Antenna for miniature implanted medical device

• US 20020042637A1
• Filed: 09/28/2001
• Published: 04/11/2002
• Est. Priority Date: 10/11/2000
• Status: Active Grant

• Current Assignee: Alfred E. Mann Foundation For Scientific Research
• Original Assignee: Alfred E. Mann Foundation For Scientific Research
• Inventors: Stover, Howard H.
• Granted Patent: US 6,804,561 B2
• Time in Patent Office: Days
• US Class Current: 607/60
• CPC Class Codes: A61N 1/05 for implantation or insertion into the body, e.g. heart electrode A61N1/06 takes precedence
• CPC Class Codes: A61N 1/08 Arrangements or circuits for monitoring, protecting, controlling or indicating for external stimulators A61N1/3603; for implantable neurostimulators A61N1/36128; for heart stimulators A61N1/37; for defibrillators A61N1/3925
• CPC Class Codes: A61N 1/37205 Microstimulators, e.g. implantable through a cannula
• CPC Class Codes: A61N 1/37229 Shape or location of the implanted or external antenna

Abstract

An improved antenna for use with an implantable microdevice, such as a microstimulator or microsensor, comprises a loop antenna on the case of the microdevice. The antenna receives data transmitted from an external device, and transmits data to an external device. Such a loop antenna may be formed from two cylindrical sections separated by an insulating material on the case of the microdevice, or by separating a metal cylinder into two parallel semi-cylinders separated by an insulating material. A tuning circuit comprising capacitors and/or varactors is used to obtain resonance in the loop antenna, thus creating a sufficiently large effective antenna aperture. In a preferred embodiment, the electrodes of the microdevice are modified to both perform their primary task of tissue stimulation and to perform a secondary task as the radiating elements of a loop antenna.

Claims

1. A loop antenna formed on the case of an implantable microdevice, the loop antenna comprising:

a radiating element, wherein the radiating element is electrically conducting and formed on the case of the microdevice;

a tuning element electrically connected to the radiating element, wherein the tuning element and radiating element combine to form a resonant circuit; and

wherein

the loop antenna is electrically connected to communications circuitry housed within the microdevice to create a telemetry system for the microdevice.

2. The loop antenna of claim 1 wherein the case of the microdevice is cylindrical in shape, and wherein the radiating element comprises two spaced apart cylindrical sleeves on the case of the microdevice, and wherein the tunning element comprises a first tuning circuit and a second tuning circuit, and wherein the first tuning circuit is electrically connected between each cylindrical sleeve at adjacent points on each sleeve, and wherein the second tuning circuit is electrically connected between each cylindrical sleeve at adjacent points on each sleeve, wherein the second tuning circuit is on the opposite side of the microdevice from the first tuning circuit.

3. The loop antenna of claim 2 wherein the second tuning circuit is a short.

4. The loop antenna of claim 2 wherein the microdevice has a plurality of electrodes and wherein the two spaced apart cylindrical sleeves are the electrodes of the microdevice.

5. The loop antenna of claim 1 wherein the radiating element comprises spaced apart, antenna sections, on the case of the microdevice, wherein the antenna sections are separated along a separation, wherein the separation runs substantially parallel to a longitudinal axis of the microdevice, and wherein the tunning element comprises a first tuning circuit and a second tuning circuit, and wherein the first tuning circuit is electrically connected between each antenna section at adjacent points on proximal ends of each antenna section, and wherein the second tuning circuit is electrically connected between each antenna section at adjacent points on distal ends of each antenna section.

6. The loop antenna of claim 5 wherein the second tuning circuit is a short.

7. The loop antenna of claim 5 wherein the microdevice has one or more electrodes and wherein the two spaced apart, antenna sections are formed from an electrode of the microdevice, wherein at least one of the electrodes has been divided by an insulator to form the two antenna sections.

8. The loop antenna of claim 1 wherein the microdevice is a microstimulator.

9. The loop antenna of claim 1 wherein the microdevice is a microsensor.

10. The loop antenna of claim 1 wherein the telemetry system receives a control signal from an external device.

11. The loop antenna of claim 1 wherein the telemetry system transmits a signal to an external device.

12. The loop antenna of claim 1 wherein the tuning element and the radiating element are electrically connected in a parallel circuit.

13. The loop antenna of claim 1 wherein the tuning element and the radiating element are electrically connected in a serial circuit.

14. The loop antenna of claim 1 wherein the operating frequency of the telemetry system is in the range of 402 to 405 MHz.

16. The telemetry system of claim 15 wherein the microdevice is a microstimulator.

17. The telemetry system of claim 15 wherein the tuning element comprises at least one capacitor.

18. The telemetry system of claim 15 wherein the operating frequency of the telemetry system is in the range of 402 to 405 MHz.

19. The telemetry system of claim 15 wherein the telemetry system includes a receiving circuit, wherein the telemetry system further comprises:

a receiver amplifier with an input and an output; and

a receiver with an input, wherein the output of the receiver amplifier in connected to the input of the receiver;

a transmit/receive switch including a first switched connection, a second switched connection, and a fixed connection;

wherein transmit/receive switch is connected between the transmit driver and the matching network, wherein the output of the transmit driver is connected to the first switched connection, and wherein the fixed connection is connected to the first connection of the matching network; and

wherein

the receiver amplifier input is connected to the second switched connection of the transmit/receive switch.

20. The telemetry system of claim 19 wherein the tuning element comprises at least one varactor.

15. A telemetry system for transmitting signals from a microdevice, the telemetry system comprising:

a transmit driver including a transmit driver output;

a matching network with a first connection and a second connection, wherein the first connection of the matching network is connected to the transmit driver output;

a tuning element; and

a radiating element formed on the case of the microdevice, wherein the radiating element electrically behaves as a loop antenna, and wherein the tuning element and the radiating element are connected in a parallel circuit, wherein the parallel circuit has a first connection and a second connection, and wherein the second connection of the matching network is connected to the first connection of the parallel circuit, and wherein the second connection of the parallel circuit is connected to ground.

21. A telemetry system for receiving signals for a microdevice, the telemetry system comprising:

a receiver with an input;

a receiver amplifier with an input and an output, wherein the output of the receiver amplifier in connected to the input of the receiver;

a matching network with a first connection and a second connection, wherein the first connection of the matching network is connected to the input of the receiver amplifier;

a tuning element;

a radiating element formed on the case of the microdevice, wherein the radiating element electrically behaves as a loop antenna; and

wherein

the tuning element and the radiating element are connected in a parallel circuit, wherein the parallel circuit has a first connection and a second connection, and wherein the second connection of the matching network is connected to the first connection of the parallel circuit, and wherein the second connection of the parallel circuit is connected to ground.

22. The telemetry system of claim 21 wherein the microdevice is a microstimulator.

23. The telemetry system of claim 21 wherein the tuning element comprises at least one capacitor.

24. The telemetry system of claim 21 wherein the tuning element comprises at least one varactor.

25. The telemetry system of claim 21 wherein the tuning element comprises at least one capacitor and at least on varactor.

26. The telemetry system of claim 21 wherein the operating frequency of the telemetry system is in the range of 402 to 405 MHz.

27. The telemetry system of claim 21 wherein the telemetry system includes a transmit circuit, wherein the telemetry system further comprises:

a transmit driver with an output;

a transmit/receive switch including a first switched connection, a second switched connection, and a fixed connection;

wherein transmit/receive switch is connected between the receiver amplifier and the matching network, wherein the first connection of the matching network is connected to the fixed connection, and wherein the second switched connection is connected to the receiver amplifier; and

wherein the output of the transmit driver is connected to the first switched connection.

29. The telemetry system of claim 28 wherein the microdevice is a microstimulator.

30. The telemetry system of claim 28 wherein the tuning element comprises at least one capacitor.

31. The telemetry system of claim 28 wherein the operating frequency of the telemetry system is in the range of 402 to 405 MHz.

32. The telemetry system of claim 28 wherein the telemetry system includes a receiving circuit, wherein the telemetry system further comprises:

a matching network with an input and an output;

a receiver amplifier with an input and an output, wherein the output of the matching network is connected to the input of the receiver amplifier;

a receiver with an input, wherein the output of the receiver amplifier in connected to the input of the receiver;

a transmit/receive switch including a first switched connection, a second switched connection, and a fixed connection;

wherein the transmit/receive switch is connected between the transmit driver and the tuning element, wherein the output of the transmit driver is connected to the first switched connection, and wherein the fixed connection is connected to the first connection of the tuning element; and

wherein

the input of the matching network is connected to the second switched connection of the transmit/receive switch.

33. The telemetry system of claim 32 wherein the tuning element comprises at least one varactor.

35. The telemetry system of claim 34 wherein the microdevice is a microstimulator.

36. The telemetry system of claim 34 wherein the tuning element comprises at least one capacitor.

37. The telemetry system of claim 34 wherein the tuning element comprises at least one varactor.

38. The telemetry system of claim 34 wherein the tuning element comprises at least one capacitor and at least one varactor.

39. The telemetry system of claim 34 wherein the operating frequency of the telemetry system is in the range of 402 to 405 MHz

40. The telemetry system of claim 34 wherein the telemetry system includes a transmitting circuit, wherein the telemetry system further comprises:

a transmit driver with an output;

a transmit/receive switch including a first switched connection, a second switched connection, and a fixed connection;

wherein transmit/receive switch is connected between the tuning element and the matching network, wherein the input of the matching network is connected to the second switched connection, and wherein the fixed connection is connected to the first connection of the tuning element; and

wherein

the output of the transmit driver is connected to the first switched connection.

28. A telemetry system for transmitting for a microdevice, the telemetry system comprising:

a transmit driver with an output;

a tuning element with a first connection and a second connection, wherein the first connection of the tuning element is connected to the output of the transmit driver;

a radiating element with a first connection and a second connection, wherein the radiating element is formed on the case of the microdevice, and wherein the radiating element electrically behaves as a loop antenna; and

wherein

the first connection of the radiating element is connected to the second connection of the tuning element, and wherein the second connection of the radiating element is connected to ground.

34. A telemetry system for receiving for a microdevice, the telemetry system comprising:

a matching network with an input and an output;

a receiver amplifier with an input and an output, wherein the receiver amplifier input is connected to the output of the matching network;

a receiver with an input, wherein the output of the receiver amplifier in connected to the input of the receiver;

a tuning element with a first connection and a second connection, wherein the first connection of the tuning element is connected to the input of the matching network;

a radiating element with a first connection and a second connection, wherein the radiating element is formed on the case of the microdevice, and wherein the radiating element electrically behaves as a loop antenna; and

wherein

the first connection of the radiating element is connected to the second connection of the tuning element, and wherein the second connection of the radiating element is connected to ground.