Method and apparatus for operating a diversity antenna system for communicating with implantable medical device

• US 20060195161A1
• Filed: 02/28/2005
• Published: 08/31/2006
• Est. Priority Date: 02/28/2005
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Rawat, Prashant, Bange, Joseph E., Vallapureddy, Vineel, Li, Hui, Quiles, Sylvia
• Granted Patent: US 7,392,092 B2
• Time in Patent Office: Days
• US Class Current: 607/60
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61N 1/37223 Circuits for electromagnetic coupling
• CPC Class Codes: H04B 7/0608 Antenna selection according to transmission parameters
• CPC Class Codes: H04B 7/0814 based on current reception conditions, e.g. switching to different antenna when signal level is below threshold
• CPC Class Codes: H04L 1/24 Testing correct operation
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

A far-field radio frequency (RF) telemetry system for communicating with an implantable medical device includes a diversity antenna system. Multi-frame messages each including multiple outgoing data frames are transmitted to the implantable medical device. In response, the implantable medical device transmits response data frames each following one or more of the outgoing data frames, according to a predetermined communication protocol. An antenna control circuit selects an antenna of the diversity antenna system for transmitting the outgoing data frames and/or receiving the response data frames based the quality of signal reception associated with the response data frames.

Claims

1. A system for communicating with an implantable medical device, the system comprising:

a diversity antenna system including a plurality of antennas configured to transmit an outgoing signal to the implantable medical device and to receive an incoming signal from the implantable medical device;

a transceiver adapted to transmit outgoing data frames by modulating the outgoing signal and to receive incoming data frames by demodulating the incoming signal;

an antenna interface circuit coupled between the diversity antenna system and the transceiver, the antenna interface circuit including a switch circuit adapted to connect an antenna of the diversity antenna system to the transceiver according to an antenna selection signal; and

an antenna control circuit adapted to produce the antenna selection signal, the antenna control circuit including;

an incoming signal monitoring timer adapted to generate incoming signal monitoring signals based on a predetermined communication protocol;

an incoming signal monitoring circuit coupled to the incoming signal monitoring timer, the incoming signal monitoring circuit adapted to produce an indication of quality of the incoming signal by detecting at least one measure of quality of the incoming signal in response to each of the incoming signal monitoring signals; and

an antenna selector coupled to the incoming signal monitoring circuit and the switch circuit, the antenna selector adapted to adjust the antenna selection signal based on the indication of quality of the incoming signal.

2. The system of claim 1, wherein the switch circuit is adapted to connect the antenna of the diversity antenna system to the transceiver for transmitting the outgoing signal and receiving the incoming signal.

3. The system of claim 1, wherein the transceiver is adapted to transmit multi-frame messages each including a plurality of data frames of the outgoing data frames.

4. The system of claim 3, wherein the incoming signal monitoring timer comprises a response timer to start a predetermined response time interval when a response frame is expected to be received according to the predetermined communication protocol, the response frame being one of the incoming data frames and responding to one or more frames of the outgoing data frames transmitted to the implantable medical device, and wherein the incoming signal monitoring circuit comprises a response failure detector adapted to detect a response failure during the predetermined response time interval, the response failure being a data transmission error associated with the response frame.

5. The system of claim 4, wherein the response failure detector comprises a lack-of-response detector adapted to detect the response frame during the predetermined response time interval, and the response failure is detected if the response frame is not detected during the predetermined response time interval.

6. The system of claim 4, wherein the response failure detector comprises a lack-of-comma detector adapted to detect a comma indicative of a receipt of the response frame during the predetermined response time interval, and the response failure is detected if the comma is not detected during the predetermined response time interval.

7. The system of claim 4, wherein the response failure detector comprises a cyclic redundancy check (CRC) failure detector adapted to detect a CRC failure in the response frame during the predetermined response time interval, and the response failure is detected if the CRC failure is detected during the predetermined response time interval.

8. The system of claim 4, wherein the antenna control circuit further comprises a nonresponsive period timer to start a predetermined nonresponsive period during a transmission of one of the multi-frame messages with a first antenna of the diversity antenna system connected to the transceiver when the response frame is expected to be received, and wherein the response timer is adapted to start the predetermined response time interval during the transmission of the one of the multi-frame messages when the response frame is expected to be received and when each of one or more subsequent response frames is expected to be received, the subsequent response frame each being one of the incoming data frames and responding to one or more frames of the outgoing data frames transmitted to the implantable medical device.

9. The system of claim 8, wherein the antenna selector is adapted to adjust the antenna selection signal for connecting a different antenna of the diversity antenna system to the transceiver if the response failure is detected during the predetermined response time interval and adapted to adjust the antenna selection signal for connecting a second antenna of the diversity antenna system to the transceiver when the predetermined nonresponsive period expires if none of the incoming data frames is received without the data transmission error during the predetermined nonresponsive period.

10. The system of claim 4, wherein the antenna control circuit further comprises a test frame generator to produce an antenna test signal causing the transceiver to transmit a test frame of the outgoing data frames prior to a transmission of one of the multi-frame messages, and wherein the response timer is adapted to start the predetermined response time interval following the transmission of the test frame.

11. The system of claim 10, wherein the antenna selector is adapted to adjust the antenna selection signal for connecting a different antenna of the diversity antenna system to the transceiver if the response failure is detected during the predetermined response time interval.

12. The system of claim 4, wherein the response timer is adapted to start the predetermined response time interval during a transmission of one of the multi-frame messages when the response frame is expected to be received.

13. The system of claim 12, wherein the antenna selector is adapted to adjust the antenna selection signal for connecting a different antenna of the diversity antenna system to the transceiver after the transmission of the one of the multi-frame messages if the response failure is detected during the transmission of the one of the multi-frame messages.

14. The system of claim 4, wherein the antenna control circuit further comprises a transmission period timer to time transmission periods each including a period during which a predetermined number of data frames of the outgoing data frames are transmitted, and wherein the response timer is adapted to start the predetermined response time interval during each of the transmission periods when the response frame is expected to be received.

15. The system of claim 14, wherein the antenna selector is adapted to adjust the antenna selection signal for connecting a different antenna of the diversity antenna system to the transceiver at an end of the each of the transmission periods if the response failure is detected during the each of the transmission periods.

16. The system of claim 3, wherein the incoming signal monitoring timer includes a signal strength calculation timer adapted to generate a signal strength calculation signal prior to a transmission of one of the multi-frame messages.

17. The system of claim 16, wherein the incoming signal monitoring circuit comprises:

a signal strength detector to measure strength parameters each representative of strength of the incoming signal associated with one antenna of the diversity antenna system;

a signal strength storage circuit to store the strength parameters; and

a signal strength calculator to calculate signal strength indices each associated with one antenna of the diversity antenna system based on the strength parameters and weighting factors each associated with one of the strength parameters and related to a timing of the measurement of that one of the strength parameters in response to the signal strength calculation signal.

18. The system of claim 17, wherein the antenna selector is adapted to adjust the antenna selection signal for connecting an antenna of the diversity antenna system to the transceiver based on the signal strength indices.

19. A method for operating a telemetry system communicating with an implantable medical device, the method comprising:

transmitting an outgoing signal to the implantable medical device and receiving an incoming signal from the implantable medical device using a diversity antenna system including a plurality of antennas, wherein transmitting the outgoing signal includes transmitting outgoing data frames by modulating the outgoing signal, and receiving the incoming signal includes receiving incoming data frames by demodulating the incoming signal;

selecting an antenna of the diversity antenna system to be an active antenna according to an antenna selection signal, the active antenna used for transmitting the outgoing signal and receiving the incoming signal;

generating incoming signal monitoring signals based on a predetermined communication protocol;

producing an indication of quality of the incoming signal by detecting at least one measure of quality of the incoming signal in response to each of the incoming signal monitoring signals; and

adjusting the antenna selection signal based on the indication of quality of the incoming signal.

20. The method of claim 19, wherein transmitting the outgoing data frames comprises transmitting multi-frame messages each including a plurality of data frames of the outgoing data frames.

21. The method of claim 20, wherein generating the incoming signal monitoring signals comprises starting a predetermined response time interval when a response frame is expected to be received according to the predetermined communication protocol, the response frame being one of the incoming data frames and responding to one or more frames of the outgoing data frames transmitted to the implantable medical device, and wherein detecting the at least one measure of quality of the incoming signal comprises detecting a response failure during the predetermined response time interval, the response failure being a data transmission error associated with the response frame.

22. The method of claim 21, wherein detecting the response failure comprises detecting the response frame during the predetermined response time interval, and wherein the response failure is detected if the response frame is not detected during the predetermined response time interval.

23. The method of claim 21, wherein detecting the response failure comprises detecting a comma indicative of a receipt of the response frame during the predetermined response time interval, and wherein the response failure is detected if the comma is not detected during the predetermined response time interval.

24. The method of claim 21, wherein detecting the response failure comprises detecting a cyclic redundancy check (CRC) failure in the response frame during the predetermined response time interval, and wherein the response failure is detected if the CRC failure is detected during the predetermined response time interval.

25. The method of claim 21, further comprising starting a predetermined nonresponsive period during a transmission of one of the multi-frame messages using a first antenna of the diversity antenna system selected to be the active antenna when the response frame is expected to be received, and wherein starting the predetermined response time interval comprises starting the predetermined response time interval during the transmission of the one of the multi-frame messages when the response frame is expected to be received and when each of one or more subsequent response frames is expected to be received, the one or more subsequent response frames each being one of the incoming data frames and responding to one or more frames of the outgoing data frames transmitted to the implantable medical device.

26. The method of claim 25, wherein adjusting the antenna selection signal comprises adjusting the antenna selection signal for selecting a different antenna of the diversity antenna system to be the active antenna if the response failure is detected during the predetermined response time interval.

27. The method of claim 26, wherein adjusting the antenna selection signal further comprises adjusting the antenna selection signal for selecting a second antenna of the diversity antenna system to be the active antenna when the predetermined nonresponsive period expires if none of the incoming data frames is received without the data transmission error during the predetermined nonresponsive period.

28. The method of claim 21, further comprising producing an antenna test signal causing a transmission of a test frame of the outgoing data frames prior to a transmission of one of the multi-frame messages, and wherein starting the predetermined response time interval comprises starting the predetermined response time interval following the transmission of the test frame.

29. The method of claim 28, wherein adjusting the antenna selection signal comprises adjusting the antenna selection signal for selecting a different antenna of the diversity antenna system to be the active antenna when the response failure is detected during the predetermined response time interval.

30. The method of claim 21, wherein starting the predetermined response time interval comprises starting the predetermined response time interval during a transmission of one of the multi-frame messages when the response frame is expected to be received.

31. The method of claim 30, wherein adjusting the antenna selection signal comprises adjusting the antenna selection signal for selecting a different antenna of the diversity antenna system to be the active antenna after the transmission of the one of the multi-frame messages if the response failure is detected during the transmission of the one of the multi-frame messages.

32. The method of claim 21, further comprising timing transmission periods each including a period during which a predetermined number of data frames of the outgoing data frames are transmitted, and wherein starting the predetermined response time interval comprises starting the predetermined response time interval during each of the transmission periods when the response frame is expected to be received.

33. The method of claim 32, wherein adjusting the antenna selection signal comprises adjusting the antenna selection signal for selecting a different antenna of the diversity antenna system to be the active antenna at an end of the each of the transmission periods if the response failure is indicated during the each of the transmission periods.

34. The method of claim 20, wherein generating the incoming signal monitoring signals comprises generating a signal strength calculation signal prior to a transmission of one of the multi-frame messages.

35. The method of claim 34, wherein producing the indication of quality of the incoming signal comprises:

measuring strength parameters each representative of strength of the incoming signal associated with one antenna of the diversity antenna system;

storing the measured strength parameters; and

calculating signal strength indices each associated with one antenna of the diversity antenna system based on the strength parameters and weighting factors each associated with one of the strength parameters and related to a timing of the measurement of that one of the strength parameters in response to the signal strength calculation signal.

36. The method of claim 35, wherein adjusting the antenna selection signal comprises adjusting the antenna selection signal for selecting an antenna of the diversity antenna system to be the active antenna based on the signal strength indices.