronic device comprising an input and an output, the input being connected to electrical ground through an electronic device coil, the electronic device being adapted to amplify an input signal to produce an output signal at the electronic device output; and

wherein the sensor circuit and the electronic device are electromagnetically coupled to obtain the input signal at the electronic device input, the output signal having characteristics associated with the resonant frequency of the sensor circuit.

2. The oscillator of claim 1, wherein the electronic device comprises an amplifier stage and a feedback network, the feedback network being connected to the input and the output and adapted to provide a feedback for the amplifier stage, the amplifier stage being adapted to amplify the input signal.

3. The oscillator of claim 2, wherein the amplifier stage comprises circuitry adapted to provide a high amplifier stage input impedance to prevent the electronic device coil from changing the resonant frequency of the sensor circuit;

and

wherein the output signal comprises a frequency that is the same as the resonant frequency.

4. The oscillator of claim 3, wherein the feedback network comprises a pulse generator configured to provide a start-up pulse and a high impedance for the feedback network at the amplifier input.

5. The oscillator of claim 2, wherein the amplifier stage comprises circuitry adapted to provide a low amplifier stage input impedance;

and

wherein the output signal comprises a frequency that is different than the resonant frequency, the difference between the resonant frequency and the output signal being used to determine a distance between the electronic device and the sensor circuit.

6. The oscillator of claim 1, wherein the electronic device coil is adapted to be electromagnetically coupled to the sensor circuit.

7. The oscillator of claim 1, wherein the sensor circuit is adapted to be associated with an object having characteristics.

8. The oscillator of claim 7, wherein the sensor circuit comprises an inductor having an inductor coil and a capacitor, the inductor coil having a diameter of between 1 millimeter and 2.5 millimeters, the capacitor being adapted to change position relative to the inductor coil based on pressure associated with the object;

wherein the electronic device coil has a diameter of between 1 millimeter and 2.5 millimeters; and

wherein the electronic device is adapted to determine characteristics associated with the object using the output signal.

9. The oscillator of claim 7, wherein the sensor circuit comprises an inductor having an inductor coil, the inductor coil having a diameter of between 1 millimeter and 100 millimeters;

wherein the electronic device coil has a diameter of between 1 millimeter and 100 millimeters; and

wherein the electronic device is adapted to determine characteristics associated with the object using the output signal.

10. A method for obtaining a resonant frequency of a sensor circuit, comprising:

providing a sensor circuit having a resonant frequency;

providing an electronic device comprising an input and an output;

connecting the electronic device input to electrical ground via an electronic device coil;

electromagnetically coupling the electronic device to the sensor circuit to obtain an output signal at the electronic device output, wherein the electronic device and the sensor circuit are disconnected; and

determining the resonant frequency of the sensor circuit based on the output signal.

11. The method of claim 10, wherein electromagnetically coupling the electronic device to the sensor circuit comprises moving the electronic device in proximity to the sensor circuit.

12. The method of claim 10, further comprising:

associating the sensor circuit with an object; and

using the output signal to determine characteristics associated with the object.

13. The method of claim 12, wherein providing the electronic device comprises providing the electronic device comprising a high input impedance, the electronic device being adapted to be electromagnetically coupled to the sensor circuit associated with the object.

14. The method of claim 13, further comprising:

decreasing the electronic device coil affects on the resonant frequency of the sensor circuit using the high input impedance.

15. The method of claim 12, wherein providing the electronic device comprises providing the electronic device comprising a low input impedance, the electronic device being adapted to be electromagnetically coupled to the sensor circuit associated with the object.

16. The method of claim 15, further comprising:

determining the resonant frequency before associating the sensor circuit with the object;

determining a frequency of the output signal after the electronic device is electromagnetically coupled to the sensor circuit;

determining a difference between the resonant frequency and the output signal frequency; and

determining characteristics associated with the object based on the difference between the resonant frequency and the output signal frequency.

17. The method of claim 10, further comprising:

providing a start-up pulse to the input to generate a high impedance at the input; and

decreasing the electronic device coil effect on the resonant frequency of the sensor circuit using the high impedance at the input.

18. The method of claim 10, wherein the sensor circuit comprises a plurality of sensor circuits, each sensor circuit comprising a resonant frequency that is different than the resonant frequency of other sensor circuits in the plurality of sensor circuits.

19. The method of claim 16, further comprising:

obtaining an output signal associated with the resonant frequency of each of the plurality of sensor circuits.