ANTENNA SYSTEMS FOR IMPLANTABLE MEDICAL DEVICE TELEMETRY
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.
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This application is a continuation of U.S. patent application Ser. No. 10/309,337, filed on Dec. 3, 2002, the specification of which is incorporated herein by reference.
TECHNICAL FIELDThis document relates generally to implantable medical devices and particularly, but not by way of limitation, to such a device including a telemetry system allowing communication with an external device.
BACKGROUNDMedical devices are implanted in human bodies for monitoring physiological conditions, diagnosing diseases, treating diseases, or restoring functions of organs or tissues. Examples of such implantable medical devices include cardiac rhythm management systems, neurological stimulators, neuromuscular stimulators, and drug delivery systems. Because such a device may be implanted in a patient for a long time, the size and power consumption of the device are inherently constrained. Consequently, an implantable device may depend on an external system to perform certain functions. Communication between the implantable device and the external system is referred to as telemetry. Examples of specific telemetry functions include programming the implantable device to perform certain monitoring or therapeutic tasks, extracting an operational status of the implantable device, transmitting real-time physiological data acquired by the implantable device, and extracting physiological data acquired by and stored in the implantable device.
One particular example of implantable medical devices is a cardiac rhythm management device implanted in a patient to treat irregular or other abnormal cardiac rhythms by delivering electrical pulses to the patient's heart. Such rhythms result in diminished blood circulation. Implantable cardiac rhythm management devices include, among other things, pacemakers, also referred to as pacers. Pacemakers are often used to treat patients with bradyarrhythmias, that is, hearts that beat too slowly or irregularly. Such pacemakers may coordinate atrial and ventricular contractions to improve the heart's pumping efficiency. Implantable cardiac management devices also include defibrillators that are capable of delivering higher energy electrical stimuli to the heart. Such defibrillators may also include cardioverters, which synchronize the delivery of such stimuli to portions of sensed intrinsic heart activity signals. Defibrillators are often used to treat patients with tachyarrhythmias, that is, hearts that beat too quickly. In addition to pacemakers and defibrillators, implantable cardiac rhythm management systems also include, among other things, pacer/defibrillators that combine the functions of pacemakers and defibrillators, drug delivery devices, and any other implantable systems or devices for diagnosing or treating cardiac arrhythmias.
An implantable cardiac rhythm management device typically communicates with an external device referred to as a programmer via telemetry. One type of such telemetry is based on inductive coupling between two closely-placed coils using the mutual inductance between these coils. This type of telemetry is referred to as inductive telemetry or near-field telemetry because the coils must be closely situated for obtaining inductively coupled communication. One example of such an inductive telemetry is discussed in Brockway et al., U.S. Pat. No. 4,562,841, entitled “PROGRAMMABLE MULTI-MODE CARDIAC PACEMAKER,” assigned to Cardiac Pacemakers, Inc., the disclosure of which is incorporated herein by reference in its entirety.
In one example of inductive telemetry, an implantable device includes a first coil and a telemetry circuit, both sealed in a metal housing (referred to as a “can”). The external programmer provides a second coil in a wand that is electrically connected to the programmer. During device implantation, a physician evaluates the patient's condition, such as by using the implanted device to acquire real-time physiological data from the patient and communicating the physiological data in real-time to the external programmer for processing and/or display. The physician may also program the implantable device, including selecting a pacing or defibrillation therapy mode, and parameters required by that mode, based on the patient's condition and needs. The data acquisition and device programming are both performed using the inductive telemetry. If the patient's condition is stable after implantation, he or she needs no attention from the physician or other caregiver until a scheduled routine follow-up. During a routine follow-up, for example, the physician reviews the patient's history with the implantable device, re-evaluates the patient's condition, and re-programs the implantable device if necessary.
One problem with inductive telemetry is its requirement that the two coils are closely placed. This typically requires placing the wand on the body surface over the implantable device. Because the wand is electrically connected to the programmer using a cable, the inductive telemetry limits the patient's mobility.
To improve communication range and patient mobility, a far-field radio-frequency (RF) telemetry may be used, in which an RF transceiver in the implantable device is used to communicate with an RF transceiver in the external programmer. With a far-field RF telemetry, the patient is typically free of any body surface attachment that limits mobility. However, the far-field RF telemetry between the implantable device and the external programmer may operate in an environment where one or more sources of interferences exist. Such sources of interferences include, for example, magnetic resonance imaging (MRI) machines, cellular phones, and other devices emitting electromagnetic waves. Such sources of interferences may also include another pair of implantable cardiac rhythm management device and external programmer communicating via far-field RF telemetry operating at the same or similar frequencies.
For these and other reasons, there is a need for ensuring the quality of far-field RF telemetry between an external system and an implanted device when interference is present.
SUMMARYAn 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 an 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.
In one embodiment, a system for communicating with an implantable medical device includes an external device that is coupled to the implantable medical device via RF telemetry. The external device includes a transceiver, an antenna system, an antenna interface circuit, and a directionality controller. The antenna system includes at least two antennas each having a predetermined directionality characteristic. The antenna interface circuit electrically connects the transceiver and the antenna system. The directionality controller connects to the antenna interface circuit and controls a directionality of the antenna system.
In one embodiment, one or more RF signals are received from an implantable medical device using one or more antennas of an antenna system, where the one or more antennas each have a predetermined directionality characteristic. A quality of each of the one or more RF signals is analyzed. A directionality of the antenna system is controlled based on an outcome of the RF signal quality analysis.
This Summary is an overview of some of the teachings of the present application and not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and appended claims. Other aspects of the invention will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which are not to be taken in a limiting sense. The scope of the present invention is defined by the appended claims and their equivalents.
BRIEF DESCRIPTION OF THE DRAWINGSIn the drawings, which are not necessarily drawn to scale, like numerals describe similar components throughout the several views. Like numerals having different letter suffixes represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.
This document discusses, among other things, antennas and antenna systems for a medical device that communicates with an implantable medical device via telemetry. The present methods and apparatuses will be described in applications involving implantable cardiac rhythm management systems such as systems including pacemakers, cardiac resynchronization therapy (CRT) devices, cardioverter/defibrillators, and pacer/defibrillators. However, it is to be understood that the present methods and apparatuses may be employed in other types of implantable medical devices, including, but not being limited to, neurological stimulators, neuromuscular stimulators, drug delivery systems, and various types of physiological signal monitoring devices.
In one embodiment, RF telemetry link 190 provides for data transmission from implanted device 110 to external device 120. This may include, for example, transmitting real-time physiological data acquired by implanted device 110, extracting physiological data acquired by and stored in implanted device 110, extracting therapy history data stored in implanted device 110, and extracting data indicating an operational status of implanted device 110 (e.g., battery status and lead impedance). In a further embodiment, RF telemetry link 190 provides for data transmission from external device 120 to implanted device 110. This may include, for example, programming implanted device 110 to acquire physiological data, programming implanted device 110 to perform at least one self-diagnostic test (such as for a device operational status), and programming implanted device 110 to deliver at least one therapy.
In one embodiment, RF telemetry link 190 is a far-field telemetry link. A far-field, also referred to as the Fraunhofer zone, refers to the zone in which a component of an electromagnetic field produced by the transmitting electromagnetic radiation source decays substantially proportionally to 1/r, where r is the distance between an observation point and the radiation source. Accordingly, far-field refers to the zone outside the boundary of r=λ/2π, where λ is the wavelength of the transmitted electromagnetic energy. In one embodiment, a communication range of RF telemetry link 190 (a distance over which data is capable of being wirelessly communicated) is at least ten feet but can be as long as allowed by the communication technology utilized. Unlike an inductive telemetry link using a wand placed near implanted device 110, typically attached to the patient, and electrically connected to external device 120 with a cable, using RF telemetry link 190 frees the patient from any physical restraints caused by the wand and the cable. On the other hand, while a relatively short communication range associated with the inductive telemetry provides for a relatively good immunity to environmental interferences, the relatively long communication range associated with the RF telemetry raises a concern that external device 120 may be sensitive to interferences such as electromagnetic waves radiated from other medical devices, such as MRI machines, and/or personal items such as cellular phones. In addition, several patients carrying the same of similar types of implantable devices may be examined, in the same area or even the same room in a cardiovascular clinic, using the same of similar types of external programmers. Under such circumstances, multiple RF telemetry links may operate within the communication ranges of each other and therefore interfere with the operations of each other. To allow RF telemetry link 190 to operate within such environments, one approach is to control its directionality.
In one embodiment, implanted telemetry module 112 includes an RF test signal generator to generate an RF test signal and send it to external device 120 via RF telemetry link 190. The RF test signal is used in processes of antenna selection or orientation that are discussed below. In one embodiment, the RF signal is modulated with a predetermined binary code to allow for analysis of data integrity by external telemetry module 122. In one embodiment, the RF signal has a duration of about 50-100 ms. In one embodiment, implanted device 110 has an operation mode being a telemetry testing mode during which the RF test signal is sent to external device 120. In a further embodiment, external device 120 sends a command to implanted device 110 to cause it to operate in the telemetry testing mode. In one embodiment, if external device 120 sends the command during an ongoing telemetry session, the telemetry session is interrupted during the telemetry testing mode and resumed automatically upon completion of the telemetry testing mode operation.
A non-directional antenna is suitable for use in an environment where no significant interference exists and only a single RF telemetry link is active. No antenna orientation is needed. However, an RF telemetry link may be required to operate in a busy clinical environment where multiple physicians and/or other caregivers evaluate multiple patients simultaneously. This may require several RF telemetry links to operate in the same area or even in the same room. If the several RF telemetry links operate in substantially the same or similar frequency bands, each RF telemetry link using non-directional antenna may interfere with other RF telemetry links. Moreover, electromagnetic energy radiated from sources such as other electronic medical equipment in all directions in the clinical environment may be received by a non-directional antenna as a noise interfering with the RF telemetry supported partially by the non-directional antenna.
With a limited beamwidth, a directional antenna is less likely to act as a source of interference to RF telemetry links associated with other antennas. This allows multiple RF telemetry links to be established for concurrent communications between multiple pairs of external devices and implanted devices, even within a small area. The directional antenna may also allow a user to locate a source of interference to avoid it. In one embodiment, the user sweeps the directional antenna over all directions to identify sources of interference.
Using the same level of electrical power, a directional antenna achieves higher gain in its forward direction as compared to the uniform gain of a non-directional antenna. This allows a longer communication range allowing external device 120 to communicate with implanted device 110 over a greater distance, as compared with the non-directional antenna, unless it also results in a radiation energy level that exceeds a limitation imposed by pertinent government regulations or other safety standards. A directional antenna generally has a higher signal-to-noise ration (S/N) as compared to a non-directional antenna because of the higher gain applied to a signal and lower gains applied to noises coming from directions outside the directional antenna's beamwidth.
The directionality of RF telemetry link 190 is controllable by controlling a directionality of implanted antenna system 114 and/or a directionality of external antenna system 124. In one embodiment, the directionality of RF telemetry link 190 is controllable by controlling the directionality of external antenna system 124. Implanted device 110 and external device 120 send signals to each other. A noise radiated from a source of interference is received by both implanted device 110 and external device 120. Because body tissue absorbs RF electromagnetic energy, implanted antenna system 114 receives the signals and the noise that are both attenuated by body tissue surrounding implanted device 110. On the other hand, while external antenna system 124 receives signals that are attenuated when being transmitted from implanted device 110 through the surrounding body tissue, the noise radiated from the source of interference is not attenuated by body tissue. Thus, an S/N associated with external antenna system 124 is more degraded by the presence of noise from the source of interference than an S/N associated with implanted antenna system 114. Furthermore, the complexity of implanted device 110 is limited by size and power consumption restraints for an implant. Because many more units of implanted device 110 are produced than units of external device 120, a cost increase associated with implanted device 110 is more of a concern than a cost increase associated with external devices 120. For at least these reasons, controlling the directionality of external antenna system 124 is a more efficient approach as compared to controlling the directionality of implanted antenna system 114 or both antenna systems.
In the embodiment of
In one embodiment, the user selects one of directional antennas 541A and 541B for an RF telemetry session. For example, when directional antenna 541A covers substantially all directions behind display screen 530 and directional antenna 541B covers substantially all directions in front of display screen 530, the user selects directional antenna 541A if the patient is behind the screen, or directional antenna 541B if the patient is in front of the screen. In another embodiment, the user observes the quality of communication, such as indicated by signals received by each of directional antennas 541A and 541B and displayed on display screen 530, to determine which antenna to select. In another embodiment, one of directional antennas 541A and 541B is automatically selected, as discussed below with reference to
In an alternative embodiment, antenna system 124 has a single directional antenna. While using a single directional antenna provides the simplest and least expensive telemetry module 122 having a directional antenna system, the user would have to align external device 120 with implanted device 110. This may require several position adjustments for external device 120 before RF telemetry link 190 is established.
Controller 670 controls whether transceiver 660 transmits or receives RF signals. In the embodiment in which one of directional antennas 541A and 541B is automatically selected, controller 679 also includes a signal analyzer 672 and an antenna selector 674. The signal analyzer analyzes signal quality of the RF signals received through each of directional antennas 541A and 541B. In one embodiment, signal analyzer 672 measures the strength (amplitude) of each of the RF signals received through each of directional antennas 541A and 541B. In a further embodiment, signal analyzer 672 examines integrity of the data recovered by transceiver 660 and generates a data integrity indicator. Antenna selector 674 is a directionality controller of antenna system 124. It controls the directionality of antenna system 124 by selecting one or more of its antennas having different orientation and/or directionality characteristics. In the embodiment of
In one embodiment, after the RF telemetry session is started at 740, controller 670 starts to repeat steps 700-740, at 750, on a predetermined periodic basis during the RF telemetry session. In another embodiment, after the RF telemetry session is started at 740, signal analyzer 672 monitors the quality of the RF signal on a continuous or periodic basis. At 750, controller 670 starts to repeat steps 700-740 whenever signal analyzer 672 determines that the quality of the RF signal is no longer satisfactory during the RF telemetry session. In one embodiment, steps 700-740 are repeated while the RF telemetry operation is ongoing without significant interruptions to the RF telemetry session. In one embodiment, external device 120 sends a command to implanted device 110 to start to repeat steps 700-740 by causing implanted device to operate in the telemetry testing mode. In this embodiment, the RF telemetry operation is interrupted at least for the period during which implanted device 110 operates in the telemetry testing mode. At the end of each repetition of steps 700-740, if a different directional antenna is selected, the telemetry session continues with the different directional antenna. This ensures that RF telemetry link 190 remains functional throughout the RF telemetry session, even when, for example, implanted device 110 changes position because the patient carrying it moves. The RF telemetry session concludes when all the data transmissions for the session are completed or stopped by an unintended interruption.
At 1030, external telemetry module 122 receives a further RF signal through directional antenna 541A. The further RF signal is substantially similar to the RF signal received at 1000 in that both RF signals are generated from the same implanted device 110 at substantially the same distance and modulated with data in substantially the same format. In one mode, the RF signal is a further portion of the RF test signal generated by the RF test signal generator of implanted telemetry module 112. At 1040, external telemetry module 122 receives a still further RF signal through directional antenna 541B. The still further RF signal is also substantially similar to the RF signal received at 1000. In one mode, the RF signal is a still further portion of the RF test signal generated by the RF test signal generator of implanted telemetry module 112. At 1050, signal analyzer 672 analyzes signal quality of both the further and still further RF signals received at 1030 and 1040. In one embodiment, signal analyzer 672 examines data integrity of each of the received RF signals by performing error-checking in accordance with the predetermined protocol. In an additional embodiment, signal analyzer 672 measures the amplitude of each of the received RF signals. At 1060, antenna selector 674 selects one of directional antennas 541A and 541B based on an outcome of analyzing the signal quality of the RF signal at 1050. In one embodiment, antenna selector 674 selects one of directional antennas 541A and 541B that provides a satisfactory data integrity according to the predetermined standard. In an additional embodiment, when directional antennas 541A and 541B each provide a satisfactory data integrity, antenna selector 674 selects one of directional antennas 541A and 541B providing a higher received RF signal strength. Once a directional antenna is selected, antenna selector 674 sends the antenna selection control signal to switching circuit 650 to electrically connect one of the directional antennas 541A and 541B to transceiver 660, thereby establishing RF telemetry link 190. At 1070, if an RF telemetry session has not been started, controller 670 issues a signal to start an RF telemetry session between external device 120 and implanted device 110. If the RF session has been started, it is continued with the antenna just selected at 1020 or 1060.
In one embodiment, after the RF telemetry session is started at 1070, controller 670 starts to repeat steps 1000-1070, at 1080, on a predetermined periodic basis during the RF telemetry session. In another embodiment, after the RF telemetry session is started at 1070, signal analyzer 672 monitors the quality of the RF signal on a continuous or periodic basis. At 1080, controller 670 starts to repeat steps 1000-1070 whenever signal analyzer 672 determines that the quality of the RF signal is no longer satisfactory during the RF telemetry session. In one embodiment, steps 1000-1070 are repeated while the RF telemetry operation is ongoing without significant interruptions to the RF telemetry session. In one embodiment, external device 120 sends a command to implanted device 110 to start to repeat steps 1000-1070 by causing implanted device to operate in the telemetry testing mode. In this embodiment, the RF telemetry operation is interrupted at least for the period during which implanted device 110 operates in the telemetry testing mode. At the end of each repetition of steps 1000-1070, if a different directional antenna is selected, the telemetry session continues with the different directional antenna. This ensures that RF telemetry link 190 remains functional throughout the RF telemetry session, even when, for example, implanted device 110 changes position because the patient carrying it moves. The RF telemetry session concludes when all the data transmissions for the session are completed or stopped by an unintended interruption.
At 1330, external telemetry module 122 receives a further RF signal through directional antenna 1143. The further RF signal is substantially similar to the RF signal received at 1300 in that both RF signals are generated from the same implanted device and modulated with data in substantially the same format. In one embodiment, where directional antenna 1143 is a detachable antenna, directional antenna 1143 is connected to external device 120 before external telemetry module 122 receives the further RF signal at 1330. At 1340, signal analyzer 672 analyzes signal quality of the further RF signal received at 1330. In one embodiment, signal analyzer 672 examines data integrity of the further RF signal by performing error-checking in accordance with a predetermined protocol. If the quality of the RF signal is found satisfactory under the predetermined protocol at 1350, controller 670 issues a signal at 1370 to start an RF telemetry session between external device 120 and implanted device 110. If the quality of the RF signal is found unsatisfactory at 1350, the user adjusts the orientation of directional antenna 1143 by re-aiming it to implanted device 110. Steps 1330-1360 are repeated until the quality of the RF signal is found satisfactory at 1350. At 1370, controller 670 issues a signal to start an RF telemetry session between external device 120 and implanted device 110.
In an alternative embodiment, where directional antenna 1143 is a detachable antenna, the user starts to use directional antenna 1143 by connecting it to external device 120 at any time. In one embodiment, the user starts to use directional antenna 1143 upon his judgment on the presence and magnitude of the interference. In one specific embodiment, the user makes the judgment based on observations of cardiac signals displayed by external device 120. In another embodiment, the user starts to use directional antenna 1143 when external device 120 indicates an unacceptable amount or rate of data transmission errors. In one specific embodiment, implanted device 110 and external device 120 each include error-checking modules to ensure the integrity of data transmitted in both directions via RF telemetry link 190. When the number and/or frequency of errors detected exceed a predetermined threshold, external device 120 provides a signal to the user to replace non-directional antenna 842 with directional antenna 1143 if non-directional antenna 842 is being used, or to reposition directional antenna 1143 if it is being used.
In one embodiment, as illustrated in
A directional antenna 1544 is substantially the same as directional antenna 1444 except that antenna 1544 has two, instead of four, antenna elements 1544A and 1544B. A radiation pattern 1582 illustrates an example of a directional characteristic of directional antenna 1544, when antenna elements 1544A and 1544B are not driven out of phase, in the plane perpendicular to circuit board 525, and hence about parallel to the floor during an RF telemetry session. As illustrated by radiation patterns 1581 and 1582, having more antenna elements provides for a narrower beamwidth centered at each effective orientation, thereby enhancing the advantage of the directional antenna in reducing chance of interference and increasing the communication range in the direction aligned with the effective orientation of the directional antenna. On the other hand, fewer antenna elements require a simpler electronic steering system.
Directional antenna 1444 or 1544 allows electronic alignment between external antenna system 124 and implanted antenna system 114 to establish RF telemetry link 190. This eliminates the need for physically positioning external device 120. As compared to an antenna system having two or more planar patch or slot directional antennas, a phased-array directional antenna is potentially more suitable when relatively fine directionality is required or desired. In other words, a phased-array directional antenna is suitable for establishing RF telemetry link 190 in a clinical environment where narrow antenna beamwidth is necessary or desired.
Controller 670 controls whether transceiver 660 transmits or receives RF signals and includes a signal analyzer 672 and an antenna steerer 1776. The signal analyzer analyzes signal quality of RF signals received at a plurality of effective orientations of directional antenna 1444. In one embodiment, signal analyzer 672 measures the amplitude of the RF signal received at each of the plurality of effective orientations. In a further embodiment, signal analyzer 672 examines integrity of the data recovered by transceiver 660 and generates a data integrity indicator. Antenna steerer 1776 is a directionality controller of antenna system 124. In the embodiment of
At 1800, directional antenna 1444 is tested for a first effective orientation. The first effective orientation is the first of the predetermined number of effective orientations at which directional antenna 1444 will be tested. Testing directional antenna 1444 at the first effective orientation includes at least four steps 1801-1804. At 1801, antenna steerer 1776 electronically steers directional antenna 1444 to a first effective orientation. In one embodiment, directional antenna 1444 is electronically steered by applying the weighting factors to RF signals received through each of antenna elements 1444A-D. In another embodiment, directional antenna 1444 is electronically steered by adjusting the transmission delays associated with antenna elements 1444A-D. At 1802, external telemetry module 122 receives an RF signal through directional antenna 1444. The RF signal is modulated with binary data and transmitted from implanted device 110. In one embodiment, external telemetry module 122 receives the RF signal after it sends out a command causing implanted device 110 to operate in the telemetry testing mode. In this mode, the RF signal is at least a portion of the RF test signal generated by the RF test signal generator of implanted telemetry module 112. At 1803, signal analyzer 672 analyzes signal quality of the RF signal received at 1802. In one embodiment, signal analyzer 672 examines data integrity of the received RF signal by performing error-checking in accordance with a predetermined protocol. In an additional embodiment, signal analyzer 672 measures the amplitude of the received RF signal. At 1804, one or more quality indicators associated with the first effective orientation, as an outcome of analyzing the quality of the RF signal at 1803, are recorded. The recording of the one or more quality indicators associated with the first effective orientation concludes the test of directional antenna 1444 for the first effective orientation.
At 1810, directional antenna 1444 is tested, one at a time, at each of the predetermined number (N) of effective orientations covering a predetermined total range of directions. This includes repeating the test procedure of 1801-1804 for a second through Nth effective orientations. In one embodiment, external telemetry module 122 starts testing the first effective orientation after it sends out a command causing implanted device 110 to operate in the telemetry testing mode. In a further embodiment, implanted device 110 operates in the telemetry testing mode until the Nth effective orientation has been tested. In this mode, the RF signal in each repetition of steps 1801-1804 is a portion of the RF test signal generated by the RF test signal generator of implanted telemetry module 112. As a result, N sets of quality indicators are recorded, corresponding to the N effective orientations. At 1820, antenna steerer 1776 compares among the N sets of quality indicators. In one embodiment, antenna steerer 1776 compares the amplitudes of the RF signals received at the N effective orientations to determine the effective orientation providing the largest RF signal amplitude. In an alternative embodiment, antenna steerer 1776 compares the amplitudes of the RF signals received at the effective orientations at which the data integrity is satisfactory to determine the effective orientation providing the largest RF signal amplitude and a satisfactory data integrity. At 1830, antenna steerer 1776 selects an effective orientation at which an RF telemetry session will be started, based on an outcome of the comparison among the quality indicators at 1820. In one embodiment, antenna steerer 1776 selects the effective orientation providing the largest RF signal amplitude. In another embodiment, antenna steerer 1776 selects an effective orientation providing a satisfactory data integrity. In a further embodiment, antenna steerer 1776 selects the effective orientation providing the largest RF signal amplitude while providing a satisfactory data integrity. After the effective orientation is selected at 1830, antenna steerer 1776 electronically steers directional antenna 1444 to the selected effective orientation and locks directional antenna 1444 in that effective direction at 1840. At 1850, controller 670 issues a signal to start an RF telemetry session between external device 120 and implanted device 110.
In one embodiment, after the RF telemetry session is started at 1850, controller 672 starts to repeat steps 1800-1850, at 1860, on a predetermined periodic basis during the RF telemetry session. In a further embodiment, at 1860, controller 670 starts to repeat steps 1800-1850 on the predetermined periodic basis with a different set of effective orientations 1 to N that is limited to cover a vicinity of the effective orientation that directional antenna 1444 has been locked into. This enables the effective orientation of directional antenna 1444 to track, for example, the direction of the patient moving within a limited area, such as running on a treadmill. In another embodiment, after the RF telemetry session is started at 1850, signal analyzer 672 monitors the quality of the RF signal on a continuous or periodic basis. At 1860, controller 670 starts to repeat steps 1800-1850 whenever signal analyzer 672 determines that the quality of the RF signal is no longer satisfactory during the RF telemetry session. In one embodiment, steps 1800-1850 are repeated while the RF telemetry operation is ongoing without significant interruptions to the RF telemetry session. In one embodiment, external device 120 sends a command to implanted device 110 to start to repeat steps 1800-1850 by causing implanted device to operate in the telemetry testing mode. In this embodiment, the RF telemetry operation is interrupted at least for the period during which implanted device 110 operates in the telemetry testing mode. At the end of each repetition of steps 1800-1850, if a new effective orientation is selected, directional antenna 1444 is locked in the new effective orientation. This ensures that RF telemetry link 190 remains functional throughout the RF telemetry session, even when, for example, implanted device 110 changes position because the patient carrying it moves. The RF telemetry session concludes when all the data transmissions for the session are completed or stopped by an unintended interruption.
In one embodiment, after the RF telemetry session is started at 1950, controller 670 starts to repeat steps 1900-1950, at 1960, on a predetermined periodic basis during the RF telemetry session. In a further embodiment, at 1960, controller 670 starts to repeat steps 1900-1950 on the predetermined periodic basis with the effective orientations A and B being limited to a vicinity of the effective orientation that directional antenna 1444 has been locked into. This enables the effective orientation of directional antenna 1444 to track, for example, the direction of the patient moving within a limited area, such as running on a treadmill. In another embodiment, after the RF telemetry session is started at 1950, signal analyzer 672 monitors the quality of the RF signal on a continuous or periodic basis. At 1960, controller 670 starts to repeat steps 1900-1950 whenever signal analyzer 672 determines that the quality of the RF signal is no longer satisfactory during the RF telemetry session. In one embodiment, steps 1900-1950 are repeated while the RF telemetry operation is ongoing without significant interruptions to the RF telemetry session. In one embodiment, external device 120 sends a command to implanted device 110 to start to repeat steps 1900-1950 by causing implanted device to operate in the telemetry testing mode. In this embodiment, the RF telemetry operation is interrupted at least for the period during which implanted device 110 operates in the telemetry testing mode. At the end of each repetition of steps 1900-1950, if a new effective orientation is selected, directional antenna 1444 is locked in the new effective orientation. This ensures that RF telemetry link 190 remains functional throughout the RF telemetry session, even when, for example, implanted device 110 changes position because the patient carrying it moves.
If dividing the predetermined total range of directions by two results in two spaces each being wider than the maximum beamwidth of directional antenna 1444, portions of the methods of
It is to be understood that the above detailed description is intended to be illustrative, and not restrictive. For example, the implantable device can be any implantable medical device having an active electronic circuit. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
Claims
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.
Type: Application
Filed: Mar 8, 2006
Publication Date: Jun 29, 2006
Applicant:
Inventors: Jeffrey Von Arx (Minneapolis, MN), Prashant Rawat (Blaine, MN), William Mass (Maple Grove, MN)
Application Number: 11/276,625
International Classification: A61N 1/08 (20060101);