Floating intermediate coil array for medical implant

Abstract

An apparatus includes a first magnetic induction (MI) antenna and circuitry in electrical communication with the first MI antenna. The apparatus further includes an array of MI antennas galvanically isolated from the first MI antenna and the circuitry. The array includes a second MI antenna and a third MI antenna. The second MI antenna has a non-zero first coupling coefficient with the first MI antenna and the third MI antenna has a non-zero second coupling coefficient with the first MI antenna and a third coupling coefficient with the second MI antenna that is substantially equal to zero.

Description

FLOATING INTERMEDIATE COIL ARRAY FOR MEDICAL IMPLANTBACKGROUNDField

[0001] The present application relates generally to systems and methods for wirelessly communicating data to and / or from a device implanted on or within a recipient’s body.Description of the Related Art

[0002] Medical devices have provided a wide range of therapeutic benefits to recipients over recent decades. Medical devices can include internal or implantable components / de vices, external or wearable components / devices, or combinations thereof (e.g., a device having an external component communicating with an implantable component). Medical devices, such as traditional hearing aids, partially or fully-implantable hearing prostheses (e.g., bone conduction devices, mechanical stimulators, cochlear implants, etc.), pacemakers, defibrillators, functional electrical stimulation devices, and other medical devices, have been successful in performing lifesaving and / or lifestyle enhancement functions and / or recipient monitoring for a number of years.

[0003] The types of medical devices and the ranges of functions performed thereby have increased over the years. For example, many medical devices, sometimes referred to as “implantable medical devices,” now often include one or more instruments, apparatus, sensors, processors, controllers or other functional mechanical or electrical components that are permanently or temporarily implanted in a recipient. These functional devices are typically used to diagnose, prevent, monitor, treat, or manage a disease / injury or symptom thereof, or to investigate, replace or modify the anatomy or a physiological process. Many of these functional devices utilize power and / or data received from external devices that are part of, or operate in conjunction with, implantable components.SUMMARY

[0004] In one aspect disclosed herein, an apparatus comprises a first magnetic induction (MI) antenna comprising an electrically conductive first coil extending around and substantially orthogonal to a first antenna axis. The apparatus further comprises circuitry in electrical communication with the first MI antenna. The circuitry is configured to provideelectrical current to the first MI antenna and / or to receive electrical current from the first MI antenna. The apparatus further comprises an array of MI antennas galvanically isolated from the first MI antenna and the circuitry. The array comprises at least a second MI antenna and a third MI antenna. The second MI antenna comprises an electrically conductive second coil extending around and substantially orthogonal to a second antenna axis substantially parallel to the first antenna axis, and the second MI antenna has a non-zero first coupling coefficient with the first MI antenna. The third MI antenna comprises an electrically conductive third coil extending around and substantially orthogonal to a third antenna axis substantially parallel to the first antenna axis, and the third MI antenna having a non-zero second coupling coefficient with the first MI antenna and a third coupling coefficient with the second MI antenna that is substantially equal to zero.

[0005] In another aspect disclosed herein, a method comprises providing a first MI antenna within a housing. The method further comprises attaching a second MI antenna to the housing. The second MI antenna is electrically floating relative to the first MI antenna and has a non-zero mutual inductance with the first MI antenna. The method further comprises attaching a third MI antenna to the housing. The third MI antenna is electrically floating relative to the first MI antenna and has a non-zero mutual inductance with the first MI antenna. The third MI antenna has a substantially zero mutual inductance with the second MI antenna.

[0006] In another aspect disclosed herein, an apparatus comprises an electrically conductive and substantially planar first coil. The apparatus further comprises circuitry in electrical communication with the first coil. The apparatus further comprises a plurality of electrically conductive and substantially planar second coils electrically isolated from the circuitry and the first coil. The plurality of second coils is substantially parallel to one another and substantially parallel to the first coil. The plurality of second coils has substantially zero magnetic inductive coupling to one another.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Implementations are described herein in conjunction with the accompanying drawings, in which:

[0008] FIG. 1A is a perspective view of an example cochlear implant auditory prosthesis implanted in a recipient in accordance with certain implementations described herein;

[0009] FIG. IB is a perspective view of an example fully implantable middle ear implant auditory prosthesis implanted in a recipient in accordance with certain implementations described herein;

[0010] FIG. 2A schematically illustrates a cross-sectional view of an example apparatus in accordance with certain implementations described herein and a device external to the recipient’s body;

[0011] FIG. 2B schematically illustrates a top view of the example apparatus of FIG. 2A in accordance with certain implementations described herein;

[0012] FIG. 3A schematically illustrates another example first MI antenna and example array of MI antennas in accordance with certain implementations described herein;

[0013] FIG. 3B schematically illustrates another example first MI antenna and example array of MI antennas in accordance with certain implementations described herein;

[0014] FIG. 4 schematically illustrates a top view of an example array of MI antennas with three coils in accordance with certain implementations described herein;

[0015] FIG. 5 is a schematic plot of the mutual coupling coefficient & as a function of the normalized displacement d / R for example second and third coils in accordance with certain implementations described herein;

[0016] FIG. 6 schematically illustrates an example inductive link between the apparatus and the device in accordance with certain implementations described herein;

[0017] FIG. 7 schematically illustrates inductive coupling between example first, second, and third coils and the external coil in accordance with certain implementations described herein;

[0018] FIG. 8 schematically illustrates another example inductive link between the apparatus and the device in accordance with certain implementations described herein;

[0019] FIG. 9 schematically illustrates an example Q-control circuitry in accordance with certain implementations described herein;

[0020] FIGs. 10A and 10B schematically illustrate top views of two example devices in accordance with certain implementations described herein;

[0021] FIG. 10C is a flow diagram of an example method for fabricating a device in accordance with certain implementations described herein;

[0022] FIG. 11 schematically illustrates an example inductive link between the apparatus and the device in which the apparatus comprises a floating MI antenna coil and the device comprises a floating MI antenna coil in accordance with certain implementations described herein; and

[0023] FIG. 12 schematically illustrates an example inductive link between the apparatus and the device in which the apparatus comprises second and third coils and the device comprises second and third coils in accordance with certain implementations described herein.DETAILED DESCRIPTION

[0024] Certain implementations described herein provide a stimulation or measurement system (e.g., a sensory prosthesis system) with enhanced wireless (e.g., transcutaneous) communication between an implantable portion and an external portion. Each portion comprises a corresponding first magnetic induction (MI) antenna coil in electrical communication with corresponding circuitry. At least one of the implantable portion and the external portion further comprises an array of MI antenna coils that are galvanically isolated from the first MI antenna coils and from the circuitry of both the implantable portion and the external portion. The array of MI antenna coils are tuned to the resonant frequency of the first MI antenna coils to sustain significant coil currents without substantial power dissipation. In this way, the array of MI antenna coils can be configured to provide intermediate (e.g., indirect) coupling between the first MI antenna coils (e.g., acting as repeater coils) that facilitates the wireless communication between the implantable portion and the external portion. The array of MI antenna coils can maintain the wireless communication link in spite of significant movement and / or misalignment between the implanted portion and the external portion (e.g., in a magnet-free link).

[0025] The teachings detailed herein are applicable, in at least some implementations, to any type of implantable or non-implantable stimulation or measurement system (e.g., implantable or non-implantable auditory prosthesis device or system). Implementations can include any type of medical device that can utilize the teachings detailed herein and / or variations thereof. Furthermore, while certain implementations are described herein in the context of auditory prosthesis devices, certain other implementations are compatible in the context of other types of devices or systems.

[0026] Merely for ease of description, apparatus and methods disclosed herein are primarily described with reference to an illustrative medical device, namely an implantable transducer assembly including but not limited to: electro-acoustic electrical / acoustic systems, cochlear implant devices, implantable hearing aid devices, middle ear implant devices, bone conduction devices (e.g., active bone conduction devices; passive bone conduction devices, percutaneous bone conduction devices; transcutaneous bone conduction devices), Direct Acoustic Cochlear Implant (DACI), middle ear transducer (MET), electro-acoustic implant devices, other types of auditory prosthesis devices, and / or combinations or variations thereof, or any other suitable hearing prosthesis system with or without one or more external components. Implementations can include any type of auditory prosthesis that can utilize the teachings detailed herein and / or variations thereof. Certain such implementations can be referred to as “partially implantable,” “semi-implantable,” “mostly implantable,” “fully implantable,” or “totally implantable” auditory prostheses. In some implementations, the teachings detailed herein and / or variations thereof can be utilized in other types of prostheses beyond auditory prostheses.

[0027] While certain implementations are described herein in the context of auditory prosthesis devices, certain other implementations are compatible in the context of other types of sensory prosthesis systems that are configured to evoke other types of neural or sensory (e.g., sight, tactile, smell, taste) percepts are compatible with certain implementations described herein, including but are not limited to: vestibular devices (e.g., vestibular implants), visual devices (e.g., bionic eyes), visual prostheses (e.g., retinal implants), somatosensory implants, and chemosensory implants. Certain other implementations are compatible with other types of medical devices that can utilize the teachings detailed herein and / or variations thereof to provide a wide range of therapeutic benefits to recipients, patients, or other users (e.g., epilepsy monitoring systems; pain control systems; bladder control systems; neurostimulators; pacemakers; other medical implants comprising an implanted power source).

[0028] FIG. 1A is a perspective view of an example cochlear implant auditory prosthesis 100 implanted in a recipient in accordance with certain implementations described herein. The example auditory prosthesis 100 is shown in FIG. 1A as comprising an implanted stimulator unit 120 and a microphone assembly 124 that is external to the recipient (e.g., a partially implantable cochlear implant). An example auditory prosthesis 100 (e.g., a totallyimplantable cochlear implant; a mostly implantable cochlear implant) in accordance with certain implementations described herein can replace the external microphone assembly 124 shown in FIG. 1 A with a subcutaneously implantable microphone assembly, as described more fully herein. In certain implementations, the example cochlear implant auditory prosthesis 100 of FIG. 1 A can be in conjunction with a reservoir of liquid medicament as described herein.

[0029] As shown in FIG. 1A, the recipient has an outer ear 101, a middle ear 105, and an inner ear 107. In a fully functional ear, the outer ear 101 comprises an auricle 110 and an ear canal 102. An acoustic pressure or sound wave 103 is collected by the auricle 110 and is channeled into and through the ear canal 102. Disposed across the distal end of the ear canal 102 is a tympanic membrane 104 which vibrates in response to the sound wave 103. This vibration is coupled to oval window or fenestra ovalis 112 through three bones of middle ear 105, collectively referred to as the ossicles 106 and comprising the malleus 108, the incus 109, and the stapes 111. The bones 108, 109, and 111 of the middle ear 105 serve to filter and amplify the sound wave 103, causing the oval window 112 to articulate, or vibrate in response to vibration of the tympanic membrane 104. This vibration sets up waves of fluid motion of the perilymph within cochlea 140. Such fluid motion, in turn, activates tiny hair cells (not shown) inside the cochlea 140. Activation of the hair cells causes appropriate nerve impulses to be generated and transferred through the spiral ganglion cells (not shown) and auditory nerve 114 to the brain (also not shown) where they are perceived as sound.

[0030] As shown in FIG. 1A, the example auditory prosthesis 100 comprises one or more components which are temporarily or permanently implanted in the recipient. The example auditory prosthesis 100 is shown in FIG. 1A with an external component 142 which is directly or indirectly attached to the recipient’s body, and an internal component 144 which is temporarily or permanently implanted in the recipient (e.g., positioned in a recess of the temporal bone adjacent auricle 110 of the recipient). The external component 142 typically comprises one or more sound input elements (e.g., an external microphone 124) for detecting sound, a sound processing unit 126 (e.g., disposed in a Behind-The-Ear unit), a power source (not shown), and an external transmitter unit 128. In the illustrative implementations of FIG. 1A, the external transmitter unit 128 comprises an external coil 130 (e.g., a wire antenna coil comprising multiple turns of electrically insulated single-strand or multi-strand platinum or gold wire) and, preferably, a magnet (not shown) secured directly or indirectly to the externalcoil 130. The external coil 130 of the external transmitter unit 128 is part of an inductive radio frequency (RF) communication link with the internal component 144. The sound processing unit 126 processes the output of the microphone 124 that is positioned externally to the recipient’s body, in the depicted implementation, by the recipient’s auricle 110. The sound processing unit 126 processes the output of the microphone 124 and generates encoded signals, sometimes referred to herein as encoded data signals, which are provided to the external transmitter unit 128 (e.g., via a cable). As will be appreciated, the sound processing unit 126 can utilize digital processing techniques to provide frequency shaping, amplification, compression, and other signal conditioning, including conditioning based on recipient-specific fitting parameters.

[0031] The power source of the external component 142 is configured to provide power to the auditory prosthesis 100, where the auditory prosthesis 100 includes a battery (e.g., located in the internal component 144, or disposed in a separate implanted location) that is recharged by the power provided from the external component 142 (e.g., via a transcutaneous energy transfer link). The transcutaneous energy transfer link is used to transfer power and / or data to the internal component 144 of the auditory prosthesis 100. Various types of energy transfer, such as infrared (IR), electromagnetic, capacitive, and inductive transfer, may be used to transfer the power and / or data from the external component 142 to the internal component 144. During operation of the auditory prosthesis 100, the power stored by the rechargeable battery is distributed to the various other implanted components as needed.

[0032] The internal component 144 comprises an internal receiver unit 132, a stimulator unit 120, and an elongate electrode assembly 118. In some implementations, the internal receiver unit 132 and the stimulator unit 120 are hermetically sealed within a biocompatible housing. The internal receiver unit 132 comprises an internal coil 136 (e.g., a wire antenna coil comprising multiple turns of electrically insulated single-strand or multistrand platinum or gold wire), and preferably, a magnet (also not shown) fixed relative to the internal coil 136. The internal receiver unit 132 and the stimulator unit 120 are hermetically sealed within a biocompatible housing, sometimes collectively referred to as a stimulator / receiver unit. The internal coil 136 receives power and / or data signals from the external coil 130 via a transcutaneous energy transfer link (e.g., an inductive RF link). Thestimulator unit 120 generates electrical stimulation signals based on the data signals, and the stimulation signals are delivered to the recipient via the elongate electrode assembly 118.

[0033] The elongate electrode assembly 118 has a proximal end connected to the stimulator unit 120, and a distal end implanted in the cochlea 140. The electrode assembly 118 extends from the stimulator unit 120 to the cochlea 140 through the mastoid bone 119. In some implementations, the electrode assembly 118 may be implanted at least in the basal region 116, and sometimes further. For example, the electrode assembly 118 may extend towards apical end of cochlea 140, referred to as cochlea apex 134. In certain circumstances, the electrode assembly 118 may be inserted into the cochlea 140 via a cochleostomy 122. In other circumstances, a cochleostomy may be formed through the round window 121, the oval window 112, the promontory 123, or through an apical turn 147 of the cochlea 140.

[0034] The elongate electrode assembly 118 comprises a longitudinally aligned and distally extending array 146 of electrodes or contacts 148, sometimes referred to as electrode or contact array 146 herein, disposed along a length thereof. Although the electrode array 146 can be disposed on the electrode assembly 118, in most practical applications, the electrode array 146 is integrated into the electrode assembly 118 (e.g., the electrode array 146 is disposed in the electrode assembly 118). As noted, the stimulator unit 120 generates stimulation signals which are applied by the electrodes 148 to the cochlea 140, thereby stimulating the auditory nerve 114.

[0035] While FIG. 1 A schematically illustrates an auditory prosthesis 100 utilizing an external component 142 comprising an external microphone 124, an external sound processing unit 126, and an external power source, in certain other implementations, one or more of the microphone 124, sound processing unit 126, and power source are implantable on or within the recipient (e.g., within the internal component 144). For example, the auditory prosthesis 100 can have each of the microphone 124, sound processing unit 126, and power source implantable on or within the recipient (e.g., encapsulated within a biocompatible assembly located subcutaneously), and can be referred to as a totally implantable cochlear implant (“TICI”). For another example, the auditory prosthesis 100 can have most components of the cochlear implant (e.g., excluding the microphone, which can be an in-the-ear-canal microphone) implantable on or within the recipient, and can be referred to as a mostly implantable cochlear implant (“MICI”).

[0036] FIG. IB schematically illustrates a perspective view of an example fully implantable auditory prosthesis 200 (e.g., fully implantable middle ear implant or totally implantable acoustic system), implanted in a recipient, utilizing an acoustic actuator in accordance with certain implementations described herein. The example auditory prosthesis 200 of FIG. IB comprises a biocompatible implantable assembly 202 (e.g., comprising an implantable capsule) located subcutaneously (e.g., beneath the recipient’s skin and on a recipient's skull). While FIG. IB schematically illustrates an example implantable assembly 202 comprising a microphone, in other example auditory prostheses 200, a pendant microphone can be used (e.g., connected to the implantable assembly 202 by a cable). The implantable assembly 202 includes a signal receiver 204 (e.g., comprising a coil element) and an acoustic transducer 206 (e.g., a microphone comprising a diaphragm and an electret or piezoelectric transducer) that is positioned to receive acoustic signals through the recipient’s overlying tissue. The implantable assembly 202 may further be utilized to house a number of components of the fully implantable auditory prosthesis 200. For example, the implantable assembly 202 can include an energy storage device and a signal processor (e.g., a sound processing unit). Various additional processing logic and / or circuitry components can also be included in the implantable assembly 202 as a matter of design choice.

[0037] For the example auditory prosthesis 200 shown in FIG. IB, the signal processor of the implantable assembly 202 is in operative communication (e.g., electrically interconnected via a wire 208) with an actuator 210 (e.g., comprising a transducer configured to generate mechanical vibrations in response to electrical signals from the signal processor). In certain implementations, the example auditory prosthesis 100, 200 shown in FIGs. 1A and IB can comprise an implantable microphone assembly, such as the microphone assembly 206 shown in FIG. IB. For such an example auditory prosthesis 100, the signal processor of the implantable assembly 202 can be in operative communication (e.g., electrically interconnected via a wire) with the microphone assembly 206 and the stimulator unit of the main implantable component 120. In certain implementations, at least one of the microphone assembly 206 and the signal processor (e.g., a sound processing unit) is implanted on or within the recipient.

[0038] The actuator 210 of the example auditory prosthesis 200 shown in FIG. IB is supportably connected to a positioning system 212, which in turn, is connected to a bone anchor 214 mounted within the recipient's mastoid process (e.g., via a hole drilled through theskull). The actuator 210 includes a connection apparatus 216 for connecting the actuator 210 to the ossicles 106 of the recipient. In a connected state, the connection apparatus 216 provides a communication path for acoustic stimulation of the ossicles 106 (e.g., through transmission of vibrations from the actuator 210 to the incus 109).

[0039] During normal operation, ambient acoustic signals (e.g., ambient sound) impinge on the recipient’ s tissue and are received transcutaneously at the microphone assembly 206. Upon receipt of the transcutaneous signals, a signal processor within the implantable assembly 202 processes the signals to provide a processed audio drive signal via wire 208 to the actuator 210. As will be appreciated, the signal processor may utilize digital processing techniques to provide frequency shaping, amplification, compression, and other signal conditioning, including conditioning based on recipient-specific fitting parameters. The audio drive signal causes the actuator 210 to transmit vibrations at acoustic frequencies to the connection apparatus 216 to affect the desired sound sensation via mechanical stimulation of the incus 109 of the recipient.

[0040] The subcutaneously implantable microphone assembly 202 is configured to respond to auditory signals (e.g., sound; pressure variations in an audible frequency range) by generating output signals (e.g., electrical signals; optical signals; electromagnetic signals) indicative of the auditory signals received by the microphone assembly 202, and these output signals are used by the auditory prosthesis 100, 200 to generate stimulation signals which are provided to the recipient’s auditory system. To compensate for the decreased acoustic signal strength reaching the microphone assembly 202 by virtue of being implanted, the diaphragm of an implantable microphone assembly 202 can be configured to provide higher sensitivity than are external non-implantable microphone assemblies. For example, the diaphragm of an implantable microphone assembly 202 can be configured to be more robust and / or larger than diaphragms for external non-implantable microphone assemblies.

[0041] The example auditory prostheses 100 shown in FIG. 1 A utilizes an external microphone 124 and the auditory prosthesis 200 shown in FIG. IB utilizes an implantable microphone assembly 206 comprising a subcutaneously implantable acoustic transducer. In certain implementations described herein, the auditory prosthesis 100 utilizes one or more implanted microphone assemblies on or within the recipient. In certain implementations described herein, the auditory prosthesis 200 utilizes one or more microphone assemblies thatare positioned external to the recipient and / or that are implanted on or within the recipient, and utilizes one or more acoustic transducers (e.g., actuator 210) that are implanted on or within the recipient. In certain implementations, an external microphone assembly can be used to supplement an implantable microphone assembly of the auditory prosthesis 100, 200. Thus, the teachings detailed herein and / or variations thereof can be utilized with any type of external or implantable microphone arrangement, and the acoustic transducers shown in FIGs. 1A and IB are merely illustrative.

[0042] Magnetic links between an implanted portion of a medical system (e.g., sensory prosthesis system) and an external portion of the medical system can be used to generate an attractive magnetic force that holds the external portion in place relative to the implanted portion to facilitate a sufficiently strong and consistent magnetic induction (MI) communication channel between the two across the maximum skin-flap separation. In contrast, magnet-free links can have highly variable misalignments between the external portion and the implanted portion, resulting in highly variable coil coupling coefficients (e.g., ranging from k = 0.1 to 0.02 or less). Thus, sufficiently strong and consistent power transfer efficiency can be difficult to achieve in view of substantial misalignments of the coils of the external portion relative to the implanted portion. In addition, for auditory prosthesis systems, the anatomy of the concha can be a source of additional variability, resulting in a wide range of behind-the-ear placements, subsequent day-to-day variations, and variability due to activity (e.g., running) by the recipient. Certain implementations described herein are configured to provide sufficiently strong and consistent MI communications between the implanted portion and the external portion despite the positional variability of a magnet-free link.

[0043] FIG. 2A schematically illustrates a cross-sectional view of an example apparatus 300 with an array of two MI antennas 330a, b in accordance with certain implementations described herein and a device 400 external to the recipient’s body. FIG. 2B schematically illustrates a top view of the example apparatus 300 of FIG. 2A in accordance with certain implementations described herein.

[0044] The apparatus 300 comprises a first magnetic induction (MI) antenna 310 comprising an electrically conductive first coil 312 extending around and substantially orthogonal to a first antenna axis 314. The apparatus 300 further comprises circuitry 320 in electrical communication with the first MI antenna 310, the circuitry 320 configured to provideelectrical current to the first MI antenna 310 and / or to receive electrical current from the first MI antenna 310. The apparatus 300 further comprises an array of MI antennas 330 galvanically isolated from the first MI antenna 310 and the circuitry 320. The array of MI antennas 330 comprises at least a second MI antenna 330a and a third MI antenna 330b. The second MI antenna 330a comprises an electrically conductive second coil 332a extending around and substantially orthogonal to a second antenna axis 334a substantially parallel to the first antenna axis 314, and the second MI antenna 330a has a non-zero first coupling coefficient ki with the first MI antenna 310. The third MI antenna 330b comprises an electrically conductive third coil 332b extending around and substantially orthogonal to a third antenna axis 334b substantially parallel to the first antenna axis 314, and the third MI antenna 330b has a nonzero second coupling coefficient fa with the first MI antenna 310 and a third coupling coefficient fa with the second MI antenna 330a that is substantially equal to zero.

[0045] In certain implementations, as schematically illustrated by FIG. 2A, the apparatus 300 is part of a transcutaneous system (e.g., auditory prosthesis system) comprising the apparatus 300 (e.g., an implanted portion of an acoustic prosthesis system) and the device 400 (e.g., an external portion of the acoustic prosthesis system). For example, the apparatus 300 can be configured to be implanted on and substantially parallel to a bone surface 510 (e.g., a surface of a portion of the skull 520 behind the auricle 110 (e.g., pinna) of the recipient; a surface of the mastoid bone 119) within a recipient and the external device 400 can be configured to be worn on the recipient’s skin 530 over the apparatus 300 (e.g., on and / or behind a concha of the recipient). In certain implementations, the apparatus 300 is configured to be implanted over a substantially flat area of the skull that is configured to accommodate the increased lateral extent of the apparatus 300 due to the second and third MI antennas 330a, b (e.g., as compared to implementations without the second and third MI antennas 330a, b). In certain implementations, the first, second, and third coils 312, 332a, b are substantially planar, while in certain other implementations, at least one of the first, second, and third coils 312, 332a, b is substantially non-planar. For example, a brain stimulator implant can comprise an array of MI antennas 330 configured to be implanted beneath and following the curvature of the scalp or skull. Such an array of MI antennas 330 can be configured to provide a wireless and transcutaneous inductive communication link with an external coil 412 of a device 400 worn on the recipient’s head (e.g., in a cap).

[0046] In certain implementations, the apparatus 300 comprises a casing 305 (e.g., housing) configured to be implanted on or within a recipient’s body and containing the first MI antenna 310, the circuitry 320, and the array of MI antennas 330. The casing 305 can comprise an electrically insulative and biocompatible material (e.g., silicone rubber; polymer; polyether-etherketone (PEEK); ceramic; titanium oxide; glass; glycerine) and can be configured to be affixed to a bone surface 510 within the recipient (e.g., with the first antenna axis 314 substantially perpendicular to the bone surface 510). For example, the casing 305 can be configured to be positioned beneath the skin 530 and other tissue (e.g., fat and / or muscular 408 layers) and above and on the bone surface 510 in a portion of the recipient’s body (e.g., the head). The casing 305 can be substantially parallel to the bone surface 510 (e.g., schematically illustrated in FIG. 2A). In certain implementations, the casing 305 can be bent to be compatible with (e.g., conforms to; follows) a curvature of the bone surface 510, while in certain other implementations, the bone surface 510 can be altered (e.g., machined) to provide a portion with which the casing 305 is compatible. In certain implementations, the casing 305 can be configured to be affixed to the bone surface 510 using at least one biocompatible anchor, screw, or adhesive. The casing 305 of certain implementations is configured to hermetically seal the first MI antenna 310, the circuitry 320, and the array of MI antennas 330 from an environment surrounding the casing 305. The casing 305 can also be substantially transparent to the electromagnetic or magnetic fields between the apparatus 300 and the device 400 (e.g., such that the casing 305 does not substantially interfere with power transmission from the device 400 to the apparatus 300 and / or data transmission to and / or from the apparatus 300).

[0047] The device 400 can comprise a housing 405 (e.g., biocompatible; skinfriendly) and at least one external MI antenna 410 comprising at least one electrically conductive coil 412 configured to provide power and / or data to the apparatus 300 and / or to receive data from the apparatus 300 via magnetic induction. For example, the first MI antenna 310 and the array of MI antennas 330 can be configured to wirelessly transmit signals to and / or receive signals from the at least one external MI antenna 410 of the device 400 positioned outside the recipient’s skin 530 and over the apparatus 300 (e.g., to inductively receive power, data, and / or control signals transmitted transcutaneously from the device 400 and / or to transcutaneously transmit data and / or control signals to the device 400).

[0048] The circuitry 320 can be configured to receive power from the first MI antenna 310 and the array of MI antennas 330 and to receive and / or transmit data signals via the first MI antenna 310 and the array of MI antennas 330. For example, the circuitry 320 can comprise one or more active elements (e.g., stimulator unit 120; assembly 202; vibrating actuator) configured to deliver stimuli (e.g., stimulation signals) to a portion of the recipient’s body and / or to detect an attribute or condition of the recipient’s body. The circuitry 320 can be in electrical communication with the portion of the recipient’s body via electrical conduits 322 (e.g., electrode assembly 118; return electrode) in electrical communication with the circuitry 320 and extending from the casing 305 to a region of the recipient’s body. In certain implementations, the first MI antenna 310, the circuitry 320, and the array of MI antennas 330 are within the same casing 305 (see, e.g., FIGs. 2A-2B), while in certain other implementations, the circuitry 320 is in a first casing and the first MI antenna 310 and the array of MI antennas 330 are in a second casing that is attached to the first casing (e.g., electrically connected by at least one electrical conductor).

[0049] The circuitry 320 can comprise one or more microprocessors (e.g., application-specific integrated circuits; generalized integrated circuits programmed by software with computer executable instructions; microelectronic circuitry; microcontrollers) and at least one storage device (e.g., at least one tangible or non-transitory computer readable storage medium; read only memory; random access memory; flash memory) configured to store information (e.g., data; commands) accessed by the one or more microprocessors during operation. The at least one storage device can be encoded with software (e.g., a computer program downloaded as an application) comprising computer executable instructions for instructing the one or more microprocessors (e.g., executable data access logic, evaluation logic, and / or information outputting logic). In certain implementations, the one or more microprocessors execute the instructions of the software to provide functionality as described herein. The circuitry 320 can be configured to receive power signals, data signals, and / or control signals wirelessly communicated from the device 400 via the at least one external coil 412, the array of MI antennas 330 and the first MI antenna 310.

[0050] In certain implementations, the first coil 312 comprises a first electrically conductive wire wound around and substantially orthogonal to the first antenna axis 314, the second coil 332a comprises a second electrically conductive wire wound around andsubstantially orthogonal to the second antenna axis 334a, and the third coil 332b comprises a third electrically conductive wire wound around and substantially orthogonal to the third antenna axis 334b. The second coil 332a can be galvanically isolated (e.g., floating) from the third coil 332b or the second and third coils 332a, b can be connected in series with one another. The first coil 312, second coil 332a, and third coil 332b can each comprise a planar electrically conductive wire portion (e.g., platinum, gold, copper, or other metal; electrically insulated single-strand or multi-strand) with multiple windings and can each have a substantially circular, rectangular, spiral, oval, obround, fabiform, reniform, or other shape. For another example, the first coil 312, second coil 332a, and third coil 332b can each comprise metal traces on a printed circuit board that run (e.g., wind) around a corresponding antenna axis. The first coil 312, second coil 332a, and third coil 332b can each have a diameter, length, and / or width (e.g., along a lateral direction substantially parallel to the bone surface 510) less than or equal to 100 millimeters (e.g., in a range of 15 millimeters to 40 millimeters; in a range of 25 millimeters to 50 millimeters; in a range of less than 30 millimeters; in a range of 20 millimeters to 60 millimeters; in a range greater than 60 millimeters). The first coil 312, second coil 332a, and third coil 332b can be substantially co-planar with one another or can be substantially parallel to one another. The first coil 312, second coil 332a, and third coil 332b can be configured to inductively receive power, data, and / or control signals from the device 400 external to the recipient’s body and / or to inductively transmit data signals and / or control signals to the device 400.

[0051] In certain implementations, at least one of the first coil 312, second coil 332a, and third coil 332b has a fixed Q value, while in certain other implementations, at least one of the first coil 312, second coil 332a, and third coil 332b has an adjustable Q value (e.g., adjusted by corresponding Q-control circuitry). At least two of the first coil 312, second coil 332a, and third coil 332b can have the same size, shape, and / or number of coil turns, and / or at least two of the first coil 312, second coil 332a, and third coil 332b can have substantially different sizes, shapes, and / or numbers of coil turns.

[0052] In the example apparatus 300 shown by FIGs. 2A and 2B, the first coil 312 comprises a plurality of first loops (e.g., 2, 3, 4, or more) having substantially equal widths. As shown in FIG. 2B, the second coil 332a can comprise a plurality of second loops (e.g., 2, 3, 4, or more) having substantially equal widths and the third coil 332b can comprise a pluralityof third loops (e.g., 2, 3, 4, or more) having substantially equal widths. For example, the width of the first loops can be substantially equal to the width of the second loops and / or the third loops (see, e.g., FIG. 2B). For another example, the width of the first loops can be substantially different from the width of the second loops and / or from the width of the third loops. For another example, the widths of the second loops and the third loops can be substantially equal to one another or can be substantially different from one another.

[0053] While FIGs. 2A and 2B show the first MI antenna 310 comprising a substantially circularly shaped coil 312 and the array of MI antennas 330 comprising two substantially circularly shaped coils 332, other shapes of coils are also compatible with certain implementations described herein. FIG. 3A schematically illustrates another example first MI antenna 310 and example array of MI antennas 330 in accordance with certain implementations described herein. As shown in FIG. 3A, the first coil 312 can have a first spiral shape, the second coil 332a can have a second spiral shape, and the third coil 322b can have a third spiral shape. The number of coil turns of at least two of the first coil 312, second coil 322a, and third coil 322b can be substantially equal to one another and / or the number of coil turns of at least two of the first coil 312, second coil 322a, and third coil 322b can be substantially different from one another. The widths of at least two of the first, second, and third spiral shapes can be substantially equal to one another and / or the widths of at least two of the first, second, and third spiral shapes can be substantially different from one another.

[0054] FIG. 3B schematically illustrates another example first MI antenna 310 and example array of MI antennas 330 in accordance with certain implementations described herein. In FIG. 3B, the first coil 312 has a first reniform (e.g., kidney-shaped) shape, the second coil 332a has a second reniform shape, and the third coil 332b has a third reniform shape. The reniform shapes can be configured to account for expected misalignments (e.g., radial and angular misalignments) of the at least one external coil 422 relative to the first MI antenna 310. The dimensions of the first, second, and third reniform shapes can be substantially equal to one another or substantially different from one another. Certain implementations with reniform- shaped coils 312, 332a, 332b are particularly suited for use in magnet-free inductive links between the apparatus 300 and the device 400, since the reniform-shaped coils can substantially match the curvature of the device 400 while positioned behind the concha (e.g.,auricle 110) of the ear. Other shapes (e.g., rectangular; square; oblong; oval; obround; fabiform; jellybean) are also compatible with certain implementations described herein.

[0055] In certain implementations, the first coil 312 bounds a first area 316, the second coil 332a bounds a second area 336a, and the third coil 332b bounds a third area 336b, with the first area 316 partially overlapping the second area 336a and the third area 336b, and the second area 336a partially overlapping the third area 336b. For example, as shown in FIG. 2B, an outer perimeter of the first loops of the first coil 312 bounds a substantially circular first area 316, an outer perimeter of the second loops of the second coil 332b bounds a substantially circular second area 336a, and an outer perimeter of the third loops of the third coil 332b bounds a substantially circular third area 336b. For another example, as shown in FIG. 3A, an outer perimeter of the first spiral-shaped first coil 312 bounds a substantially circular first area 316, an outer perimeter of the second spiral-shaped second coil 332a bounds a substantially circular second area 336a, and an outer perimeter of the third spiral-shaped third coil 332b bounds a substantially circular third area 336b. In these examples, the first area 316 partially (e.g., not completely) overlaps the second and third areas 336a, b, and the second and third areas 336a, b partially (e.g., not completely) overlap one another.

[0056] In certain implementations (see, e.g., FIGs. 2A, 2B, 3A, and 3B), the array of MI antennas 330 comprising two coils 332, while in certain other implementations, the array of MI antennas 330 comprises three coils 332 in various configurations. FIG. 4 schematically illustrates a top view of an example array of MI antennas 330 with three coils 332 in accordance with certain implementations described herein. In addition to the second MI antenna 330a and the third MI antenna 330b, the array of MI antennas 330 of FIG. 4 comprises a fourth MI antenna 330c comprising an electrically conductive and substantially planar fourth coil 332c extending around and substantially orthogonal to a fourth antenna axis 334c, the fourth antenna axis 334c substantially parallel to the first antenna axis 314. The fourth coil 332c can be galvanically isolated (e.g., floating) from the second coil 332a and / or from the third coil 332b or the fourth coil 332c can be connected in series with at least one of the second and third coils 332a, b. The fourth coil 332c can have a fourth spiral shape (e.g., the same or different from the first, second, and / or third spiral shapes) or can comprise a plurality of fourth loops having substantially equal widths (e.g., the same or different from the loop widths of the first, second, and / or third coils 312, 332a, 332b). The fourth MI antenna 330c can have a non-zero fourthcoupling coefficient k4 with the first MI antenna 310, a fifth coupling coefficient ks with the second MI antenna 330a that is substantially equal to zero, and a sixth coupling coefficient with the third MI antenna 330b that is substantially equal to zero. While each of the coils 312, 332a-c of FIG. 4 has a substantially circular shape, other shapes (e.g., spiral) and other numbers of loops or coil turns are also compatible with certain implementations described herein.

[0057] As shown in FIG. 4, the first coil 312 can bound a first area 316, the second coil 332a can bound a second area 336a, the third coil 332b can bound a third area 336b, and the fourth coil 332c can bound a fourth area 336c. As shown in FIG. 4, the first area 316 can partially (e.g., not completely) overlap each of the second, third, and fourth areas 336a-c, the second area 336a can partially (e.g., not completely) overlap the third and fourth areas 336b, c, and the third area 336b can partially (e.g., not completely) overlap the fourth area 336c. Other configurations of the first, second, and third coils 312a,b,c are also compatible with certain implementations described herein.

[0058] The second coil 332a and third coil 332b of certain implementations partially overlap one another such that the second and third MI antennas 330a,b have a mutual coupling coefficient k that is substantially equal to zero. The substantially zero coupling corresponds to substantially no magnetic flux from one of the second and third coils 332a, b coupled to the other of the second and third coils 332a, b. FIG. 5 is a schematic plot of the mutual coupling coefficient k as a function of the normalized displacement d / R for example second and third coils 332a,b in accordance with certain implementations described herein. The example second and third coils 332a,b of FIG. 5 each comprises a plurality of substantially circular loops with an outer perimeter radius R and have centers 331a,b (e.g., at second and third antenna axes 334a, b) offset from one another by a distance d.

[0059] The mutual coupling coefficient k shown in FIG. 5 has the following characteristics:• When the second and third coils 332a, b are exactly on top of each other (e.g., d / R = 0), the mutual coupling coefficient k is at a maximum.• When the second and third coils 332a, b are laterally offset from one another (e.g., 0 < d / R < 2), the mutual coupling coefficient k is reduced monotonically through zero to small and negative values. In particular, when the second and third coils 332a, b do not overlap one another (e.g., d / R ~ 2), the mutual couplingcoefficient k is small and becomes smaller as the second and third coils 332a,b are further displaced (e.g., d / R > 2).• When the second and third coils 332a, b are relatively far apart (e.g., d / R » 1), the coupling coefficient k is negative, because the flux linkage is in the opposite sense as when the coils are relatively close together (e.g., d / R « 1). Furthermore, as the second and third coils 332a, b are further laterally offset from one another (e.g., d / R oo), the mutual coupling coefficient k approaches zero asymptotically from the negative side.• Since the mutual coupling coefficient k is positive at relatively small values of d / R and is negative at relatively large values of d / R, and there cannot be discontinuities in the magnetic flux coupling, the mutual coupling coefficient k is substantially equal to zero for a value of d / R which corresponds to the second and third coils 332a,b being approximately half-overlapped with one another.While FIG. 5 shows the mutual coupling coefficient k as a function of d / R for two example circular, loop-type second and third coils 332a,b, the mutual coupling coefficient k for other types of coils (e.g., spirals) and other shapes (e.g., kidney-shaped) have the same general characteristics described above and shown in FIG. 5, though the specific values of the mutual coupling coefficient k as a function of d / R and the value of d / R at which the mutual coupling coefficient k is substantially equal to zero can be different than those in FIG. 5. For any pair of substantially coplanar or substantially parallel coils 332 of any shape (e.g., same shapes as one another; different shapes as one another), the coils 332 can be configured to have substantially zero mutual coupling, which is a result of the absence of magnetic monopoles (V ■ B = 0).

[0060] FIG. 6 schematically illustrates an example inductive link between the apparatus 300 and the device 400 in accordance with certain implementations described herein. The apparatus 300 has the first coil 312 galvanically coupled (e.g., wired) to the circuitry 320 and the second and third coils 332a, b galvanically isolated (e.g., floating) from the first coil 312 and the circuitry 320 and galvanically isolated from one another. The device 400 has a coil 412 galvanically coupled to circuitry 420 of the device 400. The dashed vertical line of FIG. 6 denotes the skin surface (e.g., the apparatus 300 is implanted below the skin surface and the device 400 is worn on the skin surface). The first coil 312 is inductively coupled toeach of the second and third coils 332a, b and to the coil 412 of the device 400. The coil 412 of the device 400 is also inductively coupled to each of the second and third coils 332a, b. The second and third coils 332a, b are positioned such that their mutual inductance is substantially equal to zero.

[0061] In certain implementations, the first, second, and third coils 312, 332a, b are substantially coplanar with one another, while in certain other implementations, the first coil 312 is substantially parallel with both the second and third coils 332a, b and is offset from the second and third coils 332a, b in a direction substantially perpendicular to the first coil 312 (e.g., the first coil 312 farther from or closer to the skin surface than are the second and third coils 332a, b). In certain implementations, the second and third coils 332a, b are substantially coplanar with one another, while in certain other implementations, the second and third coils 332a, b are substantially parallel with one another and are offset from one another in a direction substantially perpendicular to the second and third coils 332a, b (e.g., the second coil 332a farther from or closer to the skin surface than is the third coil 332b).

[0062] The first coil 312 has a first inductance Lwiand a first capacitance Cwi, the second coil 332a has a second inductance Lp and a second capacitance Cp, and the third coil 332b has a third inductance Lp and a third capacitance Cp. For simplicity and ease of tuning, each of the first, second, and third coils 312, 332a, b can have the same inductance value (e.g., Lwi= Lp = Lp = Li), however, in other implementations, at least two of these inductance values can differ from one another. The first coil 312 of the apparatus 300 and the coil 412 of the device 400 can have a coupling coefficient ko. In addition, the first coil 312 can have a coupling coefficient ki with the second coil 332a and a coupling coefficient fo with the third coil 332b, and the coil 412 can have a coupling coefficient kawith the second coil 332a and a coupling coefficient kb with the third coil 332b. For simplicity, the coupling coefficients of the first coil 312 with each of the second and third coils 332a, b can be substantially equal to one another (e.g., ki = k2) and the coupling coefficients of the coil 412 with each of the second and third coils 332a, b can be substantially equal to one another (e.g., ka= kb). However, in other implementations, coupling coefficients ki and fo differ from one another and / or coupling coefficients kaand kb differ from one another.

[0063] In certain implementations, the first, second, and third coils 312, 332a, b are each tuned to a common resonance frequency a>c. For example, with Lwi= Lp = Lp = L,Cwi= Cfi = Cf2 = C, ki = fa, and substantially zero coupling between the second and third coils 332a, b, the resonance frequency a>ccan equal 1 / h * C by having the tuning capacitance (e.g., resonant capacitance) of the first coil 312 CW1= C / (l + 2 ■ k^, and the tuning capacitances of each of the second and third coils 332a, b=2= C / (l + k^. In general, for N substantially similar coils 332 that are galvanically isolated from the first coil 312, the tuning capacitance of the first coil 312 can be CW1= C / (l + N ■ k-^. In certain implementations having substantially equally sized and substantially circular coils 332, / V is equal to one, two, or three. For example (see, e.g., FIG. 4), three substantially equally sized substantially circular coils 332a-c can be positioned in a null-coupling arrangement (e.g., a mutual inductance between each pair of the coils 332a-c substantially equal to zero) with the antenna axes 334a- c of the coils 332a-c arranged in an equilateral triangle, while each of the coils 332a-c has a non-zero coupling coefficient with the first coil 312 (e.g., having the antenna axis 314 at the center of the equilateral triangle). For more than three coils 332, either some pair of coils 332 will have a substantially non-zero coupling to each other or some coil 332 will not be substantially coupled to the first coil 312.

[0064] FIG. 7 schematically illustrates inductive coupling between example first, second, and third coils 312, 332a,b and the coil 412 in accordance with certain implementations described herein. In the top portion of FIG. 7, the first coil 312, the second coil 332a, and the third coil 332b are substantially circular coils with substantially equal coil radii R and that are substantially coplanar with one another. The second and third coils 332a,b are equally offset from the first coil 312 in opposite directions (e.g., by ±R / 2) substantially parallel to the first coil 312 and are offset from one another by the coil radius R. As a result of the offset between the second and third coils 332a, b, their mutual coupling coefficient is substantially equal to zero (see, e.g., FIG. 5) and as a result of the offset between the first coil 312 and each of the second and third coils 332a,b, the coupling coefficients fa and fa between the first coil 312 and each of the second and third coils 332a, b, respectively, is approximately 0.5 (see, e.g., FIG. 5).

[0065] The bottom portion of FIG. 7 schematically illustrates the coupling coefficient of the coil 412 of the device 400 to each of the first, second, and third coils 312, 332a, b at various positions relative to the first, second, and third coils 312, 332a, b. With only the first coil 312, the coupling coefficient fa of the coil 412 to the first coil 312 drops significantly once the coil 412 is misaligned from the first coil 312 by an offset of ±3R / 2 andcan be substantially equal to zero when the offset is ±R. However, with the second and third coils 332a, b, the coil 412 at these large offsets (e.g., ±R; ±3R / 2) can have stronger coupling to the first coil 312 by virtue of the indirect coupling provided by the second and third coils 332a, b between the coil 412 and the first coil 312. For example, the coil 412 can have a non-zero coupling coefficient kawith the second coil 332a and the second coil 332a can have a coupling coefficient of 0.5 with the first coil 312, resulting in a coupling coefficient of 0.5Z:« between the coil 412 and the first coil 312.

[0066] The galvanically isolated array of MI antennas 330 can provide aggregate coupling between the coil 412 and the first coil 312 that is significantly improved over a wider range of misalignments between the coil 412 and the first coil 312. For example, without the floating second and third coils 332a,b, the power transfer efficiency across the link between the first coil 312 and the coil 412 is halved by an offset of +R / 2 between the first coil 312 and the coil 412, and is reduced to close to zero by an offset of ±7? (e.g., rendering the link useless). However, with the floating second and third coils 332a, b, the power transfer efficiency is substantially unchanged by an offset of +R / 2 between the first coil 312 and the coil 412 and maintains a significant strength despite an offset of +R. For another example, three floating coils (e.g., second, third, and fourth coils 332a-c) arranged in a substantially equilateral triangle configuration (see, e.g., FIG. 4) can improve the power transfer efficiency for two-dimensional misalignments between the first coil 312 and the coil 412. The second and third coils 332a, b can both be substantially coplanar the first coil 312 or the second and third coils 332a, b can be substantially coplanar with one another and offset from the first coil 312 in a direction substantially perpendicular to the first coil 312 while maintaining a coupling coefficient to the first coil 312 (e.g., ki < 0.5; fe < 0.5).

[0067] FIG. 8 schematically illustrates another example inductive link between the apparatus 300 and the device 400 in accordance with certain implementations described herein. The apparatus 300 has the first coil 312 galvanically coupled (e.g., wired) to the circuitry 320 and the second and third coils 332a, b galvanically isolated (e.g., floating) from the first coil 312 and the circuitry 320. The second and third coils 332a, b galvanically coupled to one another (e.g., in series) such that the induced voltages in the second and third coils 332a, b add to one another. As in the example inductive link of FIG. 6, the coil 412 is galvanically coupled to circuitry 420 of the device 400, the first coil 312 is inductively coupled to each of the secondand third coils 332a, b (e.g., with coupling coefficients ki , ki) and to the coil 412 (e.g., with a coupling coefficient ko), the coil 412 is inductively coupled to each of the second and third coils 332a, b (e.g., with coupling coefficients ka, kb), and the second and third coils 332a, b are positioned such that their mutual inductance is substantially equal to zero. A common tuning capacitor = C / (2 ■ (1 + k^, can be used (e.g., with capacitance C equal to about 0.5C / 1 or 0.5C / 2 of FIG. 6) and common Q-control circuitry (not shown) can be used to adjust the Q values of both the second and third coils 332a, b.

[0068] The apparatus 300 can further comprise Q-control circuitry 340 (e.g., switches; digital controls) configured to control (e.g., adjust) the Q values of the array of MI antennas 330. FIG. 9 schematically illustrates an example Q-control circuitry 340 in accordance with certain implementations described herein. The Q-control circuitry 340 can be configured to adjust capacitances of tuning capacitors (e.g., Ci Cp', Cf) and / or resistances of tuning resistors (e.g., Rfp Rp-, Rf) of the second and third coils 332a, b. The Q-control circuitry 340 can be galvanically isolated from the circuitry 320 (e.g., by isolation capacitors CiSOi, CiSO2', optocoupler) such that the Q-control circuitry, the tuning capacitors, and tuning resistors do not represent additional DC or AC current paths into the implant electronics (e.g., in case of body fluids contacting external wire portions at a feedthrough area). For a power-only link, the Q-control circuitry 340 can maximize the Q values which can be dependent on the winding resistances of the coils (e.g., largely set by geometry and choice of wire metal). For a power / data link, the Q-control circuitry 340 can set the Q values to intermediate values (e.g., by using a calculated resistance on each of the second and third coils 332a, b) that provides a satisfactory tradeoff between power and data transfer. The Q adjustments can be made dynamically (e.g., to switch between power transfer optimization and data transfer optimization).

[0069] In certain implementations, as schematically illustrated by FIGs. 2A, 2B, 4, 6, and 8, the apparatus 300 that comprises the array of MI antennas 330 (e.g., both the second and third coils 332a, b) that are galvanically isolated from the first MI antenna 310 and the circuitry 320 is the implanted portion of a stimulation or measurement system (e.g., transcutaneous system; auditory prosthesis system) that is configured to be in wireless communication with a portion of the stimulation or measurement system (e.g., the device 400) external to the recipient’s body. In certain other implementations, the external device 400 (e.g.,configured to be worn on the recipient’s skin 530 over the implanted portion) comprises an array of MI antennas 430 galvanically isolated from a first MI antenna 410 and the circuitry 420 of the device 400. The array of MI antennas 430 can be configured as described herein with regard to the implanted array of MI antennas 330 and can facilitate wireless and transcutaneous power and / or data transfer to the apparatus 300 and / or to receive data from the apparatus 300 via magnetic induction with the first MI antenna 310 of the apparatus 300.

[0070] FIGs. 10A and 10B schematically illustrate top views of two example devices 400 in accordance with certain implementations described herein. The device 400 comprises a first MI antenna 410 comprising an electrically conductive and substantially planar first coil 412 extending around and substantially orthogonal to a first antenna axis (not shown). The device 400 further comprises circuitry 420 in electrical communication with the first MI antenna 410, the circuitry 420 configured to provide electrical current to the first MI antenna 410 and / or to receive electrical current from the first MI antenna 410. The device 400 further comprises an array of MI antennas 430 galvanically isolated from the first MI antenna 410 and the circuitry 420. The array of MI antennas 430 comprises at least a second MI antenna 430a and a third MI antenna 430b. The second MI antenna 430a comprises an electrically conductive and substantially planar second coil 432a extending around and substantially orthogonal to a second antenna axis (not shown) substantially parallel to the first antenna axis, and the second MI antenna 430a has a non-zero first coupling coefficient ki with the first MI antenna 410. The third MI antenna 430b comprises an electrically conductive and substantially planar third coil 432b extending around and substantially orthogonal to a third antenna axis (not shown) substantially parallel to the first antenna axis, and the third MI antenna 430b has a non-zero second coupling coefficient fa with the first MI antenna 410 and a third coupling coefficient fa with the second MI antenna 430a that is substantially equal to zero.

[0071] In certain implementations, the first MI antenna 410, the circuitry 420, and the array of MI antennas 430 are within the housing 405 (e.g., in a region bounded by an inner surface of the housing 405), while in certain other implementations, at least one MI antenna 430 of the array of MI antennas 430 is outside the housing 405 (e.g., on an outside surface of the housing 405). For example, the at least one MI antenna 430 outside the housing 405 can be affixed to the housing 405 by an adhesive layer (e.g., glue). The at least one MI antenna 430 outside the housing 405 can be configured to be removed from a first position on theoutside of the housing 405 and repositioned to a second position on the outside of the housing 405 where the at least one MI antenna 430 better facilitates improved coupling between the first MI antenna 410 and the implanted portion (e.g., apparatus 300).

[0072] FIG. 10C is a flow diagram of an example method 600 for fabricating a device 400 in accordance with certain implementations described herein. While the method 600 is described by referring to some of the structures of the example devices 400 of FIGs. 10A-10B, other apparatus and systems with other configurations of components can also be used to perform the method 600 in accordance with certain implementations described herein.

[0073] In an operational block 610, the method 600 comprises providing a first MI antenna 410 within a housing 405. In an operational block 620, the method 600 further comprises attaching a second MI antenna 430a to the housing 405. The second MI antenna 430a is electrically floating relative to the first MI antenna 410 and has a non-zero mutual inductance with the first MI antenna 410. In an operational block 630, the method 600 further comprises attaching a third MI antenna 430b to the housing 405. The third MI antenna 430b is electrically floating relative to the first MI antenna 410 and has a non-zero mutual inductance with the first MI antenna 410. The third MI antenna 430b has a substantially zero mutual inductance with the second MI antenna 430a.

[0074] In certain implementations, the first MI antenna 410 comprises a substantially planar first coil 412 (e.g., having a first size and shape and comprising a first number of coil turns), the second MI antenna 430a comprises a substantially planar second coil 432a (e.g., having a second size and shape and comprising a second number of coil turns), and the third MI antenna 430b comprises a substantially planar third coil 432b (e.g., having a third size and shape and comprising a third number of coil turns). Attaching the second MI antenna 430a can comprise placing the second MI antenna 430a to be substantially parallel to the first MI antenna 410, and attaching the third MI antenna 430b can comprise placing the third MI antenna 430b to be substantially parallel to the first MI antenna 410. At least two of the first number of coil turns, the second number of coil turns, and the third number of coil turns can be substantially equal one another. At least two of the first size and shape, the second size and shape, and the third size and shape can be substantially equal to one another.

[0075] For example, attaching the second MI antenna 430a can comprise placing the second MI antenna 430a (e.g., the second coil 432a) on an outside surface of the housing405 and attaching the third MI antenna 430b can comprise placing the third MI antenna 430b (e.g., the third coil 432b) on the outside surface of the housing 405. The second and third MI antennas 430a, b can each comprise an adhesive layer configured to hold the respective second and third coil 432a, b on the outside surface of the housing 405. The adhesive layer can be further configured to allow the respective second or third coil 432a, b to be repeatedly removed from the outer surface and reaffixed to the outer surface at a different position (e.g., a position providing improved coupling to the apparatus 300 as compared to the coupling at the initial position).

[0076] In certain implementations, the method 600 further comprises attaching a fourth MI antenna 430c to the housing 405, the fourth MI antenna 430c electrically floating relative to the first MI antenna 410 and having a non-zero mutual inductance with the first MI antenna 410 and a substantially zero mutual inductance with the second MI antenna 430a and the third MI antenna 430b. For example, attaching the fourth MI antenna 430c can comprise placing the fourth MI antenna 430c on an outside surface of the housing 405. In certain implementations, the fourth MI antenna 430c comprises a substantially planar fourth coil 432c (e.g., having a fourth size and shape and comprising a fourth number of coil turns), and attaching the fourth MI antenna 430c comprises placing the fourth MI antenna 430c to be substantially parallel to the first MI antenna 410.

[0077] In certain implementations, the apparatus 300 comprises at least one of the galvanically isolated MI antennas 330, 430 and the device 400 comprises at least one other of the galvanically isolated MI antennas 330, 430. The at least one MI antenna 330 can be galvanically isolated from the first MI antenna 310 and the circuitry 320, and the at least one other MI antenna 430 can be galvanically isolated from the first MI antenna 410 and the circuitry 420. FIG. 11 schematically illustrates an example inductive link between the apparatus 300 and the device 400 in which the apparatus 300 comprises a floating MI antenna coil 332 and the device 400 comprises a floating MI antenna coil 432 in accordance with certain implementations described herein. The mutual inductive coupling between the two floating MI antenna coils 332, 432 can be substantially equal to zero. The inductance Lp of the coil 332 can be substantially equal to the inductance Lwiof the coil 312 and the inductance Lp of the coil 432 can be substantially equal to the inductance LW2 of the coil 412. The tuningcapacitances Cfi, Cf2 can be adjusted (e.g., by corresponding Q-control circuitry) to implement the tuned frequencies for the apparatus 300 and the device 400, respectively.

[0078] FIG. 12 schematically illustrates an example inductive link between the apparatus 300 and the device 400 in which the apparatus 300 comprises second and third coils 332a, b and the device 400 comprises second and third coils 432a, b in accordance with certain implementations described herein. The two coupling coefficients (ki ; fa) between the first coil 312 and the two floating coils 332a, b can be substantially equal to one another, and the two coupling coefficients (fa; fa) between the first coil 412 and the two floating coils 432a, b, can be substantially equal to one another. There are nine coupling coefficients (ko kakb kckd kekf, kgkh) between the coils 312, 332a, b of the apparatus 300 and the coils 412, 432a, b of the device 400. The two floating coils 332a, b are positioned relative to one another such that the mutual coupling coefficient is substantially equal to zero and the two floating coils 432a, b are positioned relative to one another such that the mutual coupling coefficient is substantially equal to zero. In certain implementations, one or both of the apparatus 300 and the device 400 each comprises up to three MI antennas that are galvanically isolated (e.g., floating) from the corresponding first MI antenna 310, 410 and circuitry 320, 420.

[0079] In certain implementations, as shown in FIGs. 2A-2B, the apparatus 300 does not comprise a magnetic element within the casing 305 that is configured to generate a magnetic force with the device 400 to hold the device 400 on the recipient’s body (e.g., a magnet-free link). In certain other implementations, the apparatus 300 does comprise a magnetic element within the casing 305 (e.g., the magnetic element hermetically sealed within the casing 305). For example, the magnetic element can comprise at least one magnetic material (e.g., ferromagnetic; ferrimagnetic; permanent magnet; diamagnetic magnet) and can have a substantially planar shape (e.g., disk; plate; substantially circular, oval, or rectangular). The magnetic element can be configured to generate a magnetic force with sufficient strength to hold the device 400 on or over the skin 530 of the recipient above the apparatus 300 such that the coil 412 is in operative wireless communication with the array of MI antennas 330 to wirelessly and transcutaneously transfer energy from the device 400 to the apparatus 300 (e.g., via magnetic induction; via a radio-frequency or RF link).

[0080] In certain implementations, the first, second, and third coils 312, 332a, b extend in one or two lateral directions across a two-dimensional region that is larger than theregion covered by the first coil 312 alone. The array of MI antennas 330 galvanically isolated from the first MI antenna 310 can provide sufficient coupling to the at least one external coil 412 of the device 400 (e.g., a Behind-The-Ear unit) over a substantially larger range of positions of the at least one external coil 412 than can the single first coil 312 alone which can facilitate use in a magnet-free link between the apparatus 300 and the device 400. For example, the coils 332 of the array of MI antennas 330 can be arranged to overlap one another and the first MI antenna 310 while covering a total area larger than an area covered by the first MI antenna 310 alone. The first MI antenna 310 and the array of MI antennas 330 can bound substantially planar regions through which magnetic flux from the device 400 extends in a direction non-parallel to the regions. With the larger total area covered by the array of MI antennas 330, the apparatus 300 can tolerate larger movements and / or misalignments of the coil 412 of the external device 400 than can be tolerated using the first MI antenna 310 alone (e.g., movements / misalignments that may result from not having an attractive magnetic force holding the device 400 in place). At least one of the second and third coils 332a, b can provide sufficient coupling with the coil 412 of the external device 400 to produce an operable wireless transcutaneous communication link between the apparatus 300 and the external device 400 in view of a movement and / or misalignment of the coil 412.

[0081] In certain implementations, the first MI antenna 310 and the array of MI antennas 330 comprise coils with substantially the same shape or geometry as one another, substantially the same number of coil turns as one another, and substantially the same coil type (e.g., loop-type; spiral-type) as one another. While having the first, second, and third coils 312, 332a, b substantially identical to one another can simplify the overall design of the apparatus 300 and can be easier to model the performance of the apparatus 300, in certain other implementations, the first MI antenna 310 and the array of MI antennas 330 comprise coils that have substantial variations in shape or geometry, type, and / or number of turns from one another. For example, the size, shape, and / or number of coil turns can vary across the array of MI antennas 330 (e.g., to increase aggregate coupling in predetermined locations by having more coil turns in the nearby coils 332). For polar array distributions (e.g., for magnet-free links), the coils 332 at larger radii can have larger lengths such that the coils 332 cover the same angle of arc. Certain such implementations can improve coil overlapping while maintaining substantially zero magnetic inductive coupling between the coils 332.

[0082] Although commonly used terms are used to describe the systems and methods of certain implementations for ease of understanding, these terms are used herein to have their broadest reasonable interpretations. Although various aspects of the disclosure are described with regard to illustrative examples and implementations, the disclosed examples and implementations should not be construed as limiting. Conditional language, such as, among others, "can," "could," "might," or "may," unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain implementations include, while other implementations do not include, certain features, elements and / or steps. Thus, such conditional language is not generally intended to imply that features, elements and / or steps are in any way required for one or more implementations or that one or more implementations necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and / or steps are included or are to be performed in any particular implementation. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a nonexclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

[0083] It is to be appreciated that the implementations disclosed herein are not mutually exclusive and may be combined with one another in various arrangements. In addition, although the disclosed methods and apparatuses have largely been described in the context of various devices, various implementations described herein can be incorporated in a variety of other suitable devices, methods, and contexts. More generally, as can be appreciated, certain implementations described herein can be used in a variety of implantable medical device contexts that can benefit from certain attributes described herein.

[0084] Language of degree, as used herein, such as the terms “approximately,” “about,” “generally,” and “substantially,” represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” “generally,” and “substantially” may refer to an amount that is within ± 10% of, within ± 5% of, within ± 2% of, within ± 1 % of, or within ± 0.1% of the stated amount. As another example, the terms “generally parallel” and “substantially parallel” refer to a value, amount, or characteristic thatdeparts from exactly parallel by ± 10 degrees, by ± 5 degrees, by ± 2 degrees, by ± 1 degree, or by ± 0.1 degree, and the terms “generally perpendicular” and “substantially perpendicular” refer to a value, amount, or characteristic that departs from exactly perpendicular by ± 10 degrees, by ± 5 degrees, by ± 2 degrees, by ± 1 degree, or by ± 0.1 degree. The ranges disclosed herein also encompass any and all overlap, sub-ranges, and combinations thereof. Language such as “up to,” “at least,” “greater than,” less than,” “between,” and the like includes the number recited. As used herein, the meaning of “a,” “an,” and “said” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “into” and “on,” unless the context clearly dictates otherwise.

[0085] While the methods and systems are discussed herein in terms of elements labeled by ordinal adjectives (e.g., first, second, etc.), the ordinal adjective are used merely as labels to distinguish one element from another (e.g., one signal from another or one circuit from one another), and the ordinal adjective is not used to denote an order of these elements or of their use.

[0086] The invention described and claimed herein is not to be limited in scope by the specific example implementations herein disclosed, since these implementations are intended as illustrations, and not limitations, of several aspects of the invention. Any equivalent implementations are intended to be within the scope of this invention. Indeed, various modifications of the invention in form and detail, in addition to those shown and described herein, will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the claims. The breadth and scope of the invention should not be limited by any of the example implementations disclosed herein but should be defined only in accordance with the claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. An apparatus comprising: a first magnetic induction (MI) antenna comprising an electrically conductive first coil extending around and substantially orthogonal to a first antenna axis; circuitry in electrical communication with the first MI antenna, the circuitry configured to provide electrical current to the first MI antenna and / or to receive electrical current from the first MI antenna; and an array of MI antennas galvanically isolated from the first MI antenna and the circuitry, the array comprising at least: a second MI antenna comprising an electrically conductive second coil extending around and substantially orthogonal to a second antenna axis substantially parallel to the first antenna axis, the second MI antenna having a non-zero first coupling coefficient with the first MI antenna; and a third MI antenna comprising an electrically conductive third coil extending around and substantially orthogonal to a third antenna axis substantially parallel to the first antenna axis, the third MI antenna having a non-zero second coupling coefficient with the first MI antenna and a third coupling coefficient with the second MI antenna that is substantially equal to zero.

2. The apparatus of claim 1, wherein the first coil comprises a first wire wound around and substantially orthogonal to the first antenna axis, the second coil comprises a second wire wound around and substantially orthogonal to the second antenna axis, and the third coil comprises a third wire wound around and substantially orthogonal to the third antenna axis.

3. The apparatus of claim 1 or claim 2, wherein the first coil has a first spiral shape, the second coil has a second spiral shape, and the third coil has a third spiral shape.

4. The apparatus of any preceding claim, wherein the first coil comprises a plurality of first loops having substantially equal widths, the second coil comprises a plurality of second loops having substantially equal widths, and the third coil comprises a plurality of third loops having substantially equal widths.

5. The apparatus of any preceding claim, wherein the first coil bounds a first area, the second coil bounds a second area, and the third coil bounds a third area, the first area partially overlapping the second area and the third area, the second area partially overlapping the third area.

6. The apparatus of any preceding claim, wherein the second coil is galvanically isolated from the third coil.

7. The apparatus of any preceding claim, wherein the array of MI antennas further comprises a fourth MI antenna comprising an electrically conductive fourth coil extending around and substantially orthogonal to a fourth antenna axis, the fourth antenna axis substantially parallel to the first antenna axis, wherein the fourth MI antenna has a non-zero fourth coupling coefficient with the first MI antenna, a fifth coupling coefficient with the second MI antenna that is substantially equal to zero, and a sixth coupling coefficient with the third MI antenna that is substantially equal to zero.

8. The apparatus of claim 7, wherein the first coil bounds a first area, the second coil bounds a second area, the third coil bounds a third area, and the fourth coil bounds a fourth area, the first area partially overlapping the second area, the third area, and the fourth area, the second area partially overlapping the third area and the fourth area, and the third area partially overlapping the fourth area.

9. The apparatus of claim 7 or claim 8, wherein the fourth coil has a fourth spiral shape or comprises a plurality of fourth loops having substantially equal widths.

10. The apparatus of any of claims 7 to 9, wherein the fourth coil is galvanically isolated from the second coil and / or from the third coil.

11. The apparatus of any preceding claim, further comprising a casing containing the first MI antenna, the casing configured to be implanted device within a recipient’s body affixed to a bone surface with the first, second, and third antenna axes substantially perpendicular to the bone surface.

12. The apparatus of claim 11, wherein the first MI antenna and the array of MI antennas are configured to wirelessly transmit signals to and / or receive signals from a device external to the recipient’s body.

13. The apparatus of claim 12, wherein the first MI antenna and the array of MI antennas bound substantially planar regions through which magnetic flux from the device extends in a direction non-parallel to the regions.

14. The apparatus of claim 13, wherein the apparatus is an implantable portion of an acoustic prosthesis system configured to be positioned behind a pinna of the recipient and the bone surface comprises a skull surface.

15. A method comprising: providing a first MI antenna within a housing; attaching a second MI antenna to the housing, the second MI antenna electrically floating relative to the first MI antenna and having a non-zero mutual inductance with the first MI antenna; and attaching a third MI antenna to the housing, the third MI antenna electrically floating relative to the first MI antenna and having a non-zero mutual inductance with the first MI antenna, the third MI antenna having a substantially zero mutual inductance with the second MI antenna.

16. The method of claim 15, wherein said attaching the second MI antenna comprising placing the second MI antenna on an outside surface of the housing and attaching the third MI antenna comprising placing the third MI antenna on the outside surface of the housing.

17. The method of claim 15 or claim 16, wherein the first MI antenna comprises a substantially planar first coil, the second MI antenna comprises a substantially planar second coil, and the third MI antenna comprises a substantially planar third coil, said attaching the second MI antenna comprising placing the second MI antenna to be substantially parallel to the first MI antenna, and said attaching the third MI antenna comprising placing the third MI antenna to be substantially parallel to the first MI antenna.

18. The method of any of claims 15 to 17, wherein the first MI antenna comprises a first number of coil turns, the second MI antenna comprises a second number of coil turns, and the third MI antenna comprises a third number of coil turns, at least two of the first number, second number, and third number equal to one another.

19. The method of any of claims 15 to 18, wherein the first MI antenna comprises a first coil with a first size and shape, the second MI antenna comprises a second coil with a second size and shape, and the third MI antenna comprises a third coil with a third size and shape, at least two of the first size and shape, the second size and shape, and the third size and shape substantially equal to one another.

20. The method of any of claims 15 to 19, further comprising attaching a fourth MI antenna to the housing, the fourth MI antenna electrically floating relative to the first MI antenna and having a non-zero mutual inductance with the first MI antenna, the fourth MI antenna having a substantially zero mutual inductance with the second MI antenna and the third MI antenna.

21. The method of claim 20, wherein said attaching the fourth MI antenna comprises placing the fourth MI antenna on an outside surface of the housing.

22. The method of claim 20 or claim 21 , wherein the first MI antenna comprises a substantially planar first coil and the fourth MI antenna comprises a substantially planar fourth coil, said attaching the fourth MI antenna comprising placing the fourth MI antenna to be substantially parallel to the first MI antenna.

23. An apparatus comprising: an electrically conductive and substantially planar first coil; circuitry in electrical communication with the first coil; and a plurality of electrically conductive and substantially planar second coils electrically isolated from the circuitry and the first coil, the plurality of second coils substantially parallel to one another and substantially parallel to the first coil, the plurality of second coils having substantially zero magnetic inductive coupling to one another.

24. The apparatus of claim 23, wherein the first coil comprises a plurality of substantially coplanar coil loops and the second coils are substantially coplanar with one another.

25. The apparatus of claim 23 or claim 24, wherein the first coil overlaps the plurality of second coils.

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