US 20060122665 A1
A telemetry component according to an embodiment of the invention, such as a programmer or a monitor for an implantable medical device (“IMD”), includes at least one radio frequency (“RF”) antenna that is configured to accommodate far-field telemetry between the telemetry component and the IMD. The RF antenna is shaped, sized, positioned, and otherwise configured to account for surface current cancellation caused by induced surface current on an electrically conductive surface of the telemetry component.
1. An implanted medical device (“IMD”) telemetry device comprising:
an electrically conductive structure;
an antenna located proximate to said electrically conductive structure; and
a receiver coupled to said antenna, said receiver being-configured to receive IMD signals via said antenna, said antenna being configured to account for surface current cancellation caused by induced surface current on said electrically conductive structure.
2. An IMD telemetry device according to
3. An IMD telemetry device according to
4. An IMD telemetry device according to
5. An IMD telemetry device according to
6. An IMD telemetry device according to
7. An IMD telemetry device according to
said electrically conducting structure comprises a casting for said display element, said casting having a perimeter; and
said antenna being routed around one of said perimeter and around a corner of said casting.
8. An IMD telemetry device according to
9. An IMD telemetry device according to
10. An implanted medical device (“IMD”) telemetry device comprising:
an electrically conductive structure contained in said housing;
a first antenna contained in said housing;
a second antenna contained in said housing; and
a transceiver coupled to said first antenna and coupled to said second antenna, said transceiver being configured to convey IMD signals via at least one of said first antenna and said second antenna, said first antenna and said second antenna each being configured to account for surface current cancellation caused by induced surface current on said electrically conducting structure.
11. An IMD telemetry device according to
12. An IMD telemetry device according to
13. An IMD telemetry device according to
14. An IMD telemetry device according to
said electrically conducting structure comprises a casting for said display element, said casting having a perimeter;
said first antenna is routed around a first portion of said perimeter of said casting; and
said second antenna is routed around a second portion of said perimeter of said casting.
15. A radio frequency (“RF”) antenna for an implanted medical device (“IMD”) telemetry device having electrically conductive structures, said antenna comprising a conformal radiating element shaped to account for surface current cancellation caused by induced surface current on the electrically conducting structures.
16. An RF antenna according to
17. An RF antenna according to
18. An RF antenna according to
19. An RF antenna according to
20. An RF antenna according to
The present invention relates generally to wireless communication between an implanted medical device (“IMD”) and an external telemetry system, such as a programmer or monitor. More particularly, the invention relates to antennas for use with the external telemetry system.
An IMD and an external telemetry component, such as an IMD programmer or monitor, exchange information via wireless communication techniques. For example, the telemetry component typically transmits commands to the IMD using radio frequency (“RF”) data transmission methodologies. In addition, the IMD may transmit stored data or sensed physiological parameters to the external telemetry component. Traditional external telemetry components employ near-field RF data communication techniques that facilitate communication between the IMD and a telemetry head (attached to the telemetry component) that must be placed in close proximity to the IMD to establish the data communication link. Modem IMD telemetry systems leverage far-field RF data communication techniques that do not require close proximity between the IMD and the telemetry component. Indeed, such modem systems need not include a telemetry head, and the RF circuitry and RF antenna structures may be incorporated into the housing of the telemetry component itself.
The modern trend toward miniaturization of electronic equipment generally applies to IMD telemetry systems, where compact size, portability, and light weight may be desirable. Indeed, a practical MID programmer may resemble a small notebook computer having a display screen, electronic components, and computer-related hardware contained in a relatively small housing. Various packaging requirements may create physical space limitations that can impact the RF characteristics, RF specifications, or RF performance of the telemetry component. These space limitations are not a significant issue with a conventional near-field system because the RF telemetry head is held in close proximity to the patient and the main housing need not contain the RF components.
Accordingly, it is desirable to have an IMD telemetry component, such as a programmer or monitor, that operates efficiently and effectively in a far-field mode. In addition, it is desirable to have an IMD telemetry component that incorporates an efficient and cost effective RF antenna architecture that facilitates far-field wireless communication with an IMD. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
An antenna arrangement configured in accordance with an embodiment of the invention is suitable for use with far-field IMD telemetry equipment. The antenna arrangement is compact in size and conformal such that it can be deployed within the limited physical volume and space of the IMD telemetry equipment. Further, the antenna arrangement is configured to enhance communication between the IMD and the external telemetry component. The antenna arrangement is designed in response to the surrounding IMD telemetry equipment to enhance the antenna efficiency and, therefore, the far-field performance of the telemetry system.
The above and other aspects of the invention may be carried out in one form by an RF antenna for an IMD telemetry device having electrically conducting structures. The antenna comprises a conformal radiating element shaped to account for surface current cancellation caused by induced surface current on the electrically conducting structures.
A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures.
The following detailed description is merely illustrative in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
The invention may be described herein in terms of functional and/or logical block components and various processing steps. It should be appreciated that such block components may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of the invention may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. In addition, those skilled in the art will appreciate that the present invention may be practiced in conjunction with any number of practical medical device telemetry systems and that the particular system described herein is merely one exemplary application for the invention.
For the sake of brevity, conventional techniques related to RF antenna design, IMD telemetry, RF data transmission, signaling, IMD operation, and other functional aspects of the systems (and the individual operating components of the systems) may not be described in detail herein. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical embodiment.
The following description refers to features being “connected” or “coupled” together. As used herein, unless expressly stated otherwise, “connected” means that one feature is directly or indirectly connected to another feature, and not necessarily mechanically. Likewise, unless expressly stated otherwise, “coupled” means that one feature is directly or indirectly coupled to another feature, and not necessarily mechanically. Thus, although the various figures may depict example arrangements of elements, additional intervening elements, devices, features, or components may be present in an actual embodiment (assuming that the functionality of the circuit, system, or subsystem is not adversely affected).
IMD 102 may be an implantable pulse generator (“IPG”), for example, a pacemaker or an implantable cardioverter-defibrillator (“ICD”). It should be appreciated, however, that telemetry component 100 may be used to communicate with any type of IMD 102. Other examples of 1ID 102 include an implantable brain stimulator, an implantable gastric system stimulator, an implantable nerve stimulator, an implantable muscle stimulator, an implantable lower colon stimulator, an implantable urinary tract stimulator, an implantable drug or beneficial agent dispenser or pump, an implantable cardiac signal loop or other type of recorder or monitor, an implantable gene therapy delivery device, an implantable incontinence prevention or monitoring device, an implantable insulin pump or monitoring device, and the like.
Further, although described in terms of a programmer for purposes of illustration, the antenna configurations described herein may be used in other external devices that communicate with an IMD, such as a patient monitoring device, which need not have programming capabilities. In each case, telemetry component 100 communicates with IMD 102 to obtain IMD signals that convey IMD data such as operational information or physiological information. Depending on the type of IMD, the physiological information may include heart rate, heart rate variability, blood glucose levels, oxygen saturation, partial pressure of oxygen in the blood, blood pressure, baro-reflex measures, electrogram morphologies, lung wetness, and the like.
A user (not shown) of telemetry component 100, such as a clinician or a physician, interacts with telemetry component 100 and IMD 102 via a suitable input medium or user interface. In practice, the user interface may include a keyboard 108, a display element 110, a mouse, a touchpad, a touch screen, a trackball, or other pointing device (not shown), or the like. More specifically, telemetry component 100 provides a user interface to enable a user to provide data to telemetry component 100. Display element 110 may, for example, be a cathode ray tube (“CRT”) display, a liquid crystal display (“LCD”), a light emitting diode (“LED”) display, a plasma display, or the like.
Telemetry component 100 is in wireless RF communication with IMD 102. Telemetry component 100 communicates with IMD 102 by wireless transmission via antennas 106, which are configured and constructed as further described herein. Antennas 106 may be located within a housing 112 of telemetry component 100. In the example embodiment, antennas 106 are located within a portion of housing 112 that also contains display element 110. Antennas 106 are mounted within housing 112 for protection from the surrounding environment. In other words, housing 112 protects antennas 106 from incidental contact that may otherwise bend, break, or alter the RF characteristics and performance of antennas external to housing 112.
In one practical embodiment, housing 112 is fabricated from a nonconductive material such as plastic. Display element 110 may include an electrically conductive structure (or structures) such as a conductive backplane constructed of a metal, a metal alloy, or a metalized material that would otherwise be nonconductive. As described in more detail below, antennas 106 are arranged to provide spatial diversity as well as polarization diversity, in turn allowing telemetry component 100 to communicate with IMD 102 from several feet or meters away. Antennas 106 are suitably configured to achieve such far-field performance while reducing problems associated with polarization mismatches, antenna nulls, multi-path interference, and RF interference caused by other wireless devices such as cellular telephones.
In operation, telemetry component 100 interrogates IMD 102, via antennas 106, to retrieve measured data, along with currently programmed parameters and optimization target values stored by IMD 102. If IMD 102 is a pacemaker, the retrieved data includes data representing electrical activity sensed in the patient's heart 114, the output of various other sensors of IMD 102, and the rate response of IMD 102 over time. Telemetry component 100 displays some or all of these items to the user via display element 110. The user can program or reprogram IMD 102 via the user interface and input medium, e.g., keyboard 108. For example, the user may provide or adjust rate response parameters or target values of IMD 102 via the user interface and input medium, and such parameters or values are then relayed by telemetry component 100 to IMD 102 via a suitably configured transmitter/transceiver and antennas 106.
As mentioned above, programmer 200 communicates with an IMD using wireless data communication techniques. In a practical embodiment of the invention, programmer 200 is suitably configured to communicate with an IMD utilizing at least one data communication protocol. For example, programmer 200 may communicate with the IMD in accordance with a standardized wireless data communication protocol. Such standardized data communication protocols include, without limitation: Bluetooth; IEEE 802.11 (any variation thereof); IEEE 802.15.4 (ZigBee); or IrDA (infrared). [David—is this paragraph accurate?]
In particular, programmer 200 is configured to transmit and receive IMD signals, via antennas 210, to and from an IMD. Antennas 210 are preferably spaced apart by approximately a half wavelength (alternatively, antennas 210 may be spaced apart by approximately a quarter wavelength) to receive IMD signals from the IMD over multiple receive paths, thus providing programmer 200 with receive diversity to reduce multi-path propagation interference as well as antenna nulls. In accordance with one practical embodiment, antennas 210 are suitably configured for an operating frequency band of approximately 401 MHz to approximately 405 MHz, and to reject frequencies between approximately 450 MHz and approximately 3 GHz. With respect to diversity, antenna 210 a provides a first receive path and antenna 210 b provides a second receive path. Of course, more than two antennas 210 may be utilized in some embodiments for enhanced receive diversity.
Programmer 200 selects, via antenna switch 206 and RF module 204, the receive path with the strongest signal. More specifically, RF module 204 includes a receiver 212, and RSSI 208 is suitably configured to select the receive path having the strongest signal received by receiver 212. Processor 202 receives data collected by the IMD and currently programmed parameters from the IMD via receiver 212 and one of antennas 210, then processes the data in an appropriate manner. RF module 204 further includes a transmitter 214, which allows programmer 200 to program the IMD via antennas 210 (it should be appreciated that receiver 212 and transmitter 214 may be incorporated into an integrated transceiver component for RF module 204, where the transceiver includes receive circuitry and transmit circuitry). Such programming may include the programming of new parameters and/or optimization target values for the IMD. In practice, programmer 200 transmits IMD signals to the 1MD using one of the antennas 210.
As discussed above, programmer 200 provides a user interface 216 by which a user of programmer 200, such as a clinician or a physician, interacts with programmer 200 and the corresponding IMD. In the example shown in
As illustrated in the example of
Portion 314 of antennas 304 has a first polarization and portion 316 of antennas 304 has a second polarization. More specifically, portion 314 has a horizontal elliptical or circular polarization (indicated by arrow 318), while portion 316 has a vertical elliptical or circular polarization (indicated by arrow 320). In this manner, antennas 304 provide programmer 300 with polarization diversity. In other words, programmer 300 and, more particularly, antennas 304, receive and transmit IMD signals with horizontal polarization as well as vertical polarization, thus reducing antenna pattern nulls due to polarization mismatches.
Antennas 304 are spaced a fraction of a wavelength, e.g., a half wavelength or a quarter wavelength, apart from one another to achieve spatial diversity. [David: where is this spacing measured from? Is it the distance between the connectors?] In this manner, antennas 304 receive signals from the IMD over multiple receive paths, providing programmer 300 with spatial and polarization diversity, thereby reducing multi-path propagation interference and antenna nulls. In contrast to wands and other programmer heads that are generally placed in close proximity to the body of the patient to communicate IMD signals, the diversity arrangement of antennas 304, e.g., the spatial and polarization diversity, enables reception of IMD signals over extended distances (e.g., several feet or meters from the IMD).
The radiating elements of antennas 304 are attached to connectors 306 in order to conductively connect antennas 304 with the RF module utilized by the telemetry component (e.g., RF module 204 shown in
The practical embodiment of the invention takes advantage of the characteristics of the anti-parallel radiating element arrangement depicted in
RF antenna 700 is suitably configured in accordance with one practical embodiment of the invention. As shown in
In accordance with one practical embodiment of the invention, RF antenna 700 comprises a solid wire monopole antenna structure. For example, RF antenna 700 may include a solid copper wire 712 that serves as the radiating element. Wire 712 is preferably pliable and conformal to enable shaping as described above to account for surface current cancellation. As shown in
RF antenna 700 may include an RF connector 716 for coupling RF antenna 700 to an RF board or module (not shown) of IMD telemetry component 704. In particular, connector 716 couples RF antenna 700 to a receiver, a transmitter, and/or a transceiver of IMD telemetry component 704. In the example embodiment, RF connector 716 mates with an RF cable (not shown) coupled to the RF module of IMD telemetry component 704. The location of this RF feed point may represent a legacy design for housing 702 and, therefore, RF antenna 700 can be suitably configured for compatibility with the legacy design.
RF antenna 700 may include an element 718, located proximate RF connector 716 in the example embodiment, that includes RF matching components and an RF protection diode. Element 718 may represent an encapsulation of the RF matching components and the RF protection diode. The RF matching components facilitate impedance matching of RF antenna 700 to the RF module used by IMD telemetry component 704. The specific matching components and their topology may vary from one application to another, depending upon the desired antenna efficiency, the RF input/output impedance, the operating frequency band, the desired return loss, and other practical considerations. In this regard,
RF protection diode 804 is suitably configured to limit RF energy received by RF antenna 800 to thereby protect RF circuit components used by the IMD telemetry component. Such excess RF energy may be inadvertently received or coupled if an RF energy source, e.g., a cellular telephone, medical equipment, or the like, passes within close proximity to the IMD telemetry component. In one practical implementation, RF protection diode 804 is a PIN diode. Notably, in the example embodiment, RF protection diode 804 is incorporated into RF antenna 800 to serve as an “inline” protection means for remotely located RF circuit elements. Thus, the RF circuit board or RF module need not utilize RF protection circuitry. In lieu of RF protection diode 804, RF antenna 800 may employ other protection means, including, without limitation: one or more transistors; an RF switch; or the like.
In accordance with a practical embodiment of the invention, IMD telemetry component 704 employs RF antenna 700 in the top right corner as shown in
In practice, RF antenna 1000 has a relatively wideband characteristic (approximately 60 MHz bandwidth) and RF antenna 1000 has a relatively high efficiency rating (greater than 80 percent). The high bandwidth is achievable at the cost of having a relatively large ground plane, which is established in the practical embodiment by the metal casting for the display element. As a result of the high bandwidth, RF antenna 1000 need not employ a matching circuit or any matching components. RF antenna 1000 may be implemented using a solid wire, flex tape, or metalized plastic (as described above), or in accordance with any known antenna fabrication technique. To reduce manufacturing cost, a practical embodiment may etch RF antenna 1000 onto a relatively small flex tape or other conductive element with a modestly sized ground plane. Thereafter, the small ground plane can be capacitively coupled to electrically conducting structure 1014 to create a relatively large ground plane for RF antenna 1000.
While at least one example embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the example embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.