MINIATURIZED RADIO-FREQUENCY TRANSCEIVER IN MICRO MEDICAL IMPLANT FOR DUAL-FUNCTIONAL WIRELESS POWER TRANSFER AND DATA COMMUNICATION

Implants include a single tapped coil antenna having a first section and a second section for wireless power transfer, data downlink and data uplink. A modulated wireless power transfer signal is received by the tapped coil antenna and used to provide electrical power. The modulation is detected to generate downlink data. A switch is used to charge a section of the tapped coil antenna by establish a current which is then be interrupted by opening the switch. The switching produces a high-amplitude pulsed magnetic field (PMF) for use in data uplink over a large distance between the implant and an external transceiver.

FIELD

The disclosure pertains to implants having wireless power transfer.

BACKGROUND

Wireless power transfer (WPT) which can deliver power from outside of the human body or animal body to the inside can eliminate repeated surgical replacement of depleted batteries from the inside of the body. WPT can also reduce the sizes of implanted devices since the device battery is largely responsible for device size and weight. Numerous commercial products have adopted WPT approaches. While conventional WPT approaches can provide power transfer to implanted devices, they do not satisfactorily address data communication to and from implanted devices, i.e., combining WPT and Radio-Frequency (RF) data communication. In some approaches, different antenna pairs are used for communication and power transfer, increasing implant size. In such systems, an antenna pair is used for power transfer and communication to the implant (downlink) and another antenna pair used for communication from the implant (uplink). Unfortunately, the use of two antennas increases implant size and alternative approaches are needed.

SUMMARY

Implant and implant systems with wireless power transfer and one or more of uplink and downlink data transmission are disclosed. In some examples, wireless power transfer and communication systems comprise a tapped coil antenna having a first section and a second section situated about a common axis, wherein the tapped coil antenna is operable to couple a downlink signal based on an RF signal from a remote transmitter to an implant to provide electrical power and downlink data. A switch (such as a semiconductor-based switch) is coupled to the implant and to the tapped coil antenna, wherein the switch is operable to selectively connect the second section of the tapped coil antenna to generate a corresponding pulsed magnetic field based on an uplink data signal. In examples, a rectifier is coupled to the tapped coil antenna to provide electrical power to the implant based on the downlink signal. In further examples, the switch is operable to selectively connect and disconnect the second section of the tapped coil antenna based on the uplink data signal. In embodiments, the tapped coil antenna is operable to couple a downlink signal based on the RF signal from a remote transmitter received by the first section and the second section to the implant to provide electrical power and downlink data. In further embodiments, the second section of the tapped coil antenna is situated between and partially on top of first and second portions of the first section or the second section of the tapped coil antenna is sandwiched between first and second portions of the first section. In examples, a demodulator is provided that is operable to produce downlink data based on a modulation of the RF signal. In more examples, a demodulator is operable to produce downlink data based on an amplitude modulation of the RF signal. In some examples, the switch is operable to establish a charging state associated with establishing a current in the second section of the tapped coil antenna and an emitting state.

Methods comprise receiving an RF signal with a tapped coil antenna having a first section and a second section to produce a received electrical signal, processing the received electrical signal to produce electrical power for operating an implant, and selectively connecting and disconnecting the second section of the tapped coil antenna based on uplink data to produce a corresponding pulsed magnetic field. In examples, the pulsed magnetic field is produced by selectively disconnecting the second section of the tapped coil antenna. In more examples, methods include establishing an electrical current in at least the second section of the tapped coil antenna, wherein the pulsed magnetic field is based on a selective interruption of the established electrical current in the second section of the tapped coil antenna. In examples, the selective connecting or disconnecting the second section of the tapped coil antenna is produced with a switch. In some embodiments, the second section of the tapped coil antenna is sandwiched between portions of the first section of the tapped coil antenna or the second section of the tapped coil antenna is symmetrically sandwiched between portions of the first section of the tapped coil antenna. In representative examples, the pulsed magnetic field is oscillatory at a frequency associated with producing the electrical power. In additional examples, the received electrical signal includes a component at the frequency associated with producing the electrical power.

Communication and power transfer systems for an implant comprise an antenna comprising a first section and a second section coupled in series, a switch operable to establish a current in the second section and interrupt the established current to produce a pulsed magnetic field with the first section and the second section of the antenna, and a controller coupled to close and open the switch to produce the pulsed magnetic field. In examples, the antenna is a tapped coil or a tapped helical conductor. In more examples, a rectifier and a demodulator coupled to the antenna are provided and are operable to produce electrical power and a data signal based on an RF signal received by the antenna.

The foregoing and other features, and advantages will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.

DETAILED DESCRIPTION

Introduction and Terminology

As used herein, “implant” or “implant device” refers to an electronic device suitable for implanting in a subject such as a human or animal. Implants can include one or more sensors suitable for obtaining measurements of subject physiological, electrical, chemical, mechanical, or other parameters. Implants can also include stimulus generators that are operable to generate electrical signals to regulate subject functions such as muscle or heart activity or other functions. In some cases, stimulus generators are provided to dispense materials such as pharmaceutical compounds or other materials. Implants generally include circuitry for data communications to the implant (referred to as downlink communications herein) and from the implant to a receiver outside of the subject (uplink communication as used herein). Implants can include one or more processors, data modulators, demodulators, memory devices, timing circuits and elements such as clock circuits and other electronic components. While implants can include wireless power transfer circuitry and uplink/downlink antennas and associated electronics, circuitry for these functions is described and shown separately for convenient illustration.

Uplink communication uses an uplink signal that is coupled to an antenna to produce a modulated (e.g., amplitude, phase, or frequency modulation) magnetic field which can be referred to as a transmitted uplink signal containing uplink data. Similarly, a downlink radio frequency signal received by a suitable antenna can produce a downlink signal that is coupled to the implant to provide downlink data such as commands and procedures for implant operation and communication.

RF signal refers to an electromagnetic signal that is transmissible without direct electrical connection such as wires or other conductors.

“Coil” refers to loops of a conductor such as wire coupled in series and situated along a common axis. Loops of a coil can be circular, square, polygonal, ovoid, elliptical, or other regular or irregular shapes. A coil can comprise loops of a common shape and size or multiple shapes and sizes. In addition, loops can be situated symmetrically with respect to the axis. In typical examples, coils comprise loops that form a cylindrical shape, with diameter varying to accommodate loops that are situated on top of each other. A tapped coil is a coil that has at least one electrical connection at an intermediate location in the series-connected loops that form the coil. For convenience, tapped coils are referred to as tapped coil antennas as they serve to produce and receive RF signals for communications without direct electrical contact.

As used herein, “switch” refers to a device that makes and breaks an electrical connection. Some such devices are based on connecting and disconnecting conductors and are referred to herein as “conductor-based switches.” In other examples, such devices are based on semiconductors and are referred to herein as “semiconductor switches” or “electronic switches.

In some cases, oscillating electrical currents and voltages are referred as sinusoidal, but such oscillating signals can differ from pure sinusoids and are referred to as sinusoidal for convenient explanation.

Examples are described with reference to directions indicated as “above,” “below,” “upper,” “lower,” and the like. These terms are used for convenient description, but do not imply any particular spatial orientation.

Example 1. Representative Implanted Systems

Referring toFIG.1, a representative implantable system100includes an implant device102that includes electronics for one or more of sensing, stimulus generation, data modulation and demodulation, power management, or other functions. The device102is coupled to a tapped coil antenna104that includes a first section106and a second section108. The device102is also coupled to switches110,112that are operable to control wireless power transfer (WPT) based on a received electrical signal from the tapped antenna104that is produced in response to an RF signal. As used herein, “switch” refers to any type of switch including those based on connecting and disconnecting conductors and those based on semiconductors (electronic switches). The received electrical signal from the tapped coil antenna104is generally delivered to a rectifier114that is coupled to the implant device102by the switch110. The rectified received electrical signal can be coupled to other circuit elements for filtering, storage, voltage regulation, or other purposes but such circuit elements are not shown inFIG.1for convenient illustration.

Downlink data from the tapped coil antenna104is directed to the implant device102along a circuit path120for demodulation. In one example, the downlink data is transmitted as amplitude-shift-keying (ASK) data. During time intervals associated with WPT the switches110,112can be closed so that the rectified received electrical signal is coupled to charge capacitor122and power the implant device102. During WPT, downlink data can be obtained from a demodulation of the received electrical signal. For example, an RF signal at a fixed frequency can be used for power transfer and this RF signal can be amplitude modulated to provide downlink data. Thus, a common RF signal can be used for WPT and downlink communication. The switches110,112can be used to decouple some circuit portions as needed.

Uplink data is provided by a modulator associated with the implant device102to a switch116. Upon receipt of uplink data along path124, the switch116can be selectively toggled (open to closed or vice versa) to generate a pulsed magnetic field. By controlling the switch116based on the uplink data, a series of magnetic field pulses is produced that can be transmitted to a remote receiver. The capacitance of the capacitor122and the inductances of the tapped coil antenna104are generally selected so that the magnetic field pulses are associated with oscillations at a frequency corresponding to frequencies used for WPT and downlink communication. Signals applied to the second section108induce larger signals in the tapped coil antenna104(both sections) so that the pulsed magnetic fields (PMFs) emitted can have larger amplitudes.

A tapped coil antenna is preferably configured as shown inFIG.1A. The tapped coil antenna150includes a first section that comprises a first portion154and a second portion156. A second section158that is connected to receive data uplink signals is situated or “sandwiched” between the first portion154and the second portion156. As inFIG.1, both sections are coupled for WPT and data downlink and provide increased amplitudes for PMFs produced by uplink signal to the section158, Typically both sections are situated symmetrically situated about an axis160.

In another example shown inFIG.1B, a tapped coil antenna170includes a first section that comprises a first portion174and a second portion176. A second section178that is used for data uplink is situated or “sandwiched” between the first portion174and the second portion176as well as being situated under or on top of some loops of the first section. As inFIG.1, both sections are generally symmetrically situated about an axis180.

Example 2. Representative Tapped Coil Antennas

Referring toFIG.2A, a representative tapped coil antenna200includes a first section202that defines a first inductance L1and a second section204that defines a section inductance L2. The first section202and the second section204are situated about an axis206and are formed of circular windings of diameter d. Uplink connections are between a and b; downlink connections are between a and c.

FIGS.2B-2Eillustrate representative implementations of tapped coil antennas formed of circular windings of diameter d. For convenient illustration, total numbers of turns are used that can be smaller than typical implementations and loops associated with a second section (a section coupled to receive uplink modulations are shown with dashed lines). associated inductances L1and L2of the first and second sections are shown. All are shown as having diameter d.

In an example shown inFIG.2B, a tapped coil antenna210includes loops 3-8 that form a first section and loops 1-2 that form a second section with the loops distributed along an axis212. Taps214a,214bare associated with the second section204and taps214b,214care associated with the first section202.

In an example shown inFIG.2C, a tapped coil antenna220includes a first section (loops 3-8) situated radially on top of a second section (loops 1-2) and the loops are wound about an axis222. Taps224a,224bare associated with the second section and taps224b,224care associated with the first section.

In an example shown inFIG.2D, a tapped coil antenna230includes a first section (loops 3-8) with loops 7-8 situated radially on top of a second section (loops 1-2). The loops are wound about an axis232and the loops 1-2 are situated at an end of the tapped coil antenna230. Taps234a,234bare associated with the second section and taps234b,234care associated with the first section. In a preferred example shown inFIG.2E, a tapped coil antenna240includes a second section243(loops 1-6) situated between a first portion241and second portion242of a first section (loops 7-18) along an axis248. The loops are shown as wound along a cylindrical form246. Typically, a form used for winding loops is non-magnetic and makes little contribution to loop inductances. As noted previously, loops of other shapes can be used. Tapped connections for the first section and second section are shown with the respective inductances L1and L2. Taps244a,244bare associated with the second section243and taps244b,244care associated with the first section formed by portions241,242.

FIG.2Fis a photograph of a representative implementation of a tapped coil antenna250that includes a first section (portions256,257) and a second section258which are wrapped about a coil form254. Taps254a,254bare associated with the second section258and taps254b,254care associated with the first section formed by portions257,256.

FIG.2Gillustrates a representative prototype WPT/communication system260that includes an implant262comprising a tapped coil antenna264as discussed above and a transmitter/receiver266for uplink and downlink communications and WPT. A receiver/transmitter270configured for placement external to a subject is coupled to an external antenna272that in this example is a planar spiral conductor. The receiver/transmitter270is coupled to a center of the spiral conductor at273and to the perimeter end at274. In this example, the spiral has a diameter of 64 mm and includes about 10 turns, but other sizes can be used. The coil antenna272(external) and the tapped coil antenna (in the implant) are situated a distance D apart, wherein D is selected to provide suitable WPT and uplink/downlink communications. In this example, the tapped coil antenna264has an axal length of 15 mm and an inner diameter of 4 mm, but other sizes can be used.

With reference toFIG.3, a representative implant system300includes an implant302and an external transceiver (outside the human body)350configured to communicate with and provide power (via WPT) to the implant302. The implant302includes a load304that is associated with implant functions such as sensing or stimulus generation and uplink circuitry306. The uplink circuitry306includes capacitors307(Cm),317(C1), a tapped coil antenna310, and switch312that is operable in response to a modulator314and controller316to produce a pulsed magnetic field (PMF) emitted by tapped coil antenna310based on electrical pulses in response to toggling of the switch312. The PMF is received by an antenna352in the external transceiver350and an associated electrical signal demodulated to produce uplink data from the implant302with a controller326such as a microprocessor, a programmable logic device, or other digital control device or demodulator.

The antenna352is also situated to receive an electrical signal associated with downlink data for transmission to the implant302as well as provide a WPT signal that can be processed at the implant302with appropriate circuit elements such as a rectifier and one or more capacitors for powering the implant302. The external transceiver system350includes a downlink section360that is coupled to provide suitable modulated data (ASK data in this example) to the antenna352. The external transceiver system350also includes a WPT section362that is coupled to provide a WPT signal to the antenna352. The downlink transmission and the WPT transmission are received by the tapped coil antenna310and processed to provide data associated with implant control/sensing via a demodulator318and power for operation of the implant302. Additional switches319,320are provided to decouple WPT.

In some examples, the antenna352is a planar spiral, but other antenna configurations can be used. The tapped coil antenna310can include a sandwiched section as shown inFIG.2Eand have an internal diameter of between 0.5 mm and 10 mm, and an axial length of between 1 and 50 mm. In particular examples, an internal diameter is 4 mm and an axial length is 15 mm.

FIG.3Billustrates operation of the system ofFIG.3A. In a WPT state the entire tapped coil is used and the capacitor307(Cm) is charged to a stable value. A power-amplified sinusoid or other WPT signal (shown inFIG.3Aas generated by a Class-E amplifier at a frequency f0) is wirelessly transmitted as a magnetic field by the planar spiral coil352. The tapped coil antenna310(or a double-helix antenna) receives part of the sinusoidal magnetic field which is then processed (e.g., multiplied, rectified, filtered) and energy is stored in the capacitor307(Cm) with a voltage um. At this time, the signal from the controller316for the switch312is LOW (e.g., 0V) or otherwise configured so that the switch312is OFF and the capacitor307(Cm) is disconnected from the tapped coil antenna310. In a downlink state, downlink data transmission and WPT power transfer are performed simultaneously and the uplink circuitry306is disconnected but the amplitude of the WPT voltage at the transmitter side is modulated for downlink signal transmission. A variation of a voltage u1across the capacitor317(C1) is captured and decoded into a binary data stream using, for example, ASK demodulation.

Uplink communication is much more difficult because of the limited size of the tapped coil antenna310and the limited available power. To produce an uplink signal, power can be provided by the capacitor307(Cm) as charged as discussed above. To transmit a binary value “1” in the uplink data, a charging state and an emitting state are provided sequentially. As shown inFIG.3B, in the charging state, the control signal is HIGH, the switch312is ON, the capacitor307(Cm) is connected to the tapped coil antenna310, and a voltage umacross the capacitor307(Cm), where the phases of the voltage umand the associated current differ by 90°. Thus, when umreaches zero, the current reaches the peak value. At this time, the switch312is turned OFF to enter the emitting state. Due to a sudden cutoff of current and a voltage step-up effect of the tapped coil antenna310, a high-amplitude PMF is generated by the entire tapped coil antenna310excited by a voltage spike u1at the capacitor317(C1) for external detection. the capacitor317and coil antenna310form an oscillating LC-tank with a resonant frequency the same as the common frequency for WPT. The timing of the turning the switch312from ON to OFF can be predetermined, and the switch312controlled accordingly. As shown inFIG.3B, downlink and WPT are associated with a common frequency and the uplink PMF is associated with this common frequency as well. Different frequencies can be used, but use of common frequency tends to provide superior energy efficiency and allow the use of the same coil antenna for WPT, data downlink and data uplink, saving space within implant300.

In one example, a frequency of 4 MHz can be used for downlink and WPT, and the PMF configured to have 4 MHz oscillations. Various kinds of switches can be used to establish charging and emitting states including digital or analog switches with switching times that are suitable for the selected frequency of operation.

Use of a single frequency for both WPT and communication can be expected to change WPT performance. In the downlink state, WPT and communication are conducted simultaneously in the same direction (i.e., to an implant). The PMF circuitry can be disconnected thus has no effect on WPT efficiency. However, the amplitude of the WPT voltage is modulated for downlink signal transmission, which can have an effect on WPT but this generally small as the time for downlink (mostly for sending system commands) is relatively short. In the uplink state, on the other hand, the PMF circuitry can have an effect because within the duration of each PMF pulse, WPT is interrupted to allow uplink data transmission. However, degradation of WPT can be acceptable in order to produce a selected PMF amplitude.

Example 4. Representative WPT and Communication Method

Referring toFIG.4, a representative method400includes receiving a WPT signal at402and providing power to an implant based on the received WPT signal at404. At406, a modulation of the WPT signal (if any) is detected and demodulated to provide downlink data. At407, it is determined if uplink data is to be communicated. If not, the method can return to402to continue receiving power via WPT and decoding any downlink data. If uplink data is to be transmitted, at402, a charging state and an emitting state are alternated for each bit to be transmitted at408. In the charging state, a current is established in a section of a tapped coil antenna, typically a tapped helical coil but a tapped planar coil can also be used. In the emitting state, the established current is interrupted, typically with a digitally controlled switch. This interruption produces a pulsed magnetic field with the entire tapped coil antenna. The magnitude of the pulsed magnetic field is dependent on the section of the tapped coil antenna used in charging and the total size (for example, number of turns) of the tapped coil antenna. This can provide an unexpectedly large pulsed magnetic field, enabling uplink data transmission over a large distance. If uplink data transmission is complete as determined at410, the method returns to402. If additional data remains, the method returns to408.

Example 5. Representative Embodiments

Embodiment 1 is a wireless power transfer and communication system, including: a tapped coil antenna comprising a first section and a second section situated about a common axis, wherein the tapped coil antenna is operable to couple a downlink signal based on an RF signal from a remote transmitter to an implant to provide electrical power and downlink data; and a switch coupled to the implant and to the tapped coil antenna, wherein the switch is operable to selectively connect the second section of the tapped coil antenna to generate a corresponding pulsed magnetic field based on an uplink data signal.

Embodiment 2 includes the subject matter of Embodiment 1, and further includes a rectifier coupled to the tapped coil antenna and to provide electrical power to the implant based on the downlink signal.

Embodiment 3 includes the subject matter of any of Embodiments 1-2, and further specifies that the switch is operable to selectively connect and disconnect the second section of the tapped coil antenna based on the uplink data signal.

Embodiment 4 includes the subject matter of any of Embodiments 1-3, and further specifies that the tapped coil is the only tapped coil, thereby conserving space in an implant.

Embodiment 5 includes the subject matter of any of Embodiments 1-4 and further specifies that the tapped coil is a single tapped coil and is operably coupled for wireless power transfer, data downlink, and data uplink.

Embodiment 6 includes the subject matter of any of Embodiments 1-5, and further specifies that the tapped coil antenna is operable to couple a downlink signal based on the RF signal from a remote transmitter received by the first section and the second section to the implant to provide electrical power and downlink data.

Embodiment 7 includes the subject matter of any of Embodiments 1-6, and further specifies that the second section of the tapped coil antenna is situated between and partially on top of first and second portions of the first section.

Embodiment 8 includes the subject matter of any of Embodiments 1-7, and further specifies that the second section of the tapped coil antenna is sandwiched between first and second portions of the first section.

Embodiment 9 includes the subject matter of any of Embodiments 1-8, and further includes a demodulator operable to produce downlink data based on a modulation of the RF signal.

Embodiment 10 includes the subject matter of any of Embodiments 1-9, and further includes a demodulator operable to produce downlink data based on an amplitude modulation of the RF signal.

Embodiment 11 includes the subject matter of any of Embodiments 1-10, and further specifies that the switch is operable to establish a charging state associated with an oscillating current in the second section of the tapped coil antenna and an emitting state associated with interrupting the established current at a timepoint when the oscillating current is proximate a maximum amplitude.

Embodiment 12 is a method, including receiving an RF signal with a tapped coil antenna having a first section and a second section to produce a received electrical signal; processing the received electrical signal to produce electrical power for operating an implant; and selectively connecting and disconnecting the second section of the tapped coil antenna based on uplink data to produce a corresponding pulsed magnetic field.

Embodiment 13 includes the subject matter of Embodiment 12, where the pulsed magnetic field is produced by selectively connecting the second section of the tapped coil antenna.

Embodiment 14 includes the subject matter of any of Embodiments 12-13, and further includes establishing an electrical current in a sinusoidal waveform in at least the second section of the tapped coil antenna, wherein the pulsed magnetic field is based on a selective interruption of the established electrical current in the second section of the tapped coil antenna at a timepoint when the current is at, or close to, a peak value.

Embodiment 15 includes the subject matter of any of Embodiments 12-14, and further specifies that the selective connecting or disconnecting the second section of the tapped coil antenna is produced with a switch.

Embodiment 16 includes the subject matter of any of Embodiments 12-15, and further specifies that the switch is a conductor-based switch or a semiconductor switch.

Embodiment 17 includes the subject matter of any of Embodiments 12-16, and further specifies that the second section of the tapped coil antenna is sandwiched between portions of the first section of the tapped coil antenna.

Embodiment 18 includes the subject matter of any of Embodiments 12-17, and further specifies that the second section of the tapped coil antenna is symmetrically sandwiched between portions of the first section of the tapped coil antenna.

Embodiment 19 includes the subject matter of any of Embodiments 12-18, and further specifies that the pulsed magnetic field is oscillatory at a frequency associated with producing the electrical power.

Embodiment 20 includes the subject matter of any of Embodiments 12-19, and further specifies that the received electrical signal includes a component at the frequency associated with producing the electrical power.

Embodiment 21 is a communication and power transfer system for an implant, including an antenna comprising a first section and a second section coupled in series; a switch operable to establish a current in the second section and interrupt the established current to produce a pulsed magnetic field with the first section and the second section of the antenna; and a controller coupled to close and open the switch to produce the pulsed magnetic field.

Embodiment 22 includes the subject matter of Embodiment 21, and further specifies that the antenna is a tapped helical coil or a tapped planar coil.

Embodiment 23 includes the subject matter of any of Embodiments 21-22, and further includes a rectifier and a demodulator coupled to the antenna and operable to produce electrical power and a data signal based on an RF signal received by the antenna.