Digital delay line receiver for use with an implantable medical device

• US 6,295,473 B1
• Filed: 04/16/1999
• Issued: 09/25/2001
• Est. Priority Date: 04/16/1999
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Rosar, George
• Primary Examiner(s): Bockelman, Mark
• Application Number:
  US09/293,394
• Time in Patent Office: 893 Days
• Field of Search: 607/60, 607/30-32, 607/27, 128/903
• US Class Current: 607/60
• CPC Class Codes: A61N 1/3727 characterised by the modulation technique
• CPC Class Codes: H04L 27/2035 using a single or unspecified number of carriers
• CPC Class Codes: H04L 27/2331 wherein the received signal is demodulated using one or more delayed versions of itself
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

A body implantable medical apparatus includes circuitry for generating and transmitting a modulated analog data signal. A receiver receives and digitally demodulates the modulated analog signal. An analog-to-digital converting circuit produces an amplitude limited modulated digital signal corresponding to the modulated analog signal. The converting circuit includes an amplifier coupled to a receive antenna and a comparator having an input coupled to the amplifier and an output coupled to a digital demodulator. The digital demodulator demodulates the modulated digital signal to produce a digital information signal, such as a signal containing physiologic sensor data. The digital demodulator includes a digital delay line comprising a plurality of shift registers or, alternatively, a plurality of multiple-stage delay blocks each coupled to a tap selection device. The digital delay line includes an input coupled to an output of the converting circuit, an exclusive OR (XOR) gate having a first input coupled to an output of the digital delay line, and a conductor coupled between the input of the digital delay line and a second input of the XOR gate, such that delayed and non-delayed modulated digital signals are respectively applied to the first and second XOR gate inputs to produce a digital information signal at an output of the XOR gate. The digital demodulator may be implemented in a Field-Programmable Gate Array (FPGA), in an Application Specific Integrated Circuit (ASIC) or using a digital signal processor. A control circuit is coupled to the digital demodulator to adjust a rate at which the digital demodulator operates.

Claims

1. A system for receiving data produced by a body implantable medical apparatus, comprising:

a transmitter circuit, provided in the body implantable medical apparatus, that transmits a modulated analog signal from the body implantable medical device; and

a receiver, separate from the body implantable medical apparatus, the receives and demodulates the modulated analog signal, the receiver comprising;

an antenna;

an analog-to-digital converting circuit coupled to the antenna, the converting circuit producing a modulated digital signal produced at an output of the converting circuit in response to the modulated analog signal applied to an input of the converting circuit; and

a digital demodulator coupled to the converting circuit, the digital demodulator demodulating the modulated digital signal to produce a digital information signal.

2. The system of claim 1, wherein the converting circuit produces an amplitude limited modulated digital signal.

3. The system of claim 1, wherein the converting circuit comprises an amplifier coupled to the antenna and a comparator having an input coupled to the amplifier and an output coupled to the digital demodulator.

4. The system of claim 1, wherein the transmitter circuit transmits a differential bi-phase-shift-keyed modulated signal from the body implantable medical device.

5. The system of claim 1, wherein the digital demodulator produces the digital information signal by detecting coherent information between data bits of the modulated digital signal.

6. The system of claim 1, wherein the digital demodulator includes a digital delay line comprising a plurality of shift register elements.

7. The system of claim 1, wherein the digital demodulator includes a digital delay line comprising a plurality of multiple-stage delay blocks each coupled to a tap selection device.

8. The system of claim 1, wherein the digital demodulator comprises:

a digital delay line having an input coupled to an output of the converting circuit;

an exclusive OR (XOR) gate having a first input coupled to an output of the digital delay line; and

a conductor coupled between the input of the digital delay line and a second input of the XOR gate, a delayed modulated digital signal and a non-delayed modulated digital signal being applied to the first and second XOR gate inputs, respectively, and the digital information signal being provided at an output of the XOR gate.

9. The system of claim 1, wherein the digital demodulator is implemented in a Field-Programmable Gate Array (FPGA), in an Application Specific Integrated Circuit (ASIC), or using a digital signal processor.

10. The system of claim 1, further comprising a control circuit coupled to the digital demodulator, the control circuit providing user selection of a rate at which the digital demodulator operates.

11. The system of claim 1, wherein the implantable medical device comprises one of a pacemaker, a pacemaker/cardioverter/defibrillator (PCD), an oxygen sensing device, a nerve stimulator or a muscle stimulator.

12. An apparatus for receiving a modulated analog data signal produced by a body implantable medical apparatus, comprising:

an antenna;

an analog-to-digital converting circuit coupled to the antenna, the converting circuit producing a modulated digital signal produced at an output of the converting circuit in response to the modulated analog data signal applied to an input of the converting circuit; and

a digital delay line demodulator coupled to the converting circuit, the demodulator demodulating the modulated digital signal to produce a digital information signal.

13. The apparatus of claim 12, wherein the converting circuit produces an amplitude limited modulated digital signal.

14. The apparatus of claim 12, wherein the converting circuit comprises an amplifier coupled to the antenna and a comparator having an input coupled to the amplifier and an output coupled to the demodulator.

15. The apparatus of claim 12, wherein the modulated analog data signal is a differential bi-phase-shift-keyed modulated signal.

16. The apparatus of claim 12, wherein the demodulator produces the digital information signal by detecting coherent information between data bits of the modulated digital signal.

17. The apparatus of claim 12, wherein the demodulator comprises a plurality of shift register elements.

18. The apparatus of claim 12, wherein the demodulator comprises a plurality of multiple-stage delay blocks each coupled to a tap selection device.

19. The apparatus of claim 12, wherein the demodulator comprises:

a digital delay line having an input coupled to an output of the converting circuit;

an exclusive OR (XOR) gate having a first input coupled to an output of the digital delay line; and

a conductor coupled between the input of the digital delay line and a second input of the XOR gate, a delayed modulated digital signal and a non-delayed modulated digital signal being applied to the first and second XOR gate inputs, respectively, and the digital information signal being provided at an output of the XOR gate.

20. The apparatus of claim 12, wherein the demodulator is implemented in a Field-Programmable Gate Array (FPGA), in an Application Specific Integrated Circuit (ASIC), or using a digital signal processor.

21. The apparatus of claim 12, further comprising a control circuit coupled to the demodulator, the control circuit providing user selection of a rate at which the demodulator operates.

22. The apparatus of claim 12, wherein the implantable medical device comprises one of a pacemaker, a pacemaker/cardioverter/defibrillator (PCD), an oxygen sensing device, a nerve stimulator or a muscle stimulator.

23. A method of demodulating a modulated analog data signal produced by a body implantable medical apparatus, comprising:

receiving the modulated analog data signal;

converting the modulated analog data signal to a corresponding modulated digital signal;

delaying the modulated digital signal; and

using the modulated digital signal and the delayed modulated signal to produce a digital information signal.

24. The method of claim 23, wherein using the modulated digital signal and the delayed modulated signal comprises detecting coherent information between data bits of the modulated digital signal to produce the digital information signal.

25. The method of claim 23, wherein using the modulated digital signal and the delayed modulated signal comprises applying the modulated digital signal and the delayed modulated signal respectively to first and second inputs of an exclusive OR (XOR) gate, and producing the digital information signal at an output of the XOR gate.

26. The method of claim 23, wherein delaying the modulated digital signal comprises delaying the modulated digital signal using a fractional or integer divisor of the rate of the modulated digital signal.

27. The method of claim 23, wherein delaying the modulated digital signal comprises delaying the modulated digital signal using a plurality of shift register elements.

28. The method of claim 23, wherein delaying the modulated digital signal comprises delaying the modulated digital signal using a plurality of multiple-stage delay blocks and a tap selection device.

29. The method of claim 23, wherein converting the modulated analog data signal to the corresponding modulated digital signal further comprises amplitude limiting the modulated digital signal.

30. The method of claim 23, further comprising amplifying the received modulated analog data signal prior to converting the modulated analog data signal to the corresponding modulated digital signal.

31. The method of claim 23, wherein the modulated analog data signal is a differential bi-phase-shift-keyed modulated signal.

32. The method of claim 23, further comprising adjusting a rate at which the digital information signal is processed.

33. The method of claim 23, wherein the implantable medical device comprises one of a pacemaker, a pacemaker/cardioverter/defibrillator (PCD), an oxygen sensing device, a nerve stimulator or a muscle stimulator.

34. An apparatus for demodulating a modulated analog data signal produced by a body implantable medical apparatus, comprising:

means for receiving the modulated analog data signal;

means for converting the modulated analog data signal to a corresponding modulated digital signal;

means for delaying the modulated digital signal; and

means for producing a digital information signal using the modulated digital signal and the delayed modulated signal.

35. The apparatus of claim 34, wherein the producing means further comprises means for detecting coherent information between data bits of the modulated digital signal to produce the digital information signal.

36. The apparatus of claim 34, wherein the delaying means further comprises means for delaying the modulated digital signal using a fractional or integer divisor of the rate of the modulated digital signal.

37. The apparatus of claim 34, wherein the converting means further comprises means for amplitude limiting the modulated digital signal.

38. The apparatus of claim 34, further comprising means for amplifying the received modulated analog data signal prior to the converting means converting the modulated analog data signal to the corresponding modulated digital signal.

39. The apparatus of claim 34, wherein the modulated analog data signal is a differential bi-phase-shift-keyed modulated signal.

40. The apparatus of claim 34, further comprising means for adjusting a rate at which the digital information signal is processed.

41. The apparatus of claim 34, wherein the implantable medical device comprises one of a pacemaker,a pacemaker/cardioverter/defibrillator (PCD), an oxygen sensing device, a nerve stimulator or a muscle stimulator.