Medical device telemetry receiver having improved noise discrimination

• US 6,201,993 B1
• Filed: 12/09/1998
• Issued: 03/13/2001
• Est. Priority Date: 12/09/1998
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Jurek, David R., Kruse, John M.
• Primary Examiner(s): Layno, Carl H.
• Application Number:
  US09/208,883
• Time in Patent Office: 825 Days
• Field of Search: 607/30, 607/32, 607/60, 128/903
• US Class Current: 607/30
• CPC Class Codes: A61N 1/37211 Means for communicating with stimulators
• CPC Class Codes: A61N 1/37229 Shape or location of the implanted or external antenna
• CPC Class Codes: A61N 1/3727 characterised by the modulation technique
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

A method and apparatus for detecting an RF signal transmitted between an implantable medical device (IMD) and an external medical device programmer in a telemetry session and discriminating the telemetry transmitted RF signal from transient and steady state noise corrupting it. The external programmer includes a programmer telemetry antenna tuned circuit adapted to be driven into oscillation to generate tuned circuit output signals in response to telemetry uplink transmissions of telemetry uplink signals from the IMD, wherein the tuned circuit output signals can exhibit noise artifacts due to contamination by electrical noise. An RF telemetry receiver section detects and demodulates the telemetry uplink signals from the tuned circuit output signals and provides a demodulated uplink signal having a demodulated uplink signal amplitude that varies with time as a function of telemetry uplink signal amplitudes and noise artifacts. The receiver section includes an adaptive comparator circuit for comparing the demodulated uplink signal amplitude with an adaptive threshold signal and providing a receiver output signal when the demodulated uplink signal amplitude exceeds the adaptive threshold amplitude of the adaptive threshold signal.

Claims

1. An external programmer for receiving information-encoded, telemetry uplink signals transmitted from an implantable medical device (IMD) telemetry antenna and transmitter circuit in an IMD in a telemetry uplink transmission, said external programmer comprising:

a programmer telemetry antenna tuned circuit comprising at least one antenna coil and at least one tuning capacitor, the programmer telemetry tuned circuit adapted to be driven into oscillation to generate tuned circuit output signals in response to telemetry uplink transmissions of telemetry uplink signals and in response to electrical noise, whereby the tuned circuit output signals can exhibit noise artifacts due to contamination by such electrical noise;

a telemetry receiver section for detecting and demodulating the telemetry uplink signals from the tuned circuit output signals and providing a demodulated uplink signal having a demodulated uplink signal amplitude that varies with time as a function of telemetry uplink signal amplitudes and noise artifacts;

an adaptive comparator circuit for comparing the demodulated uplink signal amplitude with an adaptive threshold signal and providing a receiver output signal when the demodulated uplink signal amplitude exceeds the adaptive threshold amplitude of the adaptive threshold signal, the comparator circuit further comprising

means for filtering and integrating the demodulated uplink signal to derive an adaptive threshold amplitude that is proportional to and adapts to the amplitude of noise artifacts in the demodulated uplink signal; and

comparison means having a first input terminal for receiving the demodulated uplink signal and a second input terminal for receiving the adaptive threshold signal and an output terminal for comparing the demodulated uplink signal amplitude with the adaptive threshold amplitude and providing the receiver output signal at the output terminal only when the telemetry signal amplitude in the demodulated uplink signal exceeds the adaptive threshold amplitude.

2. The programmer of claim 1, wherein said telemetry receiver section further comprises an RF telemetry receiver section further comprising:

means for amplifying RF signals induced within said tuned circuit and providing an amplified RF signal;

means responsive to said amplified RF signal for shifting its phase and for providing a phase shifted, amplified RF signal; and

means for mixing said phase shifted, amplified RF signal with said amplified RF signal for providing a monophasic component of said mixed RF amplified signal, the amplitude of which is a function of frequency; and

means for demodulating said monophasic component of said mixed RF amplified signal for providing a detected DC component of said RF amplified signal.

3. The programmer of claim 2, wherein said tuned circuit resonates outside a bandpass frequency range containing said received data signals.

4. The programmer of claim 2, wherein said monophasic component of said mixed amplified RF signal has a first polarity for said amplified RF signals within a bandpass frequency range containing said received data signals and a second polarity for said amplified RF signals outside said bandpass frequency range.

5. The programmer of claim 2, wherein the information-encoded, telemetry uplink signals transmitted from an IMD telemetry antenna and transmitter circuit in an IMD in a telemetry uplink transmission are encoded via one of the encoding schemes selected from the group consisting of FM, AM, phase shift keying (PSK), frequency shift keying (FSK), biphasic frequency shift keying (BPSK) amplitude shift keying (ASK), pulse position modulation (PPM), and pulse interval modulation (PIM).

6. The programmer of claim 1, wherein the information-encoded, telemetry uplink signals transmitted from an IMD telemetry antenna and transmitter circuit in an IMD in a telemetry uplink transmission are encoded via one of the encoding schemes selected from the group consisting of FM, AM, phase shift keying (PSK), frequency shift keying (FSK), biphasic frequency shift keying (BPSK) amplitude shift keying (ASK), pulse position modulation (PPM), and pulse interval modulation (PIM).

7. The programmer of claim 1, wherein the comparison means further comprises:

an op amp having first and second input terminals and an output terminal;

means for applying the demodulated signal to the first input terminal of the op amp; and

means for applying the adaptive threshold signal to the second input terminal of the op amp, whereby the receiver output signal at the output terminal of the op amp comprises the difference between the demodulated signal amplitude and the adaptive threshold amplitude.

8. A telemetry system for receiving information-encoded, telemetry signals transmitted from one of an implantable medical device (IMD) or an external programmer to the other of the external programmer or IMD employing a telemetry antenna and transmitter circuit in a telemetry transmission, wherein each of said IMD of said external programmer comprises:

a telemetry antenna tuned circuit comprising at least one antenna coil and at least one tuning capacitor, the telemetry tuned circuit adapted to be driven into oscillation to generate tuned circuit output signals in response to telemetry transmissions of telemetry signals and in response to electrical noise, whereby the tuned circuit output signals can exhibit noise artifacts due to contamination by such electrical noise;

a telemetry receiver section for detecting and demodulating the telemetry signals from the tuned circuit output signals and providing a demodulated signal having a demodulated signal amplitude that varies with time as a function of telemetry signal amplitudes and noise artifacts;

an adaptive comparator circuit for comparing the demodulated signal amplitude with the threshold amplitude of an adaptive threshold signal and providing a receiver output signal when the demodulated signal amplitude exceeds the adaptive threshold amplitude of the adaptive threshold signal, the comparator circuit further comprising

means for filtering and integrating the demodulated signal to derive an adaptive threshold amplitude that is proportional to and adapts to the amplitude of noise artifacts in the demodulated signal; and

comparison means having a first input terminal for receiving the demodulated signal and a second input terminal for receiving the adaptive threshold signal and an output terminal for comparing the demodulated signal amplitude with the adaptive threshold amplitude and providing the receiver output signal at the output terminal only when the demodulated signal amplitude exceeds the adaptive threshold amplitude.

9. The system of claim 8, wherein the information-encoded, telemetry signals transmitted from a telemetry antenna and transmitter circuit in a telemetry transmission are encoded via one of the encoding schemes selected from the group consisting of FM, AM, phase shift keying (PSK), frequency shift keying (FSK), biphasic frequency shift keying (BPSK) amplitude shift keying (ASK), pulse position modulation (PPM), and pulse interval modulation (PIM).

10. The system of claim 8, wherein the comparison means further comprises:

an op amp having first and second input terminals and an output terminal;

means for applying the demodulated signal to the first input terminal of the op amp; and

means for applying the adaptive threshold signal to the second input terminal of the op amp, whereby the receiver output signal at the output terminal of the op amp comprises the difference between the demodulated signal amplitude and the adaptive threshold amplitude.

11. A method of receiving information-encoded, telemetry signals transmitted from one of an implantable medical device (IMD) or an external programmer to the other of the external programmer or IMD employing a telemetry antenna and transmitter circuit in a telemetry transmission, wherein each of said IMD or said external programmer comprises:

a telemetry antenna tuned circuit comprising at least one antenna coil and at least one tuning capacitor, the telemetry tuned circuit adapted to be driven into oscillation to generate tuned circuit output signals in response to telemetry transmissions of telemetry signals and in response to electrical noise, whereby the tuned circuit output signals can exhibit noise artifacts due to contamination by such electrical noise; and

a telemetry receiver section for detecting and demodulating the telemetry signals from the tuned circuit output signals and providing a demodulated signal having a demodulated signal amplitude that varies with time as a function of telemetry signal amplitudes and noise artifacts;

the method comprising the steps of;

filtering and integrating the demodulated signal to derive an adaptive threshold signal having an adaptive threshold amplitude that is proportional to and adapts to the amplitude of noise artifacts in the demodulated signal; and

comparing the demodulated signal amplitude with the adaptive threshold amplitude and providing a receiver output signal when the demodulated signal amplitude exceeds the adaptive threshold amplitude of the adaptive threshold signal.

12. The method of claim 11, wherein the comparing step further comprises the steps of:

providing an op amp having first and second input terminals and an output terminal;

applying the demodulated signal to the first input terminal of the op amp; and

applying the adaptive threshold signal to the second input terminal of the op amp, whereby the receiver output signal at the output terminal of the op amp comprises the difference between the demodulated signal amplitude and the adaptive threshold amplitude.

13. The method of claim 12, wherein the information-encoded, telemetry signals transmitted in a telemetry transmission are encoded via one of the encoding schemes selected from the group consisting of FM, AM, phase shift keying (PSK), frequency shift keying (FSK), biphasic frequency shift keying (BPSK) amplitude shift keying (ASK), pulse position modulation (PPM), and pulse interval modulation (PIM).

14. The method of claim 11, wherein the information-encoded, telemetry signals transmitted in a telemetry transmission are encoded via one of the encoding schemes selected from the group consisting of FM, AM, phase shift keying (PSK), frequency shift keying (FSK), biphasic frequency shift keying (BPSK) amplitude shift keying (ASK), pulse position modulation (PPM), and pulse interval modulation (PIM).

15. In a telemetry receiver for receiving information-encoded, telemetry signals transmitted from one of an implantable medical device (IMD) or an external programmer to the other of the external programmer or IMD employing a telemetry antenna and transmitter circuit in a telemetry transmission, wherein the receiver further comprises:

a telemetry antenna tuned circuit comprising at least one antenna coil and at least one tuning capacitor, the telemetry antenna tuned circuit adapted to be driven into oscillation to generate tuned circuit output signals in response to telemetry transmissions of telemetry signals and in response to electrical noise, whereby the tuned circuit output signals can exhibit noise artifacts due to contamination by such electrical noise;

a telemetry receiver section coupled to the telemetry antenna to detect and to demodulate the telemetry signals from the tuned circuit output signals and to provide a demodulated signal having demodulated signal amplitude that varies with time as a function of telemetry signal amplitudes; and

an adaptive comparator circuit coupled to the telemetry receiver section to receive the demodulated signal, to generate an adaptive threshold signal indicative of a level of the electric noise in the demodulated signal, and to provide a filtered receiver output signal when the adaptive threshold signal has a predetermined relationship to the demodulated signal.

16. The receiver of claim 15, wherein the comparison means further comprises:

an op amp having first and second input terminals and an output terminal;

means for applying the demodulated signal to the first input terminal of the op amp; and

means for applying the adaptive threshold signal to the second input terminal of the op amp, whereby the receiver output signal at the output terminal of the op amp comprises the difference between the demodulated signal amplitude and the amplitude of the adaptive threshold signal.

17. The receiver of claim 16, wherein the information-encoded, telemetry signals transmitted in a telemetry transmission are encoded via one of the encoding schemes of the group consisting of FM, AM, phase shift keying (PSK), frequency shift keying (FSK), biphasic frequency shift keying (BPSK) amplitude shift keying (ASK), pulse position modulation (PPM), and pulse interval modulation (PIM).

18. The receiver of claim 15, where in the information-encoded, telemetry signals transmitted in a telemetry transmission are encoded via one of the encoding schemes of the group consisting of FM, AM, phase shift keying (PSK), frequency shift keying (FSK), biphasic frequency shift keying (BPSK) amplitude shift keying (ASK), pulse position modulation (PPM), and pulse interval modulation (PIM).