Method and system for improved spectral efficiency of far field telemetry in a medical device

• US 7,069,086 B2
• Filed: 10/11/2002
• Issued: 06/27/2006
• Est. Priority Date: 08/08/2002
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Von Arx, Jeffrey A.
• Primary Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US10/269,905
• Publication Number:
  US 20040030260A1
• Time in Patent Office: 1,355 Days
• Field of Search: None
• US Class Current: 607/60
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61N 1/37223 Circuits for electromagnetic coupling
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

Radio frequency bandwidth from a far field transmitter of an implantable medical device is adjusted by controlling the data rate, the output power level, the transmitter supply voltage or combinations thereof. Adjustments are made on the basis of a sensed temperature, absence or presence of a lead or by way of wave shaping. A Surface Acoustic Wave (SAW) resonator based transmitter exhibits stable bandwidth in a temperature controlled operating environment. For temperatures outside of the range of human body temperature, the output of the SAW-based transmitter is adjusted to provide reduced bandwidth.

Claims

1. A system comprising:

an implantable temperature sensor adapted to provide an output signal based on a sensed temperature;

an implantable comparator coupled to the sensor and adapted to generate a control signal based on the output signal; and

an implantable wireless transmitter coupled to the implantable comparator and adapted to modulate a transmission bandwidth based on the control signal.

2. The system of claim 1 wherein the implantable comparator includes a processor.

3. The system of claim 1 further including an implantable therapy circuit coupled to the implantable wireless transmitter.

4. The system of claim 1 wherein the transmitter includes a surface acoustic wave (SAW) resonator.

5. The system of claim 1 wherein the wireless transmitter is adapted to transmit at two or more output power levels.

6. The system of claim 1 wherein the wireless transmitter is adapted to transmit at two or more data rates.

7. The system of claim 1 wherein the implantable wireless transmitter is adapted to be disabled based on the control signal.

8. The system of claim 1 further including a digital to analog converter (DAC) coupled to an implantable processor and adapted to provide the control signal.

9. An apparatus comprising:

a far field transmitter coupled to an implantable medical device, the transmitter having two or more selectable transmission frequency spectrums and a frequency spectrum select means;

a temperature sensor having an output signal based on a temperature; and

a controller coupled to the frequency spectrum select means and coupled to the output signal, the controller adapted to select one transmission frequency spectrum of the two or more selectable transmission frequency spectrums based on the output signal.

10. The apparatus of claim 9 further including a telemetry circuit coupled to the implantable medical device.

11. The apparatus of claim 9 wherein the controller is adapted to adjust a voltage level.

12. The apparatus of claim 9 wherein the controller is adapted to adjust a current level.

13. The apparatus of claim 9 wherein the controller is adapted to adjust a transmission data rate.

14. The apparatus of claim 9 wherein the controller is adapted to adjust a transmission output power level.

15. The apparatus of claim 9 wherein the controller is adapted to selectively enable the far field transmitter.

16. The apparatus of claim 9 wherein the controller is adapted to selectively energize the far field transmitter.

17. A method comprising:

sensing a temperature at an implantable device;

comparing the sensed temperature with a first temperature; and

disabling a far field transmitter of the implantable device if the sensed temperature is greater than the first temperature.

18. The method of claim 17 further including:

comparing the sensed temperature with a second temperature; and

disabling the far field transmitter if the sensed temperature is less than the second temperature.

19. The method of claim 17 wherein disabling includes removing a supply voltage.

20. A method comprising:

sensing a temperature at an implantable device;

comparing the sensed temperature with a first temperature; and

selecting a reduced output power level of a far field transmitter of the implantable device if the sensed temperature is above the first temperature.

21. The method of claim 20 further including:

comparing the sensed temperature with a second temperature; and

selecting the reduced output power level if the sensed temperature is below the second temperature.

22. The method of claim 21 further including transmitting data at an increased output power level if the sensed temperature is between the first temperature and the second temperature.

23. The method of claim 20 wherein selecting the reduced output power level includes disabling the far field transmitter.

24. A method comprising:

sensing a temperature at an implantable device;

comparing the sensed temperature with a first temperature; and

selecting a reduced telemetry data rate of a far field transmitter of the implantable device if the sensed temperature is above the first temperature.

25. The method of claim 24 further including:

comparing the sensed temperature with a second temperature; and

selecting the reduced telemetry data rate if the sensed temperature is below the second temperature.

26. The method of claim 25 further including transmitting data at an increased telemetry data rate if the sensed temperature is between the first temperature and the second temperature.

27. An apparatus comprising:

therapy delivery means adapted for implanting in a body;

sensing means adapted to provide a sense signal based on a temperature;

processor means coupled to the therapy means;

first telemetry means coupled to the processor and adapted to communicate using far field transmissions, the first telemetry means having a control input; and

wherein the control input receives a control signal based on the sense signal.

28. The apparatus of claim 27 further including a second telemetry means coupled to the processor and adapted to communicate using near field transmissions.

29. The apparatus of claim 27 wherein the control input is coupled to a transmitter output power control means, the transmitter output power control means selecting a transmitter output power of the first telemetry means based on the control signal.

30. The apparatus of claim 27 wherein the control input is coupled to a data rate control means, the data rate control means selecting a data transmission rate of the first telemetry means based on the control signal.

31. The apparatus of claim 27 wherein the control input is coupled to a transmitter disable means, the transmitter disable means selectively disabling the first telemetry means based on the control signal.

32. An apparatus comprising:

a lead detection circuit having a detection output;

an implantable transmitter having two or more modes of operation; and

a mode selection circuit coupled to the implantable transmitter and adapted to provide a mode selection signal based on the detection output.

33. The apparatus of claim 32 wherein the mode selection circuit includes a comparator coupled to the lead detection circuit.

34. The apparatus of claim 33 wherein the comparator includes an analog comparator.

35. The apparatus of claim 32 wherein the mode selection circuit includes a processor coupled to the lead detection circuit.

36. The apparatus of claim 32 wherein the implantable transmitter is adapted to transmit a signal having a first bandwidth if a lead is detected and adapted to transmit a signal having a second bandwidth if the lead is not detected, wherein the first bandwidth is greater than the second bandwidth.

37. The apparatus of claim 32 wherein the implantable transmitter has a first mode corresponding to a first data rate and a second mode corresponding to a second data rate.

38. The apparatus of claim 32 wherein the implantable transmitter has a first mode corresponding to a first output power level and a second mode corresponding to a second output power level.

39. The apparatus of claim 32 wherein the implantable transmitter has a first mode corresponding to enabled and a second mode corresponding to disabled.

40. A system comprising:

an implantable therapy circuit;

a processor coupled to the therapy circuit and having a signal output;

a filter having a filter input coupled to the signal output and having a filter output; and

an implantable wireless transmitter having a modulation input coupled to the filter output and wherein an output power of the wireless transmitter is modulated as a function of the modulation input.

41. The system of claim 40 wherein the filter output provides a wave shaped signal.

42. The system of claim 40 further including a digital to analog converter (DAC) having a DAC input coupled to the signal output and a DAC output coupled to the filter input.

43. The system of claim 40 wherein the implantable wireless transmitter is adapted to provide amplitude shift key (ASK) modulation.

44. A system comprising:

an implantable therapy circuit;

a processor coupled to the therapy circuit and having a signal output;

a digital to analog converter having a digital input coupled to the signal output and having an analog output; and

an implantable wireless transmitter having a modulation input coupled to the analog output and wherein an output power of the wireless transmitter is modulated as a function of the modulation input.

45. The system of claim 44 wherein the analog output provides a wave shaped signal.

46. The system of claim 45 wherein the wave shaped signal approximates a Haversine wave.

47. A method comprising:

receiving a signal from an implanted therapy circuit;

processing the signal to provide a modulation input signal;

adjusting a far field transmitter power output based on the modulation input signal; and

wirelessly transmitting data based on the signal.

48. The method of claim 47 wherein processing includes filtering.

49. The method of claim 47 wherein processing includes low pass filtering.

50. The method of claim 47 wherein processing includes converting the signal to analog format.

51. The method of claim 47 wherein the signal includes digital data and wherein processing includes converting four bit digital data to an analog signal.

52. The method of claim 47 wherein processing includes applying a Haversine wave shaping function.