Antenna systems for implantable medical device telemetry

Abstract

An implantable medical device system includes an implanted device communicating with an external device via telemetry. The implanted device and the external device each have a telemetry module connected to an antenna system to support a radio-frequency (RF) telemetry link. The antenna system of the external device has a manually or automatically controllable directionality. The controllable directionality is achieved, for example, by using two or more directional antennas, one non-directional antenna and one or more directional antennas, or an electronically steerable phased-array directional antenna.

1 . A system for communicating with an implantable medical device, the system comprising: 
 an external device adapted to be communicatively coupled to the implantable medical device via radio-frequency (RF) telemetry and adapted to control operation of the implantable medical device and receive data from the implantable medical device, the external device comprising: 
 a transceiver;  
 a phased-array directional antenna;  
 an antenna interface circuit coupled between the transceiver and the phased-array directional antenna; and  
 a controller coupled to the antenna interface circuit, the controller adapted to control an effective orientation of the phased-array directional antenna.  
   
   
   
       2 . The system of  claim 1 , wherein the phased-array directional antenna comprises two or more substantially identical planar antennas.  
   
   
       3 . The system of  claim 2 , wherein the two or more substantially identical planar antennas comprise two or more substantially identical planar dipole antennas.  
   
   
       4 . The system of  claim 2 , wherein the two or more substantially identical planar antennas are printed on a circuit board housed in the external device.  
   
   
       5 . The system of  claim 1 , wherein the controller comprises: 
 a signal analyzer coupled to the transceiver, the signal analyzer adapted to analyze a quality of each of RF signals received at a plurality of effective orientations of the phased-array directional antenna; and    an antenna steerer adapted to control the effective orientation of the phased-array directional antenna based on the quality of the each of the RF signals.    
   
   
       6 . The system of  claim 5 , wherein the antenna steerer is adapted to determine a first effective orientation associated with the best signal quality from the plurality of effective orientations of the phased-array directional antenna, to steer the phased-array directional antenna to the first effective orientation, and to lock the directional antenna in the first effective orientation.  
   
   
       7 . The system of  claim 5 , wherein the signal analyzer comprises a peak detection circuit adapted to determine an effective orientation of the plurality of effective orientations of the phased-array directional antenna at which a maximum amplitude is measured.  
   
   
       8 . The system of  claim 5 , wherein the antenna interface circuit comprises a multiplier adapted to multiply weighting signals with antenna elements of the phased-array directional antenna, and the electronic steerer comprises a weighting signal generator adapted to generate a plurality of weighting signals each corresponding to one of the antenna elements to control the effective orientation of the phased-array directional antenna.  
   
   
       9 . The system of  claim 5 , wherein the antenna interface circuit comprises a plurality of delay lines, and the electronic steerer comprises a delay line selector adapted to control the directionality of the phased-array directional antenna by selecting one of the plurality of delay lines to be coupled between each of antenna elements of the phased-array directional antenna and the transceiver.  
   
   
       10 . The system of  claim 9 , wherein each delay line of the plurality of delay lines comprises a conductive path having a predetermined length.  
   
   
       11 . A method for communicating with an implantable medical device via radio-frequency (RF) telemetry, the method comprising: 
 steering a phase-array directional antenna electronically to a plurality of effective orientations;    receiving an RF signal from the implantable medical device using the phase-array directional antenna at each effective orientation of the plurality of effective orientations;    analyzing a quality of the received RF signal to produce a set of one or more quality indicators associated with each effective orientation of the plurality of effective orientations; and    selecting an effective orientation from the plurality of effective orientations based on the sets of one or more quality indicators associated with the plurality of effective orientations.    
   
   
       12 . The method of  claim 11 , wherein the plurality of effective orientations includes effective orientations each corresponding to a range of directions, and further comprising: 
 dividing the selected effective orientation into a further plurality of effective orientations if the range of directions associated with the selected effective orientation is wider than a predetermined operating beamwidth of the phase-array directional antenna;    repeating the steering, the receiving, and the analyzing for the further plurality of effective orientations; and    selecting a further effective orientation from the further plurality of effective orientations based on the sets of one or more quality indicators associated with the further plurality of effective orientations.    
   
   
       13 . The method of  claim 12 , further comprising repeating the dividing the selected effective orientation into the further plurality of effective orientations, the repeating the steering, the receiving, and the analyzing for the further plurality of effective orientations, and the selecting the further effective orientation until the range of directions associated with the selected further effective orientation is not wider than the predetermined operating beamwidth of the phase-array directional antenna.  
   
   
       14 . The method of  claim 11 , wherein analyzing the quality of the received RF signal comprises performing an error-checking to examine data integrity of the received RF signal.  
   
   
       15 . The method of  claim 14 , wherein analyzing the quality of the received RF signal comprises measuring an amplitude of the received RF signal, and selecting the effective orientation from the plurality of effective orientations comprises selecting the effective orientation associated with the largest amplitude of the received RF signal and a satisfactory data integrity.  
   
   
       16 . The method of  claim 11 , wherein steering the phase-array directional antenna electronically comprises: 
 applying weighting factors to a plurality of antenna elements of the phase-array directional antenna; and    adjusting the values of the weighting factors to steer the phase-array directional antenna electronically to each effective orientation of the plurality of effective orientations.    
   
   
       17 . The method of  claim 11 , wherein steering the phase-array directional antenna electronically comprises: 
 controlling transmission delays each associated with one antenna element of a plurality of antenna elements of the phase-array directional antenna; and    adjusting the transmission delays to steer the phase-array directional antenna electronically to each effective orientation of the plurality of effective orientations.    
   
   
       18 . An external system for communicating with an implantable medical device via radio-frequency (RF) telemetry, the system comprising: 
 a phased-array antenna;    means for electronically steering the phased-array antenna to a plurality of effective orientations;    means for receiving an RF signal from the implantable medical device using the phased-array antenna;    means for analyzing a quality of the RF signal associated with each effective orientation of the plurality of effective orientations; and    means for selecting an effective orientation based on the quality of the RF signal associated with the each effective orientation of the plurality of effective orientations.    
   
   
       19 . The system of  claim 18 , wherein the phased-array antenna comprises a plurality of antenna elements printed on a circuit board.  
   
   
       20 . The system of  claim 19 , wherein the plurality of antenna elements comprises planar antennas.  
   
   
       21 . The system of  claim 18 , further comprising means for storing information used to electronically steer the phased-array antenna to the plurality of effective orientations.