Implantable medical device including wireless power transmission

Abstract

A system includes an implantable medical device and an external charger. The implantable medical device includes a power element and a wireless receiver to receive power to charge the power element. The external charger includes a wireless transmitter to transmit the power to the wireless receiver of the implantable medical device.

Description

Background [0001 ] A significant portion of the population suffers from various forms of sleep-related issues, some of which may involve sleep disordered breathing (SDB) and / or other conditions. In some patients, external breathing therapy devices and / or mere surgical interventions may fail to treat the sleep disordered breathing behavior. Brief Description of the Drawings

[0002] FIG. 1A is a diagram schematically representing an example method and / or example device in relation to a target tissue.

[0003] FIG. 1B is a diagram including a front view schematically representing a patient’s body including example implantable components and example external elements of example methods and / or example devices.

[0004] FIG. 1C is a block diagram of a control portion.

[0005] FIGS. 2A-2C are block diagrams schematically representing example systems including an implantable medical device (IMD) and an external charger.

[0006] FIGS. 3A-3D are diagrams schematically representing example IMDs including a wireless communication portion.

[0007] FIG. 4 is a diagram schematically representing an example antenna including three orthogonal coils that may be configured to receive wireless power.

[0008] FIG. 5 is a cross-sectional view schematically representing an example antenna including a coil arranged around a power element that may be configured to receive wireless power.

[0009] FIG. 6 is a cross-sectional view schematically representing an example antenna including a coil arranged around an interior of a housing that may be configured to receive wireless power.

[0010] FIG. 7 is a cross-sectional view schematically representing an example system including an IMD and an external charging pad that may be configured to wirelessly transmit power to the IMD.

[0011] FIG. 8 is a top view schematically representing an example array of coil structures that may be configured to wirelessly transmit power to an IMD.

[0012] FIG. 9 is a cross-sectional view schematically representing an example external charging pad that may be configured to wirelessly transmit power to an IMD.

[0013] FIG. 10 is a top view schematically representing an example patterned backing shield that may be part of an external charger.

[0014] FIG. 11 is a top view schematically representing an example metamaterial backing shield that may be part of an external charger.

[0015] FIGS. 12A-12D are diagrams schematically representing example coil structures that may be part of a wireless charger.

[0016] FIGS. 13A-13D are top views schematically representing example coil arrangements of an external charger.

[0017] FIG. 14 is a top view schematically representing an array of coil structures divided into subsets of coil structures.

[0018] FIGS. 15Aand 15B are diagrams schematically representing an example external charger including a radio frequency (RF) transmitter that may be configured to wirelessly transmit power to an IMD via far-field RF wireless power transfer.

[0019] FIGS. 16A and 16B are side views schematically representing example external chargers that may be configured to wirelessly transmit power to an IMD via far-field RF wireless power transfer.

[0020] FIGS. 17A-17E and diagrams schematically representing example antennas that may be configured to wirelessly transmit power to an IMD via far-field RF wireless power transfer.

[0021] FIG. 18 is a diagram schematically representing an example double negative metamaterial (DNG) that may be used in combination with an antenna within an IMD to form a DNG antenna.

[0022] FIGS. 19A-19E are top views schematically representing example unit cells of artificial magnetic conductor (AMO) metamaterials that may be used in combination with an antenna within an I MD to form a metamaterial antenna.

[0023] FIGS. 20A and 20B are a top view and a cross-sectional view, respectively, schematically representing an example AMC backing that may be used in combination with an antenna structure to form a metamaterial antenna.

[0024] FIG. 21 is a cross-sectional view schematically representing an example antenna arrangement including an antenna aligned with an AMC backing.

[0025] FIG. 22 is a top view schematically representing an example antenna arrangement including a patch antenna with a surrounding AMC metamaterial.

[0026] FIGS. 23A and 23B are a top view and a side view, respectively, schematically representing an example antenna arrangement including a patch antenna with AMC metamaterial beneath the patch antenna.

[0027] FIG. 24 is a top view schematically representing an example antenna arrangement including a patch antenna with AMC metamaterial beneath the patch antenna.

[0028] FIG. 25 is a diagram schematically representing an indoor environment including potential example locations for a wireless transmitter of an external charger for transmitting power to an I MD within a patient via far-field RF wireless power transfer.

[0029] FIGS. 26A and 26B are diagrams schematically representing a wireless transmitter and example reflective sheets for wirelessly transmitting power to an IMD of a patient in a bed.

[0030] FIG. 27 is a top view schematically representing an example array of sensors for sensing the location, position, and / or posture of a patient on a bed.

[0031] FIGS. 28A-28K are flow diagrams schematically representing example methods for wirelessly transmitting power to a power element of an IMD.

[0032] FIGS. 29A-29F are flow diagrams schematically representing example methods for wirelessly transmitting power to a power element of an IMD.

[0033] FIG. 30 is a flow diagram schematically representing an example method for wirelessly transmitting power to a power element of an IMD.

[0034] FIG. 31 is a diagram schematically representing an example IMD and a patch on the skin of a patient used to locate the IMD.

[0035] FIGS. 32A and 32B are block diagrams schematically representing example control portions.

[0036] FIG. 33 is a block diagram schematically representing an example user interface.

[0037] FIG. 34 is a block diagram schematically representing example communication arrangements between an IMD and external devices. Detailed Description

[0038] In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized, and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense. It is to be understood that features of the various examples described herein may be combined, in part or whole, with each other, unless specifically noted otherwise.

[0039] At least some examples of the present disclosure are directed to devices for diagnosis, therapy, and / or other care of medical conditions. At least some examples may comprise implantable devices and / or methods comprising use of implantable devices. However, in some examples, the methods and / or devices may comprise at least some external components. In some examples, a therapeutic medical device may comprise a combination of implantable components and external components.

[0040] At least some of the example devices and / or example methods may relate to sleep disordered breathing (SDB) care, which may comprise monitoring, diagnosis, evaluation, and / or treatment, which may comprise stimulation in some examples. At least some examples include implantable medical devices including a power element that may be supplied power and / or charged by an external charger via inductive wireless power transfer (e.g., 50-500 KHz) or radio frequency (RF) wireless power transfer (e.g., near-field 1-50 MHz orfar-field 9003000 MHz). Among other target tissues for stimulation and / or sensing, at least some target tissues comprise tissues of the head and / or neck regions which include nerves, muscles, and / or other tissues (e.g., tendons, bones, cartilage, etc.) related to treating sleep disordered breathing such as, but not limited to, obstructive sleep apnea. These target tissues may directly or indirectly relate to promoting upper airway patency. Other target tissues also may include those tissues relating to treating pelvic disorders such as (but not limited to) treating urinary and / or fecal incontinence. In further examples, the target tissues may comprise any other peripheral nerves and / or muscles innervated by such peripheral nerves.

[0041] These examples, and additional examples, are further described in association with at least FIGS. 1A-34.

[0042] FIG. 1A is a block diagram schematically representing an example arrangement 50 (an example device and / or example method) including an implantable medical device (IMD) 52 in operable relation to target tissue(s) 60. In some examples, the IMD 52 may comprise a sensing element 54, a stimulation element 56, and / or other element 58 (or function) such that the IMD 52 may be in sensing relation, stimulating relation, and / or other relation with the target tissue(s) 60.

[0043] FIG. 1B is a block diagram schematically representing a patient’s body 100, including example target portions 110-134 at which at least some example sensing element(s), stimulation element(s), and / or other elements may be employed to implement at least some examples of the present disclosure.

[0044] As shown in FIG. 1B, patient’s body 100 comprises a head-and-neck portion 110, including head 112 and neck 114. The head-and-neck portion comprises cranial tissue, nerves, etc., and upper airway 116 (e.g., nerves, muscles, tissues), etc. As further shown in FIG. 1B, the patient’s body 100 comprises a torso 120, which comprises various organs, muscles, nerves, other tissues, such as but not limited to those in pectoral region 122 (e.g., lungs 126, cardiac 127), abdomen 124, and / or pelvic region 129 (e.g., urinary / bladder, anal, reproductive, etc.). As further shown in FIG. 1B, the patient’s body 100 comprises limbs 130, such as arms 132 and legs 134.

[0045] It will be understood that various sensing elements (and / or stimulation elements) as described throughout the various examples of the present disclosure may be deployed within the various regions of the patient’s body 100 to sense and / or otherwise diagnose, monitor, treat various physiologic conditions such as, but not limited to those examples described below in association with FIGS. 2A-34. In some such examples, a stimulation element 117 may be located in or near the upper airway 116 for treating sleep disordered breathing (and / or near other nerves / muscles for treating other conditions) and / or a sensing element 128 may be located anywhere within the neck 114, head 112, and / or torso 120 (or other body regions) to sense physiologic information for providing patient care (e.g., SDB, other) and / or for other purposes.

[0046] In some examples, at least a portion of the stimulation element 117 may include part of an implantable component / device (e.g., IMD or IMD portion), such as an implantable pulse generator (IPG). In some examples, the IPG may comprise a full sized IMD which is chronically implantable in the torso 120 (e.g., pectoral region 122) but otherwise generally considered too large for implantation in the head-and-neck region 110. In some examples, the IPG may comprise a smaller sized IPG which is sized and shaped to be chronically implanted in the head-and-neck region 110 or neck region 114 alone, such as in locations, spaces, etc. in which a full sized IPG would not reasonably fit. In some examples in which the IMD (e.g., IPG) is generally chronically implanted in the neck region 114, a portion of the IPG or the entire IPG may be chronically implanted at a transition of a lower portion of the neck 114 and an upper portion of the torso 120, such as (but not limited to) at or near a clavicle, manubrium, sternum, etc. In some examples, the “smaller sized” IPG may sometimes be referred to as a microstimulator.

[0047] In some examples, the neck 114 may comprise submandibular locations in an anterior cervical region and includes locations superior to the clavicle. However, as noted above, in some examples, the neck 114 may comprise locations at or near transitions of the lower portion of the neck 114 and the upper portion of the torso 120.

[0048] The implantable components (e.g., IPG, other) may comprise a stimulation / control circuit, a power supply (e.g, non-rechargeable, rechargeable), communication elements, and / or other components. In some examples, the stimulation element 117 also may comprise a stimulation electrode and / or stimulation lead connected to the implantable pulse generator.

[0049] Further details regarding the location, structure, operation, and / or use of the sensing element 128, external element(s) 150, and / or stimulation element 117 are described below in association with at least FIGS. 1C-34.

[0050] In some examples, at least a portion of the stimulation element 117 may comprise part of an external component / device such as, but not limited to, the external component comprising a pulse generator (e.g., stimulation / control circuitry), power supply (e.g., rechargeable, non-rechargeable), and / other components. In some examples, a portion of the stimulation element 117 may be implantable and a portion of the stimulation element 117 may be external to the patient.

[0051] Accordingly, as further shown in FIG. 1B, the various sensing element(s) 128 and / or stimulation element(s) 117 implanted in the patient’s body may be in wireless communication (e.g., connection 137) with at least one external element 150.

[0052] As further shown in FIG. 1B, in some examples, the external element(s) 150 may be implemented via a wide variety of formats such as, but not limited to, at least one of the formats 151 including a patient support 152 (e.g., bed, chair, sleep mat, other), wearable elements 154 (e.g., finger, wrist, head, neck, shirt), noncontact elements 156 (e.g., watch, camera, mobile device, other), and / or other elements 158.

[0053] As further shown in FIG. 1B, in some examples, the external element(s) 150 may comprise one or more different modalities 170 such as (but not limited to) a sensing portion 171, stimulation portion 172, power portion 174, communication portion 176, and / or other portion 178. The different portions 171, 172, 174, 176, 178 may be combined into a single physical structure (e.g., package, arrangement, assembly), may be implemented in multiple different physical structures, and / or with just some of the different portions 171, 172, 174, 176, 178 combined together in a single physical structure.

[0054] In some examples, the external stimulation portion 172 and / or implantable portions of stimulation element 117 may comprise at least some of substantially the same features and attributes of at least the stimulation arrangements, as further described below in association with at least FIGS. 2A-34 and / or other examples throughout the present disclosure.

[0055] In some examples, the external power portion 174 and / or power components associated with stimulation element 117 (e.g., implantable portions) may comprise at least some of substantially the same features and attributes of at least the stimulation arrangements, as further described throughout the examples of the present disclosure. In some such examples, the respective power portion, components, etc. may comprise a rechargeable power element (e.g., supply, battery, circuitry elements) and / or non-rechargeable power elements (e.g., battery). In some examples, the external power portion 174 may comprise a power source by which a power component of the stimulation element 117 (e.g., implantable portions) may be recharged.

[0056] In some examples, the implantable components of (and / or associated with) stimulation element 117 which comprise power elements may receive power from (or via) external power portion 174 of external element 150 but not store the received power. Instead, the received power may be used immediately (or with minor delay) as part of transmitting a stimulation signal (received from or via stimulation portion 172) via stimulation element 117 to target tissues within the patient’s body.

[0057] In some examples, the wireless communication portion 176 (e.g., connection / link at 137) may be implemented via various forms of radiofrequency communication and / or other forms of wireless communication, such as (but not limited to) magnetic induction telemetry, Bluetooth (BT), Bluetooth Low Energy (BLE), near infrared (NIF), near-field protocols, Wi-Fi, Ultra-Wideband (UWB), ultrasonic waves, and / or other short range or long range wireless communication protocols suitable for use in communicating between implanted components and external components in a medical device environment.

[0058] Examples are not so limited as expressed by other portion 178 via which other aspects of implementing medical care may be embodied in external element(s) 150 to relate to the various implanted and / or external components described above.

[0059] FIG. 1C schematically represents a control portion 190, which may comprise at least some of substantially the same features and attributes as the control portion 1200 in FIG. 32A. The control portion 190 may be used to implement at least some of the various example devices and / or example methods of the present disclosure as described herein. In some examples, the control portion 190 may form part of, and / or be in communication with, the sensing element 128 and / or the stimulation element 117 in FIG. 1B, external element(s) 150, and / or other medical device (or portions thereof), as further described later.

[0060] FIG. 2A is a block diagram schematically representing an example system 200a including an implantable medical device (IMD) 202a and an external charger 220a. In some examples, the IMD 202a may be implanted into a patient for diagnostic, therapeutic, drug delivery, and / or other suitable purposes. In some examples, the IMD 202a may be used to apply electrical stimulation to respiratory-related tissue, such as to an upper airway patency-related tissue of a patient, to treat sleep disordered breathing (SDB) conditions. In some examples, the IMD 202a may be used to apply electrical stimulation to other tissues (e.g., pelvic, spinal) of a patient to treat other conditions (e.g., urinary and / or fecal incontinence). The external charger 220a may be used to charge a power element 204 (e.g., battery) of the medical device 202a and / or to transmit power to the medical device 202a which is immediately used by the medical device and not stored within a power element of the medical device.

[0061] In some examples, external charger 220a may be implemented as a patient neck cuff configured to be worn on the neck 114 (FIG. 1B) of a patient to supply power and / or charge the power element 204 of the IMD 202a. In some examples, external charger 220a may be implemented as a patient neck cuff pillow configured to rest on the shoulders of a patient to position the neck cuff pillow around the neck region 114 (FIG. 1B) of the patient. In some such examples, the power transfer may be implemented via inductive wireless power transfer (e.g., 50-1000 KHz) or radio frequency (RF) wireless power transfer (e.g., near-field 1-50 MHz).

[0062] The IMD 202a includes a power element 204 and a wireless receiver 206. The external charger 220a includes a wireless transmitter 222 to transmit power to the wireless receiver 206 of the IMD 202a over a wireless path 223. The wireless receiver 206 receives power transmitted from the wireless transmitter 222 to supply power (e.g., for immediate use and / or for charging or recharging) to the power element 204. In some examples, the wireless receiver 206 also receives communications from the external charger 220a over the wireless path 223. The wireless transmitter 222 may separately transmit power and communication signals to the wireless receiver 206 at different times or may combine (e.g., multiplex) power and communication signals such that power and communications are transmitted simultaneously. The power element 204 may be a liquid electrolyte battery (e.g., lithium-ion battery), a solid-state battery, a supercapacitor, or other suitable component configured to store energy that may be used to power the IMD 202a. In some examples, the solid-state battery may comprise a thin-film solid-state electrolyte, such as (but not limited to) a lithium phosphorus oxynitride (LiPON) material.

[0063] The time required to recharge the power element 204 of the IMD 202a is based upon the power element technology. For example, given a supercapacitor, a solid-state battery, and a liquid electrolyte battery each having the same energy capacity, in some examples the supercapacitor may be recharged from a 10 percent charge to a 90 percent charge faster than the solid-state battery, and the solid-state battery may be recharged from a 10 percent charge to a 90 percent charge faster than the liquid electrolyte battery. For example, when a supercapacitor is used as the power element 204, the IMD 202a may be rapidly recharged from a 10 percent charge to a 90 percent charge by the external charger 220a in under 90 seconds for example. When a solid-state battery is used as the power element 204, the IMD 202a may be quickly recharged from a 10 percent charge to a 90 percent charge by the external charger 220a in under 10 minutes for example. When a liquid electrolyte battery is used as the power element 204, the IMD 202a may be recharged from a 10 percent charge to a 90 percent charge by the external charger 220a in 20 to 30 minutes for example.

[0064] In examples in which a solid-state battery is used as the power element 204, the power element 204 and thus the IMD 202a may be made smaller since solid state batteries are more energy dense than supercapacitors and liquid electrolyte batteries. Supercapacitors and solid-state batteries are safer than liquid electrolyte batteries, since there is little risk of a liquid electrolyte leaking and the risk of fire may be reduced. Supercapacitors can withstand more charge and discharge cycles (e.g., hundreds of thousands) than solid state batteries before degrading (e.g., storing less energy), and solid-state batteries can withstand more charge and discharge cycles (e.g., about 5000) than liquid electrolyte batteries (e.g., about 1000) before degrading. Supercapacitors have an additional benefit over both solid-state batteries and liquid electrolyte batteries in that supercapacitors do not contain any toxic metals (e.g., lithium) that may involve more special handling, sealing, etc. to permit use within a patient. In some examples, the power element 204 may include two or more power storage technologies, such as a supercapacitor paired with a solid-state battery.

[0065] In some examples, as further described below with reference to at least FIGS. 4-14, the wireless transmitter 222 transmits power (and / or communications) to the wireless receiver 206 using inductive coupling or nearfield radio frequency (RF) wireless power transfer. In some examples, as further described below with reference to at least FIGS. 15A-27, the wireless transmitter 222 transmits power (and / or communications) to the wireless receiver 206 using far-field RF wireless power transfer.

[0066] FIG. 2B is a block diagram schematically representing an example system 200b including an implantable medical device (IMD) 202b and an external charger 220b. The IMD 202b is similar to the IMD 202a of FIG. 2A, except that the I MD 202b further includes a wireless transmitter 208. The wireless transmitter 208 may operate at the same frequency as the wireless receiver 206 or at a different frequency from the wireless receiver 206. In some examples, the wireless receiver 206 and the wireless transmitter 208 may be combined into a wireless transceiver. The external charger 220b is similar to the external charger 220a of FIG. 2A, except that the external charger 220b further includes a wireless receiver 224. The wireless receiver 224 may operate at the same frequency as the wireless transmitter 222 or at a different frequency from the wireless transmitter 222. In some examples, the wireless transmitter 222 and the wireless receiver 224 may be combined into a wireless transceiver.

[0067] The wireless transmitter 208 of the IMD 202b may transmit communications and / or other signals to the wireless receiver 224 of the external charger 220b through a wireless communication path 209. In some examples, the IMD 202b may transmit communications and / or other signals to the external charger 220b simultaneously with receiving power from the external charger 220b for supplying power to and / or charging the power element 204. As further described below with reference to at least FIGS. 28A-30, the communications and / or other signals transmitted to the external charger 220b from the IMD 202b may be used to configure the wireless transmitter 222 to optimize the power transfer to the IMD 202b.

[0068] FIG. 2C is a block diagram schematically representing an example system 200c including an implantable medical device (IMD) 202c and an external charger 220c. The IMD 202c is similar to the IMD 202a of FIG. 2A, except that the IMD 202c further includes a Bluetooth Low Energy (BLE) transceiver 210. The BLE transceiver 210 may operate at a different frequency (e.g., 2.45 GHz) from the wireless receiver 206. The external charger 220c is similar to the external charger 220a of FIG. 2A, except that the external charger 220c further includes a BLE transceiver 226. The BLE transceiver 226 may operate at a different frequency from the wireless transmitter 222. The BLE transceiver 210 of the IMD 202c may exchange communications with the BLE transceiver 226 of the external charger 220c through a Bluetooth communication path 211. In some examples, the IMD 202c may exchange communications with the external charger 220c simultaneously with receiving power from the external charger 220c for supplying power to and / or charging the power element 204. As further described below with reference to at least FIGS. 28A-30, the communications exchanged between the IMD 202c and the external charger 220c may be used to configure the wireless transmitter 222 to optimize the power transfer to the IMD 202c.

[0069] Communications from an external charger (e.g., 220a-220cof FIGS. 2A-2C) to an IMD (e.g., 202a-202c of FIGS. 2A-2C) may be defined as a downlink. Communications from an IMD to an external charger may be defined as an uplink. Communications that are at or near the recharge frequency may be defined as in-band communications. Communications that are outside of the recharge frequency may be defined as out-of-band communications. For in-band downlink and uplink, charging may be paused for communications and resumed once the communications are complete. For out-of-band downlink and uplink, charging and communications may occur simultaneously. For in-band downlink and out-of-band uplink, there are at least two options as follows: 1) pause charging during downlink; or 2) encode the charging energy for simultaneous charging and downlink. In either case, charging may continue during uplink.

[0070] Uplink may be performed using BLE (e.g., via BLE transceivers 210 and 226 of FIG. 2C). The external charger and the IMD may exchange security / encryption settings. This exchange may be performed once during pairing or each time a charging session begins. The external charger and the IMD may maintain an active BLE session or disconnect. If disconnected, the IMD may utilize advertisement or extended advertisement packets for uplink, without the need to stay connected to the external charger. Advertisement packets may be encrypted such that only the external charger and other paired devices can decrypt the uplink information.

[0071] FIG. 3A is a diagram schematically representing an example implantable medical device (IMD) 250a. In some examples, the IMD 250a may comprise at least some of substantially the same features as, and / or comprise an example implementation of at least some of the features of, the implantable components (e.g., 117, 128) in the arrangements of FIGS. 1A-1C and / or of IMDs 202a-202c of FIGS. 2A-2C.

[0072] As shown in FIG. 3A, in some examples, IMD 250a includes a housing 252, a wireless communication portion 253, and a stimulation element 256. In some examples, the wireless communication portion 253 may comprise a wireless receiver 206 and / or a wireless communication element 260 (e.g., antenna). In some examples, the IMD 250a may be implanted into a patient for therapeutic and / or other suitable purposes. In some examples, via the stimulation element 256, the IMD 250a may be used to apply electrical stimulation to respiratory-related tissue, such as to an upper airway patency-related tissue of a patient, to treat sleep disordered breathing (SDB) conditions. In some examples, the IMD 250a may be used to apply electrical stimulation to other tissues (e.g., pelvic, spinal) of a patient to treat other conditions (e.g., urinary and / or fecal incontinence).

[0073] The wireless receiver 206 of the wireless communication portion 253 may receive power transmitted from an external power source or charger (e.g., 174 / 150 of FIG. 1B, 220a-220c of FIGS. 2A-2C, 1370 of FIG. 34) to power the IMD 250a including the wireless receiver 206 and the stimulation element 256. In some examples, the wireless receiver 206 also receives communications from the external charger such as in association with communication portion 176 in FIG. 1B. In some examples, the wireless receiver 206 receives power (and / or communications) using inductive coupling or near-field radio frequency (RF) wireless power transfer. In some examples, the wireless receiver 206 receives power (and / or communications) using far-field RF wireless power transfer.

[0074] The wireless communication element 260 of the wireless communication portion 253 may include a coil antenna for inductive or near-field RF wireless power transfer (e.g., for frequencies less than or equal to about 50 MHz) or an RF antenna for far-field RF wireless power transfer (e.g., for frequencies greater than or equal to about 900 MHz). In the IMD 250a, the wireless communication element 260 may be arranged on the housing 252 (e.g., on an exterior wall of the housing 252 or on an interior wall of the housing 252) or integrated within (e.g., embedded within, etched into) the housing 252. The wireless communication element 260 is electrically coupled to the wireless receiver 206 and is configured to receive power from a wireless transmitter (e.g., 174 in FIG. 1B, 222 of FIGS. 2A-2C, 1370 of FIG. 34) to power the wireless receiver 206 and the stimulation element 256. In some examples, the wireless communication element 260 may also receive communication signals and / or control signals from an external charger (e.g., 176 in FIG. 1B, 220a-220c of FIGS. 2A-2C, 1370 of FIG. 34) or other device (e.g., a mobile device 1320, a remote control 1340, a clinician programmer 1350, and / or a patient management tool 1360 of FIG. 34).

[0075] In some examples, the wireless communication element 260 of the wireless communication portion 253 may include an inductor configured as a coil for use as an antenna for inductive wireless power transfer (WPT), inductive communications (e.g., inductive telemetry), and / or radio frequency (RF) communications (e.g., RF telemetry). The coil may be used for inductive wireless power transfer and / or inductive communications at a first frequency at or below the self-resonance frequency of the coil. The same coil may be used as an antenna for RF communications at a second frequency above the self-resonance frequency of the coil. In some examples, the second frequency may be greater than at least ten times the first frequency. In some examples, the coil may be used for inductive wireless power transfer and / or inductive communications at a first frequency within a range, for example, between about 9 kilohertz and about 50 megahertz, such as 6.78 megahertz or 13.56 megahertz. In some examples, the same coil may be used for RF communications at a second frequency within a range, for example, between about 100 megahertz and about 5 gigahertz, such as 400 megahertz or 2.4 gigahertz.

[0076] The simulation element 256 may include stimulation circuitry and / or at least one stimulation electrode to apply electrical stimulation to a patient. The stimulation element 256 receives power and / or control signals from the wireless receiver 206 of wireless communication portion 253. The electrical stimulation may be applied via at least one electrode of the stimulation element 256 or electrically coupled to the stimulation element 256. In some examples, at least one electrode (not shown) may be arranged on the housing 252, or as further described below with reference to at least FIG. 31, at least one electrode 1110 may be arranged on a lead 1104 electrically coupled to the stimulation element 256.

[0077] In some examples, the housing 252 encloses at least a portion of the wireless communication portion 253 (e.g., the wireless receiver 304) and at least a portion (e.g., at least stimulation circuitry) of the stimulation element 256. In some examples, housing 252 may encapsulate (e.g., overmold) the wireless receiver 206 and the stimulation element 256 to hermetically seal at least a portion (e.g., the wireless receiver 206) of the wireless communication portion 253 and at least a portion (e.g, stimulation circuitry) of the stimulation element 256. Housing 252 may include any suitable biocompatible material, such as a metal (e.g., titanium, stainless steel, MP35N), a thermoplastic polymer (e.g., silicone), a thermoset material, a blend polymer material (e.g., polyetheretherketone (PEEK)), a ceramic material (e.g., glass), ora combination thereof. Different portions of the housing 252 may be made of different materials. For example, a first portion of the housing 252 may be made of a metal (e.g., titanium) while a second portion of the housing where the wireless communication element 260 is arranged may be made of a nonconductive material (e.g., PEEK).

[0078] In some examples, the IMD 250a may include a microstimulator configured to be implanted within a patient, such as within a head-and-neck region, the torso, or pelvic region of the patient. The microstimulator may include the housing 252 to encapsulate (e.g., hermetically seal) at least a portion (e.g., wireless receiver 206) of the wireless communication portion 253 and at least a portion (e.g., stimulation circuitry) of the stimulation element 256.

[0079] FIG. 3B is a diagram schematically representing an example IMD 250b. In some examples, the IMD 250b may comprise at least some of substantially the same features and attributes as IMD 250a of FIG. 3A. As shown in FIG. 3B, the IMD 250b may include a power element 204 and a wireless receiver 206 for suppling power to and / or charging the power element 204 as previously described. In addition, the IMD 250b may include a housing 252, a control portion 254, and a wireless communication element 260 (e.g., antenna). Housing 252 encloses the power element 204, the wireless receiver 206, and the control portion 254. In some examples, housing 252 may encapsulate (e.g., overmold) the power element 204, the wireless receiver 206, and the control portion 254 to hermetically seal the power element 204, the wireless receiver 206, and the control portion 254 within the housing 252.

[0080] In some examples, the enclosure / case of power element 204 also forms at least a portion of housing 252 of IMD 250b. Accordingly, in this example power element 204 does not include a separate power element enclosure within the housing 252 of IMD 250b.

[0081] The control portion 254 may control the wireless receiver 206, the power element 204, and other circuitry (not shown) of the IMD 250b. In some examples, the control portion 254 may implement aspects of the example methods described below with reference to at least FIGS. 28A-30. The control portion 254 may include a central processing unit (CPU), a microcontroller, an application specific integrated circuit (ASIC), and / or other suitable logic circuitry. At least some example implementations of the control portion 254 are further described below with reference to at least FIGS. 32A and 32B.

[0082] It will be further understood that in some examples, at least some aspects or elements of the control portion 254 may form part of, and / or be distributed among, the other components (e.g, power, wireless communication portion 253, other) of the IMD 250b such that control portion 254 does not necessarily form a component of the IMD 250b separate from those other elements (e.g., power, wireless communication, etc.).

[0083] In some examples, an IMD 250b may comprise a power source for other IMDs in close enough proximity to be in power-exchanging relation to the IMD 250b such that IMD 250b may omit a sensing element, stimulation element, etc. and solely serve as a power resource within the patient’s body to support other IMDs within the patient’s body. In some such examples, such support to help power other IMDs within the patient may comprise the IMD 250b including a wired connection to such other IMDs, such as via a lead or other means.

[0084] Similarly, in some examples, with or without its own power element (and / or with or without elements for sensing, stimulation etc.), an IMD may provide a wireless communication node to support wireless communication with other IMDs within a patient’s body and / or wireless communication with external elements (e.g., 150 in FIG. 1B), which may support such IMDs acting as intrabody wireless communication nodes.

[0085] FIG. 3C is a diagram schematically representing an example IMD 250c. The IMD 250c is similar to the IMD 250b of FIG. 3B, except that the IMD 250c further includes stimulation element 256. In this example, the control portion 254 may include a therapy manager arranged to control the stimulation element 256 based on at least control information to apply electrical stimulation to a patient. In some examples, the therapy manager may be arranged to control (e.g., based on control information) the stimulation element 256 to apply electrical stimulation to respiratory-related tissue (e.g., upper airway patency-related tissue) to treat sleep disordered breathing (SBD) conditions or to apply electrical stimulation to other tissues, as noted above. The electrical stimulation may be applied via at least one electrode electrically coupled to the stimulation element 256. In some examples, at least one electrode (not shown) may be arranged on the housing 252, or as further described below with reference to at least FIG. 31, at least one electrode 1110 may be arranged on a lead 1106 electrically coupled to the stimulation element 256.

[0086] In some examples, the IMD 250c may include a microstimulator configured to be implanted within a patient, such as within a head-and-neck region, the torso, or pelvic region of the patient. The microstimulator may include the housing 252 to encapsulate (e.g., hermetically seal) at least the power element 204, the wireless communication portion 253 (e.g., wireless receiver 206 and / orwireless communication element 260), the stimulation element 256, and / or the control portion 254.

[0087] FIG. 3D is a diagram schematically representing an example IMD 250d. The IMD 250d is similar to the IMD 250b of FIG. 3B, except that the IMD 250d further includes a sensing element 258 and the wireless communication element 260 is integrated into or on the power element 204. In some examples, the wireless communication element 260 may be wrapped around the power element 204 or arranged on a casing of the power element 204. Alternatively, as previously described above with reference to FIG. 3A, the wireless communication element 260 may be arranged on the housing 252 or integrated within the housing 252.

[0088] In this example, the control portion 254 may include a sensing manager arranged to control the sensing element 258 based on at least control information to obtain sensing information (e.g., physiologic information) for a patient. The sensing element 258 may include at least one sensor (e.g., accelerometer, gyroscope, piezoelectric sensor, microphone, temperature sensor, pressure sensor, etc.) and / or other suitable circuitry for obtaining sensing information for a patient. The sensing information (e.g., sensed physiologic information) may include respiratory information, cardiac information, activity information, motion information, posture information, and / or other information about the patient. In some examples, the sensing element 258 of the IMD 250d may be included along with the stimulation element 256 of the IMD 250c within a single IMD. The sensing element 258 may sense sensing information of a patient via at least one electrode electrically coupled to the sensing element 258. In some examples, at least one electrode (not shown) may be arranged on the housing 252, or as further described below with reference to at least FIG. 31, at least one electrode 1110 may be arranged on a lead 1106 electrically coupled to the sensing element 258. In some examples in which a sensing element comprises at least one electrode, the at least one electrode also may, at times, be used for stimulation and / or comprise a portion of the stimulation element 256.

[0089] The sensed information may be used to initiate, terminate, pause, synchronize, and / or trigger therapy to be applied via an IMD and / or external therapy elements. In some examples, the sensed information may be used as feedback for controlling therapy (e.g., stimulation therapy), such as closed loop therapy. The sensed information also may be used for diagnostic purposes and / or for monitoring (and / or evaluation of) a particular physiologic effect, physiologic response, etc. regardless of whether the sensed information is used for other purposes (e.g., therapy). In some such examples, the sensed information may be used to evaluate open loop therapy (e.g., stimulation) which does not include a feedback loop to initiate, terminate, pause, synchronize, and / or trigger delivery of therapy.

[0090] In some examples, an IMD may comprise any one of various combinations of the above-described elements (e.g., stimulation, sensing, power, communication, control) of the respective I MDs described in association with FIGS. 2A-3D and / or FIGS. 1A-1C. In one example, a sensing element (e.g., 258 in FIG. 3D) may take the place of the stimulation element 256 of the IMD 250a in FIG. 3A, or vice versa. In another example, both the sensing and stimulation elements 258, 256 may be included in the same IMD or all three of the sensing, stimulation, and power elements 258, 256, 204 may be included in the same IMD, along with other elements such as a wireless communication portion 253 and / or control portion 254. At least some of these various combinations regarding FIGS. 1A-3D are also applicable to the various later described examples associated with FIGS. 4-34.

[0091] FIG. 4 is a diagram schematically representing an example antenna 300 including three orthogonal coils 302a, 302b, and 302c that may be configured to receive wireless power. In some examples, antenna 300 may provide wireless communication element 260 of wireless communication portion 253 of FIGS. 3A-3D. The coils 302a, 302b, and 302c may be wrapped around a power element (e.g., 204 of FIGS. 2A-3D) or a magnetic core (e.g., ferrite core) along orthogonal axes. The coils 302a, 302b, and 302c may include a single coil element (e.g., wire) with windings across the three axes, or each coil 302a, 302b, and 302c may be separate from each other (e.g., separate windings). The antenna 300 may be part of a wireless receiver (e.g., 206 of FIGS. 2A-3D) of an IMD (e.g., 200a-200c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D). By including orthogonal coils 302a, 302b, and 302c within an IMD, an external charger (e.g., 174 / 176 of FIG. 1B, 220a-220c of FIGS. 2A-2C, 1370 of FIG. 34) may maintain sufficient coupling (e.g., inductive or near-field RF) with the antenna 300 independent of the orientation of the IMD due to the position and / or posture of the patient relative to the external charger. In addition, for the transmit coil(s) of an external charger that do not have field diversity in different orthogonal axes, antenna 300 provides increased receiver diversity to improve coupling for various patient positions / postures. It is noted that near-field RF wireless power transfer is more forgiving in terms of the proximity and alignment of the transmit coil(s) in the external charger and the receiver coil(s) in the IMD than inductive wireless power transfer. While coils 302a, 302b, and 302c are illustrated as having a rectangular arrangement in FIG. 4, in some examples, coils 302a, 302b, and 302c may have another suitable geometric arrangement, such as circular, elliptical, triangular, hexagonal, etc., ora non-geometric or asymmetrical arrangement.

[0092] FIG. 5 is a cross-sectional view schematically representing an example antenna 310 including a coil 312 arranged around a power element 204 that may be configured to receive wireless power. In some examples, antenna 310 may provide wireless communication element 260 of wireless communication portion 253 of FIGS. 3A-3D. While FIG. 5 illustrates one coil 312, antenna 310 may include one or two additional orthogonal coils (e.g., see FIG. 4). While the power element 204 is illustrated as having an elliptical cross-sectional shape in FIG. 5, in some examples, the power element 204 may have another suitable crosssectional shape, such as rectangular, circular, triangular, hexagonal, etc., or a non-geometric or asymmetric shape. Thus, the coil 312 may conform to the shape of the power element 204. The shape of the power element 204, and thus the shape of the coil 312, may be selected to conform to a shape of a housing (e.g., 252 of FIGS. 3B-3D) enclosing the power element. The shape of the housing may be selected based on where the I MD is intended to be implanted within a patient. In some examples, a wireless receiver (e.g., 206 of FIGS. 2A-3D) may include a capacitor to tune the antenna 310.

[0093] FIG. 6 is a cross-sectional view schematically representing an example antenna 320 including a coil 322 arranged around an interior of a housing 252 that may be configured to receive wireless power. In some examples, antenna 320 may provide wireless communication element 260 of wireless communication portion 253 of FIGS. 3A-3D. In some examples, the coil 322 may be applied (e.g., glued, formed, printed) on an interior wall of the housing 252 or etched into the interior wall of the housing 252. While FIG. 6 illustrates one coil 322, the antenna 320 may include one or two additional orthogonal coils (e.g., see FIG. 4). While the housing 252 is illustrated as having an elliptical cross-sectional shape in FIG. 6, in some examples, the housing 252 may have another suitable cross-sectional shape, such as rectangular, circular, triangular, hexagonal, etc., or a nongeometric or asymmetric shape. The shape of the housing 252 may be selected based on where the IMD is intended to be implanted within a patient. The coil 322 may conform to the shape of the housing 252. In some examples, a wireless receiver (e.g., 206 of FIGS. 2A-3D) may include a capacitor to tune the antenna 320.

[0094] FIG. 7 is a cross-sectional view schematically representing an example system 350 including an IMD 352 and an external charging pad 360a that may be configured to wirelessly transmit power to the IMD 352 via inductive wireless power transfer. The IMD 352 may include an IMD 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D. The external charging pad 360a may be part of a wireless transmitter (e.g., 222 of FIGS. 2A-2C) of an external charger (e.g., 220a-220c of FIGS. 2A-2C). The external charging pad 360a may include a bottom cover layer 362a (e.g., a fabric cover), a backing shield layer 364 arranged on the bottom cover layer 362a, a coil(s) layer 366 arranged on the backing shield layer 364, and a top cover layer 362b (e.g., a fabric cover) arranged on the coil(s) layer 366.

[0095] The coil(s) layer 366 faces the IMD 352 to transmit power, via inductive coupling, to the IMD 352 within a patient. The coil(s) layer 366 may include a single coil or a plurality of coils. In some examples, where coil(s) layer 366 includes a plurality ofcoils, the coils may be arranged in an array of coil structures, which is further described below with reference to at least FIG. 8. The external charging pad 360a may be arranged under a patient (e.g., placed on a mattress, such as a mattress pad, or other support on which the patient is located), over a patient (e.g., such as a blanket), or may be worn by the patient (e.g., clothing). The external charging pad 360a may be somewhat pliable to conform to the mattress or other support on which the patient is located or to conform to the patient (when placed over or worn by the patient) to improve patient comfort.

[0096] The backing shield layer 364 prevents inductive coupling of the coil(s) within coil(s) layer 366 to other metal structures under, around, or near the patient, such as in the mattress, bedframe, or other support on which the patient is located. Backing shield layer 364 may include a solid structure, a patterned structure, or a Mu-Near-Zero metamaterial as further described below with reference to at least FIGS. 10 and 11. The coil(s) layer 366 may be electrically coupled to power and control portions (not shown) of a wireless transmitter (e.g., 222 of FIGS. 2A-2C) to transmit power to the IMD 352. The power and control portions of the wireless transmitter may be integrated into the pad 360a or separate from the pad 360a and connected to the pad 360a through a cord.

[0097] FIG. 8 is a top view schematically representing an example array 370 of coil structures 372 that may be configured to wirelessly transmit power to an IMD (e.g., 352 of FIG. 7) via inductive coupling. In some examples, the array 370 of coil structures 372 provides the coil(s) layer 366 of the external charging pad 360a of FIG. 7. The array 370 of coil structures 372 may be arranged in rows and columns where each row and each column includes any suitable number of coil structures 372. The array 370 of coil structures 372 may be selected to be sufficiently large such that the external charging pad 360a overlaps a majority of a patient’s body, such as the patient’s head, neck, torso, hips, and at least a portion of the legs such that at least one coil structure 372 will be aligned with the IMD during charging (or powering) of the IMD.

[0098] Each coil structure 372 may include a single coil or a plurality of coils as further described below with reference to at least FIGS. 12A-12D. In some examples, a single coil structure 372 of the array 370 of coil structures is selected at a given time to charge (or transmit power to) the power element of the IMD. In some examples, at least two coil structures 372 (e.g., a subset of adjacent coil structures) of the array 370 of coil structures are selected at a given time to charge the power element of the IMD. As will be further described below with reference to at least FIGS. 14, 27, and 28A-28K, the coil structure or subset ofcoil structures selected to charge the power element may be based on a measurement of power coupling between the wireless receiver of the IMD and the wireless transmitter of the external charger and / or a sensed location, position, and / or posture of the patient or location and / or orientation of the IMD relative to the external charger. In some examples, each coil structure 372 may correspond to a sensor 792 for sensing a location, position, and / or posture of the patient as will be described in more detail below with reference to at least FIG. 27.

[0099] In some examples, the array 370 of coil structures 372 may be used to determine the location, position, posture, motion, and / or activity of a patient based on measurements of power coupling between the wireless receiver of the IMD and each coil structure 372 without regard to charging (or powering) of the power element of the IMD. This determined location, position, posture, motion, and / or activity of the patient may be used for purposes other than for selecting the coil structure or subset of coil structures to charge the power element of the IMD, such as for diagnostic or therapeutic purposes. The array 370 of coil structures 372 may be used to determine the location, position, posture, motion, and / or activity of the patient without using any additional dedicated sensors (e.g., accelerometer, gyroscope, piezoelectric sensor, non-contact sensor, temperature sensor, pressure sensor, etc.) of the IMD or the external charger.

[0100] In some examples, each coil structure 372 or a subset of coil structures 372 may be powered simultaneously at the same frequency and at the same power level to charge (or transmit power to) the power element of the IMD. In some examples, each coil structure 372 or a subset of coil structures 372 may be powered simultaneously at the same frequency and at a different power level to charge the power element. In some examples, each coil structure 372 of the array 370 of coil structures may be powered simultaneously at a different frequency and at the same power level for selecting at least one coil structure to charge the power element. In this example, the wireless receiver may measure and communicate to the wireless transmitter the received power from each coil structure corresponding to the frequency of the coil structure. Based on the received power information, the wireless transmitter may select the coil structure or subset of coil structures having the optimum power coupling with the wireless receiver.

[0101] An external charger including the array 370 of coil structures 372 may include a single receiver multiplexed to each coil structure 372, a dedicated receiver for each coil structure 372, or multiple receivers multiplexed to multiple coil structures 372. The receiver(s) of the external charger may be used to implement methods for selecting a coil structure 372 or a subset of coil structures 372 to optimize wireless power transfer as will be described below with reference to at least FIG. 28J. In these examples, the receiver(s) may be part of a wireless transmitter (e.g., 222 of FIGS. 2A-2C) of an external charger (e.g., 220a-220c of FIGS. 2A-2C).

[0102] FIG. 9 is a cross-sectional view schematically representing an example external charging pad 360b that may be configured to wirelessly transmit power to an IMD (e.g., 352 of FIG. 7) via inductive wireless power transfer. The external charging pad 360b may be part of a wireless transmitter (e.g., 222 of FIGS. 2A-2C) of an external charger (e.g., 220a-220c of FIGS. 2A-2C). The external charging pad 360b may include a bottom cover layer 362a (e.g., fabric cover), an array 376 of backing shields 378 arranged on the bottom cover layer 362a, an array 370 of coil structures 372 arranged on the array 376 of backing shields 378, and a top cover layer 362b (e.g., fabric cover) arranged on the array 370 of coil structures 372. As illustrated in FIG. 9, the array 376 of backing shields 378 corresponds to the array 370 of coil structures 372, such that each coil structure 372 is arranged on a respective backing shield 378. In some examples, the array 376 of backing shields 378 in FIG. 9 may be replaced with the backing shield 364 of FIG. 7.

[0103] The array 370 of coil structures 372 faces the IMD to transmit power, via inductive coupling, to the IMD within a patient. The external charging pad 360b may be arranged under a patient (e.g., placed on a mattress, such as a mattress pad, or other support on which the patient is located), over a patient (e.g., such as a blanket), or may be worn by the patient (e.g., clothing). The external charging pad 360b may be somewhat pliable to conform to the mattress or other support on which the patient is located or to conform to the patient (when placed over or worn by the patient) to improve patient comfort.

[0104] The array 376 of backing shields 378 prevents inductive coupling of the coil structures 372 to other metal structures under, around, or near the patient, such as in the mattress, bedframe, or other support on which the patient is located. Each backing shield 378 may include a solid structure, a patterned structure, or a Mu-Near-Zero metamaterial as further described below with reference to at least FIGS. 10 and 11. The array 370 of coil structures 372 may be electrically coupled to power and control portions (not shown) of a wireless transmitter (e.g., 222 of FIGS. 2A-2C) to transmit power to the IMD. The power and control portions of the wireless transmitter may be integrated into the pad 360b or separate from the pad 360b and connected to the pad 360b through a cord.

[0105] FIG. 10 is a top view schematically representing an example patterned backing shield 400 that may be part of an external charger (e.g., 220a-220c of FIGS. 2A-2C). The patterned backing shield 400 may provide the backing shield 364 of the external charging pad 360a of FIG. 7 or each backing shield 378 of the external charging pad 360b of FIG. 9. The patterned backing shield 400 may include a sheet402 offerrite and copper (e.g., woven together) and a plurality of through-holes 404 extending through the sheet 402. The patterned backing shield 400 may provide increased flexibility compared to a solid backing shield. While FIG. 10 illustrates alternating oval-shaped through-holes 404 arranged in rows and columns, in some examples, through-holes 404 may be circular, rectangular, triangular, hexagonal, or other suitable shape and may be arranged through sheet 402 in any suitable pattern as long as the backing shield 400 has the intended effect of preventing inductive coupling between coils or coil structures (e.g., 366 of FIG. 7 or 372 of FIG. 9) to an unintended metal structure (e.g., bed frame).

[0106] FIG. 11 is a top view schematically representing an example metamaterial backing shield 410 that may be part of an external charger (e.g., 220a-220c of FIGS. 2A-2C). The metamaterial backing shield 410 may provide the backing shield 364 of the external charging pad 360a of FIG. 7 or each backing shield 378 of the external charging pad 360b of FIG. 9. In some examples, the backing shield 410 includes a Mu-Near-Zero metamaterial. The backing shield 410 includes a rigid or flexible substrate 412 (e.g., circuit board, ceramic, polymer, etc.) and an array of split-ring resonators 414 (e.g., copper split-ring resonators) tuned to the recharge frequency. While split-ring resonators 414 illustrated in FIG. 11 are square shaped, in some examples, split-ring resonators 414 may have another suitable shape, such as circular (e.g., 608 of FIG. 18 described below). In some examples, an array of spiral resonators (e.g., 620c of FIG. 19C described below) may be used in place of the array of split-ring resonators 414. Metamaterial backing shield 410 reduces magneticfield leakage, is more extensible compared to common shielding materials, and only has a slight effect on the efficiency.

[0107] FIG. 12A is a diagram schematically representing an example coil structure 420a that may be part of a wireless charger (e.g., 220a-220c of FIGS. 2A-2C). In some examples, the wireless transmitter (e.g., 222 of FIGS. 2A-2C) of an external charger may include a single coil structure 420a to transmit power to an IMD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D). In some examples, the coil structure 420a may provide each coil structure 372 of array 370 of FIG. 8, such that the wireless transmitter of the external charger includes an array of coil structures 420a. In this example, the coil structure 420a includes a single loop coil 422. While the single loop coil 422 illustrated in FIG. 12A has a square shape, in some examples, the single loop coil 422 may have another suitable geometric shape, such as circular, elliptical, rectangular, triangular, hexagonal, etc., or a non-geometric or asymmetric shape. The coil structure 420a may maintain sufficient inductive coupling with an antenna (e.g., 260 of FIGS. 3A-3D, 300 of FIG. 4) of an IMD over a range of patient positions / postures when the antenna of the IMD includes three orthogonal coils.

[0108] FIG. 12B is a diagram schematically representing an example coil structure 420b that may be part of a wireless charger (e.g., 220a-220c of FIGS. 2A-2C). In some examples, the wireless transmitter (e.g., 222 of FIGS. 2A-2C) of an external charger may include a single coil structure 420b to transmit power to an IMD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D). In some examples, the coil structure 420b may provide each coil structure 372 of array 370 of FIG. 8, such that the wireless transmitter of the external charger includes an array of coil structures 420b. In this example, the coil structure 420b includes a single loop coil 422 and a single figure-eight coil 424. While single loop coil 422 and single figure-eight coil 424 illustrated in FIG. 12B have an overall square shape, in some examples, single loop coil 422 and single figure-eight coil 424 may have another suitable geometric shape, such as circular, elliptical, rectangular, triangular, hexagonal, etc., ora non-geometric or asymmetric shape. By combining a single loop coil 422 with a single figure-eight coil 424 generating two orthogonal fields, coil structure 420b may maintain sufficient inductive coupling with an antenna (e.g., 260 of FIGS. 3A-3D, 300 of FIG. 4, 310 of FIG. 5, 320 of FIG. 6) of an IMD over a range of patient positions / postures.

[0109] FIG. 12C is a diagram schematically representing an example coil structure 420c that may be part of a wireless charger (e.g., 220a-220c of FIGS. 2A-2C). In some examples, the wireless transmitter (e.g., 222 of FIGS. 2A-2C) of an external charger may include a single coil structure 420c to transmit power to an IMD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D). In some examples, the coil structure 420c may provide each coil structure 372 of array 370 of FIG. 8, such that the wireless transmitter of the external charger includes an array of coil structures 420c. In this example, the coil structure 420c includes two figure-eight coils 424 and 426. The figure-eight coil 426 is arranged orthogonal to the figure-eight coil 424. While each figure-eight coil 424 and 426 illustrated in FIG. 12C have an overall square shape, in some examples, each figure-eight coil 424 and 426 may have another suitable geometric shape, such as circular, elliptical, rectangular, triangular, hexagonal, etc., or a non-geometric or asymmetric shape. By combining the figure-eight coil 424 with the figure-eight coil 426 generating two orthogonal fields, the coil structure 420c may maintain sufficient inductive coupling with an antenna (e.g., 260 of FIGS. 3A-3D, 300 of FIG. 4, 310 of FIG. 5, 320 of FIG. 6) of an IMD over a range of patient positions / postures.

[0110] FIG. 12D is a diagram schematically representing an example coil structure 420d that may be part of a wireless charger (e.g., 220a-220c of FIGS. 2A-2C). In some examples, the wireless transmitter (e.g., 222 of FIGS. 2A-2C) of an external charger may include a single coil structure 420d to transmit power to an IMD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D). In some examples, the coil structure 420d may provide each coil structure 372 of array 370 of FIG. 8, such that the wireless transmitter of the external charger includes an array of coil structures 420d. In this example, the coil structure 420d includes a single loop coil 422 and two figure-eight coils 424 and 426. While the single loop coil 422 and each figure-eight coil 424 and 426 illustrated in FIG. 12D have an overall square shape, in some examples, the single loop coil 422 and each figure-eight coil 424 and 426 may have another suitable geometric shape, such as circular, elliptical, rectangular, triangular, hexagonal, etc., or a nongeometric or asymmetric shape. By combining a single loop coil 422 with two figure-eight coils 424 and 426 generating three orthogonal fields, coil structure 420d may maintain good inductive coupling with an antenna (e.g., 260 of FIGS. 3A-3D, 300 of FIG. 4, 310 of FIG. 5, 320 of FIG. 6) of an IMD over a range of patient positions / postures.

[0111] FIG. 13A is a top view schematically representing an example coil arrangement 450a of an external charger (e.g., 220a-220c of FIGS. 2A-2C). A patient 454 including an IMD 456 may lie on a bed 452 or other support to charge (or transmit power to) the IMD 456. While the IMD 456 is illustrated in FIG. 13A as being implanted in a head-and-neck region of the patient 454, in some examples, the IMD 456 may be implanted in another region (e.g., torso, pelvis) of the patient. In some examples, the IMD 456 may be similarto an IMD 250a-250d of FIGS. 3A-3D. In this example, the external charger includes a single coil 460 for wirelessly charging (or transmitting power to) the IMD 456 via inductive wireless power transfer or near-field RF wireless power transfer. In some examples, the single coil 460 may provide the coil layer 366 of the external charging pad 360a of FIG. 7. In some examples, the single coil 460 may be integrated into a device (e.g., patient neck cuff, patient neck cuff pillow) configured to be worn on or around a patient’s neck.

[0112] The coil 460 may be sufficiently large (e.g., surrounds at least the head, neck, and torso of the patient), such that the coil 460 inductively couples (for inductive wireless power transfer) or RF couples (for near-field RF wireless power transfer) to an antenna (e.g., 260 of FIGS. 3A-3D, 300 of FIG. 4, 310 of FIG. 5, 320 of FIG. 6) of the IMD 456 despite the location, position, and / or posture of the patient 454, and thus the IMD 456, relative to the bed 452 and the coil 460. By using coil arrangement 450a, the external charger has a simpler design and requires less control logic than coil arrangement 450b described below with reference to FIG. 13B.

[0113] FIG. 13B is a top view schematically representing an example coil arrangement 450b of an external charger (e.g., 220a-220c of FIGS. 2A-2C). A patient 454 including an IMD 456 may lie on a bed 452 or other support to charge (or transmit power to) the IMD 456. While the IMD 456 is illustrated in FIG. 13B as being implanted in a head-and-neck region of the patient 454, in some examples, the IMD 456 may be implanted in another region (e.g., torso, pelvis) of the patient. In some examples, the IMD 456 may be similarto an IMD 250a-250d of FIGS. 3A-3D. In this example, the external charger includes an array 464 of coils 466 for wirelessly charging (or transmitting power to) the I MD 456 via inductive wireless power transfer or near-field RF wireless power transfer. In some examples, the array 464 of coils 466 may provide the coils layer 366 of the external charging pad 360a of FIG. 7 or the array 370 of coils 372 of the external charging pad 360b of FIG. 9. In some examples, the array 464 of coils 466 may be integrated into a device (e.g., patient neck cuff, patient neck cuff pillow) configured to be worn on or around a patient’s neck.

[0114] In the example of FIG. 13B, the coils 466 are arranged adjacent to each other and do not overlap. In some examples, each coil 466 may be a loop coil 422 of FIG. 12A or a coil structure 420b-420d of FIGS. 12B-12D. The array 464 of coils 466 (or coil structures) may be sufficiently large (e.g., proximate at least the head, neck, and torso of the patient), such that at least one coil 466 or at least a subset of the coils 466 are aligned with the IMD 456 to inductively couple (for inductive wireless power transfer) or RF couple (for near-field RF wireless power transfer) to an antenna (e.g., 260 of FIGS. 3A-3D, 300 of FIG. 4, 310 of FIG. 5, 320 of FIG. 6) of the IMD 456 despite the location, position, and / or posture of the patient 454, and thus the IMD 456, relative to the bed 452 and the array 464 of coils 466. By using coil arrangement 450b, the external charger may activate only the coil(s) 466 closest to the IMD 456 to charge (or transmit power to) the IMD, thereby using less power and exposing the patient 454 to less electromagnetic radiation than coil arrangement 450a of FIG. 13A.

[0115] FIG. 13C is a top view schematically representing an example array 470 of coils 472, which may be part of an external charger (e.g., 220a-220c of FIGS. 2A-2C). In some examples, the array 470 of coils 472 may provide the coils layer 366 of an external charging pad 360a of FIG. 7. In this example, each coil 472 partially overlaps at least one adjacent coil 472, such as two, three, four, or more adjacent coils. By overlapping the coils, inductive coupling between adjacent coils may be minimized for near-field RF wireless power transfer. The array 470 of coils 472 (or coil structures) may be sufficiently large (e.g., proximate at least the head, neck, and torso of the patient), such that at least one coil 472 or at least a subset of the coils 472 are aligned with the IMD (e.g., 456 of FIG. 13B) to RF couple (for near-field RF wireless power transfer) to an antenna (e.g., 260 of FIGS. 3A-3D, 300 of FIG. 4, 310 of FIG. 5, 320 of FIG. 6) of the IMD despite the location, position, and / or posture of the patient (e.g., 454 of FIG. 13B), and thus the IMD, relative to the array 470 of coils 472.

[0116] FIG. 13D is a top view schematically representing an example array 474 of coils 476, which may be part of an external charger (e.g., 220a-220c of FIGS. 2A-2C). In some examples, the array 474 of coils 476 may provide the coils layer 366 of an external charging pad 360a of FIG. 7 or the array 370 of coils 372 of the external charging pad 360b of FIG. 9. In this example, each coil 476 corresponds to a distributed capacitor 477 to tune each coil to a resonant frequency for near-field RF wireless power transfer. One side of each distributed capacitor 477 is electrically coupled to the corresponding coil 476, and the other side of each distributed capacitor 477 is electrically coupled to a reference node (e.g., a common or ground) 478. The array 474 of coils 476 may be sufficiently large (e.g., proximate at least the head, neck, and torso of the patient), such that at least one coil 476 or at least a subset of the coils 476 are aligned with the IMD (e.g., 456 of FIG. 13B) to RF couple (for near-field RF wireless power transfer) to an antenna (e.g., 260 of FIGS. 3A-3D, 300 of FIG. 4, 310 of FIG. 5, 320 of FIG. 6) of the IMD despite the location, position, and / or posture of the patient (e.g., 454 of FIG. 13B), and thus the IMD, relative to the array 474 of coils 476.

[0117] FIG. 14 is a top view schematically representing an array 480 of coil structures 482 divided into subsets 484i to 4844 of coil structures. In some examples, array 480 of coil structures 482 may be similar to array 370 of coil structures 372 of FIG. 8, array 464 of coils 466 of FIG. 13B, array 470 of coils 472 of FIG. 13C, or array 474 ofcoils 476 of FIG. 13D. While in this example, there are four subsets 484i to 4844 of coil structures, in some examples, the array 480 may be divided into less than four subsets (e.g., 2 or 3) or more than four subsets (e.g., 6, 8, 10, 15, etc.). Also in this example, each subset 484i to 4844 of coil structures 482 includes nine coil structures 482, but in some examples, each subset 484i to 4844 of coil structures 482 may include any suitable number of coil structures 482, such as less than nine coil structures (e.g., 2, 3, 4, 5, 6, 7, 8) or greater than nine coil structures (e.g., 10, 12, 15, 20, etc.). Further, while each subset of coil structures 484i to 4844 illustrated in FIG. 14 has a square shape, in some examples, each subset of coil structures may have another suitable shape, such as rectangular, triangular, circular, hexagonal, etc. Each subset 484i to 4844 of coil structures 482 may include a central coil structure 486i to 4864, respectively.

[0118] In some examples, the coil structure 482 (or coil structures) having the optimum inductive coupling (for inductive wireless power transfer) or optimum RF coupling (for near-field RF wireless power transfer) to the antenna (e.g., 260 of FIGS. 3A-3D, 300 of FIG. 4, 310 of FIG. 5, 320 of FIG. 6) of the IMD is selected to charge (or transmit power to) the IMD. Ina first example, each coil structure 482 may be pulsed (e.g., by wireless transmitter 222 of FIGS. 2A-2C) one at a time and the energy received by the IMD (e.g., by wireless receiver 206 of FIGS. 2A-3D) is measured (e.g., by the wireless receiver 206). The coil structure 482 resulting in the greatest received energy at the IMD is then selected to charge (or transmit power to) the IMD. In a second example, each coil structure 482 may be pulsed (e.g., by wireless transmitter 222 of FIGS. 2A-2C) one at a time while measuring the loading (e.g., via wireless transmitter 222) of the coil structure. The coil structure 482 having the greatest loading is then selected to charge (or transmit power to) the IMD.

[0119] In a third example, each subset 484i to 4844 of coil structures 482 is pulsed (e.g., each coil 482 within the selected subset is pulsed simultaneously) and the subset resulting in the greatest received energy at the IMD is selected. Then, each coil structure 482 within the selected subset is individually pulsed and the coil structure resulting in the greatest received energy at the IMD is then selected to charge (or transmit power to) the IMD. In a fourth example, each subset 484i to 4844 of coil structures 482 is pulsed (e.g., each coil 482 within the selected subset is pulsed simultaneously) and the subset having the greatest loading (e.g., greatest sum of loading of each coil structure 482 within a subset) is selected. Then, each coil structure 482 within the selected subset is individually pulsed and the coil structure having the greatest loading is then selected to charge (or transmit power to) the IMD. Compared to the first and second examples, the third and fourth examples can more quickly select the best coil structure 482 for charging (or transmitting power to) the IMD.

[0120] In a fifth example, each central coil structure 486i to 4864 is pulsed and the corresponding subset of the central coil structure resulting in the greatest received energy at the IMD is selected. Then, each coil structure 482 within the selected subset is individually pulsed and the coil structure resulting in the greatest received energy at the IMD is then selected to charge (or transmit power to) the IMD. In a sixth example, each central coil structure 486i to 4864 is pulsed and the corresponding subset of the central coil structure having the greatest loading is selected. Then, each coil structure 482 within the selected subset is individually pulsed and the coil structure having the greatest loading is then selected to charge (or transmit power to) the IMD. Compared to the first and second examples, the fifth and sixth examples can more quickly select the best coil structure 482 for charging (or transmitting power to) the IMD. These methods and additional methods for selecting a coil structure 482 for charging (or transmitting power to) the IMD are further described below with reference to at least FIGS. 28A-28K.

[0121] To monitor energy coupled to the coil structures 482, each coil structure 482 may have its own dedicated receiver circuitry. In this case, the IMD may pulse only once, and the energy coupled to each coil structure 482 may be determined simultaneously. In some examples, each coil structure 482 may be coupled to the same receiver circuitry. In this case, the IMD may pulse multiple times, and during each pulse the energy coupled to a different coil structure 482 is individually determined with each pulse. In some examples, each subset 484i to 4844 of coil structures 482 may be coupled to its own receiver circuitry (e.g., multiple receiver circuitry less than the total number of coil structures 482). In this case, the IMD may pulse multiple times and the energy coupled to a different subset of coil structures is determined with each pulse. In some examples, the optimum coil structure or subset of coil structures may be determined similarly as described above, except that instead of sending the energy (e.g., pulsing) the coil structures 482 of the external charger, the energy is sent from the IMD and received by the coil structures 482. These methods have the advantage that 34 determining the optimum coil structure or subset of coil structures for charging (or transmitting power) may be performed during telemetry uplinkfrom the IMD to the external charger. Therefore, uplink messages may be utilized as a means of measuring coupling (eg., simultaneous telemetry uplink and coil coupling determination).

[0122] Once a coil structure 482 is selected to charge (or transmit power to) the IMD, the received power at the IMD and / or the loading of the selected coil structure may be monitored. In response to the received power at the IMD and / or the loading of the selected coil structure falling below a threshold, a different coil structure 482 may be selected in a similar manner as described above. Alternatively, each coil structure 482 adjacent to the selected coil structure may be periodically pulsed to determine whether the adjacent coil structure results in a greater received power at the IMD and / or has a greater loading than the selected coil structure. In response to the adjacent coil structure 482 resulting in a greater received power at the IMD or a greater loading, then the adjacent coil structure 482 is selected to the charge (or transmit power to) the IMD.

[0123] The loading of a coil structure 482 may be measured in several different ways. In a first example, the loading of a coil structure 482 may be determined by measuring the reflected power from the coil structure 482. In a second example, the loading of a coil structure 482 may be determined by measuring the tuning frequency of the coil structure 482. In a third example, the loading of a coil structure 482 may be determined by measuring the impedance of the coil structure 482. Each of these methods inherently determines if the coil structure loading changes. In some examples, these methods may be used to detect metal and / or the presence of an IMD in the vicinity of the coil structure. If one or a subset of coil structures 482 detects the IMD through one or more of these methods, that coil structure or subset of coil structures may be selected to charge (or transmit power to) the IMD. If an excessive amount of metal is detected by a coil structure, it could be an indication of coupling to something other than the IMD, such as an orthopedic implant or an external metallic device proximate the patient, such as an electronic device (e.g., phone, tablet, etc.). In such cases, the coil structure may be prevented from sending energy to charge (or power) the IMD to ensure that the orthopedic implant does not heat up or the external device does not malfunction. In some examples, the coil structure loading may be compared to the received energy at the IMD, and if the received energy is significantly lower than the coil structure loading, it could be an indication of coil structure coupling to something other than the IMD. In such cases, power applied to that coil structure may be reduced or turned off.

[0124] While the previous FIGS. 4-14 relate to inductive wireless power transfer and / or near-field RF wireless power transfer, the following FIGS. 15A-26B relate to far-field RF wireless power transfer.

[0125] FIGS. 15Aand 15B are diagrams schematically representing an example external charger including a radio frequency (RF) transmitter 500 that may be configured to wirelessly transmit power to an IMD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D) via far-field RF wireless power transfer. In some examples, the RF transmitter 500 may provide the wireless transmitter 222 of FIGS. 2A-2C. The RF transmitter 500 includes transmitter circuitry 502 and an antenna array 504 including a plurality of antennas 506. While the antenna array 504 in FIG. 15B includes 24 antennas 506, in some examples, the antenna array 504 may include less than 24 antennas 506 (e.g., 10, 15, 20, etc.) or more than 24 antennas 506 (e.g., 100, 500, 1000, etc.). Each antenna 506 is configured to deliver power to a wireless receiver (e.g., 206 of FIGS. 2A-2C or 3A-3D), and each antenna 506 includes an adjustable phase to coherently focus the power (e.g., beamforming) at the wireless receiver (e.g., at the antenna 260 of the wireless receiver).

[0126] In some examples, a power element (e.g., 204 of FIGS. 2A-2C or 3A-3D) may be charged (or supplied power) by continuously transmitting, during a charging session via the RF transmitter 500, power to the wireless receiver. In some examples, the power element may be charged by pulsing, during a charging session via the RF transmitter 500, power to the wireless receiver. In a first example, the RF transmitter 500 may be configured to charge (or transmit power to) the IMD by receiving a calibration signal from the IMD at each antenna 506 of the antenna array 504 and adjusting the transmit settings of each antenna 506 of the antenna array 504 based on the received calibration signal as an inverse phase constant amplitude, inverse phase arbitrary amplitude, or a complex conjugate of the received calibration signal. In a second example, the RF transmitter 500 may be configured to charge (or transmit power to) the IMD by successively pulsing a calibration signal from each antenna 506 of the antenna array 504 and identifying a phase of the calibration signal received at the wireless receiver for each antenna 506 of the antenna array 504. The identified phase for each antenna 506 of the antenna array 504 is then transmitted to the RF transmitter 500 and the RF transmitter adjusts the transmit settings of each antenna 506 of the antenna array 504 based on the identified phase of the calibration signal for each antenna 506 of the antenna array 504. These methods and additional methods for adjusting the transmit settings of each antenna 506 of the antenna array 504 and / or for charging (or transmitting power to) the IMD are further described below with reference to at least FIGS. 29A-29F.

[0127] Compared to external chargers configured for inductive or near-field RF wireless power transfer, an external charger including (RF) transmitter 500 may be arranged farther away from the patient and can charge (or transmit power to) an IMD over a greater range of locations, positions, and / or postures of the patient. For example, while a patient may be restricted to a bed or another patient support (e.g., when using a charging pad) or otherwise be required to be in close proximity (e.g., for a wearable external charger) during charging of the IMD when using an external charger configured for inductive or near-field RF wireless power transfer, the patient need not be in close proximity to the external charger and may roam freely about a room or larger area during charging of the IMD when using an external charger configured for far-field RF wireless power transfer.

[0128] As further described below with reference to at least FIG. 25, an RF transmitter 500 may be arranged at any one of several suitable locations within a room of a patient to charge (or transmit powerto) an IMD within the patient. There are multiple paths for a wireless transmit signal from an antenna 506 of the antenna array 504 to reach a wireless receiver of an IMD within an indoor environment due to obstructions and / or reflections from objects, walls, the ceiling, and the floor. These signals will have different phase / amplitude values when they reach the IMD, and the highest amplitude signal will contribute the most to the recharging of the power element. Different antennas 506 may have different transmission paths, however, the path with the highest amplitude at the IMD may be determined to be the primary path and antenna. For each antenna 506, the primary path and its phase relative to the primary antenna may be determined and used to charge (or transmit power to) the IMD.

[0129] FIG. 16A is a side view schematically representing an example external charger520a that may be configured to wirelessly transmit powerto an IMD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D) via far-field RF wireless power transfer. The external charger 520a includes a wireless transmitter including at least one directive antenna (e.g., spherical helix antenna, corner reflector antenna) within a spherical housing 522a and a motion mechanism 524 to automatically and / or manually position the at least one directive antenna relative to a wireless receiver (e.g., 206 of FIGS. 2A-2C and 3A-3D) including the antenna (e.g., 260 of FIGS. 3A-3D) of an IMD. As further described below with reference to FIG. 25, the external charger 520a may be arranged at any one of several suitable locations within a room of a patient to charge (or transmit power to) an IMD within the patient.

[0130] The external charger 520a may be manually rotated or repositioned to achieve optimum coupling with the wireless receiver of the IMD. In some examples, the external charger 520a may include a coupling status indicator (e.g., light, sound, display, etc.) to aid in achieving the optimum coupling with the wireless receiver of the IMD. In some examples, a smartphone application may be used to configure the external charger 520a to achieve optimum coupling with the wireless receiver of the IMD. In some examples, the external charger 520a may be automatically rotated by motion mechanism 524 in one or more axes to achieve optimum coupling with the wireless receiver of the IMD. In some examples, the external charger 520a may include multiple directive antennas arranged inside the housing 522a, and the directive antenna or antennas with the best coupling with the wireless receiver of the IMD may be selected to transmit recharge energy (or power) to the IMD.

[0131] In addition, the methods discussed below with reference to at least FIGS. 29A-29F regarding an antenna array may also be applicable to external charger 520a when external charger 520a includes multiple directive antennas. For example, the IMD may transmit a pulse to the external charger 520a, the amplitude and / or phase of the calibration signal may be detected at each directive antenna, and the directive antenna receiving the highest amplitude calibration signal may be selected to charge (or transmit power to) the IMD. Alternatively, the transmit settings of each directive antenna may be adjusted based on the received calibration signal as an inverse phase constant amplitude, inverse phase arbitrary amplitude, or a complex conjugate of the received calibration signal to charge (or transmit power to) the IMD from multiple directive antennas simultaneously.

[0132] FIG. 16B is a side view schematically representing an example external charger 520b that may be configured to wirelessly transmit power to an IMD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D) via far-field RF wireless power transfer. The external charger 520b includes at least one directive antenna (e.g., helix antenna, log periodic antenna, corner reflector antenna) within a cylindrical housing 522b and a motion mechanism 524 to automatically and / or manually position the at least one directive antenna relative to a wireless receiver (e.g., 206 of FIGS. 2A-2C and 3A-3D) including the antenna (e.g., 260 of FIGS. 3A-3D) of an IMD. As further described below with reference to FIG. 25, the external charger 520b may be arranged at any one of several suitable locations within a room of a patient to charge (or transmit power to) an IMD within the patient. The external charger 520b may include similar features and functions as the external charger 520a described with reference to FIG. 16A.

[0133] FIG. 17A is a diagram schematically representing an example directional antenna 530a that may be configured to wirelessly transmit power to an IMD via far-field RF wireless power transfer. The directional antenna 530a is a helix antenna. In some examples, the helix antenna 530a may be included within the housing 522a of the external charger 520a of FIG. 16A or within the housing 522b of the external charger 520b of FIG. 16B.

[0134] FIG. 17B is a diagram schematically representing an example directional antenna 530b that may be configured to wirelessly transmit power to an IMD via far-field RF wireless power transfer. The directional antenna 530b is a spherical helix antenna. In some examples, the spherical helix antenna 530b may be included within the housing 522a of the external charger 520a of FIG. 16A or within the housing 522b of the external charger 520b of FIG. 16B.

[0135] FIG. 17C is a diagram schematically representing an example directional antenna 530c that may be configured to wirelessly transmit power to an IMD via far-field RF wireless power transfer. The directional antenna 530c is a log periodic antenna. In some examples, the log periodic antenna 530c may be included within the housing 522a of the external charger 520a of FIG. 16A or within the housing 522b of the external charger 520b of FIG. 16B.

[0136] FIG. 17D is a diagram schematically representing an example directional antenna arrangement 540a that may be configured to wirelessly transmit power to an IMD via far-field RF wireless power transfer. The directional antenna arrangement 540a includes four corner reflector antennas 542a symmetrically arranged about a central axis 548. Each corner reflector antenna 542a includes an antenna element 544a and a ground plane 546a, which may be separate or shared among the four corner reflector antennas 542a. The ground plane 546a may be a solid sheet, a slotted sheet, ora patterned sheet, and the ground plane 546a may include a single layer or multiple layers. In some examples, the directional antenna arrangement 540a may be included within the housing 522a of the external charger 520a of FIG. 16A or within the housing 522b of the external charger 520b of FIG. 16B. In some examples, the directional antenna arrangement 540a may have the shape of a half sphere, such that two directional antenna arrangements 540a may be arranged face to face in a single sphereshaped housing (e.g., 522A of FIG. 16A).

[0137] FIG. 17E is a diagram schematically representing an example directional antenna arrangement 540b that may be configured to wirelessly transmit power to an IMD via far-field RF wireless power transfer. The directional antenna arrangement 540b includes three corner reflector antennas 542b symmetrically arranged about a central axis 548. Each corner reflector antenna 542b includes an antenna element 544b and a ground plane 546b, which may be separate or shared among the three comer reflector antennas 542b. The ground plane 546b may be a solid sheet, a slotted sheet, ora patterned sheet, and the ground plane 546b may include a single layer or multiple layers. In some examples, the directional antenna arrangement 540b may be included within the housing 522a of the external charger 520a of FIG. 16A or within the housing 522b of the external charger 520b of FIG. 16B. In some examples, the directional antenna arrangement 540a may have the shape of a half sphere, such that two directional antenna arrangements 540b may be arranged face to face in a single sphereshaped housing (e.g., 522A of FIG. 16A). While antenna arrangement 540b of FIG. 17E includes three directional antennas and antenna arrangement 540a of FIG. 17D include four directional antennas, in some examples, similar antenna arrangements may include more than four directional antennas, such as 5, 6, 7, 8, 9, or more directional antennas.

[0138] While FIGS. 15A-17E disclose antennas and antenna arrangements for wireless transmitters of external chargers for transmitting power to IMDs via far-field RF wireless power transfer, the following FIGS. 18-24 disclose antenna components and antennas for wireless receivers within the IMDs to receive the transmitted power.

[0139] FIG. 18 is a diagram schematically representing an example double negative metamaterial (DNG) 600 that may be used in combination with an antenna within an IMD to form a DNG antenna. The DNG metamaterial 600 may be the combination of a negative-permittivity (ENG) metamaterial 602 and a negative-permeability (MNG) metamaterial 606. The ENG metamaterial 602 includes an array of thin conductors 604 (e.g., wires) arranged parallel to each other. The MNG metamaterial 606 includes an array of split-ring resonators 608 arranged parallel to each other. Accordingly, the DNG metamaterial 600 includes the array of thin conductors 604 of the ENG metamaterial 602 and the array of split-ring resonators 608 of the MNG metamaterial 606. The DNG metamaterial 600 may be used to form an artificial magnetic conductor (AMC) metamaterial that may be used in combination with an antenna (e.g., patch antenna) of an IMD to form a metamaterial antenna. By using metamaterials, such as the DNG metamaterial 600, antenna parameters (e.g., gain, bandwidth, efficiency, size, isolation, etc.) may be improved.

[0140] FIG. 19A is a top view schematically representing one unit cell 620a of an example artificial magnetic conductor (AMC) metamaterial that may be used in combination with an antenna of an IMD to form a metamaterial antenna. The unit cell 620a is a split ring resonator having a width 622a and a length 624a based on the target wavelength (A). In this example, the width 622a may be A / 23 and the length 624a may be A / 23.

[0141] FIG. 19B is a top view schematically representing one unit cell 620b of an example artificial magnetic conductor (AMC) metamaterial that may be used in combination with an antenna within an IMD to form a metamaterial antenna. The unit cell 620b is a spiral resonator including fractals and having a width 622b and a length 624b based on the target wavelength (A). In this example, the width 622b may be AMO and the length 624b may be AMO.

[0142] FIG. 19C is a top view schematically representing one unit cell 620c of an example artificial magnetic conductor (AMC) metamaterial that may be used in combination with an antenna of an IMD to form a metamaterial antenna. The unit cell 620c is a spiral resonator having a width 622c and a length 624c based on the target wavelength (A). In this example, the width 622c may be A / 46 and the length 624c may be A / 46.

[0143] FIG. 19D is a top view schematically representing one unit cell 620d of an example artificial magnetic conductor (AMC) metamaterial that may be used in combination with an antenna of an IMD to form a metamaterial antenna. The unit cell 620d is a spiral resonator including fractals and having a width 622d and a length 624d based on the target wavelength (A). In this example, the width 622d may be A / 55 and the length 624d may be A / 63.

[0144] FIG. 19E is a top view schematically representing one unit cell 620e of an example artificial magnetic conductor (AMC) metamaterial that may be used in combination with an antenna of an IMD to form a metamaterial antenna. The unit cell 620e is a split ring resonator including fractals and having a width 622e and a length 624e based on the target wavelength (A). In this example, the width 622e may be A / 73 and the length 624e may be A / 78.

[0145] Accordingly, as indicated by unit cells 620a-620e of FIGS. 19A-19E, the unit cell selected for an AMC metamaterial for a metamaterial antenna of an IMD may be selected based on the recharge frequency, size constraints, and / or other requirements of the IMD.

[0146] FIGS. 20A and 20B are a top view and a cross-sectional view, respectively, schematically representing an example AMC backing 640 that may be used in combination with an antenna structure to form a metamaterial antenna. The AMC backing 640 may be used as a reflector to increase antenna efficiency and directivity. The AMC backing 640 includes a substrate 642, an array of pillars 644 coupled to the substrate 642, and an array of AMC unit cells 620 coupled to the array of pillars 644. The substrate 642 may include a printed circuit board, a ceramic substrate, a polymer substrate, or another suitable substrate. The array of pillars 644 may include copper or another suitable material. Each unit cell 620 may include a unit cell 620a-620e of FIGS. 19A-19E or another suitable unit cell. In some examples, the AMC backing 640 may be placed on or behind a printed circuit board assembly (PCBA) of the IMD, may be part of the PCBA or power element (e.g., battery) of the IMD, or may be arranged inside a shield enclosure of the IMD. In some examples, the antenna structure may be formed on the outer surface of the shield enclosure or as part of the PCBA of the IMD. For example, fora pill shaped cylindrical IMD, multiple antenna structures (e.g., 3 or4) may be arranged around the cylinder inside or outside of the shield enclosure and spaced equally. The AMC backing may be wrapped around the battery to improve the directivity of each antenna along its primary orientation.

[0147] FIG. 21 is a cross-sectional view schematically representing an example antenna arrangement 660 including an antenna 662 aligned with an AMC backing 664. The AMC backing 664 acts as a reflector to increase antenna efficiency and directivity. The AMC backing 664 includes a ground plane 666, a dielectric substrate 668 on the ground plane 666, and an array of AMC unit cells 620 on the dielectric substrate 668. The thickness of the dielectric substrate 668 is indicated at 669, and the distance between the AMC backing 664 and the antenna 662 is indicated at 670. In some examples, the distance 670 is A / 4, where “A” is the target wavelength. Depending on the geometry of the unit cell 620, the thickness 669 of the substrate 668, and the relative dielectric permittivity of the substrate 668, the resonant frequency and the bandwidth of the antenna arrangement 660 may be tuned to the recharge frequency. In some examples, the AMC backing 664 may be placed on or behind a printed circuit board assembly (PCBA) of the IMD, may be part of the PCBA or power element (e.g., battery) of the IMD, or may be arranged inside a shield enclosure of the IMD. In some examples, the antenna 662 may be formed on the outer surface of the shield enclosure or as part of the PCBA of the IMD.

[0148] FIG. 22 is a top view schematically representing an example antenna arrangement 680 including a patch antenna 682 with a surrounding AMC metamaterial 684. The AMC metamaterial 684 includes a dielectric substrate 668 on a ground plane 666 (see FIG. 21), and an array of unit cells 620a on the dielectric substrate 668 surrounding the patch antenna 682. In some examples, the unit cells 620a may be replaced with different unit cells, such as unit cells 620b-620e of FIGS. 19B-19E. The patch antenna 682 is arranged on the dielectric substrate 682 and may include a feeding point as indicated at 683. The antenna arrangement 680 may be placed on or part of a PCBA of an IMD, may be part of a power element (e.g., battery) of an IMD, or may be part of a shield enclosure of the IMD. By using an antenna arrangement 680 including a patch antenna 682 with a surrounding AMC metamaterial 684, the total size (e.g., dimensions) of the antenna arrangement may be reduced compared to an antenna arrangement not including an AMC metamaterial. Thus, the antenna arrangement 680 may be more suitable for use within an IMD that may be implanted within the head or neck of a patient, where the IMD size should be minimized.

[0149] FIGS. 23A and 23B are a top view and a side view, respectively, schematically representing an example antenna arrangement 700 including a patch antenna 702 with AMC metamaterial 704 beneath the patch antenna 702. The AMC metamaterial 704 includes a plurality of parallel dielectric substrates 706 and a plurality of unit cells 620a on each dielectric substrate 706. The plurality of dielectric substrates 706 are arranged perpendicular to and underneath the patch antenna 702. In some examples, the unit cells 620a may be replaced with different unit cells, such as unit cells 620b-620e of FIGS. 19B-19E. While antenna arrangement 700 includes seven dielectric substrates 706 each with five unit cells 620a arranged on the substrate, in some examples, antenna arrangement 700 may include less than seven dielectric substrates 706 or more than seven dielectric substrates 706 and each substrate may include less than five unit cells 620a or more than five unit cells 620a. By using an antenna arrangement 700 including a patch antenna 702 with an underlying AMC metamaterial 704, the total size (e.g., dimensions) of the antenna arrangement may be reduced compared to an antenna arrangement not including an AMC metamaterial. Thus, the antenna arrangement 700 may be more suitable for use within an I MD that may be implanted within the head or neck of a patient, where the IMD size should be minimized.

[0150] FIG. 24 is a top view schematically representing an example antenna arrangement 720 including a patch antenna 722 with AMC metamaterial 724 beneath the patch antenna. The AMC metamaterial 724 includes a dielectric substrate 726 and a circular split-ring resonator 728 on the dielectric substrate 726. The patch antenna 722 is over the split-ring resonator 728. By including the AMC metamaterial 724, the size (e.g., length and width) of the patch antenna 722 may be reduced compared to an antenna arrangement not including the AMC metamaterial. Thus, the antenna arrangement 720 may be more suitable for use within an IMD that may be implanted within the head or neck of a patient, where the IMD size should be minimized.

[0151] FIG. 25 is a diagram schematically representing an indoor environment 740 including potential example locations for a wireless transmitter 760a-760f (collectively referred to as a wireless transmitter 760) of an external charger (e.g., 220a-220c of FIGS. 2A-2C) for transmitting power to an IMD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D) within a patient via far-field RF wireless power transfer. In some examples, the indoor environment 740 may also include a sensor 762, a sensor 764, and / or BLE transceivers 766a-766c for determining a location, position, and / or posture of a patient and / or an IMD within the patient. In this example, indoor environment 740 is a bedroom and may include a bed 742, a bedside unit 744 (e.g., bookcase, nightstand, lampstand, etc.), a dresser 746 (or wardrobe, etc.), and a table 748. The indoor environment 740 includes at least one wireless transmitter 760. The wireless transmitter 760 may include a wireless transmitter 500 including an antenna array 504 of FIGS. 15A and 15B or a wireless transmitter 520a or 520b of FIGS. 16A and 16B including at least one directive antenna 530a-530c, 542a, or 542b of FIGS. 17A-17E.

[0152] One or multiple wireless transmitters 760 may be arranged within the indoor environment 740 within wireless power transfer range of an IMD within a patient. In some examples, a wireless transmitter 760a may be arranged on or integrated into the bed 742 (e.g., on the headboard, footboard, frame, etc.). In some examples, a wireless transmitter 760b may be arranged on or integrated into the bedside unit 744. In some examples, a wireless transmitter 760c may be arranged on or integrated into the dresser 746. In some examples, a wireless transmitter 760d may be arranged on or integrated into a table 748. In some examples, a wireless transmitter 760e may be mounted on or in a wall 750. In some examples, a wireless transmitter 760f may be mounted on or in the ceiling 752.

[0153] In some examples, an external charger may also include an external sensor 762 for sensing the location, position, and / or posture of a patient and / or the location of an IMD within the patient. The sensor 762 may be arranged on or mounted to the bed 742, the bedside unit 744, dresser 746, table 748, wall 750, ceiling 752, or other suitable support. The sensor 762 may include a radio detection and ranging (radar) sensor, a light detection and ranging (lidar) sensor, an optical sensor (e.g., camera), or a combination thereof. The sensor 762 may be used for non-contact sensing of the location, position, and / or posture of a patient (e.g., lying on bed 742) to estimate the location of the IMD within the patient relative to a wireless transmitter 760. Where external sensor 762 is an optical sensor (e.g., camera), as described further below with reference to FIG. 31, the optical sensor may sense a patch 1116 on the patient to determine the location of the IMD.

[0154] In some examples, an external charger may also include an external sensor 764 for sensing the location and / or position of a patient. The sensor 764 may be arranged within the bed 742 (or bedding) and may include at least one accelerometer, pressure sensor, and / or at least one temperature sensor. The sensor 764 may be used to sense the location and / or position of a patient (e.g., lying on bed 742) to estimate the location of the I MD within the patient relative to a wireless transmitter 760. For example, an increase in the pressure and / or temperature sensed by the sensor 764 may be indicative of the patient being closer to the sensor, and a decrease in the pressure and / or temperature sensed by the sensor 764 may be indicative of the patient being farther away from the sensor. Thus, the pressure and / or temperature sensed by the sensor 764 may be indicative of the location and / or position of the patient relative to the sensor 764, which may be used to determine the location and / or position of the patient relative to a wireless transmitter 760.

[0155] In some examples, an external charger may also include BLE transceivers 766a-766c for triangulating the location of an IMD within a patient. While three BLE transceivers 766a-766c are illustrated in FIG. 25, in some examples, more than three BLE transceivers may be used. Each BLE transceiver 766a-766c may be arranged on or mounted to the bed 742, bedside unit 744, dresser 746, table 748, wall 750, ceiling 752, or other suitable support and / or integrated into a device including a wireless transmitter 760 (e.g., see external charger 220c of FIG. 2C including both a wireless transmitter 222 and a BLE transceiver 226). Each BLE transceiver 766a-766c may communicate with a BLE transceiver (e.g., 210 of FIG. 2C) of an IMD to triangulate the location of the IMD. In some examples, a received signal strength indicator (RSSI) of IMD advertisements from each BLE transceiver 766a-766c may be used to triangulate the location of the IMD since the respective RSSI is indicative of the distance between the respective BLE transceiver 766a-766c and the IMD. Triangulating the location of the IMD is a non-contact method for determining the location of the IMD. In addition, the patient may roam freely about a room or larger area while still enabling the location of the IMD to be determined using triangulation.

[0156] The external sensor 762, the external sensor 764, and / or the BLE transceivers 766a-766c may be used alone or in combination to sense the location, position, and / or posture of the patient for inductive wireless power transfer or near-field RF wireless power transfer as described above with reference to at least FIGS. 4-14 or for far-field RF wireless power transfer as described above with reference to at least FIGS. 15A-24. For inductive wireless power transfer or for near-field RF wireless power transfer, the sensed location, position, and / or posture of the patient may be used to select the coil structure (e.g., 482 of FIG. 14) or subset of coil structures (e.g., 484i to 4844 of FIG. 14) of an array of coil structures (e.g., 480 of FIG. 14) to charge (or transmit power to) the power element of the IMD. For far-field RF wireless power transfer, the sensed location, position, and / or posture of the patient may be used to adjust antenna settings (e.g., antennas 506 of FIG. 15B; 530a-530c, 540a, or 540b of FIGS. 17A-17E) and / or to adjust a position of a reflective sheet as described below with reference to FIGS. 26A and 26B.

[0157] FIG. 26A is a diagram schematically representing a wireless transmitter 760 and an example reflective sheet 770a for wirelessly transmitting power to an IMD 456 of a patient 454 in a bed 742. While IMD 456 is illustrated in FIG. 26A as being implanted in a head-and-neck region of the patient 454, in some examples, the IMD 456 may be implanted in another region (e.g., torso, pelvis) of the patient. There are multiple transmission paths between a wireless transmitter 760 and an IMD 456, which may include line of sight transmission paths 772 and reflected transmission paths 774. Transmission paths may be altered by placing reflective objects within the room to optimize power transmission or to shield objects within the room. For example, a patient sleeping in a supine position may have a good line of sight (LOS) to a ceiling mounted wireless transmitter 760. If the patient rolls over to a prone position, however, LOS may be obstructed by the neck / body of the patient. To address this, a reflective sheet 770a (e.g., metal sheet or sheets) may be embedded into the frame or mattress of the bed 742 to reflect the transmitted signals underneath the patient and strengthen the signal coupling between the wireless transmitter 760 and the IMD 456. The reflective sheet 770a may cover the entire frame of the bed 742 or a portion of the frame of the bed 742. In some examples, the reflective sheet 770a may be manually moved, rotated, and / or adjusted to optimize power transfer. In some examples, the reflective sheet 770a may be automatically moved or rotated to increase power transfer to the IMD 456. The reflective sheet 770a may be automatically moved by monitoring power coupling (e.g., via wireless transmitter 760 and / or IMD 456) and stepwise adjusting a position and / or angle of the reflective sheet 770a relative to the IMD 456 to optimize power transfer to the IMD 456.

[0158] FIG. 26B is a diagram schematically representing a wireless transmitter 760 and an example reflective sheet 770b for wirelessly transmitting power to an IMD 456 of a patient 454 in a bed 742. FIG. 26B is similar to FIG. 26A, except FIG. 26B includes a concave reflective sheet 770b. The concave reflective sheet 770b may be arranged to focus fields at a certain distance (similar to optical focusing), which may improve the efficiency of the wireless power transfer compared to when using reflective sheet 770a of FIG. 26A. In some examples, the reflective sheet 770b may be manually moved, rotated, and / or adjusted to optimize power transfer to the IMD 456. In some examples, the reflective sheet 770b may be automatically moved or rotated to increase power transfer to the IMD 456. The reflective sheet 770b may be automatically moved by monitoring power coupling (e.g., via wireless transmitter 760 and / or IMD 456) and stepwise adjusting a position or angle of the reflective sheet 770b relative to the IMD 456 to optimize power transfer to the IMD 456.

[0159] FIG. 27 is a top view schematically representing an example array 790 of sensors 792 for sensing the location, position, and / or posture of a patient 454 on a bed 742. The sensors 792 may be accelerometers, gyroscopes, piezoelectric sensors, pressure sensors, temperature sensors, or other sensors configured to sense the location, position, and / or posture of the patient 454 relative to the array 790 of sensors 792. By sensing the location (e.g., lying closer to left side of bed, lying closer to right side of bed, lying closer to head of bed, lying closer to foot of bed, etc.), position (e.g., lying parallel to sides of bed, lying diagonally across bed, etc.), and / or posture (e.g., supine, prone, left side, right side, etc.) of the patient 454, the location of the IMD 456 within the patient may be estimated relative to the array 790 of sensors 792.

[0160] In some examples, for inductive wireless power transfer or near-field RF wireless power transfer, the array 790 of sensors 792 may be integrated into the external charging pad 360a of FIG. 7, the external charging pad 360b of FIG. 9, the array 464 of coils 466 of FIG. 13B, the array 470 of coils 472 of FIG. 13C, or the array 474 of coils 476 of FIG. 13D. In these examples, each sensor 792 may correspond to a coil or coil structure or each sensor 792 may correspond to a plurality of adjacent coils or coil structures (e.g., a subset of coil structures). The sensed location, position, and / or posture of the patient may be used to select the coil, coil structure, or subset of coils orcoil structures for charging (or transmitting power to) the power element of the I MD 456.

[0161] In some examples, for far-field RF wireless power transfer, the sensed location, position, and / or posture of the patient may be used to adjust antenna settings (e.g., antennas 506 of FIG. 15B; 530a-530c, 540a, or 540b of FIGS. 17A-17E), adjust the position of a directive antenna (e.g., 530a-530c, 540a, or 540b of FIGS. 17A-17E), and / or to adjust a position of a reflective sheet (e.g., 770a or 770b of FIGS. 26A and 26B).

[0162] The IMD 456 may include a sensor 457, such as an accelerometer or gyroscope, to detect the orientation (e.g., relative to gravity) of the IMD 456, and thus the orientation of the patient 454. For inductive wireless power transfer or near-field RF wireless power transfer, sensor 457 may be used to sense the orientation of the IMD 456 relative to the external charger (e.g., charging pad 360a of FIG. 7, 360b of FIG. 9, array 464 of coils 466 of FIG. 13B), and a coil or coil structure or a subset of coils or coil structures of the external charger may be selected to charge (or transmit power to) the IMD 456 based on the sensed orientation to improve power coupling. For far-field RF wireless power transfer, sensor 457 may be used to sense the orientation of the IMD 456 relative to the external charger (e.g., 500 of FIG. 15A) and adjust transmit settings of each antenna of the antenna array (e.g., 504 of FIG. 15B) based on the sensed orientation and / or adjust a position of a reflective sheet (e.g., 770a or 770b of FIGS. 26A and 26B) based on the sensed orientation to improve power coupling.

[0163] FIGS. 28A-28K are flow diagrams schematically representing example methods 800a-800k for wirelessly transmitting power to a power element (e.g., 204 of FIGS. 2A-3D) of an IMD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D). As illustrated in FIG. 28A at 802, method 800a includes charging (or transmitting power to) a power element of an implantable medical device comprising receiving, at a wireless receiver (e.g., 206 of FIGS. 2A-3D) of the implantable medical device from a wireless transmitter (e.g., 222 of FIGS. 2A-2C) of an external charger (e.g., 220a-220c of FIGS. 2A-2C), power to charge (or supply power to) the power element. In some examples, the implantable medical device is configured to apply electrical stimulation to an upper airway patency-related tissue of a patient. In some examples, the implantable medical device is configured to sense diagnostic information of the patient.

[0164] In some examples, the wireless transmitter comprises an array of coils or coil structures (e.g., 370 of FIGS. 8 and 9, 464 of FIG. 13B, 470 of FIG. 13C, 474 of FIG. 13D, or 480 of FIG. 14). In some examples, method 800a may further include method 800b of FIG. 28B. As illustrated in FIG. 28B at 804, method 800b may include successively pulsing, via the wireless transmitter, each coil structure (e.g., 372 of FIGS. 8 and 9, 466 of FIG. 13B, 472 of FIG. 13C, 476 of FIG. 13D, or 482 of FIG. 14) or subset of coil structures (e.g., 484i to 4844 of FIG. 14) of the array of coil structures. At 806, method 800b may include measuring, via the wireless receiver, received energy from each coil structure or subset of coil structures in response to the pulsing of the respective coil structure or subset of coil structures. At 808, method 800b may include selecting, via the wireless transmitter, the coil structure or subset of coil structures for which the received energy is greatest to charge (or transmit power to) the power element.

[0165] In some examples, method 800b may further include method 800c of FIG. 28C. As illustrated in FIG. 28C at 810, method 800c may include monitoring, via the wireless receiver, received energy from the selected coil structure or subset of coil structures. At 812, method 800c may include in response to the received energy from the selected coil structure or subset of coil structures falling below a threshold, selecting another coil structure or subset of coil structures of the array of coil structures to charge (or transmit power to) the power element.

[0166] In some examples, method 800b may further include method 800d of FIG. 28D. As illustrated in FIG. 28D at 814, method 800d may include periodically pulsing, via the wireless transmitter, a coil structure or subset of coil structures of the array of coil structures adjacent to the selected coil structure or subset of coil structures. At 816, method 800d may include measuring, via the wireless receiver, received energy from the adjacent coil structure or subset of coil structures. At 818, method 800d may include in response to the received energy from the adjacent coil structure or subset of coil structures being greater than the received energy from the selected coil structure or subset of coil structures, switching to the adjacent coil structure or subset of coil structures to charge (or transmit power to) the power element.

[0167] In some examples, method 800a may further include method 800e of FIG. 28E. As illustrated in FIG. 28E at 820, method 800e may include successively pulsing, via the wireless transmitter, each subset of coil structures of the array of coil structures. At 822, method 800e may include measuring, via the wireless receiver, received energy from each subset of coil structures in response to the pulsing of the respective subset of coil structures. At 824, method 800e may include successively pulsing, via the wireless transmitter, each coil structure of the subset of coil structures for which the received energy is greatest. At 826, method 800e may include measuring, via the wireless receiver, received energy from each coil structure of the subset of coil structures for which the received energy is greatest in response to the pulsing of the respective coil structure of the subset of coil structures for which the received energy is greatest. At 828, method 800e may include selecting, via the wireless transmitter, the coil structure for which the received energy is greatest to charge (or transmit power to) the power element.

[0168] In some examples, method 800a may further include method 800f of FIG. 28F. As illustrated in FIG. 28F at 830, method 800f may include successively pulsing, via the wireless transmitter, a single coil structure (e.g., 486i to 4864 of FIG. 14) of each subset of coil structures (e.g., 484i to 4844 of FIG. 14) of the array of coil structures. At 832, method 800f may include measuring, via the wireless receiver, received energy from each single coil structure of each subset of coil structures in response to the pulsing of the respective single coil structure of the respective subset of coil structures. At 834, method 800f may include successively pulsing, via the wireless transmitter, each remaining coil structure of the subset of coil structures for which the received energy for the respective single coil structure is greatest. At 836, method 800f may include measuring, via the wireless receiver, received energy from each remaining coil structure in response to the pulsing of the respective remaining coil structure. At 838, method 800f may include selecting, via the wireless transmitter, the coil structure for which the received energy is greatest to charge (or transmit power to) the power element.

[0169] In some examples, method 800a may further include method 800g of FIG. 28G. As illustrated in FIG. 28G at 840, method 800g may include successively pulsing, via the wireless transmitter, each coil structure or subset of coil structures of the array of coil structures. At 842, method 800g may include measuring, via the wireless transmitter, loading of each coil structure or subset of coil structures in response to the pulsing of the respective coil structure or subset of coil structures. At 844, method 800g may include selecting, via the wireless transmitter, the coil structure or subset of coil structures for which the loading is greatest to charge (or transmit power to) the power element.

[0170] In some examples, method 800a may further include method 800h of FIG. 28H. As illustrated in FIG. 28H at 846, method 800h may include successively pulsing, via the wireless transmitter, each subset of coil structures of the array of coil structures. At 848, method 800h may include measuring, via the wireless transmitter, loading of each subset of coil structures in response to the pulsing of the respective subset ofcoil structures. At 850, method 800h may include successively pulsing, via the wireless transmitter, each coil structure of the subset of coil structures for which the loading is greatest. At 852, method 800h may include measuring, via the wireless transmitter, loading of each coil structure of the subset of coil structures for which the loading is greatest in response to the pulsing of the respective coil structure of the subset of coil structures for which the loading is greatest. At 854, method 800h may include selecting, via the wireless transmitter, the coil structure for which the loading is greatest to charge (or transmit power to) the power element.

[0171] In some examples, method 800a may further include method 800i of FIG. 28I. As illustrated in FIG. 28I at 856, method 800i may include successively pulsing, via the wireless transmitter, a single coil structure (e.g., 486i to 4864 of FIG. 14) of each subset of coil structures (e.g., 484i to 4844 of FIG. 14) of the array of coil structures. At 858, method 800i may include measuring, via the wireless transmitter, loading of each single coil of each subset of coil structures in response to the pulsing of the respective single coil structure of the respective subset of coil structures. At 860, method 800i may include successively pulsing, via the wireless transmitter, each remaining coil structure of the subset of coil structures for which the loading for the respective single coil structure is greatest. At 862, method 800i may include measuring, via the wireless transmitter, loading of each remaining coil structure in response to the pulsing of the respective remaining coil structure. At 864, method 800i may include selecting, via the wireless transmitter, the coil structure for which the loading is greatest to charge (or transmit power to) the power element.

[0172] In some examples, method 800a may further include method 800j of FIG. 28J. As illustrated in FIG. 28J at 866, method 800j may include pulsing, via the wireless receiver (e.g., 206 of FIGS. 2A-3D), a coil (e.g., 300, of FIG. 4, 310 of FIG. 5, 320 of FIG. 6) of the wireless receiver. At 868, method 800j may include measuring, via the wireless transmitter, energy received at each coil structure or subset of coil structures of the array of coil structures. At 870, method 800j may include selecting, via the wireless transmitter, the coil structure or subset of coil structures for which the received energy is greatest to charge (or transmit power to) the power element. In some examples, measuring the energy received at each coil structure or subset of coil structures comprises simultaneously measuring the energy received at each coil structure or subset of coil structures in response to a single pulse of the coil of the wireless receiver. By simultaneously measuring the energy received at each coil structure or subset of coil structures in response to a single pulse of the coil of the wireless receiver, the optimum coil structure or subset of coil structures for charging (or transmitting power to) the IMD may be quickly determined (e.g., in less than 50 milliseconds). In some examples, measuring the energy received at each coil structure or subset of coil structures comprises successively measuring the energy received at each coil structure or subset of coil structures in response to a respective pulse of the coil of the wireless receiver.

[0173] In some examples, method 800a may further include method 800k of FIG. 28K. As illustrated in FIG. 28K at 872, method 800k may include sensing a position, orientation, and / or location of the patient. At 874, method 800k may include selecting, via the wireless transmitter, a coil structure or subset of coil structures based on the sensed position, orientation, and / or location of the patient to charge (or transmit power to) the power element. In some examples, method 800k may further include sensing, via at least one of an accelerometer, an external pressure sensor, or an external temperature sensor (e.g., 764 of FIG. 25), a position of the patient; and selecting, via the wireless transmitter, a coil structure or subset of coil structures based on the sensed position of the patient to charge (or transmit power to) the power element.

[0174] In some examples, method 800k may further include sensing, via a radar sensor or a lidar sensor (e.g., 762 of FIG. 25), a position of the patient; and selecting, via the wireless transmitter, a coil structure or subset of coil structures based on the sensed position of the patient to charge (or transmit power to) the power element. In some examples, method 800k may further include sensing, via a Received Signal Strength Indicator (RSSI) corresponding to each coil structure of the array of coil structures, a position of the patient; and selecting, via the wireless transmitter, a coil structure or subset of coil structures based on the sensed position of the patient to charge (or transmit power to) the power element. In some examples, method 800k may further include sensing, via an array of pressure sensors (e.g., 790 of FIG. 27) corresponding to the array of coil structures, a position of the patient; and selecting, via the wireless transmitter, a coil structure or subset of coil structures based on the sensed position of the patient to charge (or transmit power to) the power element.

[0175] In some examples, method 800k may further include sensing, via an accelerometer (e.g., 457 of FIG. 27) of the implantable medical device (e.g., 456 of FIG. 27), an orientation of the patient relative to the external charger; and selecting, via the wireless transmitter, a coil structure or subset of coil structures based on the sensed orientation of the patient to charge (or transmit power to) the power element. In some examples, method 800k may further include optically sensing, via an external sensor (e.g., 762 of FIG. 25), a location of the patient relative to the external charger; and selecting, via the wireless transmitter, a coil structure or subset of coil structures based on the optically sensed location of the patient to charge (or transmit power to) the power element. In some examples, optically sensing the location of the patient comprises optically sensing a wearable patch (e.g., 1116 of FIG. 31 described below) on the patient over the implantable medical device (e.g., 1100 of FIG. 31 described below). In some examples, method 800k may further include triangulating, via a plurality of Bluetooth Low Energy (BLE) transceivers (e.g., 766a-766c of FIG. 25), a location of the implantable medical device; and selecting, via the wireless transmitter, a coil structure of the array of coil structures based on the triangulated location of the implantable medical device to charge (or transmit power to) the power element.

[0176] In some examples, method 800a of FIG. 28A may further include one or more of methods 900a-900f of FIGS. 29A-29F. FIGS. 29A-29F are flow diagrams schematically representing example methods 900a-900f for wirelessly transmitting power to a power element (e.g., 204 of FIGS. 2A-3D) of an I MD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D). In some examples, the wireless transmitter (e.g., 222 of FIGS. 2A-2C, 500 of FIG. 15A) comprises an antenna array (e.g., 504 of FIG. 15B). The wireless transmitter may be arranged on a tabletop (e.g., 748 of FIG. 25), bedside (e.g., 744 of FIG. 25), a top of a dresser (e.g., 746 of FIG. 25), a ceiling (e.g., 752 of FIG. 25), a wall (e.g., 750 of FIG 25), or other suitable location. Each antenna (e.g., 506 of FIG. 15B) of the antenna array is configured to deliver power to the wireless receiver (e.g., 206 of FIGS. 2A-3D) and each antenna comprises an adjustable phase to coherently focus the power at the wireless receiver. In some examples, charging the power element comprises continuously transmitting, via the wireless transmitter, power to the wireless receiver. In some examples, charging the power element comprises pulsing, via the wireless transmitter, power to the wireless receiver.

[0177] In some examples, method 800a of FIG. 28A may further include method 900a of FIG. 29A. As illustrated in FIG. 29A at 902, method 900a may include transmitting, via the implantable medical device, a calibration signal to the wireless transmitter. At 904, method 900a may include receiving, via the wireless transmitter, the calibration signal at each antenna of the antenna array. At 906, method 900a may include adjusting, via the wireless transmitter, transmit settings of each antenna of the antenna array based on the received calibration signal. In some examples, adjusting the transmit settings of each antenna of the antenna array may include adjusting the transmit settings as an inverse phase constant amplitude, inverse phase arbitrary amplitude, or a complex conjugate of the received calibration signal. For example, antennas that do not receive the calibration signal may be set to zero amplitude, and / or antennas that receive the calibration signal but the received calibration signal amplitude is less than a threshold may be set to zero amplitude.

[0178] In some examples, method 800a of FIG. 28A may further include method 900b of FIG. 29B. As illustrated in FIG. 29B at 908, method 900b may include successively pulsing a calibration signal, via the wireless transmitter, to each antenna of the antenna array. At 910, method 900b may include receiving, via the wireless receiver, the calibration signal from each antenna of the antenna array. At 912, method 900b may include identifying, via the wireless receiver, a phase of the calibration signal for each antenna of the antenna array. At 914, method 900b may include transmitting, via the implantable medical device, the identified phase of the calibration signal for each antenna of the antenna array to the external charger. At 916, method 900b may include adjusting, via the wireless transmitter, transmit settings of each antenna of the antenna array based on the identified phase of the calibration signal for each antenna of the antenna array.

[0179] In some examples, method 800a of FIG. 28A may further include method 900c of FIG. 29C. As illustrated in FIG. 29C at 918, method 900c may include sensing a position, orientation, and / or location of the patient. At 920, method 900c may include adjusting transmit settings of each antenna of the antenna array based on the sensed position, orientation, and / or location of the patient. In some examples, method 900c may further include sensing, via an external pressure sensor or an external temperature sensor (e.g., 764 of FIG. 25), a position of the patient; and adjusting transmit settings of each antenna of the antenna array based on the sensed position of the patient. In some examples, method 900c may further include sensing, via an accelerometer (e.g., 457 of FIG. 27) of the implantable medical device (e.g., 456 of FIG. 27), an orientation of the patient relative to the external charger; and adjusting transmit settings of each antenna of the antenna array based on the sensed orientation of the patient.

[0180] In some examples, method 900c may further include optically sensing, via an external sensor (e.g., 762 of FIG. 25), a location of the patient relative to the external charger; and adjusting transmit settings of each antenna of the antenna array based on the optically sensed location of the patient. Optically sensing the location of the patient may comprise optically sensing a wearable patch (e.g., 1116 of FIG. 31 described below) on the patient over the implantable medical device (e.g., 1100 of FIG. 31 described below). In some examples, method 900c may further include triangulating, via a plurality of Bluetooth Low Energy (BLE) transceivers (e.g., 766a-766c), a location of the implantable medical device; and adjusting transmit settings of each antenna of the antenna array based on the triangulated location of the patient.

[0181] In some examples, method 800a of FIG. 28A may further include method 900d of FIG. 29D. As illustrated in FIG. 29D at 922, method 900d may include sending a calibration request from the implantable medical device to the external charger in response to detecting a change in posture of the patient, in response to detecting motion of the patient exceeding a motion threshold, or in response to detecting a reduction in received power exceeding a power threshold at the wireless receiver. As previously described, detecting a change in posture of the patient and / or detecting motion of the patient may be performed by sensor 762 of FIG. 25, sensor 764 of FIG. 25, BLE transceivers 766a-766c of FIG. 25, array of sensors 790 of FIG. 27, accelerometer 457 of FIG. 27, or a combination thereof. At 924, method 900d may include adjusting, via the wireless transmitter, transmit settings of each antenna of the antenna array in response to the calibration request.

[0182] As previously described, charging (or transmitting power to) the power element may further include reflecting, via an external reflective sheet (e.g., 770a of FIG. 26A or 770b of FIG. 26B), power transmitted from the wireless transmitter to the wireless receiver. The reflective sheet may be embedded into a bed (e.g., 742 of FIGS. 26A and 26B), may be flat (e.g., 770a of FIG. 26A) or concave (e.g., 770b of FIG. 26B), and may be movable (e.g., manually and / or automatically).

[0183] In some examples, method 800a of FIG. 28A may further include method 900e of FIG. 29E. As illustrated in FIG. 29E at 926, method 900e may include monitoring power coupling between the wireless transmitter and the wireless receiver. At 928, method 900e may further include adjusting a position of the reflective sheet to maximize power coupling.

[0184] In some examples, method 800a of FIG. 28A may further include method 900f of FIG. 29F. As illustrated in FIG. 29F at 930, method 900f may include sensing a position of the patient. At 932, method 900f may include adjusting a position of the reflective sheet relative to the antenna array based on the sensed position of the patient. In some examples, method 900f may further include sensing, via an accelerometer, an external pressure sensor, or an external temperature sensor (e.g., 764 of FIG. 25), a position of the patient; and adjusting a position of the reflective sheet based on the sensed position of the patient. In some examples, method 900f may further include sensing, via a radar sensor or a lidar sensor (e g., 762 of FIG. 25), a position of the patient; and adjusting a position of the reflective sheet based on the sensed position of the patient. In some examples, method 900f may further include sensing, via an external array of pressure sensors (e.g., 790 of FIG. 27), a position of the patient; and adjusting a position of the reflective sheet based on the sensed position of the patient. In some examples, method 900f may further include sensing, via a Received Signal Strength Indicator (RSSI) corresponding to each antenna of at least a subset of antennas of the antenna array, a position of the patient; and adjusting a position of the reflective sheet based on the sensed position of the patient.

[0185] In some examples, method 800a of FIG. 28A may further include method 1000 of FIG. 30. FIG. 30 is a flow diagram schematically representing an example method 1000 for wirelessly transmitting power to a power element (e.g., 204 of FIGS. 2A-3D) of an IMD (e.g., 202a-202c of FIGS. 2A-2C or 250a-250d of FIGS. 3A-3D). In some examples, the wireless transmitter (e.g., 222 of FIGS. 2A-2C, 520a of FIG. 16A, or 520b of FIG. 16B) includes a directive antenna (e.g., 530a-530c of FIGS. 17A-17C or 542a-542b of FIGS. 17D-17E). Charging (or transmitting power to) the power element may include adjusting the position of the directive antenna to achieve optimum coupling with the wireless receiver. In some examples, the wireless transmitter comprises a plurality of directive antennas (e.g., 540a or 540b of FIGS. 17D and 17E). In these examples, charging (or transmitting power to) the power element may comprise receiving, at the wireless receiver, power to charge (or supply to) the power element from a directive antenna of the plurality of directive antennas having the best coupling with the wireless receiver.

[0186] As illustrated in FIG. 30 at 1002, method 1000 includes transmitting, via the implantable medical device, a calibration signal to the wireless transmitter. At 1004, method 1000 includes receiving, via the wireless transmitter, thecalibration signal at each directed antenna of the plurality of directed antennas. At 1006, method 1000 includes selecting, via the wireless transmitter, the directive antenna having the best coupling with the wireless receiver based on the received calibration signal to charge (or transmit power to) the power element.

[0187] In some examples, similarly as described in association with method 900e and 900f of FIGS. 29E and 29F, charging (or transmitting power to) the power element may include reflecting, via an external reflective sheet (e.g., 770a of FIG. 26A or 770b of FIG. 26B), power transmitted from the directed antenna to the wireless receiver. The reflective sheet may be movable as previously described. In some examples, charging (or transmitting power to) the power element may include monitoring power coupling between the directed antenna and the wireless receiver; and adjusting a position of the reflective sheet to maximize power coupling.

[0188] FIG. 31 is a diagram schematically representing an example IMD 1100 and a patch 1116 on the skin of a patient used to locate the IMD 1100. The IMD 1100 includes a first element 1102 and a second element 1104 (e.g., lead) implanted in a patient, which may include at least some of substantially the same features and attributes, as previously described in association with at least FIGS. 2A-6 and 18-24. In some examples, the first element 1102 may include a stimulation element which may be implanted in a head 1112 or neck 1114 region of the patient with the second element 1104 (e.g., lead) extending perpendicular to the long axis of the stimulation element 1102. By configuring the lead 1104 to be arranged perpendicular to the long axis of the stimulation element 1102, the lead 1104 may be placed in the neck 1114 without making a 90 degree turn in the wire(s) 1108. Accordingly, surgical implantation of the lead 1104 may be simplified and / or less stress may be applied to the wire(s) 1108. Moreover, this generally perpendicular configuration may enhance the ability to anchor the first and second elements 1102, 1104 relative to non-nerve tissues within the head-and-neck region (1112, 1114). In some examples, such as shown in FIG. 31, the conductive element 1110 (e.g., electrode portion) of the lead 1104 may be aligned / positioned for stimulation of an infrahyoid-related tissue, which comprise one or more infrahyoid strap muscles and / or infrahyoid muscle (IHM)-innervating nerves. However, it will be understood that the first and second elements 1102, 1104 may be implanted in a wide variety of positions, orientations, etc. within the head-and-neck region (1112, 1114) (and / or other regions of the body) to be placed in stimulating relation to a wide variety of upper airway patency-related tissues including nerves, nerve branches, muscles, and / or combinations thereof. For example, such tissues may comprise a hypoglossal nerve, genioglossus muscle, a phrenic nerve, diaphragm muscle, internal superior laryngeal (iSL) nerve, glossopharyngeal nerve, etc.

[0189] As previously described with reference to FIGS. 3A-3D, the first element 1102 may include stimulation element 256 (FIG. 3C) or sensing element 258 (FIG. 3D) and a power element 204 for delivering therapy or sensing diagnostic information via the second element 1104 (e.g., lead). The first element 1102 may include an electrical connector, and the second element 1104 may include a proximal portion including a corresponding electrical connector 1106, at least one wire 1108, and at least one electrode 1110 (e.g., stimulation electrode and / or sensing electrode) on a distal portion of the lead. In some examples, the second element 1104 may also include an antenna 1109 (e.g., coil antenna or RF antenna). The at least one electrode 1110 (e.g., cuff electrode) is electrically connected to circuitry (e.g., stimulation element, sensing element) of first element 1102 through the at least one wire 1108 and the electrical connector 1106. In some examples, the lead 1104 may support a plurality of electrodes 1110 (e.g., 2, 3, 4, 5, 6, 7, 8, or more) that are electrically connected to circuitry of first element 1102 through a plurality of wires 1108 and the electrical connector 1106.

[0190] The patch 1116 may include a fiducial marker, such as a checkered / striped high-contrast pattern or electromagnetic tracking marker. The patch 1116 may be used to optically sense the location of the IMD 1116 and / or antenna 1109 using a sensor (e.g., 762 of FIG. 25). As previously described above, the location of the IMD 1116 and / or the antenna 1109 may be used to select a coil structure (e.g., 482 of FIG. 14) or a subset of coil structures (e.g., 484i to 4844 of FIG. 14) of a wireless transmitter (e.g., 222 of FIGS. 2A-2C) for inductive or RF near-field wireless power transfer, adjust transmit settings of an antenna array (e.g., 504 of FIG. 15B) of a wireless transmitter (e.g., 500 of FIG. 15A) for RF far-field wireless power transfer, position a directive antenna (e.g., 530a-530c, 542a, 542b of FIGS. 17A-17C) of a wireless transmitter (e.g., 520a or 520b of FIGS. 16A and 16B), and / or adjust a reflective sheet (e.g., 770a of FIG. 26A or 770b of FIG. 26B) for an antenna array or directive antenna.

[0191] FIG. 32A is a block diagram schematically representing an example control portion 1200. In some examples, control portion 1200 provides one example implementation of a control portion forming a part of, implementing, and / or generally managing stimulation elements, power / control elements (e.g., pulse generators, microstimulators), wireless receivers, wireless transmitters, transceivers, sensors, and related elements, devices, user interfaces, instructions, information, engines, elements, functions, actions, and / or methods, as described throughout examples of the present disclosure in association with FIGS. 1A-31.

[0192] In some examples, control portion 1200 includes a controller 1202 and a memory 1210. In general terms, controller 1202 of control portion 1200 comprises at least one processor 1204 and associated memories. The controller 1202 is electrically coupled to, and in communication with, memory 1210 to generate control signals to direct operation of at least some of the charging elements, power transmission elements, stimulation elements, power / control elements (e.g., pulse generators, microstimulators), wireless receivers, wireless transmitters, transceivers, sensors, and related elements, devices, user interfaces, instructions, information, engines, elements, functions, actions, and / or methods, as described throughout examples of the present disclosure. In some examples, these generated control signals include, but are not limited to, employing instructions 1211 and / or information 1212 stored in memory 1210 for at least controlling the charging of a power element (e.g., 204 of FIGS. 2A-3D), controlling stimulation element (e.g., 256 of FIG. 3B), and / or controlling a sensing element (e.g., 258 of FIG. 3C). In some examples, such control may comprise part of diagnosing and / or directing and managing treatment of sleep disordered breathing such as obstructive sleep apnea, hypopnea, and / or central sleep apnea, with such control also comprising sensing physiologic information including but not limited to electrical brain activity, respiratory information, cardiac information, and / or monitoring sleep disordered breathing, etc. In some examples, such control may include part of diagnosing and / or directing and managing treatment of pelvic disorders including but not limited to stress incontinence. In some examples, such control may include part of diagnosing and / or directing and managing treatment of other conditions which can be treated via peripheral nerve stimulation (and / or stimulation of innervated muscles). In some instances, the controller 1202 or control portion 1200 may sometimes be referred to as being programmed to perform the above-identified actions, functions, etc. such that the controller 1202, control portion 1200 and any associated processors may sometimes be referred to as being a special purpose computer, control portion, controller, or processor. In some examples, at least some of the stored instructions 1211 are implemented as, or may be referred to as, a care engine, a sensing engine, monitoring engine, and / or treatment engine. In some examples, at least some of the stored instructions 1211 and / or information 1212 may form at least part of, and / or, may be referred to as a care engine, sensing engine, monitoring engine, and / or treatment engine.

[0193] In response to or based upon commands received via a user interface (e.g., user interface 1240 in FIG. 33) and / or via machine-readable instructions, controller 1202 generates control signals as described above in accordance with at least some of the examples of the present disclosure. In some examples, controller 1202 is embodied in a general purpose computing device while in some examples, controller 1202 is incorporated into or associated with at least some of the charging elements, power transmission elements, stimulation elements, power / control elements (e.g., pulse generators, microstimulators), wireless receivers, wireless transmitters, transceivers, sensors, and related elements, devices, user interfaces, instructions, information, engines, functions, actions, and / or methods, etc. as described throughout examples of the present disclosure.

[0194] For purposes of this application, in reference to the controller 1202, the term “processor” shall mean a presently developed or future developed processor (or processing resources) that executes machine-readable instructions contained in a memory. In some examples, execution of the machine-readable instructions, such as those provided via memory 1210 of control portion 1200 cause the processor to perform the above-identified actions, such as operating controller 1202 to implement the power transmission, charging, sensing, monitoring, determining, treatment, etc. as generally described in (or consistent with) at least some examples of the present disclosure. The machine-readable instructions may be loaded in a random access memory (RAM) for execution by the processor from their stored location in a read only memory (ROM), a mass storage device, or some other persistent storage (e.g., non-transitory tangible medium or nonvolatile tangible medium), as represented by memory 1210. In some examples, the machine-readable instructions may comprise a sequence of instructions, a processor-executable data model (e.g., machine learning, other), or the like. In some examples, memory 1210 comprises a computer readable tangible medium providing non-volatile storage of the machine-readable instructions executable by a process of controller 1202. In some examples, the computer readable tangible medium may sometimes be referred to as, and / or comprise at least a portion of, a computer program product. In some examples, hard wired circuitry may be used in place of or in combination with machine-readable instructions to implement the functions described. For example, controller 1202 may be embodied as part of at least one application-specific integrated circuit (ASIC), at least one field-programmable gate array (FPGA), and / or the like. In at least some examples, the controller 1202 is not limited to any specific combination of hardware circuitry and machine-readable instructions, nor limited to any particular source for the machine-readable instructions executed by the controller 1202.

[0195] In some examples, control portion 1200 may be entirely implemented within or by a stand-alone device. In some examples, the control portion 1200 may be partially implemented in one of the charging devices, power transmission devices, sensing devices, monitoring devices, stimulation devices, apnea treatment devices (or portions thereof), etc. and partially implemented in a computing resource separate from, and independent of, the apnea treatment devices (or portions thereof) but in communication with the apnea treatment devices (or portions thereof). In some examples, the control portion 1200 may be partially implemented in one of the charging devices, power transmission devices, sensing devices, monitoring devices, stimulation devices, pelvic or other treatment devices (or portions thereof), etc. and partially implemented in a computing resource separate from, and independent of, the pelvic or other treatment devices (or portions thereof) but in communication with the pelvic or other treatment devices (or portions thereof). For instance, in some examples control portion 1200 may be implemented via a server accessible via the cloud and / or other network pathways. In some examples, the control portion 1200 may be distributed or apportioned among multiple devices or resources such as among a server, an apnea (or pelvic, other) treatment device (or portion thereof), and / or a user interface. In some examples, control portion 1200 includes, and / or is in communication with, a user interface 1240 as shown in FIG. 33.

[0196] Figure 32B is a diagram schematically illustrating at least some example implementations of a control portion 1220 by which the control portion 1200 (FIG. 32A) can be implemented, according to one example of the present disclosure. In some examples, control portion 1220 is entirely implemented within or by a medical device 1225 (e.g., implantable pulse generator (IPG) assembly in some examples), which has at least some of substantially the same features and attributes as a medical device as previously described throughout the present disclosure. In some examples, control portion 1220 is entirely implemented within or by a remote control 1230 (e.g., a programmer) external to the patient’s body, such as a patient control 1232 and / or a physician control 1234. In some examples, the control portion 1200 is partially implemented in the medical device 1225 and partially implemented in the remote control 1230 (at least one of patient control 1232 and physician control 1234).

[0197] FIG. 33 is a block diagram schematically representing user interface 1240, according to one example of the present disclosure. In some examples, the user interface 1240 forms part of and / or is accessible via a device external to the patient and by which the therapy system may be at least partially controlled and / or monitored. The external device which hosts user interface 1240 may be a patient remote (e.g., 1232 in FIG. 32B), a physician remote (e.g., 1234 in FIG. 32B) and / or a clinician portal. In some examples, the user interface 1240 comprises a user interface or other display that provides for the simultaneous display, activation, and / or operation of at least some of the charging elements, power transmission elements, stimulation elements, power / control elements (e.g., pulse generators, microstimulators), wireless receivers, wireless transmitters, transceivers, sensors, and related elements, devices, user interfaces, instructions, information, engines, functions, actions, and / or method, etc., as described in association with FIGS. 1A-31. In some examples, at least some portions or aspects of the user interface 1240 are provided via a graphical user interface (GUI) and may comprise a display 1244 and input 1242.

[0198] FIG. 34 is a block diagram 1300 which schematically represents some example implementations by which a medical device (IMD) 1310, such as a pulse generator and / or sensing monitor (either or both of which may be implantable in some examples), may communicate wirelessly with external devices outside the patient. As shown in FIG. 34, in some examples, the IMD 1310 may communicate with at least one of a patient app 1330 on a mobile device 1320, a patient remote control 1340, a clinician programmer 1350, a patient management tool 1360, and an external charger (or power transmission device) 1370. As previously described, the external charger 1370 may be used to charge a power element (e.g., battery) of the medical device 1310 and / or to transmit power to the medical device 1310 which is immediately used by the medical device and not stored within a power element of the medical device. The patient management tool 1360 may be implemented via a cloud-based portal 1362, the patient app 1330, and / or the patient remote control 1340. Among other types of data, these communication arrangements enable the IMD 1310 to communicate, display, manage, etc. data for wirelessly charging or transmitting power to IMD 1310 and / or for patient management as well as to allow for adjustment to control information (e.g., 1212 of FIG. 32A) if / where needed. It will be understood that at least some of the various devices / elements 1320, 1340, 1350, patient management tool 1360, and external charger 1370 also may communicate with each other, with or without communicating with the medical device 1310.

[0199] Although specific examples have been illustrated and described herein, a variety of alternate and / or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein.

Claims

1. A system comprising:an implantable medical device to apply electrical stimulation to an upper airway patency-related tissue of a patient, the implantable medical device comprising:a power element; anda wireless receiver to receive power to charge the power element; andan external charger comprising a wireless transmitterto transmit the power to the wireless receiver of the implantable medical device.

2. The system of claim 1, wherein the wireless transmitter comprises a single loop coil and two figure-eight coils.

3. The system of claim 1, wherein the wireless transmitter comprises a single loop coil and a single figure-eight coil.

4. The system of claim 1, wherein the wireless transmitter comprises a single coil.

5. The system of claim 1, wherein the wireless transmitter comprises an array of coil structures.

6. The system of claim 5, wherein each coil structure of the array of coil structures comprises a single loop coil.

7. The system of claim 5, wherein each coil structure of the array of coil structures comprises a single loop coil and two figure-eight coils.

8. The system of claim 5, wherein each coil structure of the array of coil structures comprises a single loop coil and a single figure-eight coil.

9. The system of claim 5, wherein the external charger comprises a backing shield, andwherein the array of coil structures are arranged on the backing shield.

10. The system of claim 5, wherein a single coil structure of the array of coil structures is selected at a given time to charge the power element.

11. The system of claim 5, wherein at least two coil structures of the array of coil structures are selected at a given time to charge the power element.

12. The system of claim 5, wherein each coil structure of the array of coil structures is powered simultaneously at a same frequency and at a different power level to charge the power element.

13. The system of claim 1, wherein the wireless transmitter comprises an array of coils.

14. The system of claim 13, wherein each coil of the array of coils partially overlaps an adjacent coil of the array of coils.

15. The system of claim 1, wherein the external charger comprises a backing shield, andwherein the wireless transmitter comprises at least one coil arranged on the backing shield.

16. The system of claim 15, wherein the backing shield comprises a Mu-Near-Zero metamaterial.

17. The system of claim 1, wherein the wireless transmitter comprises an antenna array.

18. The system of claim 1, wherein the wireless transmitter comprises a directive antenna.

19. The system of claim 1, wherein the implantable medical device comprises a microstimulator arranged to be implanted within a head-and-neck region of the patient, the microstimulator comprising a housing to encapsulate at least:the power element;the wireless receiver;stimulation circuitry; anda control portion including a therapy manager arranged to control the stimulation circuitry based on at least control information to apply the electrical stimulation to the upper airway patency-related tissue of the patient.

20. The system of claim 1, wherein the wireless receiver comprises an antenna tuned to a recharge frequency,wherein the implantable medical device comprises a therapy lead to apply electrical stimulation to the upper airway patency-related tissue of the patient, andwherein the antenna is integrated into the therapy lead of the implantable medical device.

21. The system of claim 5, wherein each coil structure of the array of coil structures comprises two figure-eight coils.

22. The system of claim 5, wherein the external charger comprises an array of backing shields, andwherein each coil structure of the array of coil structures is arranged on a respective backing shield of the array of backing shields.

23. The system of claim 5, wherein each coil structure of the array of coil structures is powered simultaneously at a same frequency and at a same power level to charge the power element.

24. The system of claim 5, wherein each coil structure of the array of coil structures is powered simultaneously at a different frequency and at a same power level for selecting at least one coil structure to charge the power element.

25. The system of claim 13, wherein each coil of the array of coils corresponds to a distributed capacitor to tune each coil to a resonant frequency.

26. The system of claim 15, wherein the backing shield comprises a solid structure.

27. The system of claim 15, wherein the backing shield comprises a patterned structure.

28. The system of claim 1, wherein the wireless receiver receives power and communications simultaneously from the wireless transmitter.

29. The system of claim 1, further comprising:a Bluetooth Low Energy (BLE) transceiver for communications between the implantable medical device and the external charger,wherein the wireless receiver receives power from the wireless transmitter simultaneously with the BLE transceiver communicating with the external charger.

30. The system of claim 1, wherein the implantable medical device comprises a wireless transmitter to transmit communications simultaneously with receiving power to charge the power element.

31. The system of claim 1, wherein the implantable medical device comprises a further wireless receiver to receive communications simultaneously with receiving power to charge the power element.

32. The system of claim 1, wherein the wireless receiver comprises a single coil element with windings across at least two axes.

33. The system of claim 1, wherein the wireless receiver comprises at least two coil elements arranged along different axes.

34. The system of claim 1, wherein the wireless receiver comprises at least one coil with windings wrapped around the power element.

35. The system of claim 1, wherein the implantable medical device comprises a housing enclosing the power element and the wireless receiver, andwherein the wireless receiver comprises at least one coil with windings arranged around an interior of the housing.

36. The system of claim 1, wherein the power element comprises a battery or a super capacitor.

37. The system of claim 1, wherein the wireless transmitter comprises at least three coils arranged along orthogonal axes.

38. The system of claim 1, wherein the wireless transmitter comprises two figure-eight coils.

39. The system of claim 1, wherein the wireless transmitter comprises a coil comprising a circular, elliptical, rectangular, triangular, or hexagonal geometry.

40. The system of claim 1, wherein the wireless receiver comprises an antenna tuned to a recharge frequency.

41. The system of claim 40, wherein the implantable medical device comprises a housing enclosing the power element and the wireless receiver, andwherein the antenna is etched or printed on the housing of the implantable medical device.

42. The system of claim 40, wherein the antenna is integrated into the power element.

43. The system of claim 40, wherein the antenna comprises a coil structure, andwherein the wireless receiver comprises a capacitor to tune the antenna.

44. The system of claim 40, wherein the antenna comprises a metamaterial antenna.

45. The system of claim 44, wherein the metamaterial antenna comprises a Double Negative Meta mate ri a I (DNG) antenna.

46. The system of claim 40, wherein the wireless receiver comprises a reflector aligned with the antenna, the reflector comprising an Artificial Magnetic Conductor (AMC) material.

47. The system of claim 18, wherein the directive antenna comprises a helical antenna, a spherical helix antenna, a corner reflector antenna, or a log periodic antenna.

48. The system of claim 18, wherein the external charger comprises a motion mechanism to automatically position the directive antenna relative to the wireless receiver.

49. The system of claim 18, wherein the wireless transmitter comprises a plurality of directive antennas.

50. The system of claim 49, wherein the plurality of directive antennas are arranged in a spherical or cylindrical structure.

51. A method comprising:charging a power element of an implantable medical device, the implantable medical device configured to apply electrical stimulation to an upper airway patency-related tissue of a patient, the charging comprising:receiving, at a wireless receiver of the implantable medical device from a wireless transmitter of an external charger, power to charge the power element,wherein the wireless transmitter comprises an array of coil structures.

52. The method of claim 51, wherein charging the power element comprises:successively pulsing, via the wireless transmitter, each coil structure of the array of coil structures;measuring, via the wireless receiver, received energy from each coil structure in response to the pulsing of the respective coil structure; andselecting, via the wireless transmitter, the coil structure for which the received energy is greatest to charge the power element.

53. The method of claim 52, further comprising:monitoring, via the wireless receiver, received energy from the selected coil structure; andin response to the received energy from the selected coil structure falling below a threshold, selecting another coil structure of the array of coil structures to charge the power element.

54. The method of claim 52, further comprising:periodically pulsing, via the wireless transmitter, a coil structure of the array of coil structures adjacent to the selected coil structure;measuring, via the wireless receiver, received energy from the adjacent coil structure; andin response to the received energy from the adjacent coil structure being greater than the received energy from the selected coil structure, switching to the adjacent coil structure to charge the power element.

55. The method of claim 51, wherein charging the power element comprises:successively pulsing, via the wireless transmitter, each subset of coil structures of the array of coil structures;measuring, via the wireless receiver, received energy from each subset of coil structures in response to the pulsing of the respective subset of coil structures; andselecting, via the wireless transmitter, the subset of coil structures for which the received energy is greatest to charge the power element.

56. The method of claim 51, wherein charging the power element comprises:successively pulsing, via the wireless transmitter, each subset of coil structures of the array of coil structures;measuring, via the wireless receiver, received energy from each subset of coil structures in response to the pulsing of the respective subset of coil structures;successively pulsing, via the wireless transmitter, each coil structure of the subset of coil structures for which the received energy is greatest;measuring, via the wireless receiver, received energy from each coil structure of the subset of coil structures for which the received energy is greatest in response to the pulsing of the respective coil structure of the subset of coil structures for which the received energy is greatest; andselecting, via the wireless transmitter, the coil structure for which the received energy is greatest to charge the power element.

57. The method of claim 51, wherein charging the power element comprises:successively pulsing, via the wireless transmitter, a single coil structure of each subset of coil structures of the array of coil structures;measuring, via the wireless receiver, received energy from each single coil structure of each subset of coil structures in response to the pulsing of the respective single coil structure of the respective subset of coil structures;successively pulsing, via the wireless transmitter, each remaining coil structure of the subset of coil structures for which the received energy for the respective single coil structure is greatest;measuring, via the wireless receiver, received energy from each remaining coil structure in response to the pulsing of the respective remaining coil structure; andselecting, via the wireless transmitter, the coil structure for which the received energy is greatest to charge the power element.

58. The method of claim 51, wherein charging the power element comprises: successively pulsing, via the wireless transmitter, each coil structure of the array of coil structures;measuring, via the wireless transmitter, loading of each coil structure in response to the pulsing of the respective coil structure; andselecting, via the wireless transmitter, the coil structure for which the loading is greatest to charge the power element.

59. The method of claim 51, wherein charging the power element comprises: successively pulsing, via the wireless transmitter, each subset of coil structures of the array of coil structures;measuring, via the wireless transmitter, loading of each subset of coil structures in response to the pulsing of the respective subset of coil structures; andselecting, via the wireless transmitter, the subset of coil structures for which the loading is greatest to charge the power element.

60. The method of claim 51, wherein charging the power element comprises:successively pulsing, via the wireless transmitter, each subset of coil structures of the array of coil structures;measuring, via the wireless transmitter, loading of each subset of coil structures in response to the pulsing of the respective subset of coil structures;successively pulsing, via the wireless transmitter, each coil structure of the subset of coil structures for which the loading is greatest;measuring, via the wireless transmitter, loading of each coil structure of the subset of coil structures for which the loading is greatest in response to the pulsing of the respective coil structure of the subset of coil structures for which the loading is greatest; andselecting, via the wireless transmitter, the coil structure for which the loading is greatest to charge the power element.

61. The method of claim 51, wherein charging the power element comprises: successively pulsing, via the wireless transmitter, a single coil structure of each subset of coil structures of the array of coil structures;measuring, via the wireless transmitter, loading of each single coil of each subset of coil structures in response to the pulsing of the respective single coil structure of the respective subset of coil structures;successively pulsing, via the wireless transmitter, each remaining coil structure of the subset of coil structures for which the loading for the respective single coil structure is greatest;measuring, via the wireless transmitter, loading of each remaining coil structure in response to the pulsing of the respective remaining coil structure; andselecting, via the wireless transmitter, the coil structure for which the loading is greatest to charge the power element.

62. The method of claim 51, wherein charging the power element comprises: pulsing, via the wireless receiver, a coil of the wireless receiver;measuring, via the wireless transmitter, energy received at each coil structure of the array of coil structures; andselecting, via the wireless transmitter, the coil structure for which the received energy is greatest to charge the power element.

63. The method of claim 62, wherein measuring the energy received at each coil structure comprises simultaneously measuring the energy received at each coil structure in response to a single pulse of the coil of the wireless receiver.

64. The method of claim 62, wherein measuring the energy received at each coil structure comprises successively measuring the energy received at each coil structure in response to a respective pulse of the coil of the wireless receiver.

65. The method of claim 51, wherein charging the power element comprises: pulsing, via the wireless receiver, a coil of the wireless receiver;measuring, via the wireless transmitter, energy received at each subset of coil structures of the array of coil structures; andselecting, via the wireless transmitter, the subset of coil structures for which the received energy is greatest to charge the power element.

66. The method of claim 65, wherein measuring the energy received at each subset of coil structures comprises simultaneously measuring the energy received at each subset of coil structures in response to a single pulse of the coil of the wireless receiver.

67. The method of claim 65, wherein measuring the energy received at each subset of coil structures comprises successively measuring the energy received at each subset of coil structures in response to a respective pulse of the coil of the wireless receiver.

68. A method comprising:charging a power element of an implantable medical device, the charging comprising:receiving, at a wireless receiver of the implantable medical device from a wireless transmitter of an external charger, power to charge the power element, wherein the wireless transmitter comprises an array of coil structures.

69. The method of claim 68, wherein charging the power element comprises: sensing, via at least one of an accelerometer, an external pressure sensor, or an external temperature sensor, a position of the patient; andselecting, via the wireless transmitter, a coil structure of the array of coil structures based on the sensed position of the patient to charge the power element.

70. The method of claim 68, wherein charging the power element comprises: sensing, via a radar sensor or a lidar sensor, a position of the patient; and selecting, via the wireless transmitter, a coil structure of the array of coil structures based on the sensed position of the patient to charge the power element.

71. The method of claim 68, wherein charging the power element comprises: sensing, via a Received Signal Strength Indicator (RSSI) corresponding to each coil structure of the array of coil structures, a position of the patient; and selecting, via the wireless transmitter, a coil structure of the array of coil structures based on the sensed position of the patient to charge the power element.

72. The method of claim 68, wherein charging the power element comprises: sensing, via an array of pressure sensors corresponding to the array of coil structures, a position of the patient; andselecting, via the wireless transmitter, a coil structure of the array of coil structures based on the sensed position of the patient to charge the power element.

73. The method of claim 51, wherein charging the power element comprises:sensing, via an external pressure sensor or an external temperature sensor, a position of the patient; andselecting, via the wireless transmitter, a subset of coil structures of the array of coil structures based on the sensed position of the patient to charge the power element.

74. The method of claim 51, wherein charging the power element comprises:sensing, via an accelerometer of the implantable medical device, an orientation of the patient relative to the external charger; andselecting, via the wireless transmitter, a coil structure of the array of coil structures based on the sensed orientation of the patient to charge the power element.

75. The method of claim 51, wherein charging the power element comprises: optically sensing, via an external sensor, a location of the patient relative to the external charger; andselecting, via the wireless transmitter, a coil structure of the array of coil structures based on the optically sensed location of the patient to charge the power element.

76. The method of claim 75, wherein optically sensing the location of the patient comprises optically sensing a wearable patch on the patient over the implantable medical device.

77. The method of claim 51, wherein charging the power element comprises: triangulating, via a plurality of Bluetooth Low Energy (BLE) transceivers, a location of the implantable medical device; andselecting, via the wireless transmitter, a coil structure of the array of coil structures based on the triangulated location of the implantable medical device to charge the power element.

78. A method comprising:charging a power element of an implantable medical device, the implantable medical device configured to apply electrical stimulation to an upper airway patency-related tissue of a patient, the charging comprising:receiving, at a wireless receiver of the implantable medical device from a wireless transmitter of an external charger, power to charge the power element,wherein the wireless transmitter comprises an antenna array.

79. The method of claim 78, wherein the wireless transmitter is arranged on a tabletop, bedside, a top of a dresser, a ceiling, or a wall.

80. The method of claim 78, wherein each antenna of the antenna array is configured to deliver power to the wireless receiver and each antenna comprises an adjustable phase to coherently focus the power at the wireless receiver.

81. The method of claim 78, wherein charging the power element comprises continuously transmitting, via the wireless transmitter, power to the wireless receiver.

82. The method of claim 78, wherein charging the power element comprises pulsing, via the wireless transmitter, power to the wireless receiver.

83. The method of claim 78, wherein charging the power element comprises: transmitting, via the implantable medical device, a calibration signal to the wireless transmitter;receiving, via the wireless transmitter, the calibration signal at each antenna of the antenna array; andadjusting, via the wireless transmitter, transmit settings of each antenna of the antenna array based on the received calibration signal as an inverse phase constant amplitude, inverse phase arbitrary amplitude, ora complex conjugate of the received calibration signal.

84. The method of claim 78, wherein charging the power element comprises:successively pulsing a calibration signal, via the wireless transmitter, to each antenna of the antenna array;receiving, via the wireless receiver, the calibration signal from each antenna of the antenna array;identifying, via the wireless receiver, a phase of the calibration signal for each antenna of the antenna array;transmitting, via the implantable medical device, the identified phase of the calibration signal for each antenna of the antenna array to the external charger; andadjusting, via the wireless transmitter, transmit settings of each antenna of the antenna array based on the identified phase of the calibration signal for each antenna of the antenna array.

85. The method of claim 78, wherein charging the power element comprises: sensing, via an external pressure sensor or an external temperature sensor, a position of the patient; andadjusting transmit settings of each antenna of the antenna array based on the sensed position of the patient.

86. The method of claim 78, wherein charging the power element comprises:sensing, via an accelerometer of the implantable medical device, an orientation of the patient relative to the external charger; andadjusting transmit settings of each antenna of the antenna array based on the sensed orientation of the patient.

87. The method of claim 78, wherein charging the power element comprises: optically sensing, via an external sensor, a location of the patient relative to the external charger; andadjusting transmit settings of each antenna of the antenna array based on the optically sensed location of the patient.

88. The method of claim 87, wherein optically sensing the location of the patient comprising optically sensing a wearable patch on the patient over the implantable medical device.

89. The method of claim 78, wherein charging the power element comprises: sending a calibration request from the implantable medical device to the external charger in response to detecting a change in posture of the patient, in response to detecting motion of the patient exceeding a motion threshold, or in response to detecting a reduction in received power exceeding a power threshold at the wireless receiver; andadjusting, via the wireless transmitter, transmit settings of each antenna of the antenna array in response to the calibration request.

90. The method of claim 78, wherein charging the power element comprises: triangulating, via a plurality of Bluetooth Low Energy (BLE) transceivers, a location of the implantable medical device; andadjusting transmit settings of each antenna of the antenna array based on the triangulated location of the patient.

91. A method comprising:charging a power element of an implantable medical device, the charging comprising:receiving, at a wireless receiver of the implantable medical device from a wireless transmitter of an external charger, power to charge the power element, wherein the wireless transmitter comprises an antenna array.

92. The method of claim 91, wherein charging the power element comprises reflecting, via an external reflective sheet, power transmitted from the wireless transmitter to the wireless receiver.

93. The method of claim 92, wherein the reflective sheet is embedded into a bed.

94. The method of claim 92, wherein the reflective sheet is concave.

95. The method of claim 92, wherein the reflective sheet is movable.

96. The method of claim 95, wherein charging the power element comprises:monitoring power coupling between the wireless transmitter and the wireless receiver; andadjusting a position of the reflective sheet to maximize power coupling.

97. The method of claim 95, wherein charging the power element comprises: sensing, via an accelerometer, an external pressure sensor, or an external temperature sensor, a position of the patient; andadjusting a position of the reflective sheet based on the sensed position of the patient.

98. The method of claim 95, wherein charging the power element comprises: sensing a position of the patient; and adjusting a position of the reflective sheet relative to the antenna array based on the sensed position of the patient.

99. The method of claim 95, wherein charging the power element comprises: sensing, via a radar sensor or a lidar sensor, a position of the patient; and adjusting a position of the reflective sheet based on the sensed position of the patient.

100. The method of claim 95, wherein charging the power element comprises: sensing, via an external array of pressure sensors, a position of the patient;andadjusting a position of the reflective sheet based on the sensed position of the patient.

101. The method of claim 95, wherein charging the power element comprises: sensing, via a Received Signal Strength Indicator (RSSI) corresponding to each antenna of at least a subset of antennas of the antenna array, a position of the patient; andadjusting a position of the reflective sheet based on the sensed position of the patient.

102. A method comprising:charging a power element of an implantable medical device, the charging comprising:receiving, at a wireless receiver of the implantable medical device from a wireless transmitter of an external charger, power to charge the power element, wherein the wireless transmitter comprises a directive antenna.

103. The method of claim 102, wherein charging the power element comprises adjusting a position of the directive antenna to achieve optimum coupling with the wireless receiver.

104. The method of claim 102, wherein the wireless transmitter comprises a plurality of directive antennas, andwherein charging the power element comprises receiving, at the wireless receiver, power to charge the power element from a directive antenna of the plurality of directive antennas having best coupling with the wireless receiver.

105. The method of claim 104, wherein charging the power element comprises: transmitting, via the implantable medical device, a calibration signal to the wireless transmitter;receiving, via the wireless transmitter, the calibration signal at each directed antenna of the plurality of directed antennas; andselecting, via the wireless transmitter, the directive antenna having the best coupling with the wireless receiver based on the received calibration signal to charge the power element.

106. The method of claim 102, wherein charging the power element comprises reflecting, via an external reflective sheet, power transmitted from the directed antenna to the wireless receiver.

107. The method of claim 106, wherein the reflective sheet is movable.

108. The method of claim 107, wherein charging the power element comprises: monitoring power coupling between the directed antenna and the wireless receiver; andadjusting a position of the reflective sheet to maximize power coupling.

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