Bi-directional telemetry system and method for transmitting data at high transmission rate

• US 6,577,898 B2
• Filed: 04/26/2001
• Issued: 06/10/2003
• Est. Priority Date: 04/26/2001
• Status: Expired due to Fees

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Silvian, Sergiu
• Primary Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US09/844,190
• Publication Number:
  US 20020183799A1
• Time in Patent Office: 775 Days
• Field of Search: 607/4, 607/5, 607/9, 607/32, 607/60, 128/903
• US Class Current: 607/32
• CPC Class Codes: A61N 1/3727 characterised by the modulation technique
• CPC Class Codes: H04L 27/365 Modulation using digital generation of the modulated carrier (not including modulation of a digitally generated carrier)

Abstract

A bi-directional telemetry system includes an implanted unit that allows a high-speed transfer of digital data with minimal complexity of the electronic circuitry. A corresponding external unit is capable of decoding the high-data-rate transmitted information and, in turn, communicates with the implanted unit using pulse amplitude modulation. The data transmission rate of the implanted unit to the external device is 32 kbps, a four-fold increase over conventional data transmission rates, without increasing the carrier frequency. To this end, the implanted unit using a modified implementation of the quadrature amplitude modulation (QAM) method that generates the required symbols from readily available squarewave signals. Simulated sinewaves are generated within the transmitter by an inverting amplifier stage with variable input resistance determined by a pair of switches that are ultimately controlled by 16 k and 32 k clocks in the implanted unit. Data is encoded by changing the amplitude and polarity of the simulated sinewaves. Quadrupling of the data rate is achieved by taking advantage of the orthogonality of I and Q components, whose phases are in quadrature.

Claims

1. A telemetry system for use in an implantable cardiac stimulation device, comprising:

a telemetry coil;

a transmitter module, coupled to the telemetry coil, that transmits data at a predetermined transmission rate over the telemetry coil, the transmitter module configured to perform a modified quadrature amplitude modulation process;

a controller coupled to the transmitter module that provides the transmitter module with a squarewave input clock signal, the controller further causing the transmitter module to execute the modified quadrature amplitude modulation process to convert the squarewave signal into simulated sinewave symbols, and further to encode data bits of information in each of the simulated sinewave symbols.

2. The telemetry system according to claim 1, wherein the data transmission rate is approximately 32 kbps.

3. The telemetry system according to claim 1, wherein the transmitter module includes a switch circuit coupled to, and selectively regulated by the input clock signal.

4. The telemetry system according to claim 3, wherein the transmitter module further includes an inverting amplifier stage connected intermediate the switch circuit and the telemetry coil, to generate the simulated sinewave symbols.

5. The telemetry system according to claim 4, wherein the inverting amplifier stage includes an input resistance stage having a variable resistance that is determined by the switch circuit.

6. The telemetry system according to claim 5, wherein the switch circuit includes a first switch and a second switch that are connected to the input resistance stage.

7. The telemetry system according to claim 6, wherein the squarewave input clock signal includes a first pulse train at a frequency of approximately 8 kbps.

8. The telemetry system according to claim 7, wherein the squarewave input clock signal includes a second pulse train at a frequency of approximately 16 kbps.

9. The telemetry system according to claim 8, wherein the squarewave input clock signal includes a third pulse train at a frequency of approximately 32 kbps.

10. The telemetry system according to claim 4, wherein the transmitter module encodes the data bits of information by changing the amplitude and polarity of the simulated sinewave symbols.

11. The telemetry system according to claim 10, wherein the transmitter module includes an I transmitter that generates an I component to be transmitted, and a Q transmitter that generates a Q component to be transmitted;

and

wherein the I component and the Q component are orthogonal with phases in quadrature to enable an external decoder to decode the input data.

12. The telemetry system according to claim 11, wherein each of the I transmitter and the Q transmitter implements a two-bit modulation of the data to be transmitted.

13. The telemetry system according to claim 12, wherein the transmitter module encodes four data bits Ibit1, Ibit0, Qbit1, Qbit0 during one symbol period.

14. The telemetry system according to claim 13, wherein the symbol period is approximately 122 μ

s.

15. The telemetry system according to claim 13, wherein the data bits Ibit1 and Ibit0 are encoded in an I transmitter signal;

and

wherein the data bits Qbit1 and Qbit0 are encoded in a Q transmitter using a carrier frequency that is 90 degrees out of phase with respect to a carrier frequency used by the I transmitter.

16. The telemetry system according to claim 15, wherein the inverting amplifier stage feeds the four data bits Ibit1, Ibit0, Qbit1, Qbit0 into a telemetry coil for transmission.

17. The telemetry system according to claim 16, wherein the data bit Ibit1 determines the polarity of the simulated sinewave symbols of the I transmitter.

18. The telemetry system according to claim 17, wherein the data bit Ibit0 independently controls the amplitude of the simulated sinewave symbols of the I transmitter.

19. The telemetry system according to claim 17, wherein the data bit Qbit1 determines the polarity of the simulated sinewave symbols of the Q transmitter.

20. The telemetry system according to claim 19, wherein the data bit Qbit0 independently controls the amplitude of the simulated sinewave symbols of the Q transmitter.

21. The telemetry system according to claim 11, wherein the transmitter module shifts starting points of the I and Q components by a predetermined value with respect to the input clock signal.

22. The telemetry system according to claim 21, wherein the input clock signal includes a first pulse train at a frequency of approximately 8 kbps;

and

wherein the transmitter module shifts the starting points of the I and Q components by 45 degrees with respect to the 8 kbps input clock signal.

23. In a telemetry system for use in an implantable cardiac stimulation device, a method of telemetering data comprising the steps of:

providing a squarewave signal at a predetermined frequency;

processing the squarewave signal utilizing a modified quadrature amplitude modulation process to thereby generate simulated sinewaves,

telemetering the simulated sinewaves to a remote receiver.

24. The method of claim 23 comprising the step of encoding data bits of information into the simulated sinewaves.

25. The method of claim 24 whereby the encoding step includes the step of changing the amplitude and polarity of the simulated sinewaves.

26. The method of claim 25 wherein the step of processing the squarewave signal includes the step of generating a pair of simulated sinewaves in phase quadrature.

27. The method of claim 26 wherein the step of encoding includes the step of encoding two data bits of information in each one of the pair of simulated sinewaves.

28. The method of claim 27 wherein the step of encoding further includes the step of utilizing one of the two data bits of information for changing the magnitude of a respective simulated sinewave and the other bit of information for changing the polarity of said respective simulated sinewave.

29. The method of claim 28 wherein the simulated sinewaves have a predefined period, the encoding step further comprising the step of encoding four data bits of information during said period, two of said data bits being encoded in each one of the simulated sinewaves.

30. The method of claim 29 comprising the step of utilizing a predetermined frequency of 8192 Hz.

31. A telemetry system for use in an implantable cardiac stimulation device, comprising:

telemetry coil means for telemetering data;

transmitter means for transmitting data to be telemetered over the telemetry coil means at a predetermined transmission rate; and

control means for providing the transmitter means with a squarewave input clock signal, the transmitter means utilizing the input clock signal for executing a modified quadrature amplitude modulation process for converting the squarewave input clock signal into simulated sinewave symbols, the transmitter means further for encoding data bits of information in each of the simulated sinewave symbols.

32. The telemetry system according to claim 31, wherein the transmitter means includes an inverting amplifier means for generating the simulated sinewave symbols.

33. The telemetry system according to claim 31, wherein the transmitter means includes an I transmitting means for generating an I component, and a Q transmitting means for generating a Q component;

and

wherein the I component and the Q component are orthogonal with phases in quadrature to enable a decoding means to decode input data.

34. The telemetry system according to claim 33, wherein the transmitter means encodes four data bits Ibit1, Ibit0, Qbit1, Qbit0 during a symbol period;

wherein the data bits Ibit1 and Ibit0 are encoded in an I transmitter signal; and

wherein the data bits Qbit1 and Qbit0 are encoded in a Q transmitter using a carrier frequency that is 90 degrees out of phase with respect to a carrier frequency used by the I transmitter.