SYSTEM AND METHOD FOR MEASURING THE SHAPE OF AN OBJECT USING A MAGNETIC INDUCTION RADIO SENSOR

• US 20110148409A1
• Filed: 12/21/2009
• Published: 06/23/2011
• Est. Priority Date: 12/21/2009
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Aerts, Steven
• Granted Patent: US 8,542,017 B2
• Time in Patent Office: Days
• US Class Current: 324/307
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/0806 by whole-body plethysmography measuring blood flow using plethysmography A61B5/0295; impedance plethysmography A61B5/053; measuring volume of the body or parts thereof A61B5/1073
• CPC Class Codes: A61B 5/1135 by monitoring thoracic expansion
• CPC Class Codes: G01B 7/28 for measuring contours or curvatures

Abstract

A system and method for measuring the shape of an object using a magnetic induction radio sensor involves at least partially enclosing the object with a magnetic loop antenna of the magnetic induction radio sensor, where the inductance of the magnetic loop antenna depends on the shape of the object, and providing a particular capacitance at an antenna matching circuit coupled to the magnetic loop antenna in response to the inductance of the magnetic loop antenna such that the magnetic loop antenna and the antenna matching circuit form a resonant circuit and the resonant circuit has a fixed resonant frequency, where the particular capacitance is used to measure the shape of the object.

Claims

1. A magnetic induction radio sensor for measuring the shape of an object, the magnetic induction radio sensor comprising:

a magnetic loop antenna configured to at least partially enclose the object, wherein the inductance of the magnetic loop antenna depends on the shape of the object;

an antenna matching circuit coupled to the magnetic loop antenna, wherein the antenna matching circuit comprises an adjustable capacitance module configured to provide a particular capacitance such that the magnetic loop antenna and the antenna matching circuit form a resonant circuit and the resonant circuit has a fixed resonant frequency; and

a measuring unit configured to generate a measurement value using the particular capacitance of the adjustable capacitance module, the measurement value representing a measurement of the shape of the object.

2. The magnetic induction radio sensor of claim 1, wherein the magnetic loop antenna is configured to deform as a result of expansion and/or contraction of the object.

3. The magnetic induction radio sensor of claim 1, wherein the adjustable capacitance module comprises an array of switchable capacitors to provide the particular capacitance.

4. The magnetic induction radio sensor of claim 3, wherein the array of switchable capacitors comprises capacitor branches that are connected in parallel with the magnetic loop antenna, and wherein each of the capacitor branches comprises a switch and a capacitor.

5. The magnetic induction radio sensor of claim 4, wherein capacitances of the capacitors in the capacitor branches have a numeric relationship of factors of two.

6. The magnetic induction radio sensor of claim 3, wherein capacitances of the capacitors in the capacitor branches are equal.

7. The magnetic induction radio sensor of claim 1 comprising multiple magnetic loop antennas configured to at least partially enclose the object, wherein the inductances of the magnetic loop antennas depend on the shape of the object, the magnetic induction radio sensor further comprising an array of switches for selecting the magnetic loop antennas.

8. The magnetic induction radio sensor of claim 1 further comprising a transmitter configured to transmit the generated measurement value to a remote device using the magnetic loop antenna.

9. The magnetic induction radio sensor of claim 8 further comprising a scheduling unit configured to repetitively schedule measurement of the shape of the object and transmission of the generated measurement value to the remote device according to predefined slots in a time division multiplexing scheme.

10. The magnetic induction radio sensor of claim 9, wherein the scheduling unit is further configured to schedule the measurement of the shape of the object after reception of a synchronization word from the remote device.

11. The magnetic induction radio sensor of claim 1 further comprising:

an inductive charging circuit; and

a rechargeable battery, wherein the rechargeable battery is charged when the magnetic loop antenna is placed in a magnetic field generated by the inductive charging circuit;

or the magnetic loop antenna is further configured to receive direct inductive power such that the magnetic induction radio sensor of claim 1 is configured to operate without a battery using the received direct inductive power.

12. The magnetic induction radio sensor of claim 2, wherein the object is an organ of a patient, and wherein the magnetic loop antenna is integrated in a stretchable strap that at least partially encloses the organ of the patient.

13. The magnetic induction radio sensor of claim 12 further comprising contact electrodes integrated in the stretchable strap and configured to measure bio-potentials of the patient.

14. The magnetic induction radio sensor of claim 13, wherein the organ is a lung of the patient, and wherein the stretchable strap wraps around the chest and/or abdomen of the patient to measure expansion and/or contraction of the torso of the patient to measure respiration of the patient.

15. The magnetic induction radio sensor of claim 13, wherein the organ is a limb of the patient, and wherein the stretchable strap wraps around the limb of the patient to measure expansion and/or contraction of muscles of the limb.

16. A method for measuring the shape of an object using a magnetic induction radio sensor, the method comprising:

at least partially enclosing the object with a magnetic loop antenna of the magnetic induction radio sensor, wherein the inductance of the magnetic loop antenna depends on the shape of the object;

providing a particular capacitance at an antenna matching circuit coupled to the magnetic loop antenna such that the magnetic loop antenna and the antenna matching circuit form a resonant circuit and the resonant circuit has a fixed resonant frequency; and

generating a measurement value using the particular capacitance, the measurement value representing a measurement of the shape of the object.

17. The method of claim 16 further comprising adjusting the particular capacitance in response to a deformation of the magnetic loop antenna as a result of expansion and/or contraction of the object such that the resonant circuit still has the fixed resonant frequency.

18. The method of claim 17, wherein the providing the particular capacitance comprises providing the particular capacitance using an array of switchable capacitors, wherein the array of switchable capacitors comprises capacitor branches that are connected in parallel with the magnetic loop antenna, and wherein each of the capacitor branches comprises a switch and a capacitor.

19. A magnetic induction radio system for measuring the shape of an object, the magnetic induction radio system comprising:

a magnetic induction radio sensor comprising;

a magnetic loop antenna configured to at least partially enclose the object, wherein the inductance of the magnetic loop antenna depends on the shape of the object;

an antenna matching circuit coupled to the magnetic loop antenna, wherein the antenna matching circuit comprises an adjustable capacitance module configured to provide a particular capacitance such that the magnetic loop antenna and the antenna matching circuit form a resonant circuit and the resonant circuit has a fixed resonant frequency;

a measuring unit configured to generate a measurement value using the particular capacitance of the adjustable capacitance module, the measurement value representing a measurement of the shape of the object; and

a transmitter configured to transmit the generated measurement value using the magnetic loop antenna; and

a remote device configured to receive the transmitted measurement value from the transmitter of the magnetic induction radio sensor.

20. The magnetic induction radio system of claim 19, wherein the object is an organ of a patient, wherein the magnetic loop antenna is integrated in a stretchable strap that at least partially encloses the organ of the patient, and wherein the adjustable capacitance module comprises an array of switchable capacitors to provide the particular capacitance.