Wireless Power Transmission

Abstract

The present disclosure relates to wireless power transmission devices and related systems and methods. Embodiments of the present technology relate to devices, systems, and methods for powering an implantable device, such as an implantable neuromodulation device configured to modulate a patient's hypoglossal nerve. According to certain embodiments, the technology includes an external system including a control unit connected to an external device. The external device can include a carrier carrying an antenna configured to conduct a current, the antenna generating an electromagnetic field. When the implantable neuromodulation device is placed within the electromagnetic field generated by the antenna, a current is induced in the antenna of the implantable neuromodulation device, thereby powering the implantable neuromodulation device.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Application No. 63 / 483,961, filed February 8, 2023, the contents of which are incorporated herein by reference in their entirety.

[0002] This application is related to the following applications, each of which is incorporated herein by reference in its entirety: U.S. Patent Application No. 2006 / 0129999, filed on even date herewith, entitled "Wireless Power Transmission" [Attorney Docket No. 1012006001]; No. XII.010a], U.S. Provisional Application No. 63 / 377,969, filed September 30, 2022, and entitled "Neuromodulation Devices and Associated Systems and Methods," U.S. Patent Application No. 16 / 865,541, filed May 4, 2020, and entitled "Implantable Stimulation Power Receivers, Systems and Methods," U.S. Patent Application No. 16 / 866,488, filed May 4, 2020, and entitled "Systems and Methods for Improving Sleep-Disordered Breathing Using Closed-Loop Feedback," U.S. Patent Application No. 16 / 866,523, filed May 4, 2020, and entitled "Systems and Methods for Improving Sleep-Disordered Breathing," and U.S. Patent Application No. 16 / 865,668, filed May 4, 2020, and entitled "Biased Neuromodulation Leads and Methods of Use Thereof," are incorporated herein by reference in their entireties.

[0003] TECHNICAL FIELD The present technology relates to devices, systems and methods for wireless power transmission. Various embodiments of the present technology relate to devices, systems and methods for powering implantable neuromodulation devices. [Background technology]

[0004] Sleep-disordered breathing (SDB), including upper airway sleep-disordered breathing (UASD), shortens sleep duration and reduces sleep quality, causing patients to experience symptoms such as daytime sleepiness, fatigue, and impaired concentration. Obstructive sleep apnea (OSA) is the most common type of sleep-disordered breathing, affecting one in five adults in the United States. One in 15 adults has moderate to severe OSA and requires treatment. Untreated obstructive sleep apnea can lead to a decreased quality of life and increased risk of hypertension, stroke, and heart disease.

[0005] OSA is characterized by complete airway obstruction, resulting in the complete cessation of breathing (apnea) or partial cessation of breathing (hypopnea). During sleep, the tongue muscles relax. In this relaxed state, the tongue may lack the muscle tone to maintain its normal tonic shape and position. Collapse of the base of the tongue and / or soft tissues of the upper airway obstructs the upper airway, resulting in an apneic event. Upper airway obstruction prevents air from entering the lungs, causing a decrease in the patient's blood oxygen level and a corresponding increase in blood pressure and cardiac dilation. This reflexively forces the upper airway to open, restoring normal patency, after which normal breathing resumes until the next apneic event occurs. This reflexive forceful opening briefly awakens the patient.

[0006] Current treatment options include medications, noninvasive techniques, and even more invasive surgical procedures. In many cases, patient acceptance and adherence rates are significantly lower than desired, making current treatments ineffective as long-term solutions. For example, continuous positive airway pressure (CPAP) is the standard treatment for OSA. While CPAP is noninvasive and highly effective, it is not well tolerated by all patients and has several side effects. Patient adherence and / or tolerance to CPAP are often reported to range from 40% to 60%. Surgical treatments for OSA include anterior tongue muscle repositioning, orthognathic maxillary and mandibular advancement, uvulopalatopharyngoplasty, and tracheotomy. However, these procedures are highly invasive and irreversible, and tend to provide insufficient or inconsistent results. Even the more effective surgical procedures usually require multiple invasive and irreversible operations, can alter the patient's appearance (e.g., maxillary advancement surgery), can be associated with social stigma (e.g., tracheotomy), and have a high risk of complications. Summary of the Invention

[0007] The present technology will be exemplified in accordance with each aspect described below, for example, with reference to Figures 1A to 26E. Examples of each aspect of the present technology will be described as numbered configurations (1, 2, 3, etc.) for convenience. These are merely examples and are not intended to limit the present technology. 1. A device for use with an implant implanted in a first anatomical region of a patient, comprising: a carrier configured to be disposed on a surface, the carrier having a first region and a second region that do not overlap one another; an antenna carried by the carrier and configured to generate a magnetic field that is denser in the first region of the carrier than in the second region of the carrier, the magnetic field being configured to power the implant when the carrier is placed on the surface and near the patient such that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with a second anatomical region of the patient, the second anatomical region having a lower soft tissue to bone ratio than the first anatomical region, and such that when the magnetic field is powering the implant, a specific absorption rate (SAR) parameter in the patient's tissue does not exceed a predetermined threshold. 2. The device described in claim 1, wherein the first region of the carrier has a greater amount of magnetic flux from the antenna than the second region of the carrier. 3. The device described in claim 1 or 2, wherein the magnetic field has a component configured to extend through the antenna of the implant in a direction substantially perpendicular to the radial dimension of the antenna of the implant. 4. The device of claim 3, wherein the component of the magnetic field is substantially perpendicular to the surface. 5. The device of claim 3 or 4, wherein the component of the magnetic field is configured to extend through the antenna of the implant in a direction substantially perpendicular to the radial dimension of the antenna of the implant over a range of nodding angles, head axial angles, head positions, and / or head rotations. 6. A device described in any one of claims 3 to 5, wherein the average strength of said component of said magnetic field is at least 2 A / m within a volume of at least 25 cubic centimeters. 7. The device described in any one of claims 1 to 6, wherein the magnetic field is configured to supply approximately 5 mW to approximately 50 mW of power to the implant when the carrier is placed on the surface and near the patient so that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with the second anatomical region of the patient. 8. The device described in claim 7, wherein the magnetic field is configured to supply about 5 mW to about 50 mW of power to the implant when the carrier is placed on the surface and near the patient such that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with the second anatomical region of the patient, and the implant is substantially oval and has a diameter of about 2 cm to about 4 cm. 9. The device described in any one of claims 1 to 8 above, wherein the first anatomical region includes the patient's head. 10. A device described in any one of claims 1 to 9 above, wherein the second anatomical region is located below the patient's head. 11. The device described in any one of claims 1 to 10 above, wherein the second anatomical region includes the patient's neck and / or back. 12. The device described in any one of claims 1 to 11 above, wherein the second anatomical region has a second electrical conductivity greater than the first electrical conductivity of the first anatomical region. 13. A device described in any one of claims 1 to 12, wherein the second anatomical region is positioned closer to the carrier than the first anatomical region along a dimension substantially perpendicular to the surface. 14. A device described in any one of claims 1 to 13, wherein the first region of the antenna comprises a first length made of a conductive material and the second region of the antenna comprises a second length made of a conductive material. 15. The device of claim 14, wherein the first length is greater than the second length. 16. The device of claim 14 or 15, wherein the second length forms a single loop. 17. The device of any one of claims 14 to 16, wherein the first length forms at least a first loop and a second loop. 18. The device of claim 17, wherein the second loop is contained within an interior region defined by the first loop. 19. The device of claim 17 or 18, wherein the first loop is electrically connected in series with the second loop. 20. The antenna includes a transition region, the transition region comprising: a first segment configured to carry a radio frequency (RF) current in a first direction, the first segment including a first end of a first length and a first end of a second length; a second segment including a second end of the first length and a second end of the second length configured to conduct a radio frequency (RF) current in a second direction opposite the first direction; 20. A device described in any one of claims 14 to 19, wherein at least a portion of the first segment and at least a portion of the second segment overlap along the thickness direction of the antenna in the transition region. 21. The device of claim 20, wherein the first segment and the second segment are arranged at an angle of less than about 30 degrees relative to each other in a plane substantially perpendicular to the thickness direction. 22. The device described in claim 20 or 21, wherein the first segment and the second segment are aligned along the thickness direction of the carrier. 23. The device described in any one of claims 1 to 22, further comprising at least one capacitor electrically connected to the conductive material. 24. The device of claim 23, wherein the at least one capacitor is electrically connected in series with the conductive material. 25. A device according to any one of claims 1 to 24, wherein the first region of the carrier is substantially coplanar with the second region of the carrier. 26. A device described in any one of claims 1 to 25 above, wherein the surface is a surface on which the patient lies while sleeping. 27. A device described in any one of claims 1 to 26, wherein the first region is located on one side of the center line of the carrier and the second region is located on the other side of the center line of the carrier. 28. The device of claim 27, wherein the direction of current flow through the antenna reverses at the center line. 29. A device as described in claim 27 or 28, wherein the center line substantially bisects the carrier. 30. 30. A device according to any one of claims 1 to 29, wherein the antenna has a large quadrupole moment and a small dipole moment such that electromagnetic radiation generates a small electromagnetic field at a distance from the antenna. 31. A device described in any one of claims 1 to 30, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 30 minutes or less in any 1 gram of tissue of the patient excluding the patient's extremities, and the predetermined threshold is 1.6 W / kg. 32. A device described in any one of claims 1 to 31 above, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 30 minutes or less in any 10 grams of tissue in the patient's limb, and the predetermined threshold is 4 W / kg. 33. A device described in any one of claims 1 to 32, wherein the SAR parameters include an average SAR averaged over the patient's whole body over a period of no more than 30 minutes, and the predetermined threshold is 0.08 W / kg. 34. A device described in any one of claims 1 to 33, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 6 minutes or less in any 1 gram of tissue of the patient excluding the patient's extremities, and the predetermined threshold is 8 W / kg. 35. A device described in any one of claims 1 to 34, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 6 minutes or less in any 10 grams of tissue in the patient's limb, and the predetermined threshold is 20 W / kg. 36. A device described in any one of claims 1 to 35 above, wherein the SAR parameters include an average SAR averaged over the patient's whole body over a period of no more than 6 minutes, and the predetermined threshold is 0.4 W / kg. 37. A device for use with an implant implanted in a first anatomical region of a patient, comprising: a carrier configured to be disposed on a surface, the carrier having a first region and a second region that do not overlap one another; an antenna carried by the carrier, the antenna comprising a conductive material having a first length in a first configuration with one or more loops in the first region and a second length in a second configuration with one or more loops in the second region; the first configuration and the second configuration have different amounts of the conductive material; The device, wherein the antenna is configured to generate a magnetic field configured to power the implant when the carrier is placed on the surface and near the patient such that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with a second anatomical region of the patient, and wherein the magnetic field is configured to prevent a specific absorption rate (SAR) parameter in the patient from exceeding a predetermined threshold when powering the implant. 38. The device described in claim 37, wherein the magnetic field has a component configured to extend through the antenna of the implant in a direction substantially perpendicular to the radial dimension of the antenna of the implant. 39. The device of claim 38, wherein the component of the magnetic field is substantially perpendicular to the surface. 40. The device described in claim 38 or 39, wherein the component of the magnetic field is configured to extend through the antenna of the implant in a direction substantially perpendicular to the radial dimension of the antenna of the implant over a range of nodding angles, head axial angles, head positions, and / or head rotations. 41. A device described in any one of claims 1 to 40, wherein the average strength of the component of the magnetic field is at least 2 A / m within a volume of at least 25 cubic centimeters. 42. A device described in any one of claims 1 to 41, wherein the magnetic field is configured to supply approximately 5 mW to approximately 50 mW of power to the implant when the carrier is placed on the surface and near the patient so that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with the second anatomical region of the patient. 43. A device described in any one of claims 1 to 42, wherein the first anatomical region includes the patient's head. 44. A device described in any one of claims 1 to 43 above, wherein the second anatomical region is located below the patient's head. 45. A device as described in any one of claims 1 to 44 above, wherein the second anatomical region includes the patient's neck and / or back. 46. ​​A device described in any one of claims 1 to 45 above, wherein the second anatomical region has a larger volume than the first anatomical region and / or is less rounded than the first anatomical region. 47. A device described in any one of claims 1 to 46, wherein the second anatomical region is positioned closer to the carrier than the first anatomical region along a dimension substantially perpendicular to the surface. 48. A device described in any one of claims 1 to 47, wherein the first region of the antenna comprises a conductive material of a first density and the second region of the antenna comprises a conductive material of a second density. 49. The device of claim 48, wherein the first density is greater than the second density. 50. The device of any one of claims 1 to 49, wherein the second length forms a single loop. 51. The device described in any one of claims 1 to 50 above, wherein the first length forms at least a first loop and a second loop. 52. The device described in claim 51, wherein the second loop is disposed within an inner region defined by the first loop. 53. The device of claim 51 or 52, wherein the first loop is electrically connected in series with the second loop. 54. A device described in any one of claims 1 to 53, wherein the first configuration and the second configuration differ in at least one of length, number of loops, or loop size. 55. A device according to any one of claims 1 to 54, wherein the first region of the carrier has a greater amount of magnetic flux from the antenna than the second region of the carrier. 56. The antenna includes a transition region, the transition region comprising: a first segment configured to conduct radio frequency (RF) in a first direction, the first segment including a first end of the first length and a first end of the second length; a second segment including a second end of the first length and a second end of the second length configured to conduct radio frequency (RF) in a second direction opposite the first direction; A device described in any one of claims 1 to 55, wherein at least a portion of the first segment and at least a portion of the second segment overlap along the thickness direction of the antenna in the transition region. 57. The device of claim 56, wherein the first segment and the second segment are arranged at an angle of less than about 30 degrees relative to each other in a plane substantially perpendicular to the thickness direction. 58. The device described in claim 56 or 57, wherein the first segment and the second segment are aligned along the thickness direction of the carrier. 59. The device described in any one of claims 1 to 58, further comprising at least one capacitor electrically connected to the conductive material. 60. The device of claim 59, wherein the at least one capacitor is electrically connected in series with the conductive material. 61. A device described in any one of claims 1 to 60, wherein the first region of the carrier is substantially coplanar with the second region. 62. A device described in any one of claims 1 to 61 above, wherein the surface is a surface on which the patient lies while sleeping. 63. A device described in any one of claims 1 to 62, wherein the first region is located on one side of a center line of the carrier and the second region is located on the other side of the center line of the carrier. 64. The device of claim 63, wherein the direction of current flow through the antenna reverses at the center line. 65. A device as described in claim 63 or 64, wherein the center line substantially bisects the carrier. 66. A device described in any one of claims 1 to 65, wherein the antenna has a large quadrupole moment and a small dipole moment so as to generate an electromagnetic field with less electromagnetic radiation at a distance from the antenna. 67. A device described in any one of claims 1 to 66, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 30 minutes or less in any 1 gram of tissue of the patient excluding the patient's extremities, and the predetermined threshold is 1.6 W / kg. 68. A device described in any one of claims 1 to 67, wherein the SAR parameters include peak spatial average SAR averaged over a time period of no more than 30 minutes in any 10 grams of tissue in the patient's limb, and the predetermined threshold is 4 W / kg. 69. A device described in any one of claims 1 to 68, wherein the SAR parameters include an average SAR averaged over the patient's whole body over a period of no more than 30 minutes, and the predetermined threshold is 0.08 W / kg. 70. A device described in any one of claims 1 to 69, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 6 minutes or less in any 1 gram of tissue of the patient excluding the patient's extremities, and the predetermined threshold is 8 W / kg. 71. A device described in any one of claims 1 to 70, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 6 minutes or less in any 10 grams of tissue in the patient's limbs, and the predetermined threshold is 20 W / kg. 72. A device as described in any one of claims 1 to 71 above, wherein the SAR parameters include an average SAR averaged over the patient's whole body over a period of no more than 6 minutes, and the predetermined threshold is 0.4 W / kg. 73. A device for use with an implant implanted in a first anatomical region of a patient, comprising: a carrier configured to be disposed on a surface, the carrier having a first side and a second side opposite the first side; and an antenna carried by the carrier; the carrier includes a first region located between the first side and a centerline and a second region located between the second side and the centerline, wherein current flows in a first direction through the first region and in a direction opposite to the first direction through the second region such that current flow through the antenna is reversed at the centerline; 1. A device comprising: a carrier having an antenna comprising a conductive material forming at least two first loops in the first region of the carrier and a second loop in the second region of the carrier; wherein when the carrier is positioned on the surface and near the patient such that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with a second anatomical region of the patient, the antenna generates a magnetic field configured to power the implant; and wherein when the magnetic field is powering the implant, a specific absorption rate (SAR) parameter in the patient does not exceed a predetermined threshold. 74. The device of claim 73, wherein the antenna is configured to generate a magnetic field having a component substantially aligned with a width dimension of the antenna. 75. A device as described in claim 74, wherein said component of said magnetic field is substantially perpendicular to said surface. 76. A device as described in claim 74 or 75, wherein the component of the magnetic field is configured to extend through the antenna in a direction substantially perpendicular to the radial dimension of the antenna of the implant over a range of nodding angles, head axial angles, head positions, and / or head rotations. 77. A device described in any one of claims 1 to 76, wherein the component has an average intensity at the implant of at least 2 A / m when the magnetic field is powering the implant. 78. A device described in any one of claims 1 to 77 above, wherein when the magnetic field is powering the implant, the component has an average intensity of at least 2 A / m over a volume of at least 25 cubic centimeters. 79. A device described in any one of claims 1 to 78, wherein at least two of the first loops are electrically connected in series to the second loop. 80. A device described in any one of claims 1 to 79, wherein at least two of the first loops are electrically connected to each other in series. 81. A device described in any one of claims 1 to 80, wherein each of at least two of the first loops is configured to allow current to flow in a first direction, and the second loop is configured to allow current to flow in a second direction opposite to the first direction. 82. The device described in any one of claims 1 to 81, wherein the at least two first loops include a major loop and a minor loop. 83. The device of claim 82, wherein the major loop encircles a first area and the minor loop encircles a second area that is smaller than the first area. 84. A device described in any one of claims 81 to 83, wherein the at least two first loops include a major loop and at least two minor loops. 85. 85. The device of claim 84, wherein the at least two minor loops are spaced apart from each other along the length of the carrier, the length of the carrier being substantially perpendicular to the width of the carrier. 86. The device of claim 84 or 85, wherein the at least two minor loops enclose substantially equal areas. 87. The device described in any one of claims 1 to 86, wherein the first region of the carrier has a greater amount of magnetic flux from the antenna than the second region of the carrier. 88. The antenna includes a first region comprising a first length of conductive material, a second region comprising a second length of conductive material, and the antenna further includes a transition region, the transition region comprising: a first segment configured to carry a current in a first direction, the first segment including a first end of a first length and a first end of a second length; a second segment including a second end of the first length and a second end of the second length configured to conduct current in a second direction; A device described in any one of claims 1 to 87, wherein at least a portion of the first segment and at least a portion of the second segment overlap along the thickness direction of the antenna in the transition region. 89. The device of claim 88, wherein the first segment and the second segment are disposed at an angle of less than about 30 degrees relative to each other in a plane substantially perpendicular to the thickness direction. 90. The device described in claim 88 or 89, wherein the first segment and the second segment are aligned along the thickness direction of the carrier. 91. A device described in any one of claims 1 to 90, wherein the antenna is configured to operate at a frequency of approximately 6.78 MHz. 92. A device described in any one of claims 1 to 91, wherein the antenna includes a capacitor electrically connected to the conductive material to produce a real input impedance of the antenna at the operating frequency. 93. A device described in any one of claims 1 to 92, wherein the antenna includes a capacitor electrically connected in series with the conductive material. 94. A device described in any one of claims 1 to 93, wherein the antenna includes a capacitor electrically connected in parallel to the conductive material. 95. A device described in any one of claims 92 to 94, wherein the capacitor has a capacitance of about 500 pF to about 2000 pF. 96. A device described in any one of claims 92 to 95 above, wherein the capacitor has a variable capacitance. 97. A device described in any one of claims 92 to 96, wherein the antenna includes a plurality of capacitors electrically connected in series to the conductive material. 98. The device of claim 97, wherein adjacent ones of the plurality of capacitors are spaced apart along the length of the conductive material. 99. The device of claim 97 or 98, wherein the plurality of capacitors comprises about 8 to about 15 capacitors. 100. A device described in any one of claims 97 to 99, wherein at least two of the plurality of capacitors have different capacitances. 101. A device described in any one of claims 1 to 100, wherein the maximum voltage of the antenna is 600V or less. 102. A device described in any one of claims 97 to 101, wherein the voltage across a length of the conductive material between a first pair of capacitors of the plurality of capacitors is substantially equal to the voltage between a second pair of capacitors of the plurality of capacitors. 103. A device described in any one of claims 1 to 102 above, wherein the first anatomical region is the patient's head. 104. A device described in any one of claims 1 to 103 above, wherein the second anatomical region is the patient's neck. 105. A device as described in any one of claims 1 to 104 above, wherein the second anatomical region is the patient's back. 106. The device of any one of claims 1-105 above, wherein the second anatomical region has a greater soft tissue to bone ratio than the first anatomical region. 107. A device described in any one of claims 1 to 106, wherein the second anatomical region is positioned closer to the carrier than the first anatomical region along a dimension substantially perpendicular to the surface. 108. A device described in any one of claims 1 to 107, wherein the carrier comprises a fabric. 109. A device described in any one of claims 1 to 108, wherein the carrier comprises a perforated material. 110. A device described in any one of claims 1 to 109, wherein the carrier comprises a foam material. 111. A device described in any one of claims 1 to 110 above, wherein the carrier comprises at least two layers. 112. The device of claim 111, wherein the at least two layers comprise different materials. 113. The device of claim 111 or 112, wherein the conductive material is disposed between the at least two layers. 114. A device described in any one of claims 1 to 113, wherein the carrier comprises a conductive material. 115. A device described in any one of claims 1 to 114, wherein the carrier comprises a ferromagnetic material. 116. A device described in any one of claims 1 to 115, wherein the antenna includes a substrate carrying the conductive material, the substrate being carried by the carrier. 117. The device of claim 116, wherein the substrate comprises polyimide. 118. A device described in any one of claims 1 to 117, wherein the antenna has a large quadrupole moment and a small dipole moment such that electromagnetic radiation generates a small electromagnetic field at a distance from the antenna. 119. A device described in any one of claims 1 to 118, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 30 minutes or less in any 1 gram of tissue of the patient excluding the patient's extremities, and the predetermined threshold is 1.6 W / kg. 120. A device described in any one of claims 1 to 119, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 30 minutes or less in any 10 grams of tissue in the patient's extremities, and the predetermined threshold is 4 W / kg. 121. A device described in any one of claims 1 to 120, wherein the SAR parameters include an average SAR averaged over the patient's whole body over a period of no more than 30 minutes, and the predetermined threshold is 0.08 W / kg. 122. A device described in any one of claims 1 to 121, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 6 minutes or less in any 1 gram of tissue of the patient excluding the patient's extremities, and the predetermined threshold is 8 W / kg. 123. A device described in any one of claims 1 to 122, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 6 minutes or less in any 10 grams of tissue in the patient's extremities, and the predetermined threshold is 20 W / kg. 124. A device described in any one of claims 1 to 123, wherein the SAR parameters include an average SAR averaged over the patient's whole body over a period of no more than 6 minutes, and the predetermined threshold is 0.4 W / kg. 125. Neuromodulation systems are An external system, An external device comprising the device according to any one of claims 1 to 124, wherein the carrier of the external device is configured to be placed outside the body between the patient and a surface on which the external device is placed; a control unit electrically connected to an antenna of the external device, the control unit configured to supply a radio frequency (RF) current to the antenna so that the antenna generates a magnetic field; 1. A neuromodulation system comprising: an implantable neuromodulation device configured to be implanted in a first anatomical region of the patient, the implantable neuromodulation device comprising a second antenna and a lead extending from the second antenna and carrying an electrode, the second antenna configured to inductively couple with an antenna of the external device when positioned within a magnetic field generated by the antenna of the external device, thereby inducing a radio frequency (RF) current in the second antenna. 126. The neuromodulation system described in claim 125, wherein the implantable neuromodulation device does not include a battery. 127. A neuromodulation system described in any one of claims 1 to 126, wherein the radio frequency (RF) current induced in the second antenna is supplied to the electrode carried by the lead. 128. A neuromodulation system described in any one of claims 1 to 127, wherein the implantable neuromodulation device is configured to supply electrical stimulation energy from the electrodes to tissue in the first anatomical region of the patient. 129. The neuromodulation system described in claim 128, wherein the tissue is the patient's hypoglossal nerve. 130. The neuromodulation system described in 128 or 129 above, wherein the tissue is the patient's genioglossus muscle. 131. A neuromodulation system as described in any one of claims 1 to 130, wherein the control unit comprises a variable matching circuit. 132. The neuromodulation system of claim 131, wherein the variable matching circuit is configured to change the impedance presented to the antenna of the external device. 133. The neuromodulation system described in claim 131 or 132, wherein the variable matching circuit is configured to optimize the impedance presented to the antenna of the external device. 134. A neuromodulation system described in any one of claims 131 to 133, wherein the variable matching circuit comprises a plurality of capacitors and a plurality of switches. 135. A neuromodulation system described in any one of claims 131 to 134, wherein the variable matching circuit is configured to selectively activate or deactivate each of the plurality of capacitors via the plurality of switches.

[0008] Many aspects of the present disclosure may be more clearly understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. [Brief explanation of the drawings]

[0009] [Figure 1A]1 is a midsagittal cross-sectional view of a portion of the upper airway of a human patient. [Figure 1B] FIG. 1 illustrates the musculature of the human tongue and the innervation of the hypoglossal nerve. [Figure 1C] 1 is a schematic superior view showing the distal arborization of the right and left hypoglossal nerves of a human patient, where the hypoglossal nerves are shown extending anteriorly from inferior to superior (e.g., from the hyoid bone to the anterior mandible). [Figure 2A] FIG. 1 is a schematic diagram illustrating a neuromodulation system configured in accordance with embodiments of the present technology. [Figure 2B] FIG. 1 is a perspective view of a neuromodulation device configured in accordance with embodiments of the present technology. [Figure 2C] FIG. 2C is a top view of the neuromodulation device of FIG. 2B. [Figure 2D] FIG. 2C is a side view of the neuromodulation device of FIG. 2B. [Figure 3] FIG. 3A illustrates the neuromodulation device shown in FIGS. 2B-2D implanted in a human patient. FIG. 3B illustrates the neuromodulation device shown in FIGS. 2B-2D implanted in a human patient. FIG. 3C illustrates the neuromodulation device shown in FIGS. 2B-2D implanted in a human patient. FIG. 3D illustrates the neuromodulation device shown in FIGS. 2B-2D implanted in a human patient. FIG. 3E illustrates the neuromodulation device shown in FIGS. 2B-2D implanted in a human patient. FIG. 3F illustrates the neuromodulation device shown in FIGS. 2B-2D implanted in a human patient. [Figure 4A] FIG. 1 is a plan view of an external device in accordance with embodiments of the present technology. [Figure 4B] 4B is a close-up view of both ends of a first length of the antenna of the external device of FIG. 4A. [Figure 4C] 4B is a close-up view of both ends of a second length of the antenna of the external device of FIG. 4A. [Figure 5] 4B is a two-dimensional diagram of the magnetic field generated by the antenna of the external device of FIG. 4A in accordance with embodiments of the present technology. [Figure 6]4B is a plan view of the electric field generated by the antenna of the external device of FIG. 4A in accordance with embodiments of the present technology. [Figure 7] Figure 7A is a side view of a patient showing the specific absorption rate (SAR) at each location on the patient when placed in the electromagnetic field generated by the antenna of the external device of Figure 4A. Figure 7B is a top view of a patient showing the specific absorption rate (SAR) at each location on the patient when placed in the electromagnetic field generated by the antenna of the external device of Figure 4A. [Figure 8A] FIG. 1 illustrates typical locations of antennas of a neurostimulation device implanted at treatment sites in the submandibular and sublingual areas of a patient's head while the patient is asleep. [Figure 8B] FIG. 10 is a diagram showing an example of a patient's nodding angle. [Figure 8C] 1A-1C illustrate examples of axial angles of a patient's head. [Figure 8D] FIG. 10 is a diagram showing an example of the rotation angle of the patient's head. [Figure 9] FIG. 4B is a contour plot of the average strength (magnetic field amplitude) of magnetic field components perpendicularly penetrating the antenna of the implantable device under the maximum spatial specific absorption rate (psSAR) limit, as a function of different patient chin positions relative to the antenna of the external device of FIG. 4A. [Figure 10] FIG. 1 is a plan view of an external device in accordance with embodiments of the present technology. [Figure 11] 11 is a plan view of the electric field generated by the antenna of the external device of FIG. 10 in accordance with embodiments of the present technology. [Figure 12] FIG. 1 is a plan view of an external device in accordance with embodiments of the present technology. [Figure 13] 13 is a two-dimensional diagram of the magnetic field generated by the antenna of the external device of FIG. 12 in accordance with embodiments of the present technology. [Figure 14]Figure 14A is a side view of a patient showing the specific absorption rate at each location on the patient when the patient is placed in the electromagnetic field generated by the antenna of the external device of Figure 12. Figure 14B is a top view of a patient showing the specific absorption rate at each location on the patient when the patient is placed in the electromagnetic field generated by the antenna of the external device of Figure 12. [Figure 15] FIG. 1 is a plan view of an external device in accordance with embodiments of the present technology. [Figure 16] 16 is a two-dimensional diagram of the magnetic field generated by the antenna of the external device of FIG. 15 in accordance with embodiments of the present technology. [Figure 17] Figure 17A is a side view of a patient showing the specific absorption rate at each location on the patient when placed in the electromagnetic field generated by the antenna of the external device of Figure 15. Figure 17B is a top view of a patient showing the specific absorption rate at each location on the patient when placed in the electromagnetic field generated by the antenna of the external device of Figure 15. [Figure 18] FIG. 1 is a plan view of an external device in accordance with an embodiment of the present technology. [Figure 19] FIG. 1 is a plan view of an external device in accordance with an embodiment of the present technology. [Figure 20] FIG. 1 is a plan view of an external device in accordance with an embodiment of the present technology. [Figure 21] FIG. 1 is a plan view of an external device in accordance with an embodiment of the present technology. [Figure 22] FIG. 1 is a plan view of an external device in accordance with an embodiment of the present technology. [Figure 23] FIG. 10 is a block diagram of a control unit and a second antenna of an external system in accordance with embodiments of the present technology. [Figure 24A] FIG. 10 is a block diagram of a control unit and a second antenna of an external system in accordance with an embodiment of the present technology. [Figure 24B] FIG. 10 is a block diagram of a control unit and a second antenna of an external system in accordance with an embodiment of the present technology. [Figure 25A] FIG. 1 is a schematic diagram illustrating an example of a series matching circuit in accordance with embodiments of the present technology; [Figure 25B] FIG. 1 is a schematic diagram illustrating an example of a series-parallel matching circuit, in accordance with embodiments of the present technology. [Figure 26A] FIG. 1 is a perspective view of an external device in accordance with an embodiment of the present technology. [Figure 26B] FIG. 1 is a perspective view of an external device in accordance with an embodiment of the present technology. [Figure 26C] FIG. 2 is a cutaway perspective view of the external device. [Figure 26D] FIG. 2 is a side cross-sectional view of the external device. [Figure 26E] FIG. 2 is a plan view of the antenna of the external device. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure relates to devices, systems, and methods for wirelessly powering implantable medical devices. For example, an external system of the present technology can include a control unit connected to the external device. The external device includes a carrier carrying an antenna configured to conduct radio frequency (RF) current, which generates an electromagnetic field. When the implantable device is placed within the electromagnetic field generated by the antenna, a radio frequency (RF) current is induced in the antenna of the implantable device, and the current can be used to power one or more electronic components carried by the implantable device. In certain embodiments, the external devices and systems disclosed herein are used to power a neuromodulation system, which can provide various electrical therapies, including neuromodulation therapies such as neural stimulation and / or muscle stimulation. The stimulation can induce excitatory or inhibitory neural or muscle activity. Such therapies can be used at various appropriate sites within a patient's anatomy. According to an embodiment, the neuromodulation system of the present technology is configured to treat sleep-disordered breathing (SDB), including obstructive sleep apnea (OSA) and / or mixed sleep apnea, via neuromodulation of the hypoglossal nerve (HGN).

[0011] To understand the structure and operation of the neuromodulation systems and devices disclosed herein, the following first describes some of the relevant anatomy and physiology. Note that the headings herein are provided for convenience only and are not intended to interpret the scope or meaning of the claims. Embodiments described under any heading may be used in combination with embodiments described under any other heading. For example, any of the neuromodulation systems and devices described in connection with Sections II and III may be used in combination with any of the external systems and devices described in connection with Section IV.

[0012] I. Anatomy and Physiology As previously mentioned, in patients with sleep-disordered breathing (SDB), breathing is impaired due to obstruction, narrowing, or collapse of the upper airway during sleep. As shown in Figure 1A, the upper airway includes the nasal cavity, oral cavity, pharynx, and larynx. The patency of the upper airway and the resistance to airflow within it are controlled by a complex muscular network under both voluntary and involuntary neuromuscular control. For example, the tongue, suprahyoid muscles (e.g., geniohyoid, mylohyoid, stylohyoid, hyoglossus, and anterior belly of the digastric muscle), and muscles of the soft palate (e.g., palatal muscles) open, widen, or stabilize the upper airway during inspiration, working against the negative pressure that draws air into the airways and lungs.

[0013] Referring to FIG. 1B, the tongue includes both intrinsic and extrinsic tongue muscles. Generally, contraction of the intrinsic muscles changes the shape of the tongue, while contraction of the extrinsic muscles shifts the position of the entire tongue. The extrinsic muscles originate from bony attachments and insert within the tongue (i.e., originate from bone and insert within the tongue). The extrinsic muscles include the genioglossus, styloglossus, hyoglossus, and palatoglossus. The intrinsic muscles originate and insert within the tongue and include the superior longitudinalis, inferior longitudinalis, transversalis, and verticalis. In awake patients, the brain supplies nerve impulses to these muscles via the hypoglossal nerve (HGN) to maintain the shape and position of the tongue and prevent it from obstructing the airway.

[0014] Tongue muscles are functionally classified as either retrusor or protrusor muscles, and both intrinsic and extrinsic muscles fall into these categories. Retrusor muscles include the intrinsic superior and inferior longitudinal muscles and the extrinsic hyoglossus and styloglossus muscles. Protrusor muscles include the intrinsic vertical and transverse muscles and the extrinsic genioglossus muscle. Contraction of the styloglossus muscle elevates the tongue, while downward movement of the hyoid and genioglossus muscles depresses the tongue. Figure 1B also shows the geniohyoid muscle, which is a member of the suprahyoid muscle group and contributes to maintaining upper airway patency as an important protrusive and pharyngeal dilator. Effective treatment of obstructive sleep apnea (OSA) is believed to require stimulation of protrusive muscles while minimizing or completely inhibiting retrusive muscle activity. Therefore, to effectively perform neuromodulation therapy, it is considered desirable to localize stimulation of the advancing muscles while avoiding activation of the retracting muscles.

[0015] The genioglossus, the largest of the tongue muscles, can be morphologically and functionally divided into two compartments based on the distribution of muscle fibers, action, and innervation. The first compartment, the oblique compartment (GGo), contains vertical muscle fibers that, upon contraction, depress the tongue downward without substantially affecting pharyngeal patency. The second compartment, the horizontal compartment (GGh), contains longitudinal muscle fibers that, upon activation, propel the posterior portion of the tongue forward and widen the pharyngeal opening. The GGo contains fatigable type II muscle fibers, while the GGh contains less fatigable type I muscle fibers. Therefore, to effectively protrude the tongue while preventing or minimizing tongue fatigue, stimulating the GGh with little or no stimulation of the GGo may be advantageous.

[0016] The suprahyoid muscle group, consisting of the mylohyoid, geniohyoid, stylohyoid, and digastric muscles (only a portion of which is shown in Figure 1B), extends between the mandible and hyoid bone, forming the floor of the mouth. The geniohyoid muscle lies inferior to the genioglossus muscle of the tongue, which in turn lies inferior to it. Contraction of the geniohyoid muscle and tension of the sternohyoid muscle (not shown, part of the infrahyoid muscle group) work in concert to pull the hyoid bone forward, opening and / or expanding the pharyngeal cavity and stabilizing the anterior wall of the hypopharyngeal region. In contrast to the genioglossus and geniohyoid muscles, which are considered muscles that propel the tongue forward, the hyoglossus and styloglossus muscles are considered muscles that retract the tongue backward (retrusors). Activation of the hyoglossus and styloglossus muscles pulls the tongue backward, reducing the size of the pharyngeal opening and increasing airway resistance, tending to obstruct breathing.

[0017] As mentioned above, all extrinsic and intrinsic muscles of the tongue, except for the Palatoglossus, are innervated by the hypoglossal nerve (HGN). The Palatoglossus is innervated by the vagus nerve. There are two hypoglossal nerves in the body, one on the right side of the head and one on the left side. Each hypoglossal nerve originates in the hypoglossal nucleus in the medulla oblongata of the brainstem, exits the skull via the hypoglossal canal, then descends through the retrostyloid space (part of the lateral pharyngeal space) to the occipital artery. The hypoglossal nerve then curves forward to the tongue muscles, passing between the anterior border of the hyoglossus muscle and the posterior border of the mylohyoid muscle to the hypoglossal area, where it divides into terminal branches.

[0018] Figure 1C is a top-view schematic diagram of the distal dendritic branches of the right and left hypoglossal nerves. Referring to Figures 1B and 1C together, the hypoglossal nerve includes (1) a portion of the distal dendritic branch that innervates the tongue retractors, the styloglossus and hyoglossus muscles, and (2) a portion of the distal dendritic branch that innervates the intrinsic tongue muscles, the genioglossus and geniohyoid muscles. Furthermore, the portion of the distal dendritic branch that innervates the tongue retractors tends to be located more posteriorly than the portion of the distal dendritic branch that innervates the tongue advancers.

[0019] Decreased activity of muscles involved in maintaining the airway can increase airway resistance, potentially resulting in a variety of adverse effects on a patient's breathing and health. For example, genioglossus muscle activity can decrease during sleep, which, alone or in combination with other factors (e.g., airway length, airway diameter, soft tissue volume, early awakenings, etc.), can lead to increased airway resistance and / or airway collapse, potentially resulting in sleep-related breathing disorders such as obstructive sleep apnea (OSA). Effective neuromodulation therapy is thought to primarily focus on stimulation of the distal hypoglossal nerve branch that innervates the tongue advancing muscles, while avoiding or suppressing stimulation of the branch that activates the tongue retracting muscles.

[0020] II. Neuromodulation Systems Various embodiments of the present technology relate to devices, systems, and methods for modulating neural activity and / or controlling one or more nerves associated with one or more muscles involved in maintaining an airway. Such neuromodulation can enhance the activity of target muscles, such as the genioglossus and geniohyoid muscles, reducing airway resistance and improving breathing in patients. Furthermore, targeted modulation of specific portions of the distal dendritic branches of the hypoglossal nerve can enhance the activity of the tongue advancing muscles without significantly increasing the activity of the tongue retracting muscles, providing highly effective treatment. Additionally or alternatively, selective modulation of the distal dendritic branches of the hypoglossal nerve that innervate the horizontal compartment (GGh) of the genioglossus muscle, while sparing the portion innervating the oblique compartment (GGo), can effectively protrude the tongue while preventing or reducing tongue fatigue.

[0021] 2A illustrates a neuromodulation system 10 for treating sleep-disordered breathing (SDB) configured in accordance with the present technology. The system 10 can include an implantable neuromodulation device 100 and an external system 15 configured to wirelessly connect to the neuromodulation device 100. The neuromodulation device 100 can include a lead 102 having a plurality of conductive elements 114 and an electronics package 108 having a first antenna 116 and electronic components 118. The neuromodulation device 100 is configured to be implanted in a treatment site on a patient's head, including the submandibular and sublingual regions, as described below with reference to FIGS. 3A-3F.

[0022] In use, electronics package 108, or some of its components, may be configured to deliver stimulation energy of a set pulse width, amplitude, duration, frequency, duty cycle, and / or polarity to conductive elements 114, which then apply an electric field to the treatment site to modulate the hypoglossal nerve. This stimulation energy may be delivered according to a periodic waveform, including, for example, a charge-balanced square wave with alternating anodic and cathodic pulses.

[0023] The one or more pulses of stimulation energy may have a pulse width of about 10 μs to about 1000 μs, about 50 μs to about 950 μs, about 100 μs to about 900 μs, about 150 μs to about 800 μs, about 200 μs to about 850 μs, about 250 μs to about 800 μs, about 300 μs to about 750 μs, about 350 μs to about 700 μs, about 400 μs to about 650 μs, about 450 μs to about 600 μs, about 500 μs to about 550 μs, or about 600 μs to about 750 μs. In some embodiments, the pulse or pulses of stimulation energy may have a pulse width of between about 50 μs and about 450 μs.

[0024] The one or more pulses of stimulation energy may have an amplitude sufficient to increase the desired phasic movement of the muscle. For example, the one or more pulses of stimulation energy may have a current-controlled amplitude of about 0.1 mA to about 5 mA. In some embodiments, the stimulation energy may have an amplitude of about 0.3 mA, about 0.4 mA, about 0.5 mA, about 0.6 mA, about 0.7 mA, about 0.8 mA, about 0.9 mA, about 1 mA, about 1.5 mA, about 2 mA, about 2.5 mA, about 3 mA, about 3.5 mA, about 4 mA, about 4.5 mA, and / or about 5 mA. Additionally or alternatively, the amplitude of the one or more pulses of stimulation energy may be voltage-controlled. The amplitude of the one or more pulses of stimulation energy may be based at least in part on the size and / or configuration of the conductive element 114, the location of the conductive element 114 within the patient, etc.

[0025] The frequency of the stimulation energy pulses may be about 10 Hz to about 50 Hz, about 20 Hz to about 40 Hz, about 10 Hz, about 15 Hz, about 20 Hz, about 25 Hz, about 30 Hz, about 35 Hz, about 40 Hz, about 45 Hz, and / or about 50 Hz. In some embodiments, the frequency may be determined based on the desired effect of the stimulation energy on one or more muscles or nerves. For example, a low frequency may induce muscle twitching, while a high frequency may induce complete muscle contraction.

[0026] The external system 15 may include an external device 11 and a control unit 30 communicatively coupled to the external device 11. In some embodiments, the external device 11 may be configured to be placed near the patient's head while the patient is sleeping. The external device 11 may include a carrier 9 having a second antenna 12 integrated therewith. Details regarding the external system 15 and the external device 11 are described below with reference to FIGS. 4-26E. While the control unit 30 is shown separate from the external device 11 in FIG. 2A, in some embodiments, the control unit 30 may be integrated into or form part of the external device 11. The second antenna 12 may be configured for multiple purposes. For example, the second antenna 12 may be configured to provide power to the neuromodulation device 100 via electromagnetic resonance. When the first antenna 116 is positioned above the second antenna 12 of the external device 11, i.e., within the electromagnetic field generated by the second antenna 12, a current may be induced in the first antenna 116. The first and second antennas 116, 12 may also be configured to transmit and receive data to and from each other to enable communication between the neuromodulation device 100 and the external system 15, which may include communication via one or more wireless communication technologies (e.g., Bluetooth, WiFi, USB, etc.). This communication may include, for example, programming, i.e., uploading software / firmware updates to the neuromodulation device 100, changing / adjusting stimulation settings and / or parameters, and adjusting parameters of control algorithms.

[0027] The control unit 30 of the external system 15 may include a processor and / or memory, and the memory may store instructions (e.g., in the form of software, code, or program instructions executable by a processor or controller) for causing an external device to generate an electromagnetic field according to predetermined parameters. The external system 15, or a portion thereof (e.g., the control unit 30), may be connected to or include a power source, such as a direct current (DC) power source, an alternating current (AC) power source, and / or a power source switchable between DC and AC. The processor may be used to control various parameters of the energy output from the power source, such as intensity, amplitude, duration, frequency, duty cycle, polarity, etc. As an alternative to or complement to a processor, the external system may include a driver circuit. In such an embodiment, the external system 15, or a portion thereof (e.g., the control unit 30), may include hardwired circuitry for providing the desired waveform output, rather than a software-based waveform generator. The drive circuit may include analog circuit elements, such as resistors, diodes, switches, etc., that are configured to cause the power source to provide energy to the second antenna 12 to generate an electromagnetic field according to desired parameters. In some embodiments, the neuromodulation device 100 may be configured to communicate with an external system via resonant inductive coupling.

[0028] The system 10 may further include a user interface 40 in the form of a patient device 70 and / or a physician device 75. The user interface 40 may be configured to transmit and receive data to and from the external system 15, the second antenna 12, the control unit 30, the neuromodulation device 100, and / or a remote computing device 80 via wired and / or wireless communication technologies (e.g., Bluetooth, WiFi, USB, etc.). In the example configuration shown in FIG. 2A, both the patient device 70 and the physician device 75 are smartphones. However, other types of devices may also be used. One or both of the patient device 70 and the physician device 75 may have installed thereon applications tailored to their respective users (hereinafter, “apps”). That is, the patient is provided with a patient app, and the physician is provided with a physician app. The patient app allows the execution of specific commands necessary to control the operation of the neuromodulation device 100 (e.g., start / stop treatment, increase / decrease stimulation intensity or power, select a stimulation program, etc.). In addition to the controls provided to patients, the clinician app allows for the modification of stimulation settings (pulse settings (e.g., pattern, duration, waveform), stimulation frequency, amplitude settings, electrode configuration, etc.), closed-loop and open-loop control settings, and tuning parameters of the embedded software that controls therapy delivery.

[0029] The patient device 70 and / or the physician device 75 may be configured to communicate with other components of the system 10 via the network 50. The network 50 may include a wired network, a wireless network, a metropolitan area network (MAN), a local area network (LAN), a wide area network (WAN), a virtual local area network (VLAN), the Internet, an extranet, an intranet, and any other suitable type of network or combination thereof. The patient device 70 and / or the physician device 75 may communicate with one or more remote computing devices 80 via the network 50, enabling data transfer between these devices 70, 75 and the remote computing devices 80. In addition, the external system 15 may also be configured to communicate with other components of the system 10 via the network 50, enabling data transfer between the external system 15 and the remote computing devices 80.

[0030] The external system 15 can receive programs, software / firmware, settings / parameters via any of the communication paths described above, i.e., direct communication (wired or wireless) from the user interface 40 and / or via the network 50. These communication paths can also be used to download data, such as measurement data regarding completed stimulation therapy sessions, from the neuromodulation device 100 to the external system 15. The external system 15 can transmit the downloaded data to the user interface 40, which can then transmit / upload the data via the network 50 to the remote computing device 80.

[0031] Additionally, the various communication paths shown in FIG. 2A, in addition to allowing local control of the system 10, eg, the external system 15 and the neuromodulation device 100, also allow for the following:

[0032] Delivering software / firmware updates to the patient device 70, physician device 75, external system 15 and / or neuromodulation device 100 from the remote computing device 80.

[0033] Downloading treatment settings / parameters from the remote computing device 80 to be implemented by the patient device 70, physician device 75, external system 15 and / or neuromodulation device 100.

[0034] Allowing a remote physician to adjust treatment settings / parameters and / or adjust algorithms.

[0035] Uploading data recorded during a therapy session.

[0036] Distributing changes and adjustments across system components to maintain consistency in settings / parameters.

[0037] Therapeutic approaches implemented by the present technology may include implanting only the neuromodulation device 100, leaving the external system 15 as an external component used only during the delivery of therapy. To this end, the neuromodulation device 100 may be configured to be powered by the external system 15 via electromagnetic induction. In use, a second antenna 12, driven by the control unit 30, may be configured to be positioned outside the patient's body in proximity to the neuromodulation device 100, such that the second antenna 12 is positioned in proximity to the first antenna 116 of the neuromodulation device 100. In one embodiment, the second antenna 12 is supported by a flexible carrier 9, which may be configured to be positioned on, under, within, or sufficiently close to the patient's surface so that the first antenna 116 remains within the target region of the electromagnetic field generated by the second antenna 12. The surface may be a surface on which a patient lies (e.g., a sleep surface on which a patient lies while sleeping, a surgical table on which a patient lies while the neuromodulation device 100 is implanted, a clinic table on which a patient lies while the neuromodulation device 100 is adjusted, etc.). Alternatively, the surface may be a surface on which a patient leans (e.g., a mattress with a raised headrest, a recliner, etc.). In various embodiments, the surface may be a vertical surface that a patient approaches while standing or sitting. This approach enables system 10 to provide therapy for sleep-related breathing disorders (SDB), such as obstructive sleep apnea (OSA), through a shorter, less invasive procedure, for example, by stimulating the hypoglossal nerve (HGN). The use of electromagnetic induction power eliminates the need for an internal power source, eliminating the need for batteries and their replacement.

[0038] In some embodiments, system 10 may include one or more sensors (not shown), which may be implanted and / or external. For example, system 10 may include one or more sensors supported by (and co-implanted with) neuromodulation device 100. Such sensors may be located anywhere on lead 102 and / or electronic package 108. In some embodiments, one, more, or all of conductive elements 114 may be configured for both sensing and stimulation. Sharing a single structure or element as both a sensing electrode and a stimulation electrode reduces the invasiveness of the surgical procedure associated with implanting the system and also reduces the number of foreign bodies introduced into the patient's body. In certain embodiments, at least one of conductive elements 114 may be dedicated to sensing.

[0039] In addition to or instead of including one or more sensors in neuromodulation device 100, system 10 may include one or more sensors separate from neuromodulation device 100. In some embodiments, one or more of such sensors may be wired to neuromodulation device 100 but implanted at a different location than neuromodulation device 100. In some embodiments, system 10 may include one or more sensors configured to wirelessly connect to neuromodulation device 100 and / or an external computing device (e.g., control unit 30, user interface 40, etc.). Such sensors may be implanted at the same or different location as neuromodulation device 100, or may be placed on the patient's skin.

[0040] The one or more sensors may be configured to record and / or detect physiological data (e.g., data from the patient's body), including changes over time. Such physiological data may be used to select specific stimulation parameters and / or adjust one or more stimulation parameters during treatment. Physiological data may include electromyography (EMG) signals, temperature, movement, body posture, electroencephalography (EEG), airflow, audio data, heart rate, transcutaneous oxygen saturation, eye movement, and combinations thereof. In some embodiments, the physiological data may be used to detect and / or predict other physiological parameters. For example, one or more sensors may be configured to sense EMG signals, which may be used to detect and / or predict physiological events such as phasic contractions of the anterior tongue muscles (e.g., genioglossus phasic contractions) and measure physiological data such as sustained tonic activity of the anterior tongue muscles (e.g., genioglossus tonic activity). Phasic contractions of the genioglossus may be indicative of inspiration, particularly as phasic activity superimposed on baseline genioglossus tone. The changes in physiological data may include changes in one or more parameters of the measured signal (e.g., frequency, amplitude, spike rate, etc.), the onset and termination of phasic contractions of the anterior tongue muscles (e.g., phasic contractions of the genioglossus), changes in the baseline tonic activity of the anterior tongue muscles (e.g., tonic activity of the genioglossus), and combinations thereof. In particular, changes in the phasic activity of the genioglossus may indicate changes in respiration or inspiration and may be used as a trigger for stimulation. Such physiological data and changes therein may be identified in signals recorded from the sensors during each phase of respiration, including inspiration. Accordingly, the one or more sensors may include an EMG sensor. Such sensors may also include wireless or wired sensors measuring, for example, body temperature, movement (e.g., acceleration sensor), respiratory sounds (e.g., voice sensor), heart rate, transcutaneous oxygen saturation, eye movement, etc.

[0041] During operation, physiological data provided by one or more sensors enables closed-loop operation of neuromodulation device 100. For example, electromyographic (EMG) responses detected from the genioglossus, a hypoglossal muscle, enable closed-loop operation of neuromodulation device 100 without the need for chest leads to detect respiration. Operating in a closed loop allows neuromodulation device 100 to maintain stimulation synchronized with respiration while retaining the ability to detect and correct, for example, temporary blockages. Neuromodulation device 100 can also detect and respond to snoring.

[0042] System 10 may be configured to provide open-loop control and / or closed-loop stimulation to set stimulation parameters. In other words, for closed-loop stimulation, system 10 may be configured to track the subject's breathing (e.g., each breath) and apply stimulation, for example, at or before the onset of inspiration. For open-loop stimulation, stimulation may be applied without tracking specific physiological data, such as respiration or inspiration. However, even in such an "open-loop" scenario, system 10 can still adjust stimulation, record data, and act on that information. For example, system 10 may act on that information by setting stimulation parameters to apply stimulation in an open-loop manner while monitoring the subject's breathing to determine when to switch back to a closed-loop, breath-by-breath stimulation regime, where system 10 constantly evaluates and acts on the data based on a closed-loop algorithm. System treatment parameters may be automatically adjusted in response to physiological data. Physiological data may be stored over time and analyzed to modify treatment parameters. For example, the treatment data may be analyzed in real time and used to modify treatment parameters in real time. In certain embodiments, treatment parameters may be learned from physiological data stored over time and used to adjust treatment in real time, and this learning may be subject-specific or global across multiple subjects.

[0043] When operating in real time, the neuromodulation device 100 can record data related to stimulation sessions (e.g., stimulation settings, EMG responses, respiration, sleep states including different stages of REM and non-REM sleep, etc.) via, for example, one or more sensors. For example, changes in phasic and tonic EMG activity of the genioglossus muscle during inspiration can serve as stimulation triggers, and stimulation can be modified based on changes in these activities during inspiration or across different sleep states. This recorded data can be uploaded to the user interface 40 and the remote computing device 80. The patient can also use the interface 40 to record data regarding subjective sleep quality, which can also be uploaded to the remote computing device 80. Offline, the remote computing device 80 can run a software application to analyze the recorded data and determine whether settings or control parameters can be adjusted to further optimize the stimulation therapy. The software application can include, for example, an artificial intelligence (AI) model that learns from the recorded treatment sessions how specific adjustments affect the patient's treatment outcome. In this way, through AI learning, the model can provide an optimized treatment for each patient.

[0044] 2B-2D illustrate various perspectives of an exemplary configuration of a neuromodulation device 100. Specific features of the neuromodulation device 100 are described with reference to FIGS. 2B-2D, although other configurations of the neuromodulation device 100 are possible within the scope of the present technology. Exemplary configurations of the neuromodulation device 100 within the scope of the present technology include those disclosed in U.S. Patent Application No. 18 / 475,818 (filed September 27, 2023), U.S. Provisional Patent Application No. 63 / 377,969 (filed September 30, 2022), U.S. Patent Application No. 16 / 865,541 (filed May 4, 2020), U.S. Patent Application No. 16 / 866,488 (filed the same day), U.S. Patent Application No. 16 / 866,523 (filed the same day), and U.S. Patent Application No. 16 / 865,668 (filed the same day). As previously described, device 100 is configured to be implanted at a treatment site in the submental and sublingual regions of a patient's head and can be configured to deliver electrical energy at the treatment site to stimulate the hypoglossal nerve (HGN) and / or one or more anterior tongue retractor muscles (e.g., genioglossus, geniohyoid, etc.). Device 100 can include an electronics housing 108 and a lead 102 connected to and extending from the electronics housing 108. Lead 102 can include a lead body 104 having a plurality of conductive elements 114 and an extension 106 extending between the lead body 104 and the electronics housing 108. Extension 106 can have a proximal end 106a connected to electronics housing 108 via a first connector 110 and a distal end 106b connected to lead body 104 via a second connector 112.

[0045] The electronics housing 108 may be configured to supply electrical current to the conductive element 114 (e.g., for stimulation) and / or receive electrical energy from the conductive element 114 (e.g., for sensing physiological data). The extension 106 of the lead 102 may mechanically and / or electrically connect the electronics housing 108 and the lead body 104. The extension 106 may comprise a polymeric material, such as a thermoplastic elastomer, a thermoplastic polyurethane, a silicone, or other suitable material. The extension 106 has sufficient flexibility to bend the lead body 104 to position the lead body 104 above and away from the electronics housing 108. As described in more detail below with reference to FIGS. 3A-3F , the neuromodulation device 100 is configured to be implanted in both the submental and sublingual regions, with the electronics housing 108 and the lead body 104 stacked vertically with one or more muscle and / or other tissue layers between them. The flexibility of extension 106 allows for such a configuration.

[0046] In one embodiment, the extension 106 includes a sidewall defining a lumen therethrough. The conductive elements 114 may be electrically connected to the first antenna 116 and / or the electronic component 118 via one or more electrical connections extending through the lumen of the extension 106. For example, the proximal end of the electrical connection may be routed to the electronic component 118 on the electronic component housing 108 via the first connector 110. The electrical connections may include, for example, one or more wires, cables, conductor patterns (traces), vias, etc. extending through the extension 106 and the lead body 104. The electrical connections may include a conductive material such as silver, copper, etc., and each electrical connection may be insulated along its entire length or a portion thereof. In one embodiment, the device 100 includes a separate electrical connection corresponding to each conductive element 114. For example, in embodiments (and other embodiments) in which device 100 includes eight conductive elements 114, device 100 may include eight electrical connections with proximal ends connected to electronic component 118 and distal ends connected to one of each conductive element 114.

[0047] In some embodiments, electronic component 118 includes an application-specific integrated circuit (ASIC), discrete electronic components, and / or electrical connectors. In these and other embodiments, electronic component 118 may include, for example, processing and memory components (such as a microcomputer, microprocessor, computer-on-chip (CoC)), charge storage and / or supply components (such as batteries, capacitors, electrical conductors) for receiving, storing, and / or supplying electrical energy, and switching components (such as solid-state, pulse-width modulated, etc.) for selecting and / or controlling conductive elements 114. In some embodiments, electronic component 118 includes a data communications unit for communicating with an external device (e.g., external system 15) via a communications standard such as near-field communication (NFC), infrared radio, Bluetooth, ZigBee, Wi-Fi, inductive coupling, capacitive coupling, or other suitable wireless communications standard. In some examples, electronic component 118 includes one or more processors with one or more computing components configured to control the energy supply via conductive elements 114 and / or process energy and / or data received by conductive elements 114 based on instructions stored in memory. The memory may be a tangible, non-transitory, computer-readable medium configured to store instructions executable by one or more processors. For example, the memory may be a data storage device that can store one or more software components executable by one or more processors to perform a predetermined function. In one example, the function is to cause the conductive elements 114 to acquire data characterizing the patient's muscle activity. In another example, the function is to process the data to determine one or more parameters of the data (e.g., changes in muscle activity, etc.). According to various embodiments, the electronic components 118 may include a wireless charging unit for powering other electronic components 118 of the device 100 and / or charging a battery of the device 100 (if included).

[0048] The electronics package 108 may be configured to wirelessly receive energy from a power source to power the neuromodulation device 100. In one embodiment, the electronics package 108 includes a first antenna 116 configured to wirelessly communicate with an external system 15. As shown in FIG. 2B , in one embodiment, the electronics 118 may be disposed within an opening in the center of the first antenna 116. In other embodiments, the electronics 118 and antenna 116 may have other configurations and arrangements.

[0049] The second antenna 12 may be configured to emit an electromagnetic field to induce a current in the first antenna 116, which may be supplied to the electronic component 118 and / or the conductive element 114. In some embodiments, the first antenna 116 comprises a coil or multiple coils. For example, the first antenna 116 may include one or more coils disposed on a flexible substrate. The substrate may include a single substrate or multiple substrates secured together by an adhesive material. For example, in some embodiments, the substrate may include multiple layers of a heat-resistant polymer (e.g., polyimide) with an adhesive material interposed between adjacent layers. Whether single-layer or multi-layer, the substrate may have one or more vias extending partially or completely through its thickness, and one or more electrical connectors may extend through these vias to electrically connect the first antenna 116 and / or certain electronic components of the electronic package 108, such as the aforementioned electronic component 118.

[0050] In some embodiments, the first antenna 116 may include multiple coils. For example, the first antenna 116 may include a first coil disposed on a first side of the substrate and a second coil disposed on a second side of the substrate. Such configurations are susceptible to power losses due to substrate losses and parasitic capacitance between the multiple coils and between the individual coil windings. Substrate losses arise from eddy currents in the substrate due to non-zero resistivity of the substrate material. Parasitic capacitance arises when adjacent components are at different potentials, creating electric fields and accumulating charge. All circuit elements have such internal capacitances that can cause their operation to differ from that of an "ideal" circuit element.

[0051] Preferably, in one embodiment, the first antenna 116 includes a two-layer pancake coil configuration, with the upper and lower coils configured in parallel. This allows the coils to generate equal or nearly equal induced potentials when exposed to an electromagnetic field. This equalizes the potentials of each coil during use, which has been shown to significantly reduce the parasitic capacitance of the first antenna 116. In this parallel coil configuration, the upper and lower coils are short-circuited within each turn. This design retains the reduced series resistance advantage of a two-coil configuration while significantly reducing parasitic capacitance and enabling higher maximum output power. Additional details regarding this two-coil configuration are described in U.S. Application No. 16 / 866,523 (filed May 4, 2020), which is incorporated herein by reference in its entirety.

[0052] The first antenna 116 (or a portion thereof) may be flexible, allowing the first antenna 116 to at least partially conform to the patient's anatomy after implantation. In some embodiments, the first antenna 116 may include an exterior coating configured to cover and / or support the antenna. The coating may include a biocompatible material, such as, for example, an epoxy, a urethane, a silicone, or other biocompatible polymer. In some embodiments, the coating may be composed of multiple layers of different materials.

[0053] 2B-2D, the lead body 104 may include a substrate carrying one or more conductive elements 114 configured to supply and / or receive electrical energy. In certain embodiments, the lead body 104 (or a portion thereof) may include a flexible tube having a lumen defined by a sidewall. The lead body 104 may include a polymeric material such as, for example, a thermoplastic elastomer, a thermoplastic polyurethane, a silicone, or other suitable material. The lead body 104 may include the same material as the extension 106 or a different material. The lead body 104 may be the same material as the extension 106 but with a different durometer (hardness). In certain embodiments, the lead body 104 has a lower durometer than the extension 106, which may improve patient comfort.

[0054] As shown in FIGS. 2B-2D , the lead body 104 has a bifurcated shape and includes a first arm 122 and a second arm 124. To enable this configuration, for example, the second connector 112 may be bifurcated or bifurcated. The first arm 122 and the second arm 124 may extend distally and laterally from the distal end 106b of the second connector 112 and / or the extension 106, respectively. The first arm 122 may include a proximal portion 122a, a distal portion 122b, and an intermediate portion 122c extending between the proximal portion 122a and the distal portion 122b. Similarly, the second arm 124 may include a proximal portion 124a, a distal portion 124b, and an intermediate portion 124c extending therebetween. In some embodiments, the first arm 122 may include a cantilevered free end 123, and the second arm 124 may similarly include a free end 125. The first arm 122 and / or the second arm 124 may include one or more fixation elements 130. For example, as shown in Figures 2B-2D, the fixation elements 130 may be located on the distal portions 122b, 124b of the first arm 122 and the second arm 124. The fixation elements 130 may be configured to securely (and optionally removably) engage patient tissue to prevent or limit movement of the lead body 104 relative to the tissue.

[0055] The lead 102 and / or portions thereof (e.g., lead body 104, extension 106, etc.) may be configured to be flexible yet retain a desired shape. This characteristic may be achieved, for example, by an electrical conductor electrically connecting the conductive element 114 carried by the lead body 104 to the electronics package 108, by an internal shape-retaining support structure (e.g., metal, shape-memory alloy, etc.) (not shown), or by a shape-memory treatment of the substrate comprising the lead 102. In either case, the portions of the lead 102 may have physical properties (e.g., ductility, elasticity, etc.) that enable the lead 102 to be deformed to a desired shape or to maintain a preset shape. Additionally or alternatively, the lead 102 and / or portions thereof (e.g., lead body 104, extension 106, etc.) may be flexible enough to at least partially conform to a patient's anatomy or to enhance patient comfort after implantation.

[0056] The conductive elements 114 may be carried on the sidewalls of the lead body 104. For example, the conductive elements 114 may be disposed on the outer surface of the sidewalls and / or within recesses in the sidewalls. In some embodiments, one or more of the conductive elements 114 may be disposed on the outer surface of the sidewalls and extend at least partially around the periphery of the sidewalls. The lumen of the lead body 104 may house one or more electrical conductors from the conductive elements 114, through the lumen of the extension 106, to the electronics package 108. The sidewalls may have one or more openings formed therein through which electrical connectors extend.

[0057] Each conductive element 114 may comprise an electrode, an exposed portion of conductive material, printed conductive material, or other suitable form. In some embodiments, one or more of the conductive elements 114 may comprise a ring electrode. The conductive elements 114 may be crimped, welded, glued, or disposed on the outer surface and / or recess of the lead body 104. Additionally or alternatively, each conductive element 114 may be electrically connected to a corresponding electrical connector by welding, soldering, crimping, or other means. In some embodiments, one or more of the conductive elements 114 may comprise a flexible conductive material disposed on the lead body 104 by printing, thin film deposition, or other suitable technique. Each conductive element 114 may comprise platinum, iridium, silver, gold, nickel, titanium, copper, combinations thereof, or other suitable conductive material. For example, one or more of the conductive elements 114 may be a ring electrode comprised of a platinum-iridium alloy. In certain embodiments, one or more of the conductive elements 114 may include a coating to improve biocompatibility, electrical conductivity, corrosion resistance, surface roughness, durability, or other parameters. As one example, one or more of the conductive elements 114 may include a coating made of titanium and nitride.

[0058] In certain embodiments, the length of one or more of the conductive elements 114 may be about 1 mm. Additionally or alternatively, the length of one or more of the conductive elements 114 may be about 0.25 mm, about 0.5 mm, about 0.75 mm, about 1.25 mm, about 1.5 mm, about 1.75 mm, about 2 mm, about 2.25 mm, about 2.5 mm, about 2.75 mm, about 3 mm, about 3.25 mm, about 3.5 mm, about 3.75 mm, about 4 mm, about 4.25 mm, about 4.5 mm, about 4.75 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 10 mm, or may be greater than 10 mm or less than 0.25 mm in length. In either case, adjacent conductive elements 114 located on either the first arm 122 or the second arm 124 may be spaced apart along the length of the arm by about 0.25 mm, about 0.5 mm, about 0.75 mm, about 1 mm, about 1.25 mm, about 1.5 mm, about 1.75 mm, about 2 mm, about 2.25 mm, about 2.5 mm, about 2.75 mm, about 3 mm, about 3.25 mm, about 3.5 mm, about 3.75 mm, about 4 mm, about 4.25 mm, about 4.5 mm, about 4.75 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 10 mm, more than 10 mm, or less than 0.25 mm. The conductive elements 114 may be the same length or different lengths.

[0059] 2B-2D includes eight conductive elements 114 (four in the first arm 122 and four in the second arm 124), other numbers and configurations are within the scope of the present technology. For example, the first arm 122 may have the same number of conductive elements 114 as the second arm 124, or they may have different numbers of conductive elements 114. The first arm 122 and / or the second arm 124 may each include one, two, three, four, five, six, seven, eight, nine, ten, or more than ten conductive elements 114. In some embodiments, either the first arm 122 or the second arm 124 may not have any conductive elements 114 at all.

[0060] The conductive element 114 may be configured for stimulation and / or sensing. The stimulating conductive element 114 may be configured to deliver energy to an anatomical structure, such as a nerve or a muscle. In one embodiment, the conductive element 114 may be configured to deliver energy to a patient's hypoglossal nerve to increase activity of the patient's tongue protractor muscles. The sensing conductive element 114 may be used to acquire data characterizing the patient's physiological activity (e.g., muscle activity, temperature, etc.). In one embodiment, the sensing conductive element 114 may be configured to detect electrical energy generated by the patient's muscles to acquire EMG data characterizing the activity of the muscles. In another embodiment, the sensing conductive element may be configured to measure impedance between the conductive elements. As an example, in one embodiment, the conductive element 114 may be configured to deliver energy to a patient's hypoglossal nerve to increase activity of the genioglossus and / or geniohyoid muscles and acquire EMG data characterizing the activity of the patient's genioglossus and / or geniohyoid muscles. Additionally, the conductive elements 114 may be configured to deliver energy to and / or measure physiological electrical signals from other patient tissue.

[0061] The function that each conductive element 114 is configured to perform (e.g., delivering energy to, receiving energy from, etc.) may be controlled by a processor included in the electronics 118 of the electronics package 108. In certain embodiments, one or more conductive elements 114 are configured to deliver energy to, or receive energy from, the patient tissue. In various embodiments, one or more conductive elements 114 are configured to both deliver energy to, and receive energy from, the patient tissue. In certain embodiments, the function of the conductive elements 114 may be determined, at least in part, based on the intended placement location of the device 100 within the patient and / or the location of the conductive elements 114 on the lead body 104. One, some, or all of the conductive elements 114 may be positioned relative to patient tissue, such as nerves and / or muscles, where it may be desirable for such conductive elements 114 to both deliver energy to, and receive energy from, the patient tissue. Additionally or alternatively, some of the conductive elements 114 having predetermined placement locations relative to particular patient tissue may be configured such that only the delivery of stimulation energy is desired, while other conductive elements 114 are desired only to receive sensing energy. Advantageously, the configuration of the conductive elements 114 may be configured to be easily changeable by software settings, which may be performed by the electronic components 118 of the electronics package 108.

[0062] Whether configured for stimulation and / or sensing, each conductive element 114 may be configured and used independently of the other conductive elements 114. Thus, when administering a stimulation therapy, all or a portion of the conductive elements 114 determined to be most effective in a particular implementation may be used. For example, one of the conductive elements 114 in the first arm 122 may be used as a cathode and one of the conductive elements 114 in the second arm 124 may be used as an anode (or vice versa); two or more conductive elements 114 in the first arm 122 may be used (one as a cathode and one as an anode) and none of the conductive elements 114 in the second arm 124 may be used (or vice versa); multiple pairs of conductive elements 114 in the first and second arms 122, 124 may be used; or any other suitable combination may be used. The conductive elements 114 used for sensing and / or stimulation may be selected based on the desired data to be collected and / or the desired modulation of neural or muscular activity. For example, a particular pair of conductive elements 114 may be used to generate a tailored electric field to stimulate a particular region of the muscle and / or HGN that causes a favorable change in tongue position and / or pharyngeal expansion. Additionally or alternatively, conductive elements 114 that are positioned to contact muscle tissue when device 100 is implanted may be preferable for use in EMG sensing over conductive elements 114 that are not in contact with muscle tissue.

[0063] The lead body 104 may be shaped and configured to facilitate delivery of electrical energy to a particular treatment site within the patient and / or detection of electrical energy from a sensing site within the patient. The conductive element 114 carried by the first arm 122 may be configured to deliver electrical stimulation energy to one of the patient's hypoglossal nerves (e.g., the right hypoglossal nerve or the left hypoglossal nerve), and the conductive element 114 carried by the second arm 124 may be configured to deliver electrical stimulation energy to the patient's other hypoglossal nerve (i.e., the other of the right hypoglossal nerve or the left hypoglossal nerve).

[0064] Without being bound by theory, it is believed that increased activity of the tongue protrusor muscle during sleep reduces upper airway resistance and improves breathing.Accordingly, the device of the present technology is configured to supply stimulation energy to the motor nerve that controls the tongue protrusor muscle.In some embodiments, the device 100 is configured to supply stimulation energy to the hypoglossal nerve to cause forward protrusion of the tongue.In addition or alternatively, the device 100 may be configured to receive sensing energy generated by activity of one or more muscles (e.g., the genioglossus muscle) of the patient, thereby enabling closed-loop delivery of stimulation energy, evaluation of the patient's breathing, etc.

[0065] The device may be configured for implantation in an anatomical region bounded anteriorly and laterally by a patient's mandible, superiorly by the superior surface of the tongue, and inferiorly by the platysma muscle. Such anatomical regions may include, for example, the submental region and the sublingual region. The sublingual region is bounded superiorly by the mucosa of the floor of the mouth and inferiorly by the mylohyoid muscle, and includes the plane between the genioglossus and geniohyoid muscles. The submental region is bounded superiorly by the mylohyoid muscle and inferiorly by the platysma muscle. Figures 3A-3F show various views of a device 100 implanted within a patient. As shown in Figures 3A-3F, the neuromodulation device 100 is configured such that the electronics package 108 is positioned on or near the inferior surface of the mylohyoid muscle in the submental region, the lead body 104 is positioned in the tissue plane between the geniohyoid and genioglossus muscles in the sublingual region, and the arms 122, 124 are positioned along the left and right hypoglossal nerves. The arms 122, 124 can be positioned such that the conductive element 114 is positioned near the distal dendrites of the hypoglossal nerve that innervate the genioglossus muscle. In particular, the conductive element 114 can be positioned near the portion of the hypoglossal nerve distal dendrites that innervate the horizontal fibers of the genioglossus muscle and can limit and / or avoid stimulation of the portion of the hypoglossal nerve distal dendrites that activate the retractor tongue muscle. When implanted, the extension 106 of the lead 102 can extend anteriorly (toward the mandible) from the electronics package 108, curve superiorly to pass through the geniohyoid muscle, and then curve posteriorly to extend in the tissue plane between the geniohyoid muscle and the genioglossus muscle. In some embodiments, the extension 106 extends across both the left and right geniohyoid muscles.

[0066] Electronics package 108 may be sufficiently flexible to at least partially follow the curvature of the mylohyoid muscle after implantation. Additionally or alternatively, electronics package 108 may have a shape that reflects the curvature of the mylohyoid muscle. In some embodiments, electronics package 108 may include a fixation element (e.g., similar to fixation element 130 or otherwise) configured to engage the mylohyoid muscle (or other surrounding tissue) and prevent or limit movement of electronics package 108 after implantation.

[0067] The lead body 104 is configured to be positioned between the patient's genioglossus and geniohyoid muscles, thereby positioning the conductive element 114 near the hypoglossal nerve. Although not shown in FIGS. 3A-3F , the hypoglossal nerve is located between the genioglossus and the fascia and / or fat located between the genioglossus and geniohyoid muscles. In one embodiment, the lead body 104 is configured to be positioned in or just below the fat between the hypoglossal nerve and the geniohyoid muscle, without being positioned in direct contact with the hypoglossal nerve. In either case, when the device 100 is implanted, the lead body 104 can extend posteriorly from the distal end 106b of the extension 106 and then bifurcate laterally, such that a first arm 122 of the lead body 104 is positioned near one hypoglossal nerve and a second arm 124 is positioned near the opposite hypoglossal nerve. The fixation element 130 may be configured to engage patient tissue (e.g., fat underlying the hypoglossal nerve) to prevent or limit movement of the first arm 122 and the second arm 124 relative to the patient tissue.

[0068] 3C, the arms 122, 124 of the lead body 104 can extend laterally from the extension 106 while curving out of the plane of the extension 106, causing the arms 122, 124 to describe a slightly concave shape. This concave shape advantageously allows the arms 122, 124 to conform to the convex undersurface of the genioglossus muscle while maintaining the arms 122, 124 in proximity to the distal dendrites of the hypoglossal nerve.

[0069] In certain embodiments, conductive elements 114 configured to selectively activate the patient's protrusive muscles are selected. In these and other embodiments, the specific location of the first and second arms 122, 124 relative to specific branches of the hypoglossal nerve need not be determined prior to stimulation. For example, in embodiments in which the lead body 104 includes two or more conductive elements 114, the combination of conductive elements 114 used for treatment may be selected based on the physiological response to trial stimulation. Specifically, multiple combinations of conductive elements 114 may be used to deliver stimulation energy to the hypoglossal nerve, and the physiological response (e.g., electromyography (EMG) data, tongue position, pharyngeal opening, etc.) and / or functional outcome (e.g., Fatigue Severity Scale, Epworth Sleepiness Scale, etc.) for each combination may be evaluated. Based on the results of this evaluation, the conductive elements 114 used to deliver stimulation energy may be those conductive elements 114 associated with a favorable response or outcome.

[0070] IV. External Device Selection Example As discussed above with reference to FIG. 2 , the neuromodulation system 10 of the present technology can include an external system 15 configured to wirelessly couple with an implantable neuromodulation device 100 (also referred to herein as “implantable device 100” or “neuromodulation device 100”). For example, the external system 15 can be configured to provide power to and / or communicate with the implantable device 100. The external system 15 can include an external device 11 including a carrier 9 carrying a second antenna 12, the second antenna 12 being communicatively coupled to a control unit 30 of the external system 15. The control unit 30 provides a radio frequency (RF) current to the second antenna 12, which causes the second antenna 12 to generate an electromagnetic field. When the first antenna 116 of the implantable device 100 is placed within this electromagnetic field, an electromotive force is induced in the first antenna 116, which in turn induces a radio frequency (RF) current in the first antenna 116, which can be used to operate the implantable device 100.

[0071] As described herein, the implantable neuromodulation device 100 of the present technology may be configured to deliver stimulation energy to a treatment site to stimulate the hypoglossal nerve (HGN) and / or genioglossus muscle while the patient is sleeping, thereby improving breathing during sleep. Accordingly, the external system 15 may be configured to provide power to operate the implantable device 100 while the patient is sleeping. In such an embodiment (and other embodiments), the external device 11 may be configured to be positioned between the patient's body and a sleep surface on which the patient lies, leans, or otherwise contacts while sleeping. For example, the external device 11 may be configured to be positioned between the patient's head, neck, upper back, or other anatomical region and the surface of the patient's mattress or other suitable sleep surface. Additionally or alternatively, the external system 15 may be configured to provide power to the implantable device 100 during and / or after implantation of the implantable device 100 (e.g., to assess device positioning), for titration of the implantable device 100, for testing of the implantable device 100, and other clinical settings. In such scenarios, the patient may or may not be asleep. External device 11 may be configured to be placed between the patient's body and a surface on which the patient lies or leans, such as the back side of the patient when lying supine. In some embodiments, external device 11 may be configured to be placed between the patient's body and a vertical surface adjacent to the patient when the patient is sitting or standing.

[0072] The second antenna 12 mounted on the carrier 9 of the external device 11 may be configured to generate an electromagnetic field having a particular magnitude and distribution such that, when a patient is positioned in proximity to the external device 11, the electromagnetic field can provide operating power to the implantable device 100 located at a treatment site, including the submental and sublingual regions of the patient's head. In various embodiments, the operating power ranges from about 5 mW to about 50 mW, although this can vary depending on the power requirements of the implantable device 100, the size of the first antenna 116, the design of the first antenna 116, etc.

[0073] Power is delivered from the external system 15 to the implantable device 100 by placing the first antenna 116 within the electromagnetic field generated by the second antenna 12, which induces an electromotive force in the first antenna 116. Specifically, a change in magnetic flux (i.e., the amount of magnetic field that penetrates the first antenna 116 perpendicularly) induces an electromotive force in the first antenna 116. Thus, it is the electromagnetic field having a component perpendicular to the radial direction of the first antenna 116 that induces the electromotive force in the first antenna 116. Because the first antenna 116 of the implantable device 100 is configured to be placed in the submental region, directly beneath the mylohyoid muscle of the patient, the radial direction of the first antenna 116 may be positioned to generally coincide with the patient's anatomical cross-section. Thus, the second antenna 12 may be configured to generate an electromagnetic field having a component substantially perpendicular to the patient's cross-section, thereby enabling power delivery to the implantable device 100.

[0074] The magnitude of the electromotive force induced by the electromagnetic field in the first antenna 116 is based, at least in part, on the magnitude of the electromagnetic field component perpendicular to the radial direction of the first antenna 116. Therefore, the second antenna 12 may be configured to generate an electromagnetic field having such a directional component of sufficient magnitude at the location of the first antenna 116. Furthermore, because the patient (and thereby the first antenna 116) may move while sleeping or during other uses of the implantable device 100, the second antenna 12 may be configured to generate an electromagnetic field with a desired directional component and having a desired magnitude over a large three-dimensional space. Thus, sufficient power can be supplied to the implantable device 100 even if the patient moves or is misaligned with the external device 11. Furthermore, the second antenna 12 may be configured to generate an electromagnetic field of a magnitude and distribution sufficient to supply a predetermined power to the implantable device 100, while limiting absorption of electromagnetic radiation in patient tissue in compliance with regulatory guidelines.

[0075] 4A, 10, 12, 15, and 18-22 illustrate representative examples of various configurations of external devices 400, 1000, 1200, 1500, and 1800-2200 according to embodiments of the present technology. The characteristics of external devices 400, 1000, 1200, 1500, and external devices 1800-2200 may be generally similar to the characteristics of external device 11 of FIG. 2, the characteristics of carriers 402, 1002, 1202, 1502, and 1802-2202 may be generally similar to the characteristics of carrier 9 of FIG. 2, and the characteristics of antennas 404, 1004, 1204, 1504, and 1804-2204 may be generally similar to the characteristics of second antenna 12 of FIG. 2. 4A, 10, 12, 15, and 18-22, like numbers (e.g., antenna 404 and antenna 1004) are used to identify similar or identical components. The description of external devices 400, 1000, 1200, 1500, and 1800-2200 in FIGS. 4A, 10, 12, 15, and 18-22 is limited to features that differ from each other and from external device 11 in FIG. 2. Furthermore, any features of external devices 400, 1000, 1200, 1500, and 1800-2200 shown in FIGS. 4A, 10, 12, 15, and 18-22 can be combined with each other or with features of external device 11 in FIG. 2, and features of external device 11 in FIG. 2 can be combined with features of any of the external devices shown in FIGS. 4A, 10, 12, 15, and 18-22.

[0076] 4A is a plan view of an external device 400 according to some embodiments of the present technology. The external device 400 may include a carrier 402 carrying an antenna 404. The antenna 404 may include a conductive material (e.g., copper, gold, silver, or other suitable metal) in a particular shape and configured such that the antenna 404 generates an electromagnetic field when an electric current is passed through the conductive material. The conductive material may be etched into, deposited on, co-extruded with, glued to, or mechanically secured to the carrier 402. In some embodiments, the antenna 404 may include a substrate carrying the conductive material, which may be supported by the carrier 402. The conductive material may be a wire, a trace, a conductive tape, a conductive fabric, or the like.

[0077] The antenna 404 may include a single layer of conductive material or multiple layers of conductive material carried by the carrier 402. For example, the antenna 404 may include one, two, three, four, five, or more than five layers of conductive material. In embodiments in which the antenna 404 includes multiple layers of conductive material, each layer may define the same shape and be aligned with the conductive material of an adjacent layer. The multiple layers of conductive material may be electrically connected in parallel with each other. In such a configuration, each layer of conductive material may be shorted at one or more locations, for example, using a conductive connector extending between adjacent layers. In some embodiments, the conductive connector is a via formed by drilling, laser etching, or the like, which may be plated and / or filled with conductive material. Adjacent conductive layers may also be mechanically connected by pins, rivets, or the like. In any case, connecting adjacent conductive layers in parallel reduces the series resistance of the antenna 404 compared to a single-layer design, while providing high power output with low parasitic capacitance.

[0078] The carrier 402 and / or the substrate carrying the conductive material may include one or more flexible materials, such as cloth, nonwoven fabric, foam, tape, polyurethane, thermoplastic polyester, thermoplastic elastomer, polyimide, rubber, etc. The carrier 402 and / or the substrate may include a substrate for a printed circuit board (PCB). For example, the carrier 402 and / or the substrate may include FR4, CEM1, CEM3, FR2, PET, elastomer, or other suitable PCB substrate. The carrier 402 and / or the substrate may include a dielectric material with good heat resistance. In some embodiments, the carrier 402 and / or the substrate may include a single layer of material. Additionally or alternatively, the carrier 402 and / or the substrate may be composed of multiple layers of one material, multiple layers of different materials, etc. If the carrier 402 includes at least two layers, the antenna 404 may be disposed between the two layers. Additionally or alternatively, the antenna 404 may be disposed on the outer surface of the carrier 402.

[0079] In various embodiments, the carrier 402 may include shielding material configured to block electromagnetic radiation outward from the antenna 404. The shielding material may be conductive and / or ferromagnetic. The shielding material may be configured to be placed between the antenna 404 and a surface on which a patient rests during patient use and / or implantable device testing (e.g., a patient's mattress or other sleeping surface during use, such as a surgical table or examination table during implantation and / or titration). Such shielding material may be configured to interpose the antenna 404 and the springs of a mattress. The electromagnetic field generated by the antenna 404 may induce eddy currents in the metal springs of a spring mattress. The buildup of eddy currents in the springs can cause heating of the mattress and temporal fluctuations and high variability in the impedance of the antenna 404. The shielding material may prevent or limit the electromagnetic field generated by the antenna 404 from reaching the mattress springs, thereby preventing or limiting the buildup of these eddy currents. Thus, the shielding material may prevent or limit changes in the impedance of the antenna 404 due to surfaces and the surrounding environment. It should be noted that the shielding material may cause a known shift in the impedance of the antenna 404, which may then be compensated for when calculating the impedance of one or more components of the control unit and / or implantable device antenna.

[0080] As shown in FIG. 4A , the carrier 402 has a width dimension W and a length dimension L that is generally perpendicular to the width dimension W. The width dimension W and the length dimension L may define a two-dimensional plane in which the antenna 404 resides. In various embodiments, the carrier 402 may include a first region 402a and a second region 402b that are located opposite each other along the length dimension L. For example, as shown in FIG. 4A , the first region 402a is located on one side of a first centerline M1, and the second region 402b is located on the other side of the centerline M1. The centerline M1 may be defined as a location where the direction of current flow through the antenna 404 reverses. In various embodiments, the first centerline M1 of the carrier 402 may be configured to approximately bisect the carrier 402 along the length dimension L. In any case, the first region 402a and the second region 402b may be configured not to overlap each other along the length dimension L and / or the width dimension W.

[0081] In one embodiment, the external device 400 is configured to be positioned between a surface beneath a patient such that the length dimension L of the carrier 402 is approximately aligned with the patient's vertical (e.g., major axis) and the width dimension W is approximately aligned with the patient's horizontal (e.g., coronal) plane. In either case, the first region 402a may be configured to be positioned adjacent to a first anatomical region of the patient, and the second region 402b may be configured to be positioned adjacent to a second anatomical region of the patient. For example, the first region 402a may be configured to be positioned adjacent to the patient's head, and the second region 402b may be configured to be positioned adjacent to the patient's upper back.

[0082] In one embodiment, the carrier 402 includes a first major surface and a second major surface that are opposed to each other along a thickness direction. The thickness direction of the carrier 402 is generally perpendicular to the length dimension L and the width dimension W. Each of the first major surface and the second major surface may have a perimeter that defines the respective surface. The perimeter of the first major surface may be generally the same as or different from the perimeter of the second major surface. In other words, the first major surface may have the same shape as the second major surface or a different shape. In various embodiments, the first major surface and / or the second major surface may have a quadrilateral shape (e.g., rectangular, square, trapezoid, etc.). The first major surface and / or the second major surface may also have any other shape, such as a circle, an ellipse, a triangle, a hexagon, another polygon, or an irregular shape. The thickness direction dimension of the carrier 402 may be generally constant or may vary along the length dimension L and / or the width dimension W. The thickness of carrier 402 may be determined at least in part based on the desired flexibility. For example, if carrier 402 is configured to be placed under a patient while the patient sleeps, a thinner carrier 402 may provide more flexibility, allowing the patient to sleep more comfortably.

[0083] The antenna 404 may include a first portion 404a and a second portion 404b opposed to each other along the longitudinal dimension L. In various embodiments, the first portion 404a of the antenna 404 is disposed in a first region 402a of the carrier 402, and the second portion 404b is disposed in a second region 402b. This allows the first portion 404a of the antenna 404 to be positioned adjacent to a first anatomical region of the patient, and the second portion 404b to be positioned adjacent to a second anatomical region of the patient. The first portion 404a and the second portion 404b may be positioned on substantially the same plane (see, for example, FIG. 4A ). Alternatively, the first portion 404a and the second portion 404b may be positioned on different planes along the thickness direction of the carrier 402. These different planes may or may not be substantially parallel.

[0084] The length of antenna 404 along its longitudinal dimension L may be about 20 cm to about 100 cm, about 30 cm to about 90 cm, about 40 cm to about 80 cm, about 50 cm to about 70 cm, or about 20 cm, about 30 cm, about 40 cm, about 50 cm, about 60 cm, about 70 cm, about 80 cm, about 90 cm, about 100 cm, etc., or any other suitable length. Similarly, the width of antenna 404 along its width dimension W may be about 20 cm to about 100 cm, about 30 cm to about 90 cm, about 40 cm to about 80 cm, about 50 cm to about 70 cm, or about 20 cm, about 30 cm, about 40 cm, about 50 cm, about 60 cm, about 70 cm, about 80 cm, about 90 cm, about 100 cm, etc.

[0085] The antenna 404 can include one or more lengths of conductive material that form an inductor, e.g., a current passing through the conductive material causes the antenna 404 to generate a magnetic field. In various embodiments, the first portion 404a of the antenna 404 includes a first length 406 of conductive material, and the second portion 404b includes a second length 408 of conductive material. The first length 406 can be longer (e.g., see FIG. 4A ), the same as, or shorter than the second length 408. The relative lengths of conductive material in the first and second portions 404a and 404b of the antenna 404 can affect the spatial distribution of the magnetic field generated by the antenna 404.

[0086] 4A , a first length 406 of conductive material can extend from a first end 410 to a second end 412, or a second length 408 of conductive material can extend from a first end 414 to a second end 416. In some embodiments, the first length 406 can form a first loop 418, or the second length 408 can form a second loop 420. The first end 410 of the first length 406 can be co-located with the second end 412 of the length, or the first end 414 of the second length 408 can be co-located with the second end 416 of the length. In some embodiments, the first and second ends 410, 412 of the first length 406 and the first and second ends 414, 416 of the second length 408 are co-located along the width dimension W and / or the length dimension L of the antenna 404. In these and other embodiments, the first end 410 of the first length 406 and the first end 414 of the second length 408 may be located at a first location in the thickness direction of the carrier 402, while the second end 412 of the first length 406 and the second end 416 of the second length 408 may be located at a second location in the thickness direction that is different from the first location. The first length 406 and the second length 408 made of conductive material may be electrically connected in series with each other (e.g., by connecting the first ends 410, 414 together and the second ends 412, 416 together).

[0087] A first length 406 of conductive material may include multiple regions extending substantially along a width dimension W and / or a length dimension L. As shown in FIG. 4A , one or both ends of each region may be curved (e.g., transitioning from a region extending along the width dimension W to a region extending along the length dimension L, or vice versa). The first length 406 includes a first region 406a extending in a first lengthwise direction along the length dimension L from a first end located at a first end 410 to a second end, a second region 406b extending in a first widthwise direction along the width dimension W from a first end located at a second end of the first region 406a to a second end, a third region 406c extending in a first lengthwise direction from a first end located at a second end of the second region 406b to a second end, and a third region 406c extending in a first widthwise direction from a first end located at a second end of the third region 406c to a second end. The fifth region 406e may include a fourth region 406d extending in a second width direction, which is the opposite direction to the first length direction, from a first end located at a second end of the fourth region 406d to a second end, in a second length direction, which is the opposite direction to the first length direction, a sixth region 406f extending in the first width direction from the first end located at the second end of the fifth region 406e to the second end, and a seventh region 406g extending in the first length direction from the first end located at the second end of the sixth region 406f to the second end.

[0088] The fourth through seventh regions 406d through 406g may collectively form a first sub-loop 422a. The first sub-loop 422a may encompass an area smaller than that encompassed by the first loop 418. For example, as shown in FIG. 4A, the second region 406b may occupy a greater distance along the width dimension W than the fourth region 406d and / or the sixth region 406f. The fifth region 406e may also occupy a smaller distance along the length dimension L than the third region 406c and / or the seventh region 406g. The sixth region 406f may be spaced apart along the length dimension L from the first end 410 of the first length of conductive material 406 and / or the second region 406b. This allows for the generation of a magnetic field of at least the desired strength over a range of distances along the thickness of the carrier 402 that corresponds to the expected location of the neuromodulation device. This is because the distribution of the magnetic field generated by the current flowing through the first sub-loop 422a depends at least in part on the distance in the longitudinal dimension L between the sixth region 406f and the first intermediate line M1.

[0089] As shown in FIG. 4A , the first length 406 of conductive material may include an eighth region 406h beginning at the second end of the seventh region 406g and extending along the second width direction. The eighth region 406h may extend a greater distance along the width direction W than the second region 406b, the fourth region 406d, and / or the sixth region 406f. For example, the eighth region 406h may extend across a second centerline M2 of the carrier 402. The second centerline M2 may be located at a position that bisects the carrier 402 along the width direction W. Furthermore, the second centerline M2 may be defined by the position of a feed 426 (schematically indicated by an arrow in FIG. 4A ) through which the antenna 404 is electrically connected to the control unit. In some embodiments, the shape formed by the first length 406 of conductive material may be symmetrical about the second centerline M2.

[0090] As shown in FIG. 4A, the first length 406 of conductive material may include a ninth region 406i extending in a second length direction from a first end located at the second end of the eighth region 406h to a second end, a tenth region 406j extending in a first width direction from a first end located at the second end of the ninth region 406i to a second end, an eleventh region 406k extending along the first length direction from a first end located at the second end of the tenth region 406j to a second end, and a twelfth region 406l extending along the second width direction from a first end located at the second end of the eleventh region 406k to a second end. The ninth through twelfth regions 406i through 406l may collectively form a second subloop 422b. The second subloop 422b may enclose an area smaller than the area enclosed by the first loop 418. In one embodiment, the second sub-loop 422b formed by the ninth to twelfth regions 406i to 406l may surround an area of ​​the same area as the first sub-loop 422a formed by the fourth to seventh regions 406d to 406g. In one embodiment, the first sub-loop 422a may be positioned apart from the second sub-loop 422b along the width direction W. For example, the fifth region 406e and the eleventh region 406k may be spaced apart from each other along the width direction W.

[0091] The first length 406 made of conductive material may include a thirteenth region 406m extending in a second length direction from a first end located at the second end of the twelfth region 406l to a second end, a fourteenth region 406n extending in a first width direction from a first end located at the second end of the thirteenth region 406m to a second end, and a fifteenth region 406o extending in a first length direction from a first end located at the second end of the fourteenth region 406n to a second end 412 of the first length 406.

[0092] In various embodiments, the antenna 404 may be asymmetric with respect to the first midline M1 of the carrier 402. For example, the second length 408 of conductive material may have a different overall length than the first length 406, the second portion 404b of the antenna 404 may have a different conductive material density than the first portion 404a, the second length 408 may form a different number of loops than the first length 406, or the second length 408 may have a different shape than the first length 406. This asymmetry may allow the antenna 404 to be configured to generate a desired magnetic field large enough to power an implantable device in proximity to the external device 400 while avoiding excessive electromagnetic radiation to the patient (as discussed below).

[0093] As shown in FIG. 4A , the second length 408 of conductive material includes a first region 408a extending in a second length direction from a first end located at a first end 414 of the second length 408 to a second end, a second region 408b extending in a second width direction from a first end located at the second end of the first region 408a to a second end, a third region 408c extending in the second length direction from a first end located at the second end of the second region 408b to a second end, and a third region 408c extending in the second length direction from a first end located at the second end of the third region 408c to a second end. The second length 408 may include a fourth region 408d extending in a first width direction from a first end to a second end, a fifth region 408e extending in a first length direction from a first end located at the second end of the fourth region 408d to a second end, a sixth region 408f extending in a second width direction from a first end located at the second end of the fifth region 408e to a second end, and a seventh region 408g extending in the first length direction from a first end located at the second end of the sixth region 408f to a second end 416 of the second length 408. The first to seventh regions 408a to 408g may collectively form a second loop 420.

[0094] The first length 406 and the second length 408 of conductive material may be shaped to generate a desired magnetic field when a radio frequency (RF) current is passed through the antenna 404. For example, the first length 406 and the second length 408 may be configured to cause the antenna 404 to have a large quadrupole moment and a small dipole moment, thereby enabling the antenna 404 to generate an electromagnetic field with little electromagnetic radiation in the distance. The dipole moment and quadrupole moment of the antenna 404 may be based at least in part on the area enclosed by the first loop 418, the second loop 420, the first sub-loop 422a, and / or the second sub-loop 422b. For example, if the total area enclosed by the first loop 418, the first sub-loop 422a, and the second sub-loop 422b is substantially equal to the area enclosed by the second loop 420, the antenna 404 may have a large quadrupole moment and a small dipole moment. Additionally or alternatively, the dipole and quadrupole moments of the antenna 404 may be based at least in part on the distance between the first midline M1 and the first loop 418, the second loop 420, the first sub-loop 422a, and / or the second sub-loop 422b.

[0095] In some embodiments, the second region 408b and the sixth region 408f of the second length 408 of conductive material may be spaced apart from the fourth region 408d along the length direction L. For example, the second region 408b and the sixth region 408f may be spaced apart from the fourth region 408d along the length direction L by about 19 cm. The third region 408c of the second length 408 of conductive material may also be spaced apart from the fifth region 408e along the width direction W. For example, the distance between the third region 408c and the fifth region 408e along the width direction W may be about 70 cm. This allows the second loop 420 to be spaced apart from the fourth region 408d along the length direction L by about 19 cm. 2 can enclose an area of

[0096] The second region 406b and the fourteenth region 406n of conductive material of the first length 406 may be spaced apart along the length direction L from the sixth region 408f and the second region 408b of the second length 408 of conductive material, respectively. For example, the second region 406b and the fourteenth region 406n may be spaced apart along the length direction L from the sixth region 408f and the second region 408b, respectively. In some embodiments, these distances may range from about 1 cm to about 15 cm, or from about 5 cm to about 10 cm. Increasing the distance between the second region 406b and the sixth region 408f or the fourteenth region 406n and the second region 408b may provide a horizontal magnetic field of sufficient strength to power the implantable device even at distances from the external device 400 perpendicular to the plane of the antenna 404.

[0097] In some embodiments, the second region 406b of the first length 406 made of conductive material may be spaced apart along the length direction L from the sixth region 406f of the first length 406, or the fourteenth region 406n may be spaced apart along the length direction L from the tenth region 406j. For example, the second region 406b and / or the fourteenth region 406n may be spaced apart along the length direction L from the sixth region 406f and the tenth region 406j, respectively. In some embodiments, these distances may range from about 1 cm to about 15 cm, from about 5 cm to about 10 cm, etc. Increasing these distances may ensure that the horizontal component of the magnetic field is strong enough to power the implantable device, even when the antenna 404 is positioned at an increased distance from the external device 400 in a direction perpendicular to the plane of the antenna 404.

[0098] The fourth region 406d and / or the twelfth region 406l of the first length 406 made of conductive material may be spaced apart from the eighth region 406h along the length direction L. For example, the distance between them may be about 10 cm. In some embodiments, the distance between them may be in a range from about 1 cm to about 15 cm, from about 5 cm to about 10 cm, etc.

[0099] 4A, the third region 406c of the first length 406 of conductive material may be spaced apart along the width direction W from the seventh region 406g, and the ninth region 406i may be spaced apart along the width direction W from the thirteenth region 406m. For example, these distances may be about 2 cm. In some embodiments, these distances may range from about 0.1 cm to about 5 cm, from about 0.5 cm to about 1 cm, etc.

[0100] In some embodiments (e.g., as shown in FIG. 4A ), the first region 406a of the first length 406 of conductive material may be spaced apart along the width direction W from the fifteenth region 406o, or the first region 408a of the second length 408 of conductive material may be spaced apart along the width direction W from the seventh region 408g. For example, these distances may be about 2 cm. In some embodiments, these distances may range from about 0.1 cm to about 5 cm, from about 0.5 cm to about 1 cm, etc.

[0101] As previously described, the first end 410 of the first length 406 of conductive material may be connected to the first end 414 of the second length 408 of conductive material, and the second end 412 of the first length 406 of conductive material may be connected to the second end 416 of the second length 408 of conductive material. In some embodiments, the first ends 410, 414 may be positioned differently than the second ends 412, 416 across the thickness of the carrier 402, allowing the first ends 410, 414 to be aligned in the same position as the second ends 412, 416 along the width direction W and length direction L (e.g., the first ends 410, 414 may be positioned above the second ends 412, 416, or the second ends 412, 416 may be positioned above the first ends 410, 414). In some embodiments, the location where the first ends 410, 414 and the second ends 412, 416 meet may be located in a portion of the external device 400 referred to herein as a “transition region.” The transition region may include at least a portion of the first region 406a of the first length 406 of conductive material, at least a portion of the fifteenth region 406o, at least a portion of the first region 408a of the second length 408 of conductive material, and at least a portion of the seventh region 408g. Within the transition region, radio frequency (RF) current may flow in a first direction (e.g., clockwise or counterclockwise) between the first region 406a of the first length 406 of conductive material and the first region 408a of the second length 408 of conductive material, and between the fifteenth region 406o and the seventh region 408g, radio frequency (RF) current may flow in a second direction, opposite the first direction, between the fifteenth region 406o and the seventh region 408g. Generally, a high density of conductive material in the transition region increases the resultant magnetic field vector and magnetic flux density in this region, which can undesirably increase SAR. However, by placing antenna portions with opposite radio frequency (RF) currents flowing in opposite directions closer together, the magnetic field strength in the transition region can be reduced.For example, a portion of the second antenna having a radio frequency (RF) current (in a first direction) passing between the first region 406a of the first length 406 made of conductive material and the first region 408a of the second length 408 may be positioned proximate to a portion of the second antenna having a radio frequency (RF) current (in an opposite direction) passing between the fifteenth region 406o of the first length 406 made of conductive material and the seventh region 408g of the second length 408. The closer these antenna portions with opposite RF currents are to each other, the more their respective magnetic field strength contributions cancel each other out, thereby reducing the effect of the transition region on the overall SAR.

[0102] The close proximity may be achieved, for example, by positioning the two portions of the second antenna (portions through which radio frequency (RF) currents flow in opposite directions) close to one another along one or more of the thickness, width, and / or length directions. In some embodiments, some or all of the portions of the second antenna within the transition region may overlap one another along the thickness direction of the carrier (e.g., within 2 cm, 1 cm, 0.5 cm, 0.25 cm, etc. along the thickness direction).

[0103] In some embodiments, at least a portion of the first region 406a of the first length 406 of conductive material, the fifteenth region 406o of the first length 406 of conductive material, the first region 408a of the second length 408 of conductive material, or the seventh region 408g of the second length 408 of conductive material may extend obliquely from the corresponding end along the width direction W and / or length direction L of the carrier 402. For example, as shown in FIG. 4B , the first region 406a of the first length 406 of conductive material may have a first portion 406a1 extending obliquely from the first end 410 along the length direction L and width direction W, and a second portion 406a2 extending substantially linearly along the length direction L from the first portion 406a1. And / or, the fifteenth region 406o of the first length 406 made of conductive material may have a first portion 406o1 extending obliquely from the second end 412 along the length direction L and width direction W, and a second portion 406o2 extending substantially linearly from the first portion 406o1 along the length direction L. Alternatively, the first region 408a of the second length 408 made of conductive material may have a first portion 408a1 extending obliquely from the first end 414 along the length direction L and the width direction W and a second portion 408a2 extending substantially linearly from the first portion 408a1 along the length direction L, or the seventh region 408g of the second length 408 made of conductive material may have a first portion 408g1 extending obliquely from the second end 416 along the length direction L and the width direction W and a second portion 408g2 extending substantially linearly from the first portion 408g1 along the length direction L. As shown in FIG. 4B , an angle β may be defined between the first portion 406a1 of the first region 406a of the first length 406 made of conductive material and the first portion 406o1 of the fifteenth region 406o.

[0104] As discussed above, the magnetic field generated by the antenna 404 in the transition region may be large, at least in part, due to the high density of conductive material in this region. It may be desirable to reduce the magnitude of the magnetic field in this region, for example, to prevent excessive increases in SAR in anatomical regions of a patient located proximate to the region of the antenna 404. Referring to Figures 4B and 4C, in various embodiments, decreasing the angle β in the transition region allows for closer placement of portions of the second antenna through which radio frequency (RF) current flows in the opposite direction. When the angle β is large (e.g., Figure 4B), the magnetic field generated by the radio frequency (RF) current flowing in a first direction between the first regions 406a and 408a tends to add with the magnetic field generated by the radio frequency (RF) current flowing in a second direction (opposite to the first direction) between the fifteenth region 406o and the seventh region 408g. However, as angle β decreases (e.g., as shown in FIG. 4C ) and first regions 406 a, 408 a and fifteenth and seventh regions 406 o, 408 g become more parallel to the longitudinal direction L, the magnetic field generated by currents flowing in the first direction tends to cancel out the magnetic field generated by currents flowing in the second direction, thereby reducing the magnitude of the magnetic field in the transition region of antenna 404. In some embodiments, for example, angle β may be less than about 45 degrees, less than about 30 degrees, less than about 15 degrees, less than about 10 degrees, less than about 5 degrees, or less than about 2 degrees. Furthermore, angle β may range from about 2 degrees to about 45 degrees, from about 2 degrees to about 30 degrees, or from about 5 degrees to about 15 degrees. In some embodiments, angle β may be approximately 0 degrees. For example, some or all of the portions of the antenna 404 in the transition region through which radio frequency (RF) current flows in opposite directions may be parallel to one another (e.g., adjacent in the width-length plane of the external device or overlapping one another along the thickness of the external device), and in addition to being positioned at any of these angles β, the portions of the antenna 404 in the transition region through which radio frequency (RF) current flows in opposite directions may be positioned closely together along the thickness of the carrier (e.g., within 2 cm, 1 cm, 0.5 cm, 0.25 cm, etc. along the thickness).

[0105] According to various embodiments, the antenna 404 may be configured to be electrically connected to a control unit at a feed 426. The control unit may provide current to the antenna 404 via the feed 426. The feed 426 may include two terminals, such that current is provided from the control unit to the antenna 404 via a first terminal of the feed 426 and returned from the antenna 404 to the control unit via a second terminal of the feed 426. As shown in FIG. 4A , in some embodiments, the feed 426 may be located in an eighth region 406h of the first length 406 of conductive material. Thus, the eighth region 406h may be discontinuous at the location of the feed 426. The feed 426 may be located in any suitable region of the first length 406 and / or the second length 408 of conductive material. Although only one feed 426 is depicted in FIG. 4A , the antenna 404 may include multiple feeds 426 (e.g., two, three, four, etc.). In some examples, two or more of the first loop 418, the second loop 420, the first sub-loop 422a, or the second sub-loop 422b may be configured to receive current from different feeds 426. While providing current to the antenna 404 from multiple feeds 426 can reduce the power required by each feed 426 and lower the voltage across the antenna 404, it can also increase the complexity of the circuitry in the control unit.

[0106] The antenna 404 may include one or more capacitors 428 electrically connected to the first length 406, the second length 408, and / or the feed 426. Some or all of the capacitors 428 may be connected in series or parallel with the conductive material. These capacitors 428 may be configured to partially or fully resonate the antenna 404, thereby facilitating power transfer to the antenna 404 and / or the implantable device. The capacitors 428 may also reduce or limit the peak value of the electric field along the antenna 404. Each capacitor 428 may have a capacitance value based on the inductance of the conductive material, the impedance of the conductive material, and / or the resonant frequency of the antenna 404. For example, the one or more capacitors 428 may have a capacitance of about 100 pF, about 200 pF, about 300 pF, about 400 pF, about 500 pF, about 600 pF, about 700 pF, about 800 pF, about 900 pF, about 1000 pF, about 1100 pF, about 1200 pF, about 1300 pF, about 1400 pF, about 1500 pF, about 1600 pF, about 1700 pF, about 1800 pF , about 1900 pF, about 2000 pF, about 500 pF to about 2000 pF, about 600 pF to about 1900 pF, about 700 pF to about 1800 pF, about 800 pF to about 1700 pF, about 900 pF to about 1600 pF, about 1000 pF to about 1500 pF, about 1100 pF to about 1400 pF, or about 1200 pF to about 1300 pF. In some embodiments, the capacitance value of one or more of the capacitors 428 may be variable.

[0107] The capacitance value of each capacitor 428 may be based, at least in part, on the expected impedance presented by the antenna 404 and / or the impedance of components of the control unit configured to be electrically connected to the antenna 404. This facilitates power transfer from the power source through the control unit to the antenna 404. According to the maximum power transfer theorem, to deliver maximum power from a power source (e.g., the control unit) to a load (e.g., the antenna 404), the impedance of the power source must match the impedance of the load. The impedance of the antenna 404 is determined based on the resistance, capacitance, inductance, and reactance of the antenna 404. Thus, in one embodiment, the antenna capacitors 428 may have a capacitance value based on the expected impedance of the antenna 404, which may correspond to the impedance of one or more components of the control unit.

[0108] However, even if the antenna's impedance is initially matched to the impedance of one or more components of the control unit, the antenna's impedance may vary due to environmental changes (e.g., temperature, the surface on which the external device is placed, weight on the external device, etc.). For example, the antenna's impedance may change when a patient lies on a mat, when the patient moves relative to the mat, when a foreign object is placed on the mat, etc. The capacitor 428 in the antenna 404 helps to accommodate such impedance changes. In general, a matching circuit (such as described herein) can compensate for changes in the real component of the antenna's 404 impedance more effectively than changes in the imaginary component. Thus, in certain embodiments, the capacitor 428 helps to stabilize (i.e., prevent or suppress) variations in the imaginary component of the antenna's 404 impedance during operation (e.g., in response to patient movement or the presence of a foreign object), and the matching circuit can optimize the presented impedance of the antenna 404 by accommodating variations in the real component of the impedance.

[0109] As shown in FIG. 4A , the antenna 404 may include multiple capacitors 428. For example, the antenna 404 may include 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more capacitors 428. In some embodiments, the antenna 404 may include a single capacitor 428. Some or all of the capacitors 428 may be spaced approximately equally along the conductive material of the antenna 404. In other embodiments, some or all of the capacitors 428 may be spaced unevenly along the first length 406 and / or the second length 408. As described below in connection with FIG. 6 , the capacitors 428 may be spaced along the conductive material such that the peak voltage of the antenna 404 does not exceed a predetermined threshold. In an embodiment, the peak voltage of the antenna 404 does not exceed about 400V, about 500V, about 600V, or about 700V.

[0110] In some embodiments, the antenna 404 may include one or more resistor-capacitor (RC) networks (not shown in FIG. 4A ) electrically connected to the conductive material of the antenna 404. Parasitic resonances of the antenna 404 may occur due to the coiled geometry of the antenna 404, particularly at high frequencies. For example, the capacitive connection between the first and second ends 410, 412 of the first length 406 and the first and second ends 414, 416 of the second length 408 may interact with the inductive second length 408, forming the second loop 420, resulting in parasitic resonances. Placing an RC network between the first region 408a and the seventh region 408g of the second length 408 can reduce or eliminate the quality factor (Q) of such parasitic resonances. Reducing or eliminating parasitic resonances may be useful, for example, for complying with radio wave emission regulations. The RC networks may be placed at specific locations along the first length 406 and / or the second length 408 based on the geometry and / or the environment of use of the antenna 404.

[0111] FIG. 5 shows a sagittal cross-section of a simulated magnetic field 500 generated by the antenna 404 of the external device 400 of FIG. 4A. For reference, FIG. 5 shows a patient positioned on top of the external device 400. As shown in FIG. 5, in some cases, the external device 400 is configured to be placed on the patient's back. For example, the patient may lie supine (FIG. 5) with the external device 400 positioned underneath the patient. In either case, the antenna 502 of the implantable device positioned in the submental and sublingual treatment areas of the patient's head may be oriented with a radiation direction that is approximately perpendicular to the width and length of the antenna 404 of the external device 400.

[0112] Radio frequency (RF) current supplied to the antenna 404 at the feed 426 may flow in a first direction through the first length 406 and in a second direction opposite the first direction through the second length 408. The radio frequency (RF) current flowing through the first length 406 generates a first magnetic field, and the current flowing through the second length 408 generates a second magnetic field opposite the first magnetic field. The first magnetic field and the second magnetic field may interfere with each other, for example, constructively (additively) or destructively (destructively) to form a magnetic field 500 generated by the antenna 404. The magnetic field 500 may have a horizontal component that is generally parallel to a plane containing the first length 406 and the second length 408 of the antenna 404 (e.g., a plane defined by the width and length directions of the antenna 404, a plane generally parallel to the broadside of the carrier 402, etc.). When the external device 400 is positioned on the patient's back and the implantable device antenna 502 is tilted relative to the plane, the horizontal component of the magnetic field 500 may be substantially perpendicular to the implantable device antenna 502 and may generate an electromagnetic induction force on the antenna 502. In some embodiments, the magnetic field may be oriented substantially horizontally along the length L and width W of the carrier 402 at locations substantially aligned with the first and second ends 410, 412, 414, 416 of the first and second lengths 406, 408 (e.g., at the transition region between the first loop 418 and the second loop 420).

[0113] FIG. 5 uses arrows to indicate the magnitude, density, and direction of the magnetic field 500 at each point in the sagittal cross section. The thickness and dashed pattern of the arrows generally indicate the magnitude of the magnetic field 500 at that location (e.g., the thickest solid arrow indicates the location where the magnitude of the magnetic field 500 is greatest, the thinnest dashed arrow indicates the location where the magnitude of the magnetic field 500 is least, etc.). As shown in FIG. 5, the density (i.e., the amount of magnetic flux) of the magnetic field 500 may be greatest near the antenna 404 and decrease with increasing distance from the antenna 404. In particular, the density of the magnetic field 500 may decrease with increasing distance from the antenna 404 along a height direction perpendicular to the length direction L and width direction W of the antenna 404. The density of the magnetic field 500 may also decrease with increasing distance from the antenna 404 along the width direction W of the antenna 404. In some embodiments, the magnetic field 500 may be denser in the first region 402a of the carrier 402 and / or the first portion 404a of the antenna 404 than in the second region 402b of the carrier 402 and / or the second portion 404b of the antenna 404. As described in more detail below, such a distribution of the magnetic field 500 may enable a desired amount of power to be delivered to the antenna 502 of the implantable device while preventing or reducing absorption of electromagnetic radiation in the patient's tissue. The preferential distribution of the magnetic field 500 toward the first portion 404a of the antenna 404 may be due, at least in part, to the antenna 404 being asymmetric with respect to the first centerline M1.

[0114] FIG. 6 is a coronal cross-sectional view showing an intensity map of the electric field generated by antenna 404. In particular, FIG. 6 shows the electric field in the plane in which antenna 404 resides. When current flows through the conductive material of antenna 404, the voltage within antenna 404 increases proportionally to the distance from feed 426. Because the electric field is a function of the voltage within antenna 404, the electric field also increases with distance from feed 426. However, the voltage across each capacitor 428 is approximately equal in magnitude and opposite in polarity to the voltage along the length of conductive material immediately preceding it. Thus, the voltage across capacitor 428 cancels the voltage along the conductive material, and the voltage across the discrete lengths of conductive material between capacitors 428 is significantly less than the voltage across the conductive material throughout antenna 404. Limiting the voltage across antenna 404 has important benefits: ensuring patient safety, increasing the system's robustness to varying loads on antenna 404, and reducing the manufacturing costs of antenna 404.

[0115] As previously described, the antenna 404 of the external device 400 is configured to generate an electromagnetic field having a predetermined magnitude and distribution so that, when a patient is positioned near the external device 400, it can power an implanted device located at a treatment site, including the submandibular and sublingual regions. However, the magnitude and distribution of this electromagnetic field must be such that energy absorption in the patient's tissue is limited in accordance with regulatory guidelines. For example, the U.S. Federal Communications Commission (FCC) requires that, in a general environment where electromagnetic exposure is not controlled, the patient's whole-body specific absorption rate (SAR) must not exceed 0.08 W / kg, and the peak local average SAR (psSAR) in any 1 g of tissue must not exceed 1.6 W / kg (47 CFR §1.1310). Therefore, the antenna 404 can be configured to generate a magnetic field such that energy absorption in the patient's tissue does not exceed these regulatory thresholds.

[0116] When the implant is driven by the magnetic field generated by the antenna 404, the SAR parameter in the patient's tissue must not exceed a predetermined threshold. The SAR parameter may include a psSAR averaged over any 1 g of tissue in the patient's tissue (excluding the patient's extremities), a psSAR averaged over any 10 g of tissue in the patient's extremities, and / or an average SAR averaged over the patient's entire body. The predetermined threshold may be based at least in part on whether exposure to the magnetic field generated by the antenna 404 is controlled. For example, if exposure is uncontrolled, the SAR parameter may include a psSAR averaged over any 1 g of tissue excluding the patient's extremities within 30 minutes, and the threshold may be 1.6 W / kg. Meanwhile, if exposure is controlled, the SAR parameter may include a psSAR averaged over 1 g of tissue within 6 minutes, and the threshold may be 8 W / kg. If exposure is uncontrolled, the SAR parameter may include a psSAR averaged over any 10 g of tissue in the patient's extremities within 30 minutes, and the threshold may be 4 W / kg. In contrast, a controlled exposure may include a psSAR averaged over the same 10 g of tissue within 6 minutes, and the threshold may be 20 W / kg. In an embodiment, if the exposure is uncontrolled, the SAR parameter may include an average SAR averaged over the patient's whole body within 30 minutes, and the threshold may be 0.08 W / kg. Alternatively, for a controlled exposure, the SAR parameter may include an average SAR averaged over the patient's whole body within 6 minutes, and the predetermined threshold may be 0.4 W / kg.

[0117] 7A and 7B are sagittal and coronal views illustrating simulated SAR in a patient exposed to the electromagnetic field generated by antenna 404. As shown in FIGS. 7A and 7B, a patient placed in the electromagnetic field generated by antenna 404 experiences an SAR that does not exceed the regulatory threshold of 1.6 W / kg. However, as discussed above in connection with FIG. 5, the magnetic field generated by antenna 404 has a horizontal component large enough to provide operating power for the implantable device antenna 502. The asymmetric shape of antenna 404 achieves this balance between performance and safety. By connecting a first length 406 of conductive material in series with a second length 408 of conductive material with alternating current flow directions, antenna 404 can generate an electromagnetic field with the desired horizontal component. Furthermore, the individual magnetic fields generated by the first sub-loop 422a and the second sub-loop 422b constructively interfere with the magnetic field generated by the first loop 418, increasing the strength of the magnetic field and expanding the volume of space in the vicinity of the external device 400 in which there exists a magnetic field having a horizontal component large enough to supply the desired power to the implantable device.

[0118] The magnetic field generated by the antenna 404 increases in magnitude the closer it is to the conductive material of the antenna 404. Therefore, the magnetic field is stronger in the first portion 404a of the antenna 404 (including the first sub-loop 422a and the second sub-loop 422b). By asymmetrically distributing the conductive material and magnetic field strength toward the first portion 404a of the antenna 404, more power can be delivered to the implantable device without exceeding the predetermined SAR limit. SAR is proportional to the electrical conductivity of the target tissue absorbing energy. The first portion 404a of the antenna 404 is configured to be placed near the patient's head, which contains a large amount of bone tissue. Bone tissue has lower electrical conductivity than other soft tissues, such as muscle and fat, and therefore is less susceptible to electromagnetic energy absorption. Additionally, the head is small and rounded, and may be placed on a pillow, which may place the head at a greater distance from the antenna 404. 7A and 7B, the SAR at the patient's head is below the regulatory threshold despite the presence of additional conductive material in the first portion 404a of the antenna 404. Furthermore, as shown in FIGS. 7A and 7B, the SAR is highest near the patient's armpits, back, and neck, i.e., the areas directly above the conductive material in the second portion 404b of the antenna 404. Tissues such as skin, muscle, and fat present in these areas have higher electrical conductivity than the head and are therefore more likely to absorb electromagnetic energy. Therefore, the antenna 404 of the present technology can vary the density of the conductive material based on the conductivity of the patient's tissue configured to be placed in a particular portion of the antenna 404. For example, the first portion 404a, which is configured to be placed near the patient's head, can have a higher density of conductive material than the second portion 404b (which is configured to be placed near the patient's back).

[0119] As previously described, the antenna 404 may include a conductive material of a particular shape configured to generate an electromagnetic field having a horizontal component large enough to induce a desired current in the implanted device antenna at the intended location of the implanted device antenna. However, the actual location of the implanted device antenna may vary depending on the patient's position relative to the external device 400, the patient's movements during sleep, etc. For example, FIG. 8A illustrates various positions of the implanted device antenna 800 (only one antenna 800 is labeled for convenience). The implanted device antenna 800 may be positioned in such positions during normal use of the neuromodulation system of the present technology. As shown in FIG. 8A , the position of the implanted device antenna 800 may vary in three dimensions (e.g., x, y, and z). In various embodiments, the x direction and y direction shown in FIG. 8A generally correspond to the width direction W and length direction L of the antenna 404, respectively (e.g., the antenna 404 may lie on the x-y plane). The antenna 404 may be configured to generate an electromagnetic field having a horizontal component configured to penetrate the implant's antenna in a direction generally perpendicular to the radial direction of the implant's antenna over a range of head positions. For example, the antenna 404 may be configured to generate an electromagnetic field having a horizontal component large enough to induce a desired current in the antenna of an implantable device located within the active volume. This active volume may be at least 25 cubic centimeters. In some embodiments, the active volume may extend over at least 20 cm in the x direction, at least 50 cm in the y direction, and at least 1 cm in the z direction. In various embodiments, the active volume may be approximately 76 cm in the x direction, approximately 51 cm in the y direction, and approximately 25 cm in the z direction.

[0120] As shown in FIGS. 8B-8D, the patient's head may be positioned or moved over a range of head nodding angles θ (FIG. 8B), head axial angles φ (FIG. 8C), and / or head rotation angles ξ (FIG. 8D). To ensure power is delivered to the implantable device even when the patient moves during sleep, antenna 404 may be configured to generate an electromagnetic field having a horizontal component configured to extend through the implantable device antenna in a direction generally perpendicular to the radial direction of the implantable device antenna over a range of head nodding angles θ, head axial angles φ, and / or head rotation angles ξ. Antenna 404 may be configured to generate such an electromagnetic field when the patient's head nodding angle θ varies from about 0 degrees to about 30 degrees, when the head axial angle φ varies from about −60 degrees to about 60 degrees, and / or when the head rotation angle ξ varies from about −30 degrees to about 30 degrees.

[0121] The performance of the antenna 404 of the external device 400 relates to its ability to provide operating power to the implanted device antenna without exceeding regulated exposure limits, even when the implanted device antenna may be positioned in various positions over time. FIG. 9 summarizes such performance of the antenna 404. Specifically, FIG. 9 is a contour plot showing the psSAR-limited average strength of the magnetic field component (H) penetrating vertically through the implanted device antenna over various relative positions of the patient's jaw and the antenna 404. FIG. 9 illustrates the strength of the magnetic field corresponding to the position of the patient's jaw in the x-direction (e.g., width direction W of the antenna 404) and y-direction (e.g., length direction L of the antenna 404). At 0 mm in the x-direction and 0 mm in the y-direction, the patient's jaw is positioned at the first ends 410, 414 and second ends 412, 416 of the first and second lengths 406, 408 of conductive material. 9 shows the magnetic field strength (hereinafter referred to as magnetic field strength) when the patient's chin is fixed at a position 5 mm from the antenna 404 in the height direction (direction perpendicular to the length direction L and width direction W of the antenna 404). The magnetic field strength represents the maximum average strength of the magnetic field component that penetrates perpendicularly through the antenna of the implantable device, without causing the psSAR in the patient to exceed the regulatory threshold (1.6 W / kg).

[0122] In the neuromodulation system of the present technology, a minimum magnetic field strength can be set based on the power requirements of the implanted device. For example, a psSAR-limited magnetic field strength of approximately 3.4 A / m (2.4 A / m rms) can provide sufficient power for the implanted device to perform its desired function. Thus, the contour line labeled 3.4 A / m in FIG. 9 indicates the boundary separating patient positions where the magnetic field strength is below 3.4 A / m (i.e., the inactive region) from patient positions where the magnetic field strength exceeds 3.4 A / m (i.e., the active region). Patient positions within the active region are positions where the implanted device receives sufficient power from the electromagnetic field generated by the antenna 404. As shown in FIG. 9, the magnetic field strength is greatest when the patient's chin is centered over the antenna 404, and decreases as the jaw moves in the x and / or y directions. A greater magnetic field strength indicates a greater amount of power that can be provided to the implanted device at that location before the patient's psSAR reaches the regulatory threshold.

[0123] As mentioned above, FIG. 9 shows the magnetic field strength when the patient's chin is fixed 5 mm from the antenna 404 in the vertical direction. Generally, the active volume where the magnetic field strength is at a level that can supply the desired power to the implantable device antenna increases as the vertical distance between the patient's chin and the antenna 404 increases. This is because the magnetic field strength decreases rapidly with the distance from the conductive material of the antenna 404, so even a small vertical separation can significantly reduce the psSAR. Meanwhile, the magnetic field strength at the height of the implantable device antenna also decreases with distance from the antenna 404, but the decrease rate is more gradual than at the height of the conductive material, so the magnetic field strength is still sufficient to supply power to the implantable device antenna. Therefore, in some embodiments, the carrier 402 of the external device 400 may be configured to include a portion disposed between the antenna 404 and the patient, thereby defining a minimum distance between the antenna 404 and the patient and increasing the size of the active volume.

[0124] While FIG. 4A illustrates an antenna 404 having a specific shape and dimensions, other configurations of the antenna 404 are within the scope of the present technology. In various embodiments, the shape of the conductive material, the placement of the capacitor, and the like may be selected based on the desired performance of the antenna. As an example, FIG. 10 illustrates an external device 1000 including a carrier 1002 carrying an antenna 1004. The antenna 1004 may be similar to the antenna 404. For example, the antenna 1004 may include a conductive material of the same shape as the antenna 404. However, in contrast to the capacitor 428 shown in FIG. 4A, the antenna 1004 shown in FIG. 10 does not include a capacitor connected in series with the conductive material. The presence or absence of a series capacitor may not substantially affect the strength or distribution of the magnetic field generated by the antenna 1004. Therefore, the magnetic field and psSAR generated by the antenna 1204 may be substantially similar to those shown in FIGS. 5, 7A, and 7B, respectively.

[0125] FIG. 11 is a coronal section view showing an intensity map of the electric field generated by the antenna 1004 in the plane of the antenna 1004. As shown in FIGS. 6 and 11, the electric field generated by the antenna 1004 without the series capacitor (FIG. 11) is greater in the plane of the antenna than the electric field generated by the antenna 404 with the series capacitor 428 (FIG. 6). As previously mentioned, the series capacitor 428 divides the conductive material of the antenna 404, limiting the peak voltage (and therefore the peak electric field) that can appear across the antenna 404. Without the series capacitor, the voltage across the antenna 1004 increases from the input terminal to the output terminal of the feed 1026. In antennas of the present technology, it is useful to limit the peak voltage across the antenna for patient safety.

[0126] FIG. 12 illustrates an external device 1200 including a carrier 1202 carrying an antenna 1204. Similar to antenna 404, antenna 1204 shown in FIG. 12 includes a first portion 1204a including a first length 1206 of conductive material and a second portion 1204b located opposite first portion 1204a along the length direction L of carrier 1202 and including a second length 1208 of conductive material. However, as shown in FIG. 12, antenna 1204 may be symmetrical about a first centerline M1. In these and other embodiments, first length 1206 of conductive material may have a total length comparable to or identical to second length 1208 of conductive material.

[0127] 12, a first length 1206 of conductive material may extend from a first end 1210 to a second end 1212, and a second length 1208 of conductive material may extend from a first end 1214 to a second end 1216. In some embodiments, the first length 1206 may form a first loop 1218, and the second length 1208 may form a second loop 1220. In some embodiments, the first length 1206 may not form a sub-loop, and the area enclosed by the first loop 1218 may be substantially equal to the area enclosed by the second loop 1220. The first length 1206 and the second length 1208 of conductive material may be electrically connected in series with each other (e.g., by the connection of the first ends 1210 and 1214 and the connection of the second ends 1212 and 1216).

[0128] As shown in FIG. 12 , the first length 1206 includes a first region 1206a extending in a first length direction from a first end located at the first end 1210 to a second end, a second region 1206b extending in a first width direction from a first end located at the second end of the first region 1206a to a second end, a third region 1206c extending in the first length direction from a first end located at the second end of the second region 1206b to a second end, and a third region 1206b extending in a first length direction from a first end located at the second end of the third region 1206c to a second end. The first length 1206 may include a fourth region 1206d extending in a second width direction from the first end to the second end, a fifth region 1206e extending in a second length direction from a first end located at the second end of the fourth region 1206d to a second end, a sixth region 1206f extending in a first width direction from the first end located at the second end of the fifth region 1206e to the second end, and a seventh region 1206g extending in a second length direction from the first end located at the second end of the sixth region 1206f to the second end. The first through seventh regions 1206a through 1206g of the first length 1206 collectively form a first loop 1218.

[0129] The second length 1208 includes a first region 1208a extending in a second length direction from a first end located at the first end 1214 to a second end, a second region 1208b extending in a second width direction from a first end located at the second end of the first region 1208a to a second end, a third region 1208c extending in a second length direction from a first end located at the second end of the second region 1208b to a second end, and a third region 1208c extending in a second length direction from a first end located at the second end of the third region 1208c to a second end. The second length 1208 may include a fourth region 1208d extending in a first width direction to the end thereof, a fifth region 1208e extending in a first length direction from a first end located at a second end of the fourth region 1208d to a second end thereof, a sixth region 1208f extending in a second width direction from a first end located at the second end of the fifth region 1208e to a second end thereof, and a seventh region 1208g extending in a first length direction from a first end located at the second end of the sixth region 1208f to a second end thereof. The first through seventh regions 1208a through 1208g of the second length 1208 collectively form a second loop 1220.

[0130] FIG. 13 is a two-dimensional diagram illustrating a magnetic field 1300 generated by the antenna 1204. Similar to the magnetic field 500 generated by the antenna 404, the magnetic field 1300 illustrated in FIG. 13 may have a horizontal component that is generally parallel to a plane containing the first length 1206 and the second length 1208 of the antenna 1204 (e.g., a plane defined by the width and length of the antenna 1204, a plane generally parallel to the broad surface of the carrier 1202, etc.). When the external device 1200 is placed between the patient and a surface and the implantable device antenna 1302 is angled relative to the plane containing the first and second lengths 1206, 1208, the horizontal component of the magnetic field 1300 becomes generally perpendicular to the implantable device antenna 1302 and can induce an electromotive force in the antenna 1302. However, in contrast to the magnetic field 500 generated by the antenna 404, the magnetic field 1300 generated by the antenna 1204 of FIG. 12 may be substantially symmetrical about the first centerline M1 of the carrier 1202.

[0131] As shown in FIG. 13 , the magnetic field 1300 generated by the antenna 1204 may generally have a lower strength than the magnetic field 500 generated by the antenna 404 in response to the same excitation energy. The reduced strength of the magnetic field 1300 is due to the reduced number of loops in the antenna 1204 and the reduced density of the conductive material. This change in magnetic field strength may also cause a change in the SAR resulting from exposure to the magnetic field 1300. For example, as shown in FIGS. 14A and 14B , the SAR generated in a patient's head in response to the magnetic field 1300 may be lower than the SAR generated in the head in response to the magnetic field 500. This relative decrease in SAR may be due to the reduced strength of the magnetic field 1300 in the first portion 1204 a of the antenna 1204. Furthermore, as shown in FIGS. 17A and 17B , the SAR may be greater in areas where the magnetic field 1300 strength and the electrical conductivity of the tissue are higher. For example, peak SAR occurs at axillary height near fourth region 1208d of second length 1208 of antenna 1204. In general, SAR tends to be greatest in anatomical regions located directly above or near first length 1206 and second length 1208 of conductive material.

[0132] FIG. 15 illustrates an external device 1500 including an antenna 1504 supported on a carrier 1502. The antenna 1504 includes a first portion 1504a including a first length 1506 made of a conductive material and a second portion 1504b located opposite the first portion 1504a along the length direction L of the carrier 1502 and including a second length 1508 made of a conductive material. Similar to the antenna 1204, the antenna 1504 illustrated in FIG. 15 may be symmetrical about a first centerline M1. For example, the first length 1506 may form a first loop 1518, and the second length 1508 may form a second loop 1520. However, unlike the antenna 1204, the first length 1506 may form a first sub-loop 1522a, and the second length 1508 may form a second sub-loop 1522b. The first sub-loop 1522a and / or the second sub-loop 1522b may enclose a smaller area than the first loop 1518 and / or the second loop 1520, respectively.

[0133] 15, the first length 1506 may include a first region 1506a extending in a first length direction from a first end located at a first end 1510 of the first length 1506 to a second end, a second region 1506b extending in a first width direction from a first end located at a second end of the first region 1506a to a second end, a third region 1506c extending in the first length direction from a first end located at a second end of the second region 1506b to a second end, and a fourth region 1506d extending in a second width direction from a first end located at a second end of the third region 1506c to a second end. The fourth region 1506d may extend in the width direction W a distance similar to or different from that of the second region 1506b.

[0134] The first length 1506 may include a fifth region 1506e, which extends in a second width direction from the first end to the second end. As shown in FIG. 15 , in some embodiments, the first length 1506 includes a first transition region 1528a that transitions from the first loop 1518 to the first sub-loop 1522a. In the first transition region 1528a, the first length 1506 extends obliquely relative to the length direction L and the width direction W to connect between the second end of the fourth region 1506d and the first end of the fifth region 1506e. This causes the second end of the fourth region 1506d and the first end of the fifth region 1506e to be offset along the width direction W and the length direction L. The fifth region 1506e may include a sixth region 1506f extending in a second length direction from a first end to a second end thereof, a seventh region 1506g extending in a first width direction from a first end to a second end thereof, an eighth region 1506h extending in a first length direction from a first end to a second end thereof, and a ninth region 1506i extending in a second width direction from a first end to a second end thereof. These fifth to ninth regions 1506e to 1506i may collectively form a first sub-loop 1522a.

[0135] The first length 1506 may include a tenth region 1506j, which extends in a second width direction from a first end to a second end of the tenth region 1506j. As shown in FIG. 15 , in some embodiments, the first length 1506 extends obliquely with respect to the length direction L and the width direction W to connect between the second end of the ninth region 1506i and the first end of the tenth region 1506j. As such, the second end of the ninth region 1506i and the first end of the tenth region 1506j are offset along the width direction W and the length direction L. The first length 1506 may further include an eleventh region 1506k extending in a second length direction from a first end located at the second end of the tenth region 1506j to a second end, a twelfth region 1506l extending in a first width direction from a first end located at the second end of the eleventh region 1506k to a second end, and a thirteenth region 1506m extending in a second length direction from a first end located at the second end of the twelfth region 1506l to a second end 1512 of the first length 1506. The first through fourth regions 1506a through 1506d and the tenth through thirteenth regions 1506j through 1506m may collectively form a first loop 1518. According to various embodiments, the area enclosed by the first loop 1518 may be greater than the area enclosed by the first sub-loop 1522a.

[0136] 15, the second length 1508 may include a first region 1508a extending from a first end of the first region 1508a at a first end 1514 of the second length 1508 to a second end in a second lengthwise direction. The second length 1508 may further include a second region 1508b (extending in a second widthwise direction from the second end of the first region 1508a), a third region 1508c (extending in a second lengthwise direction from the second end of the second region 1508b), and a fourth region 1508d (extending in a first widthwise direction from the second end of the third region 1508c). The fourth region 1508d may extend a similar distance along the widthwise direction W as the second region 1508b, or a different distance.

[0137] The second length 1508 may include a fifth region 1508e extending in a first width direction from a first end to a second end of the fifth region 1508e. As shown in FIG. 15 , in some embodiments, the second length 1508 includes a second transition region 1528b that transitions from the second loop 1520 to the second sub-loop 1522b. In the second transition region 1528b, the second length 1508 extends obliquely relative to the length direction L and the width direction W to connect between the second end of the fourth region 1508d and the first end of the fifth region 1508e. Thus, the second end of the fourth region 1508d and the first end of the fifth region 1508e are offset along the width direction W and the length direction L. The second length 1508 may further include a sixth region 1508f extending in a first length direction from a first end located at the second end of the fifth region 1508e to a second end, a seventh region 1508g extending in a second width direction from a first end located at the second end of the sixth region 1508f to a second end, an eighth region 1508h extending in a second length direction from a first end located at the second end of the seventh region 1508g to a second end, and a ninth region 1508i extending in a first width direction from a first end located at the second end of the eighth region 1508h to a second end. These fifth to ninth regions 1508e to 1508i may collectively form a second sub-loop 1522b.

[0138] The second length 1508 may include a tenth region 1508j that extends in a first width direction from a first end to a second end of the tenth region 1508j. As shown in FIG. 15 , in some embodiments, the second length 1508 extends obliquely with respect to the length direction L and the width direction W to connect between the second end of the ninth region 1508i and the first end of the tenth region 1508j at the second transition region 1528b. As such, the second end of the ninth region 1508i and the first end of the tenth region 1508j are offset along the width direction W and the length direction L. The second length 1508 may further include an eleventh region 1508k extending in a first length direction from a first end located at the second end of the tenth region 1508j to a second end, a twelfth region 1508l extending in a second width direction from a first end located at the second end of the eleventh region 1508k to a second end, and a thirteenth region 1508m extending in the first length direction from a first end located at the second end of the twelfth region 1508l to a second end 1516 of the second length 1508. These first through fourth regions 1508a through 1508d and tenth through thirteenth regions 1508j through 1508m may collectively form a second loop 1520. In various embodiments, the area enclosed by the second loop 1520 may be greater than the area enclosed by the second sub-loop 1522b.

[0139] 4A, the antenna 1504 shown in FIG. 15 may include a feed 1526 that receives current from and supplies current to the control unit. In FIG. 15, the feed 1526 is located approximately at the second centerline M2, but the feed 1526 may be located at any suitable location on the antenna 1504. While FIG. 15 shows a single feed 1526, in various embodiments, the antenna 1504 may have multiple feeds 1526 or no feed at all, as described elsewhere herein.

[0140] The first transition region 1528a and / or the second transition region 1528b may be located on either side of the second centerline M2 along the width direction W, or may be aligned with the second centerline M2. Symmetry of the antenna 1504 with respect to the second centerline M2 may affect the electronics of the control unit that provides power to the antenna 1504 (e.g., via the feed 1526). For example, in various embodiments, the control unit may include a balanced amplifier for driving the antenna. Therefore, it may be advantageous for antennas of the present technology to be approximately symmetrical with respect to the second centerline M2 to prevent or reduce the generation of stray currents in the antenna or to the control unit. In some embodiments, such symmetry may be achieved by positioning the transition regions 1528a, 1528b near or directly above the second centerline M2. As shown in FIG. 15, in some embodiments, the feed 1526 is positioned at the second center line M2, in which case the first transition region 1528a is positioned near the second center line M2, but not directly on it.

[0141] 16, the magnetic field 1600 generated by the antenna 1504 may have a stronger strength than the magnetic field 1300 generated by the antenna 1204 and may therefore more efficiently facilitate power transfer from the antenna 1504 to the antenna of the implantable device 1602. The inclusion of sub-loops 1522a and 1522b increases the strength of the magnetic field compared to the individual first and second loops 1218, 1220 of the antenna 1204 of FIG. 12. The individual magnetic fields generated by each of the first loop 1518 and the first sub-loop 1522a may at least partially constructively interfere, resulting in a composite magnetic field strength that is greater than the magnetic field strength generated by either the first loop 1518 or the first sub-loop 1522a alone. Similarly, the magnetic fields generated by each of the second loop 1520 and the second sub-loop 1522b may also at least partially constructively interfere with each other, resulting in a composite magnetic field strength that is greater than the magnetic field strength of either the second loop 1520 or the second sub-loop 1522b alone.

[0142] 17A and 17B show sagittal and coronal views, respectively, of simulated SAR (specific absorption rate) in a patient exposed to magnetic field 1600 generated by antenna 1504. SAR is generally higher in anatomical regions located in areas of high magnetic field 1600 strength. Furthermore, as discussed herein, the head contains a large amount of bone tissue, which has lower electrical conductivity and is more resistant to electromagnetic exposure than other soft tissues. Therefore, the SAR of the patient's head in FIGS. 17A and 17B may not be greater than the SAR of the head shown in FIGS. 14A and 14B, even if the magnetic field 1600 strength at the head is higher than the magnetic field 1300 strength. On the other hand, soft tissues (e.g., muscle, fat, etc.), such as those in the neck and upper back, are more sensitive to increased SAR. 17A and 17B, the magnetic field 1600 generated by the antenna 1504 can significantly increase the SAR in the shoulders, armpits, neck, and upper back of a patient compared to the magnetic field 1300 generated by the antenna 1204. Because the magnitude (strength) of the magnetic field is greatest near the conductive material of the antenna 1504, the increased density of the conductive material in the second portion 1504b of the antenna 1504 increases the SAR in the patient's upper back. Therefore, in antennas according to the present technology, a configuration in which the conductive material is reduced in density in regions of the carrier positioned near highly conductive anatomical sites may be advantageous to prevent excessive SAR absorption in the patient.

[0143] FIG. 18 illustrates an example external device 1800, comprising a carrier 1802 and an antenna 1804 carried by the carrier 1802. A second portion 1804b of the antenna 1804 is configured with a lower density of conductive material in a second region 1802b of the carrier 1802, the second region 1802b being configured to be positioned near the patient's back and / or neck. Meanwhile, a first portion 1804a of the antenna 1804 is disposed in the first region 1802a of the carrier 1802 and is configured with a higher density of conductive material, the first portion 1804a being configured to be positioned near the patient's head. The first portion 1804a includes a first length 1806 of conductive material, the first length 1806 extending from a first end 1810 to a second end 1812. The second portion 1804b includes a second length 1808 made of a conductive material, the second length 1808 extending from the first end 1814 to the second end 1816. The first length 1806 may have a longer overall length than the second length 1808. The first length 1806 may form a first loop 1818, and the second length 1808 may form a second loop 1820. As shown in FIG. 18 , the first length 1806 may also form a sub-loop 1822. Unlike the antenna 404 of FIG. 4A , the first length 1806 may form a single sub-loop 1822 extending along the width direction W, rather than the two sub-loops 422a and 422b spaced apart along the width direction W as shown in FIG. 4A .

[0144] The antenna 1804 may be configured to generate a magnetic field having a magnitude and distribution similar to that of the antenna 404. However, the magnetic field generated by the antenna 1804 of FIG. 18 may be greater at the second center line M2 than the magnetic field generated by the antenna 404 of FIG. 4A. This is because the fifth region 406e and the eleventh region 406k of the first length 406 of the antenna 404 are configured so that currents flow in opposite directions, respectively, which may at least partially cancel out the magnetic fields generated near the respective regions, thereby reducing the strength of the magnetic field near the second center line M2. However, because the first length 1806 of the antenna 1804 of FIG. 18 does not include adjacent regions in which currents flow in opposite directions, the magnetic field generated by the antenna 1804 may be greater near the second center line M2 than the magnetic field generated by the antenna 404.

[0145] As shown in FIG. 18 , in some embodiments, a transition region 1828 between the first loop 1818 and the sub-loop 1822 may be located on one side of a second centerline M2 along the width direction W. Symmetry of the antenna 1804 with respect to the second centerline M2 may affect the electronics of the control unit that provides power to the antenna 1804 (e.g., via a feed 1826). For example, in various embodiments, the control unit includes a balanced amplifier for driving the antenna. Therefore, configuring an antenna in accordance with the present technology to be substantially symmetrical with respect to the second centerline M2 may be advantageous for preventing or reducing stray currents in the antenna and their arrival at the control unit. In some embodiments, such symmetry can be achieved by locating the transition region 1828 near or on the second centerline M2.

[0146] In some embodiments, the transition regions between loops and / or sub-loops may be spaced apart from the second centerline M2. FIG. 19 illustrates an example of an antenna 1904 similar to antenna 1804 of FIG. 18. For example, antenna 1904 includes a first length 1906 of conductive material, which defines a first loop 1918 and a sub-loop 1922. Antenna 1904 also includes a second length 1908 of conductive material, which defines a second loop 1920. First length 1906 includes first through eleventh regions 1906a through 1906k connected sequentially from a first end 1910 to a second end 1912, and second length 1908 includes first through seventh regions 1908a through 1908g connected sequentially from a first end 1914 to a second end 1916. Thus, the first length 1906 can have a greater overall length than the second length 1908, except that the transition region 1928 between the first loop 1918 and the sub-loop 1922 is positioned away from the second centerline M2 along the width direction W.

[0147] FIG. 20 illustrates an example of an external device 2000 in which an antenna 2004 having multiple sub-loops is carried on a carrier 2002. Similar to previously described antennas, the antenna 2004 illustrated in FIG. 20 includes a first portion 2004a and a second portion 2004b, where the first portion 2004a includes a first length 2006 of conductive material and the second portion 2004b includes a second length 2008 of conductive material disposed on the opposite side of the first portion 2004a along the length L of the carrier 2002. As illustrated in FIG. 20, the antenna 2004 may be asymmetric about a first centerline M1 and symmetric about a second centerline M2. In various embodiments, the feed 2026 of the antenna 2004 is substantially located on the second centerline M2.

[0148] A first length 2006 of conductive material may extend from a first end 2010 to a second end 2012. A second length 2008 of conductive material may extend from a first end 2014 to a second end 2016. The first length 2006 and the second length 2008 may be electrically connected to each other in series (e.g., connecting the first ends 2010 and 2014 together and connecting the second ends 2012 and 2016 together). The first length 2006 may form a first loop 2018, and the second length 2008 may form a second loop 2020. Furthermore, as shown in FIG. 20 , the first length 2006 may form a first sub-loop 2022a, a second sub-loop 2022b, a third sub-loop 2022c, and a fourth sub-loop 2022d (collectively “sub-loops 2022”). In some embodiments, the first length 2006 and / or the second length 2008 can be configured to form one sub-loop 2022, multiple sub-loops 2022, or no sub-loops 2022. Some or all of the sub-loops 2022 can be connected in series with the first loop 2018 and / or other adjacent sub-loops 2022. In some embodiments, some or all of the sub-loops 2022 can be independently fed, independently driven, and have their own currents. Some or all of the sub-loops 2022 can be passive, ie, currents are induced by being in the magnetic field generated by the antenna 2004, without being supplied with current through a feed or series connection with the first / second loops 2018, 2020. Some or all of the sub-loops 2022 can be configured to enclose the same area. Additionally or alternatively, some or all of the sub-loops 2022 can be spaced equidistantly from the first centerline M1 along the length direction L.

[0149] In various embodiments, radio frequency (RF) current can flow in opposite directions within the first loop 2018 and the second loop 2020. Radio frequency (RF) current can be configured to flow in the same direction as the first loop 2018 through one, more, or none of the sub-loops 2022. As shown in FIG. 20 , in some embodiments, each sub-loop 2022 is continuous with the first loop 2018 through a transition region 2028a-d. These transition regions 2028a-d may be similar to other transition regions disclosed herein, and any transition region disclosed herein may have similar characteristics as the transition regions 2028a-d. In each transition region 2028a-d, the first length 2006 may cross itself to provide an electrical path for current to flow between the region forming the first loop 2018 and the region forming the respective sub-loop 2022.

[0150] Because the antenna 2004 includes individual sub-loops 2022 spaced apart along the width direction W, the strength of the magnetic field generated by the antenna 2004 can vary along the width direction W. When current flows in the same direction through each sub-loop 2022, current flows in opposite directions in adjacent regions of the first length 2006 along the width direction W (e.g., regions extending along the length direction L). Thus, the magnetic fields generated in these regions can destructively interfere with each other. In various embodiments, this destructive interference can limit the strength of the magnetic field along the width direction W. In contrast, the larger sub-loops in the first portion of each of the antennas 1504, 1804, and 1904 of FIGS. 15, 18, and 19 can produce a higher magnetic field strength at the second centerline M2. In some embodiments, the strength of the magnetic field and / or some of its components can be configured to be relatively constant or exhibit only small variations across the width direction W.

[0151] FIG. 21 illustrates an example of an external device 2100 in which an antenna 2104 including multiple sub-loops is supported on a carrier 2102. Similar to antennas previously described, the antenna 2104 illustrated in FIG. 21 includes a first portion 2104a and a second portion 2104b disposed opposite the first portion 2104a along the length L of the carrier 2102. The first portion 2104a includes a first length 2106 of conductive material, and the second portion 2104b includes a second length 2108 of conductive material. The first length 2106 of conductive material may extend from a first end 2110 to a second end 2112, and the second length 2108 of conductive material may extend from a first end 2114 to a second end 2116. The first length 2106 may form a first loop 2118, and the second length 2108 may form a second loop 2120. Additionally, as shown in Figure 21, the first length 2106 may form two or more sub-loops 2122 (e.g., two, three, four sub-loops 2122, etc.). In one embodiment shown in Figure 21, the first length 2106 forms a first sub-loop 2122a, a second sub-loop 2122b, and / or a third sub-loop 2122c. Unlike conventional antennas, the sub-loops 2122 shown in Figure 21 are spaced apart along the length direction L.

[0152] The first length 2106 and the second length 2108 of conductive material may be electrically connected in series (e.g., by connecting the first ends 2110, 2114 together and the second ends 2112, 2116 together) to form a series configuration. Some or all of the sub-loops 2122 may be connected in series with the first loop 2118 and / or adjacent sub-loops 2122. In some embodiments, one, more, or all of the sub-loops 2122 may be configured to be independently powered, such that they are independently driven and each may have its own current. One, more, or all of the sub-loops 2122 may be passive, in which case the sub-loops are not powered but have a current induced in them by being located in the magnetic field generated by the antenna 2104. Some or all of the sub-loops 2122 may enclose the same area. Additionally or alternatively, some or all of the sub-loops 2122 may be disposed substantially aligned along the width direction W of the carrier 2102. As shown in FIG. 21, the antenna 2104 may be asymmetric about a first centerline M1, while being symmetric about a second centerline M2.

[0153] In various embodiments, current may flow in opposite directions through the first loop 2118 and the second loop 2120. Current may be configured to flow in one, more, or none of the sub-loops 2122, and may flow in the same direction as the first loop 2118. In some embodiments, current may flow in opposite directions between adjacent sub-loops 2122. Although not explicitly shown in FIG. 21 , in some embodiments, one, more, or all of the sub-loops 2122 are continuous with the first loop 2118 through one or more transition regions, which may be similar to other transition regions disclosed herein. In some embodiments, the first length 2106 may include additional regions other than those shown in FIG. 21 to achieve transitions between the sub-loops 2122, the first loop 2118, and / or the second loop 2120.

[0154] In some embodiments, the size of the second loop of the antenna may be varied based on the magnetic field and / or SAR (Specific Absorption Rate) threshold expected to be generated by the antenna. For example, FIG. 22 illustrates an external device 2200 in which a carrier 2202 carries an antenna 2204 including a first loop 2218 and a second loop 2220 having a larger area than the first loop 2218 and the previously illustrated second loop. Similar to the antennas previously described, the antenna 2204 illustrated in FIG. 22 includes a first portion 2204a including a first length 2206 of conductive material disposed along the length direction L of the carrier 2202, and an opposite second portion 2204b including a second length 2208 of conductive material. The first length 2206 of conductive material may form the first loop 2218, and the second length 2208 of conductive material may form the second loop 2220. Optionally, first length 2206 may form one or more sub-loops 2222 (e.g., first sub-loop 2222a, second sub-loop 2222b, etc.). In an embodiment, first length 2206 may form one or more secondary sub-loops 2224 (e.g., first secondary sub-loop 2224a, second secondary sub-loop 2224b, etc.). In an embodiment, secondary sub-loop 2224 is disposed inside sub-loop 2222 and encloses a smaller area than sub-loop 2222.

[0155] The area of ​​the second loop 2220 may be determined based on the width of the second loop 2220 along the width direction W and / or the length of the second loop 2220 along the length direction L. In certain embodiments, the width and / or length of the second loop 2220 may be determined with reference to placing the external device 2200 in an intended position relative to one or more anatomical locations on a patient. For example, the length of the second loop 2220 may be selected such that when the first portion 2204a is placed proximate the patient's head, one or more regions of the second length 2208 are placed proximate anatomical locations that have low electrical conductivity and are less susceptible to SAR. For example, the fourth region 2208d of the second length 2208 may be positioned more distant from the second region 2208b and the sixth region 2208f such that the fourth region 2208d is positioned further below the patient when the external device 2200 is placed between the patient and an underlying surface. In such an example, the fourth region 2208d may be configured to align with an area that has lower electrical conductivity and is less susceptible to SAR absorption than the axillae or chest, such as the buttocks.

[0156] In some embodiments, the area of ​​the second loop 2220 may be determined based at least in part on the magnetic moment intended by the antenna 2204. Having the quadrupole magnetic moment of the antenna 2204 significantly greater than the dipole magnetic moment is advantageous in suppressing magnetic field radiation over long distances. The magnetic moment of the antenna 2204 may be determined at least in part on the symmetry of the antenna 2204 in the length direction L (e.g., comparing the area enclosed by the first loop 2218 and each sub-loop 2222 with the area enclosed by the second loop 2220, comparing the distance between a particular region of the first length 2206 and the first centerline M1 with the distance between a particular region of the second length 2208 and the first centerline M1, etc.). If the first portion 2204a of the antenna 2204 comprises a denser conductive material than the second portion 2204b, the length and / or width of the second loop 2220 may be greater than the corresponding length and / or width of the first loop 2218 and / or one or more sub-loops 2222. In an embodiment, the antenna 2204 may be symmetrical about a centerline (e.g., second centerline M2) along the width direction W.

[0157] The areas of the first loop 2218, sub-loop 2222, and / or secondary sub-loop 2224 may be determined based at least in part on the intended magnetic moment of the antenna 2204. For example, if the area of ​​the second loop 2220 is substantially larger than the combined area of ​​the first loop 2218 and sub-loop 2222, the addition of the secondary sub-loop 2224 may cause the magnetic field generated by the first loop 2218, sub-loop 2222, and secondary sub-loop 2224 to substantially balance the magnetic field generated by the second loop 2220. In various embodiments, each of the secondary sub-loops 2224 may be configured to be substantially contained within one or more sub-loops 2222.

[0158] FIG. 23 is a block diagram illustrating a control unit of an external system (e.g., control unit 30 of external system 15) of the present technology and a second antenna of the external system (e.g., second antenna 12 of external system 15). The control unit may include a power source or be configured to be electrically connected to a power source and provide power to the antenna of the external system (e.g., second antenna 12). The control unit may be configured to convert direct current (DC) to alternating current (AC) and provide it to the second antenna to generate an alternating magnetic field by passing the AC current through the antenna. As shown in FIG. 23 , the control unit may include or be electrically connected to an amplifier configured to convert DC to AC based on an operating frequency defined by an oscillator. The control unit may include or be electrically connected to an electromagnetic interference (EMI) filter configured to reduce energy at frequencies other than the operating frequency (e.g., to comply with regulatory requirements regarding radio frequency emissions). In various embodiments, the control unit may be configured to include or be electrically connected to a matching circuit (matching circuit) disposed between the amplifier and / or EMI filter and the second antenna. As described in more detail below, the matching circuit can increase the efficiency of power transfer from the amplifier (e.g., via the EMI filter) to the second antenna.

[0159] The power supply may include any suitable DC power source. For example, in one embodiment, the power supply may include a medical-grade power supply. The power supply may be configured to receive AC power, for example, from a wall outlet, and convert it to DC for supply to the amplifier. In one embodiment, the control unit is configured to be electrically connected to the medical-grade power supply and may further include or be electrically connected to a programmable power supply. The programmable power supply is configured to receive DC, for example, from the medical-grade power supply and / or other DC power sources, and provide DC to the amplifier. The programmable power supply advantageously allows the power supplied to be variable because the amount of power to be supplied to the amplifier may vary based at least in part on the impedance of the second antenna. If the impedance of the second antenna differs from the impedance of the amplifier, more power may need to be supplied to the amplifier to generate a magnetic field of sufficient size and strength for the implantable device. Furthermore, the programmable power supply may include short-circuit protection, thereby maintaining the safety of the control unit in the event of component failure or overheating of the amplifier. In one embodiment, the programmable power supply is configured to measure the power supplied to the amplifier, which may be used as an input to the matching circuit control algorithm of the present technology. Additionally or alternatively, measuring the power delivered to the amplifier can be used to improve system safety. For example, it may be desirable to limit the power delivered to the amplifier so that an external system does not generate a magnetic field that is too large for the patient, exceeding safety thresholds. This can also help prevent or limit burnout of components downstream of the amplifier. To reduce heat generation, the programmable power supply may have a high efficiency, e.g., 80%, 85%, 90%, or 95% or greater.

[0160] The control unit may include or be electrically connected to an oscillator, which may define an operating frequency for the external system. In some embodiments, the operating frequency is defined in accordance with regulatory requirements for electromagnetic emissions. For example, the oscillator may set the operating frequency within the Industrial, Scientific, and Medical (ISM) band of frequencies as required by the Federal Communications Commission (FCC). In some embodiments, the operating frequency is 6.78 MHz or 13.56 MHz.

[0161] As shown in FIG. 23 , the control unit may include or be electrically connected to an amplifier, which can convert DC to AC at the operating frequency of the oscillator. In some embodiments, the amplifier may include a Class D amplifier or a Class E amplifier. The EMI filter may be configured to reduce electromagnetic noise present in the AC generated by the amplifier. For example, the push-pull operation of a Class D amplifier may generate a large number of harmonic components at the operating frequency, and the EMI filter may be configured to reduce or eliminate these. The EMI filter may include an inductor-capacitor (LC) filter including one or more inductors and one or more capacitors. In some embodiments, the EMI filter may be a multi-stage low-pass or band-pass filter. The EMI filter may be configured to at least partially block energy at undesired frequencies other than the operating frequency (e.g., harmonics of the operating frequency). Parameters of the EMI filter may be selected to maximize blocking characteristics at harmonic frequencies while minimizing power loss. In one embodiment, the EMI filter may be configured to reduce the energy of odd harmonics (e.g., the 3rd, 5th, 7th, 11th harmonics, etc.) since the differential operation reduces the energy of even harmonics.

[0162] An EMI filter may include tight-tolerance capacitors and inductors configured to reliably reject harmonics while passing energy at operating frequencies with little attenuation. In some embodiments, an EMI filter may include an LC filter augmented with one or more resistor-capacitor (RC) networks connected to the filter's inductors. EMI filters augmented with RC networks can improve the rejection of certain harmonics compared to standard LC filters. Augmenting an LC filter with one or more RC networks can also increase the filter's bandwidth.

[0163] Continuing with reference to FIG. 23 , the control unit may include or be electrically connected to a matching circuit configured to receive AC from the amplifier and / or EMI filter and provide AC to the second antenna. The matching circuit is configured to improve power transfer efficiency between the amplifier and the second antenna. When a power source (e.g., an amplifier) ​​with a fixed output impedance operates on a load (e.g., the second antenna), maximum power is delivered to the load when its impedance matches the complex conjugate of the power source's impedance. To improve power transfer, the second antenna may be designed to have a natural impedance that matches the complex conjugate of the amplifier's impedance; however, the impedance of the second antenna may change over time. For example, this impedance may change when a metal object is placed in the electromagnetic field generated by the second antenna, when a patient lies on the second antenna, or when the patient moves relative to the second antenna. To address these challenges, the matching circuit may be configured to change the impedance seen by the amplifier and / or EMI filter (e.g., the impedance of the second antenna) to reduce or eliminate the difference between the impedance of the second antenna and the impedance of the amplifier, thereby improving power transfer from the amplifier to the second antenna.

[0164] One or more components of the control unit of the present technology may be configured to operate in a differential or single-ended common ground manner. For example, FIGS. 24A and 24B are block diagrams of a control unit (e.g., control unit 30) according to the present technology, with matching circuits configured for differential and single-ended operation, respectively. The components of the control unit shown in FIGS. 24A and 24B may have similar features to the corresponding components of the control unit described with reference to FIG. 23. For example, as shown in both FIGS. 24A and 24B, the control unit may include or be electrically connected to an amplifier configured to convert direct current (DC) from a power supply to alternating current (AC) based on the operating frequency of the oscillator, similar to that described with reference to FIG. 23. The amplifier of the control unit configured according to various embodiments of the present technology can generate a differential AC by driving both sides of the differential output with two field effect transistors (FETs) in a push-pull configuration. The on / off times of the four FETs, two on each side of the differential output, may be tightly controlled to minimize or limit power loss in the FETs and improve power transfer to a second antenna, such as second antenna 12. The differential output from the amplifier is fed to an EMI filter, which may also produce a differential output.

[0165] In some embodiments, the control unit may include or be electrically connected to one or more baluns for converting between differential operation and single-ended, common-ground operation. For example, as shown in both FIGS. 24A and 24B, the control unit may include a first balun configured to support conversion from differential to single-ended operation and / or a second balun configured to support conversion from single-ended operation to differential operation. Furthermore, in some embodiments, the control unit may include or be electrically connected to only a single balun for converting the differential output from the amplifier to a single-ended output that feeds the second antenna. Components operating in single-ended operation (e.g., components between the first and second baluns as shown in FIGS. 24A and 24B, or components downstream of the single balun) may have the advantage of reducing energy at certain harmonics, such as the second harmonic. Additionally, the first balun can transform the impedance of the output from the amplifier and / or EMI filter to a standard impedance (e.g., about 50 ohms) to facilitate characterization of the output using standard components operating at that standard impedance. The second balun can transform from the standard impedance to the characteristic impedance of one or more downstream components. The first and / or second baluns may have custom impedance ratios and operating frequencies based on the characteristics of other elements in the system (e.g., the characteristic impedance of the EMI filter, the characteristic impedance of the second antenna, etc.).

[0166] The control unit may include or be electrically connected to a low-pass filter configured to reduce noise in the alternating current (AC) generated by the amplifier. As shown in FIGS. 24A and 24B, the low-pass filter may be located downstream of the first balun, in which case the first balun can provide single-ended AC to the low-pass filter. Alternatively, the low-pass filter may be located upstream of the first balun, in which case the low-pass filter may operate differentially. The low-pass filter may be configured to reduce or eliminate energy at frequencies other than the operating frequency defined by the oscillator (e.g., harmonics, etc.). In some embodiments, the low-pass filter is configured to further reduce or eliminate energy at specific frequencies not reduced or eliminated by the EMI filter. In some embodiments, the low-pass filter has a wide bandwidth and is configured to reduce or eliminate high-frequency components (components that may easily pass through the EMI filter). As an example, the low-pass filter may have a cutoff frequency of approximately 10 MHz. The low-pass filter may be configured to output single-ended AC, for example, when located downstream of the first balun.

[0167] In various embodiments (e.g., as shown in FIGS. 24A and 25B ), the control unit may include or be electrically connected to a coupler. The coupler may be located downstream of the low-pass filter, the EMI filter, and / or the amplifier. Additionally or alternatively, the coupler may be located downstream of the first balun, in which case the coupler is configured for single-ended operation. In some embodiments, the low-pass filter may be configured to provide single-ended AC to the coupler, for example, when the low-pass filter and the coupler are located downstream of the first balun. In various embodiments, the coupler may include a directional coupler. In some embodiments, the coupler has a coupling value of approximately 20 dB. The coupler may be configured to obtain a first signal representing power propagating from the amplifier toward the second antenna and a second signal representing power propagating from the second antenna toward the amplifier. As shown in FIGS. 24A and 24B , the coupler can provide these first and second signals to a gain and phase detection unit. In an embodiment, the processor of the control unit may attenuate, filter, AC couple, or input the first and second signals to a gain and phase detection unit.

[0168] The gain and phase detection unit may be configured to compare the first signal and the second signal to determine a gain relationship and a phase relationship between the two signals. The gain relationship may correspond to or represent a voltage standing wave ratio (VSWR), which is a measure of how efficiently power is transferred from the amplifier to the second antenna, i.e., how well the impedance of the second antenna matches the impedance of the amplifier. The more power reflected from the second antenna (represented by the second signal picked up by the coupler), the worse the impedance match between the second antenna and the amplifier, and the correspondingly less efficient power transfer to the second antenna. The gain relationship may be used in the matching circuit to determine the magnitude of the impedance change required to bring the impedance of the second antenna closer to that of the amplifier. The phase relationship may be useful in determining the direction in which the impedance should be changed in the matching circuit. In various embodiments, a software algorithm (e.g., an algorithm executed by a processor of the control unit) may determine, based on the detected gain and / or phase relationships, how to adjust the matching circuit to minimize or reduce reflected power from the second antenna.

[0169] In some embodiments, the second antenna may be configured to be differentially driven. Accordingly, as shown in FIGS. 24A and 24B, the control unit may include a second balun configured to convert single-ended AC to differential AC for supply to the second antenna. Alternatively, in some embodiments, the second antenna may be configured to be driven with a single-ended input, and the control unit may not include a second balun. In embodiments in which the second antenna is differentially driven, the second antenna may be located downstream of the second balun. As shown in FIG. 24A, the matching circuit may be located downstream of the second balun, in which case the matching circuit operates differentially. Alternatively, as shown in FIG. 24B, in some embodiments, the matching circuit may be located upstream of the second balun, in which case the matching circuit operates in a single-ended manner.

[0170] As described above, the matching circuit of the present technology may be configured to change the impedance seen by the amplifier (e.g., the impedance of a circuit including the second antenna and the matching circuit) to improve energy transfer from the amplifier to the second antenna. The matching circuit may be configured to add capacitance and / or inductance to a drive signal from the amplifier (e.g., via an EMI filter), and changing these values ​​can change the natural frequency (e.g., impedance) of the circuit including the second antenna. The natural frequency of the circuit including the second antenna may be changed to approach the operating frequency of the system defined by the oscillator, thereby maximizing or improving power transfer from the amplifier to the second antenna.

[0171] The matching circuit of the present technology may include any number and configuration of reactive elements (e.g., inductors and / or capacitors). In some embodiments, the matching circuit may include one or more programmable capacitance arrays. The programmable capacitance array can change the impedance seen by the amplifier by adding or removing capacitance from the matching circuit. In some embodiments, such capacitance changes may be controlled by a processor (e.g., a processor in a control unit). Capacitance is added or removed from the matching circuit by connecting or disconnecting capacitors with different capacitance values ​​from the matching circuit. Thus, the programmable capacitance array may include multiple capacitors and multiple switches for adding or removing the capacitors from the matching circuit. The switches may include micromachined electromechanical switches (MEMS switches) digitally controlled by software and a processor. MEMS switches are useful for high-frequency RF applications and may generate little or no harmonics and operate more linearly, even in high-power, high-frequency systems. MEMS switches may also have a small form factor. In some embodiments, the switches may include solid-state relays (SSRs) in addition to or instead of MEMS switches. MEMS switches may not be suitable for "hot switching," which involves turning the switch on and off while power is being applied to the second antenna. SSRs, on the other hand, are suitable for hot switching, which allows for active tuning of the second antenna while it is powered and generating an electromagnetic field. SSRs may also be easier to implement. In some embodiments, the switch may include a gallium nitride (GaN) switch, which has lower capacitance and a wider tuning range than a silicon SSR. Changing the capacitance in the matching circuit may be accomplished by adding or removing capacitors from the circuit, as well as by changing the value of a tunable capacitor in the matching circuit.

[0172] To determine the capacitance change required for the matching circuit to optimize or improve power transfer from the amplifier to the second antenna, one or more measurements related to the impedance of the amplifier and / or the second antenna may be obtained. For example, measurements of the AC magnetic field generated by the second antenna may be used to determine the amount of capacitance change required for the matching circuit. If the measured AC magnetic field differs from a corresponding expected value, a capacitance change may be performed by the matching circuit to bring the measured AC magnetic field closer to the expected value. For example, if the magnitude of the magnetic field generated by the second antenna is smaller than expected, the impedance of the second antenna may not match the impedance of the amplifier, resulting in reduced power transfer efficiency from the amplifier to the second antenna. In such a case, the impedance of the second antenna may be brought closer to the impedance of the amplifier by changing the capacitance of the matching circuit. In various embodiments, one or more portions of the external device (e.g., carrier 9 of external device 11) may include one or more pickup antennas. The pickup antennas may be configured to measure the AC magnetic field generated by the second antenna. Each pickup antenna may be separate from the second antenna. One or more pickup antennas may be positioned around the periphery of the second antenna or within the periphery of the second antenna. In some embodiments, each pickup antenna may be constructed from a length of conductive material forming a coil with 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 turns. Measurements of the AC magnetic field generated by the second antenna may be obtained using multiple pickup antennas, and information about the impedance of the second antenna may be determined from these measurements. In some embodiments, the amount and / or type of capacitance change required in the matching circuit may be determined based on measurements obtained by the multiple pickup antennas.

[0173] In one embodiment, the amount of capacitance change required in the matching circuit may be determined by measuring and evaluating the input current to the amplifier at a given voltage level. When power transfer from the amplifier to the second antenna is maximized (e.g., when the amplifier's impedance matches the second antenna's impedance), the input current to the amplifier is also maximized. Therefore, by measuring the input current to the amplifier, the impedance match between the amplifier and the second antenna can be evaluated and the amount of capacitance change required to bring the second antenna's impedance closer to that of the amplifier can be determined.

[0174] One or more parameters (e.g., phase, amplitude, etc.) of the forward and reflected power between the amplifier and the second antenna may be measured and evaluated to determine the capacitance change to be performed by the matching circuit. As the impedance of the second antenna deviates from that of the amplifier, a portion of the power transmitted from the amplifier to the second antenna is reflected back toward the amplifier. These forward and reverse waves interfere with each other, generating a standing wave on the transmission line. The standing wave voltage ratio (VSWR) characterizes the maximum and minimum voltages of the standing wave and provides information about the impedance difference between the amplifier and the second antenna. Measuring and evaluating the VSWR can identify the amount of capacitance change required to reduce the impedance mismatch between the amplifier and the second antenna. In one embodiment, the VSWR is measured by a gain and phase detection unit, which can provide information about the amount of capacitance change required to match the impedance of the second antenna to that of the amplifier and in which direction the capacitance should be changed (e.g., whether capacitance should be added or removed).

[0175] The tuning range of the matching circuit (e.g., the range of impedance change of the second antenna that can be produced by the matching circuit) may be proportional to the initial impedance of the second antenna, which may be based, at least in part, on the value and location of a capacitor electrically connected to the second antenna. The tuning range of the matching circuit can be expanded by increasing the impedance of the second antenna, which may be achieved by changing the capacitance value of the capacitor connected to the second antenna. Increasing the tuning range of the matching circuit is advantageous because it enables the matching circuit to accommodate large variations in the impedance of the second antenna due to changes in environmental conditions, load fluctuations, etc.

[0176] 25A and 25B are schematic diagrams illustrating an example of a matching circuit configured in accordance with various embodiments of the present technology. FIG. 25A illustrates a series-type matching circuit (e.g., that shown in FIG. 24A ) configured for differential operation. FIG. 25B illustrates a series-parallel (series-shunt) matching circuit (e.g., that shown in FIG. 24B ) configured for single-ended operation. While the series-shunt matching circuit is described and illustrated with respect to single-ended operation, in some embodiments, a matching circuit configured for differential operation (e.g., that shown in FIG. 24A ) may also include a series-shunt matching circuit such as that shown in FIG. 25B . Operating a series-shunt matching circuit in differential operation may be simpler than operating it in single-ended operation. However, a matching circuit operating in single-ended operation has the advantage of requiring half the number of matching elements (e.g., capacitors, etc.) compared to a corresponding matching circuit operating in differential operation.

[0177] FIG. 25A is a schematic diagram illustrating an example of a series matching circuit configured to support differential operation in accordance with various embodiments of the present technology. As described above with reference to FIG. 24A , AC may be differentially supplied to the matching circuit from the amplifier via the EMI filter, first balun, low-pass filter, coupler, and second balun. The matching circuit may then supply the differential AC to the second antenna. While FIG. 25A illustrates an example in which the matching circuit is directly disposed between the second balun and the second antenna, in various embodiments, other components may be interposed between the matching circuit and the second balun or between the matching circuit and the second antenna. As shown in FIG. 25A , the series matching circuit may include two variable capacitance elements, one on each side of the differential output (each line output from the amplifier and EMI filter through the second balun). The variable capacitance elements may include a capacitor array in which multiple capacitors can be connected or disconnected within the matching circuit via a switch or the like to change the overall capacitance value of the matching circuit. In some embodiments, the variable capacitance elements include a programmable capacitor array. The capacitor array may have any suitable configuration, number and / or type of capacitors, and number and / or type of switches. Additionally or alternatively, the variable capacitance elements may include variable capacitors whose capacitance values ​​can be changed to adjust the overall capacitance value of the matching circuit. The change of these variable capacitance elements in the matching circuit may be controlled by a processor in the control unit in various embodiments.

[0178] In some embodiments, a fixed capacitance element (e.g., a bulk series capacitance element shown in FIG. 25A) may be disposed in series between the second balun and each variable capacitance element. Additionally or alternatively, a fixed capacitance element (e.g., a bulk parallel capacitance element shown in FIG. 25A) may be disposed in parallel with each variable capacitance element. The bulk series capacitance element and / or the bulk parallel capacitance element can reduce the voltage applied to each variable capacitance element, thereby enabling the use of smaller, less expensive switches in the programmable capacitor array and reducing the risk of switch failure. The bulk parallel capacitance element allows some AC to bypass the variable capacitance element, reducing power loss through the variable capacitance element and thereby reducing the risk of switch failure in the programmable capacitor array. Additionally or alternatively, the bulk parallel capacitance element may be configured to at least partially resonate with the second antenna.

[0179] FIG. 25B shows an example of a series-shunt matching circuit configured for single-ended operation. As mentioned above, in some embodiments, the series-shunt matching circuit shown in FIG. 25B may be configured for differential operation. In either case, the series-shunt matching circuit may include one or more variable capacitance elements connected in series between the amplifier and / or EMI filter (and components located between them and the matching circuit) and the second antenna (and components located between the second antenna and the matching circuit). For example, as shown in FIG. 25B, a series-shunt matching circuit configured for use in the control unit shown in FIG. 24B may be disposed between the coupler and the second balun. As shown in FIG. 25B, the series-shunt matching circuit may include one or more variable capacitance elements connected in series with the amplifier and / or EMI filter (and components located between them and the matching circuit) and shunted to ground. For example, it may include a variable capacitance element located downstream of the coupler and shunted to ground. The single-ended output from the variable capacitance element that is not shunted to ground may be converted to a differential output by a second balun and supplied to the second antenna. If the second antenna is compatible with single-ended operation, the second balun may be omitted, and the single-ended output from the variable capacitance element may be supplied directly to the second antenna (or may be supplied via a component compatible with single-ended operation). As described above in connection with FIG. 25A, the variable capacitance element may include multiple capacitors (e.g., a programmable capacitor array, etc.) and / or a variable capacitor.

[0180] A series-shunt matching circuit may be less susceptible to changes in the impedance of the second antenna than a series matching circuit (e.g., due to metal in the vicinity of the second antenna or environmental loads caused by physical loads on the second antenna). Furthermore, a series-shunt matching circuit may allow the use of components with larger impedances, thereby reducing the generation of energy in harmonics. Additionally, a series-shunt matching circuit is useful because it allows operation at lower currents than a series matching circuit. This is particularly useful when the variable capacitance elements form a capacitance array containing solid-state relays (SSRs), GaN switches, or MEMS switches. For example, using a smaller current can prevent or suppress switch failure. On the other hand, a series matching circuit may have a wider matching range (tuning range) than a series-shunt matching circuit. Therefore, both series and shunt matching circuits have their own unique advantages and usefulness.

[0181] The electronic components (e.g., amplifiers, matching circuits, etc.) disclosed herein may be physically located within, on, or attached to a portion of the control unit (e.g., control unit 30) and / or external device (e.g., external device 11) of the present technology. In some embodiments, as described below with reference to FIGS. 26A-26E, the external device may include a carrier (e.g., a mat) that carries both the control unit and the second antenna. For example, a control unit configured according to the block diagram of FIG. 24A or a control unit configured according to the block diagram of FIG. 24B may be located within a mat or other suitable carrier that includes the second antenna. However, in some embodiments, at least a portion of the control unit may be located separately from the carrier that includes the second antenna. For example, a first portion of the control unit (configured according to the block diagram of FIG. 24A or 24B) may be located on an external device separate from the carrier that includes the second antenna, and a second portion of the control unit may be located on the carrier. The first and second portions may be operatively connected by an appropriate cable or other connection means. This cable, for example, allows the first portion to operate at a distance (e.g., 0.5 meters, 1 meter, 1.5 meters, etc.) from the carrier. In some embodiments, a control unit configured according to the block diagram of FIG. 24B may include a first portion (distant from the carrier) that includes components located upstream of the second balun, and a second portion (located within or near the carrier) that includes the second balun and all components located downstream of it. In some of these embodiments, the second portion of the control unit may include a matching circuit (e.g., the series matching circuit shown in FIG. 25A).

[0182] Any feature of the external system 15 or one or more of its components (e.g., the control unit 30, the external device 11, the second antenna 12, etc.) may vary depending on the intended use of the external system 15. For example, in one use case, the external system 15 may be used by a patient every night for several days, weeks, months, or years. In another use case, the external system 15 may be used in a clinical setting during implantation and / or titration of stimulation parameters of the implantable device 100. During implantation and / or titration, the external system 15 may be used to drive the implantable device 100 to assess its positioning, evaluate the effectiveness of stimulation by particular conductive elements 114 of the implantable device, and determine parameters of the stimulation energy to be delivered during treatment. Requirements associated with home use cases may differ from those associated with clinical use cases, and therefore one or more features of the external system 15 may vary depending on the intended use case. Nevertheless, in some embodiments, an external system 15 configured for home use may have similar features as an external system 15 configured for clinical use.

[0183] 26A-26E illustrate an example of an external device 2600. In some embodiments, the external device 2600 may be configured for use in a clinical environment. Features of the external device 2600 may be generally similar to features of the external device 11 shown in FIG. 2. Any features of the external device 2600 shown in FIGS. 26A-26E may be used in combination with each other or with features of the external device 11 shown in FIG. 2. Conversely, any features of the external device 11 shown in FIG. 2 may be used in combination with features of the external device 2600 shown in FIGS. 26A-26E. Furthermore, although the external device 2600 is described for use in a clinical environment, it may be used in any environment or use case (e.g., in the home, etc.).

[0184] The external device 2600 may include a carrier 2601 containing a substrate 2602 that supports an antenna 2604. Figures 26A and 26B are perspective views of the carrier 2601 of the external device 2600, Figures 26C and 26D are cross-sectional views of the external device 2600, and Figure 26E is a plan view of the antenna 2604 of the external device 2600.

[0185] As shown in FIGS. 26A and 26B , in some embodiments, carrier 2601 may include an upper portion 2603 and a lower portion 2605. The upper portion 2603 and the lower portion 2605 may be integrally formed, permanently secured, or removably secured. The joining edges of the upper portion 2603 and the lower portion 2605 may be joined by adhesive bonding, welding, mechanical fastening, or other means. The lower portion 2605 may be configured to be positioned on a surface beneath a patient (e.g., a surgical table, examination table, sleep surface, etc.). At least a portion of the upper portion 2603 may be configured to be positioned between the lower portion 2605 of carrier 2601 and the patient. As shown in FIG. 26B , the lower portion 2605 may be substantially flat. In some embodiments, the lower portion 2605 of carrier 2601 may define one or more openings 2611 (see FIG. 26B ) configured to receive fasteners for securing carrier 2601 to substrate 2602.

[0186] As shown in FIG. 26A, in some embodiments, the upper portion 2603 may include a generally flat region 2603a and a sloped region 2603b. As shown in FIG. 26C, a substrate 2602 carrying an antenna 2604 may be disposed in the generally flat region 2603a. The flat region 2603a, and thus the substrate 2602 and antenna 2604, may be configured to be disposed between a lower portion 2605 of the carrier 2601 and a patient. The sloped region 2603b and the lower portion 2605 of the carrier 2601 define a contained volume 2617 that may be larger than the contained volume defined by the generally flat region 2603a and the lower portion 2605 of the upper portion 2603 and / or may have a larger cross-sectional area than the cross-sectional area defined by the flat region 2603a. One or more electronic components 2615 (e.g., a control unit, a power supply, etc.) may be located within this contained space 2617 (see FIGS. 26C and 26D). Angled region 2603b may be configured to be located near, but not below, a patient during use. For example, generally flat region 2603a may be configured to be located between the patient's head and a surface below it, and angled region 2603b may be configured to be located to the side or above the patient's head.

[0187] 26A-26D show device 2600 with a single carrier 2601 for carrying substrate 2602 and electronic component 2615; however, as noted above, in some embodiments, device 2600 may include multiple separate carriers. For example, device 2600 may include a first carrier 2601 carrying substrate 2602 and a second, separate carrier 2601 carrying electronic component 2615. Antenna 2604 may be electrically connected to electronic component 2615 via a connector extending between the first and second carriers (see above). Separating antenna 2604 from electronic component 2615 allows electronic component 2615 to be positioned away from the patient's head and / or body, preventing or reducing thermal conduction from electronic component 2615 to the patient. Furthermore, each separate carrier 2601 may be constructed from a different material depending on the specific requirements of that carrier.

[0188] In some embodiments, device 2600 may include cushioning. For example, the cushioning may be supported on carrier 2601 of device 2600, and during use, device 2600 may be positioned near a patient, with the cushioning positioned between carrier 2601 and the patient's head. Even if a patient is asleep while using device 2600, lying on a hard surface for an extended period of time may cause discomfort upon awakening. Therefore, the cushioning may have a low hardness parameter to enhance patient comfort. The cushioning may be supported on substantially flat region 2603a and / or sloped region 2603b. The cushioning may be made of a sufficiently soft material, such as foam. Additionally or alternatively, the cushioning may be configured to dissipate heat from the patient's head.

[0189] The external device 2600 may include one or more controls 2614 to facilitate manipulation by a user. For example, as shown in FIG. 26A, the controls 2614 may be an opening in the carrier 2601 that forms a graspable handle. In a clinical setting where the external device 2600 is used on a patient under anesthesia, the controls 2614 may be used by a medical professional to grasp the external device 2600 and easily change its position relative to the patient.

[0190] The carrier 2601 of the external device 2600 may include materials such as polycarbonate, polymethyl methacrylate, acrylonitrile butadiene styrene, nylon, polylactic acid, polyethylene, polypropylene, polystyrene, polysulfone, and polyethersulfone. The carrier 2601 may be substantially rigid when used in clinical applications. If the external device is intended for nightly use by a patient, a flexible and / or soft substrate and / or carrier may be desirable for patient comfort. However, in clinical applications, the external device 2600 is used for a short time per patient, and the patient is often under anesthesia during use, so comfort requirements are less stringent. Furthermore, in clinical applications, it is desirable for the carrier 2601 to be made of a material that is resistant to liquid penetration and easy to clean to facilitate use on multiple patients. In some embodiments, the carrier 2601 may be made of a material with excellent heat resistance to prevent or reduce deformation of the substrate 2602 during use of the external device 2600.

[0191] The external device 2600 may be configured for use during a procedure to implant an implantable device in a patient's head. This procedure may be performed in an operating room with the patient lying on an operating table. Operating tables often contain significant amounts of material, such as metal or carbon fiber, that may alter the impedance of the antenna 2604. To prevent or reduce the impedance of the antenna 2604 from being altered by the operating table, the external device 2600 may include shielding material. This shielding material may be configured to be disposed between the antenna 2604 and the lower portion 2605 of the carrier 2601 or between the lower portion 2605 of the carrier 2601 and the operating table.

[0192] In some embodiments, the antenna 2604 may be driven at a higher power when used in an operating room compared to when used in a home environment. Driving the antenna 2604 at a higher power may compensate for detuning or preloading of the antenna 2604 that may occur in an operating room. Driving the antenna 2604 at a higher power may cause the control unit and / or the antenna 2604 to generate more heat. To address this concern, the external device 2600 may include insulation 2607 to adjust and / or control heat dissipation from the antenna 2604. As shown in FIGS. 26C and 26D , the insulation 2607 may be disposed between the antenna 2604 and the top 2603 of the carrier 2601 and configured to prevent or reduce heat transfer from the antenna 2604 to the patient. In addition to the locations shown in FIGS. 26C and 26D , the insulation 2607 may be disposed at any suitable location inside and / or outside the carrier 2601. In some embodiments, the insulation 2607 may be comprised of a substantially flat sheet. The insulation 2607 may define one or more openings 2613 (see FIG. 26C) for attachment to the carrier 2601 through fasteners. In some embodiments, the insulation 2607 does not include openings 2613. The insulation 2607 may include high-temperature resistant synthetic fibers, such as aramid fibers, and / or other suitable felt or insulating materials. In some embodiments, the insulation 2607 may be resistant to moisture absorption.

[0193] The substrate 2602 is disposed between the upper portion 2603 and the lower portion 2605 of the carrier 2601. In some embodiments, the substrate 2602 may be disposed between the lower portion 2605 of the carrier 2601 and the thermal insulation 2607. The substrate 2602 may be comprised of a printed circuit board (PCB) substrate. For example, the substrate 2602 may include FR4, CEM1, CEM3, FR2, PET, elastomer, or other suitable PCB substrates. The substrate 2602 may be comprised of a heat-resistant dielectric material. In some embodiments, a substrate suitable for use in a clinical environment may be more rigid than a substrate suitable for use in a home environment. The substrate 2602 may define one or more openings 2616, which may be formed as through-holes. Similar to the openings 2613 in the thermal insulation 2607, the openings 2616 in the substrate 2602 may be configured to receive fasteners to secure the substrate 2602 to the carrier 2601. Apertures 2616 may be configured to receive posts on carrier 2601, for example, to secure carrier 2601 to substrate 2602. In some embodiments, apertures 2613 may be configured to be bonded, glued, welded, or otherwise secured to these posts. In various embodiments, substrate 2602 may define the same number of apertures 2616 as there are apertures 2613 defined in insulation 2607, or may be configured such that apertures 2616 in substrate 2602 align with apertures 2613 in insulation 2607. This allows a single fastener to be fastened through both apertures 2616 in substrate 2602 and apertures 2613 in insulation 2607.

[0194] The fasteners configured to extend through openings 2611 in carrier 2601, openings 2613 in insulation 2607, and / or openings 2616 in substrate 2602 may comprise screws, posts, pillars, nails, or any other suitable fasteners. In various embodiments, carrier 2601 may include the fasteners. For example, the fasteners may be integrally molded with carrier 2601. The fasteners may be comprised of an electrically or magnetically non-conductive material to avoid interference with antenna 2604. By way of example, the fasteners may be comprised of a polymer such as polyetheretherketone. In some embodiments, one or more of openings 2611, 2613, and 2616 may be configured to accept a grommet comprised of a resilient material.

[0195] In some embodiments, carrier 2601 may be configured to be bonded to substrate 2602 and / or thermal insulator 2607. Bonding carrier 2601 to substrate 2602 and / or thermal insulator 2607 may increase the strength and rigidity of device 2600. For example, bonding substrate 2602 to carrier 2601 may prevent or reduce deformation of substrate 2602, which may prevent or reduce unintended changes to the magnetic field generated by antenna 2604.

[0196] 26E, antenna 2604 may have a configuration similar to other antennas disclosed herein (e.g., second antenna 12, antennas 404, 1004, 1204, 1504, 1804, 1904, 2004, 2104, 2204, etc.). For example, antenna 2604 may include a first length 2606 of conductive material forming a first loop 2618, a first sub-loop 2622a, and a second sub-loop 2622b, and a second length 2608 of conductive material forming a second loop 2620. Additionally, antenna 2604 may include a feed 2626 for electrically connecting to a control unit and one or more capacitors 2628 disposed on or near feed 2626 or along first length 2606 and / or second length 2608.

[0197] The width of the antenna 2604 may be based at least in part on the width of the surface on which the antenna 2604 will be placed in a clinical environment. Operating tables are often as narrow as 50 cm (e.g., compared to the 97 cm width of a twin-size bed). As such, the antenna 2604 may be configured to have a smaller width to accommodate use in a clinical environment. For example, an antenna configured for use by a patient at home may have a width of about 20 cm to about 100 cm, e.g., about 70 cm, while an antenna (e.g., antenna 2604) suitable for use in a clinical environment may have a width of about 40 cm to about 55 cm, e.g., about 42 cm. The antenna 2604 may be less than 50 cm wide when configured for placement on a 50 cm wide operating table. In certain embodiments, the width of the antenna 2604 may be about 50 cm, about 48 cm, about 46 cm, about 44 cm, about 42 cm, about 40 cm, about 38 cm, about 36 cm, about 34 cm, about 32 cm, or about 30 cm.

[0198] When configured for use in a clinical environment, the antenna 2604 may be configured to generate an electromagnetic field with a small active volume. During normal sleep, patient movement can cause the implantable device in the patient's head to move relative to the antenna of the external device. However, when the patient is anesthetized or restrained (e.g., in an operating room or during implant placement), there is little or no relative movement between the patient and the external device. Therefore, the relative position of the implant antenna and the external antenna should remain generally constant during use of the external device 2600.

[0199] To facilitate powering the implant-side antenna with a small active volume of electromagnetic field, the carrier 2601 of the external device 2600 may include one or more markings to assist in positioning the patient on or above the external device 2600. For example, as shown in FIG. 26A , the carrier 2601 may include a first marking 2609a and a second marking 2609b (collectively, “markings 2609”), which indicate where the patient's anatomical landmarks (e.g., chin, nose, ears, etc.) should be placed on the external device 2600. The markings 2609 may be comprised of recesses in the carrier 2601, protrusions on the carrier 2601, separate elements fixed to the carrier 2601, material printed on the carrier 2601, etc.

[0200] In some embodiments, the predetermined thresholds of specific absorption rate (SAR) parameters allowed within a patient during use of the external device may be higher for systems used in a clinical environment than for home systems used repeatedly by patients. In clinical environments, controlled exposure regulations may apply. Under these regulations, the peak spatial average SAR threshold averaged over 6 minutes over any 1 gram of tissue excluding the patient's extremities is 8 W / kg, the peak spatial average SAR threshold averaged over 6 minutes over any 10 grams of tissue in the patient's extremities is 20 W / kg, and the average SAR threshold averaged over 6 minutes over the patient's whole body is 0.4 W / kg.

[0201] [summary] While many of the above-described embodiments have been described with respect to systems, devices, and methods for modulating a patient's hypoglossal nerve, the technology is applicable to other applications and approaches, such as modulating other nerves in a patient. Furthermore, in addition to the embodiments described herein, other embodiments are within the scope of the technology. Also, other embodiments of the technology may differ from the configurations, components, or procedures described herein. Thus, those skilled in the art will understand that the technology may include other elements, and that embodiments that do not include some of the features described above with reference to FIGS. 1A-26E are also within the scope of the technology.

[0202] The description of the embodiments of the present technology is not intended to be exhaustive or to limit the technology to the precise form set forth above. Where the context allows, singular terms shall include the plural, and plural terms shall include the singular. While specific embodiments and examples of the present technology have been described above, this is for convenience of explanation only, and those skilled in the art will recognize that various equivalent modifications are possible within the scope of the present technology. For example, steps may be presented in a particular order, but may be performed in a different order in other embodiments. Additionally, various embodiments described herein may be combined to form further embodiments.

[0203] As used herein, terms such as "generally," "substantially," and "about" are used in the sense of approximation, not degree, and take into account inherent variations in measurements and calculations, as would be understood by one of ordinary skill in the art.

[0204] Additionally, in a list of two or more items, unless the word "or" explicitly limits the list to one item at the exclusion of other items, "or" shall be construed to mean: (a) any one item in the list; (b) all items in the list; or (c) any combination of items in the list. The term "comprising" always refers to the inclusion of at least the recited features, and does not exclude the inclusion of more of the same features or additional features of other types. It should also be understood that while specific embodiments have been described for illustrative purposes, various modifications are possible without departing from the present technology. Furthermore, advantages described in connection with a particular embodiment of the present technology may also be exhibited by other embodiments, and not necessarily by all embodiments. Accordingly, this specification and related technology may encompass other embodiments not expressly set forth herein.

Claims

1. 1. A device for use with an implant implanted in a first anatomical region of a patient, comprising: a carrier configured to be disposed on a surface, the carrier having a first region and a second region that do not overlap one another; an antenna carried by the carrier and configured to generate a magnetic field that is denser in the first region of the carrier than in the second region, the magnetic field configured to power the implant when the carrier is placed on the surface and near the patient such that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with a second anatomical region of the patient, the second anatomical region having a lower soft tissue to bone ratio than the first anatomical region, and configured such that when the magnetic field is powering the implant, a specific absorption rate (SAR) parameter in the patient's tissue does not exceed a predetermined threshold.

2. The device of claim 1 , wherein the first region of the carrier receives a greater amount of magnetic flux from the antenna than the second region of the carrier.

3. 3. The device of claim 1 or 2, wherein the magnetic field has a component configured to extend through the antenna of the implant in a direction substantially perpendicular to a radial dimension of the antenna of the implant.

4. The device of claim 3 , wherein the component of the magnetic field is substantially perpendicular to the surface.

5. 5. The device of claim 3 or 4, wherein the component of the magnetic field is configured to extend through the implant antenna in a direction substantially perpendicular to a radial dimension of the implant antenna over a range of head nod angles, head axial angles, head positions, and / or head rotations.

6. A device according to any one of claims 3 to 5, wherein the average strength of said component of said magnetic field is at least 2 A / m within a volume of at least 25 cubic centimetres.

7. 7. The device of claim 1, wherein the magnetic field is configured to deliver between about 5 mW and about 50 mW of power to the implant when the carrier is positioned on the surface and near the patient such that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with the second anatomical region of the patient.

8. 8. The device of claim 7, wherein the magnetic field is configured to deliver about 5 mW to about 50 mW of power to the implant when the carrier is positioned on the surface and near the patient such that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with the second anatomical region of the patient, and the implant is substantially ovoid and has a diameter of about 2 cm to about 4 cm.

9. The device of any one of claims 1 to 8, wherein the first anatomical region comprises the patient's head.

10. The device of any one of claims 1 to 9, wherein the second anatomical region is located below the patient's head.

11. The device of any one of claims 1 to 10, wherein the second anatomical region comprises the neck and / or back of the patient.

12. The device of any one of claims 1 to 11, wherein the second anatomical region has a second electrical conductivity that is greater than the first electrical conductivity of the first anatomical region.

13. 13. The device of claim 1, wherein the second anatomical region is positioned closer to the carrier than the first anatomical region along a dimension substantially perpendicular to the surface.

14. 14. The device of claim 1, wherein the first region of the antenna comprises a first length of conductive material and the second region of the antenna comprises a second length of conductive material.

15. The device of claim 14 , wherein the first length is greater than the second length.

16. 16. The device of claim 14 or 15, wherein the second length forms a single loop.

17. The device of any one of claims 14 to 16, wherein the first length forms at least a first loop and a second loop.

18. 18. The device of claim 17, wherein the second loop is contained within an interior region defined by the first loop.

19. 19. The device of claim 17 or 18, wherein the first loop is electrically connected in series with the second loop.

20. The antenna includes a transition region, the transition region comprising: a first segment configured to carry a radio frequency (RF) current in a first direction, the first segment including a first end of a first length and a first end of a second length; a second segment including a second end of the first length and a second end of the second length configured to conduct a radio frequency (RF) current in a second direction opposite the first direction; The device of any one of claims 14 to 19, wherein at least a portion of the first segment and at least a portion of the second segment overlap along a thickness direction of the antenna in the transition region.

21. 21. The device of claim 20, wherein the first segment and the second segment are disposed at an angle of less than about 30 degrees relative to each other in a plane substantially perpendicular to the thickness direction.

22. 22. The device of claim 20 or 21, wherein the first segment and the second segment are aligned along a thickness direction of the carrier.

23. The device of any one of claims 1 to 22, further comprising at least one capacitor electrically connected to the conductive material.

24. 24. The device of claim 23, wherein the at least one capacitor is electrically connected in series with the conductive material.

25. A device according to any preceding claim, wherein the first region of the carrier is substantially coplanar with the second region of the carrier.

26. A device according to any preceding claim, wherein the surface is a surface on which the patient lies while sleeping.

27. 27. The device of any preceding claim, wherein the first region is located on one side of a center line of the carrier and the second region is located on the other side of the center line of the carrier.

28. 28. The device of claim 27, wherein the direction of current flow through the antenna reverses at the centerline.

29. 29. The device of claim 27 or 28, wherein the centerline substantially bisects the carrier.

30. 30. The device of any one of claims 1 to 29, wherein the antenna has a large quadrupole moment and a small dipole moment such that electromagnetic radiation generates a small electromagnetic field at a large distance from the antenna.

31. 31. The device of any one of claims 1 to 30, wherein the SAR parameter comprises a peak spatial average SAR averaged over a time period of 30 minutes or less in any one gram of tissue of the patient excluding the patient's extremities, and wherein the predetermined threshold is 1.6 W / kg.

32. 32. The device of any one of claims 1 to 31, wherein the SAR parameter comprises a peak spatial average SAR averaged over any 10 grams of tissue in the patient's extremity within a 30 minute time period, and wherein the predetermined threshold is 4 W / kg.

33. 33. The device of any one of claims 1 to 32, wherein the SAR parameter comprises an average SAR averaged over the patient's whole body over a period of no more than 30 minutes, and wherein the predetermined threshold is 0.08 W / kg.

34. 34. The device of any one of claims 1 to 33, wherein the SAR parameters comprise peak spatial average SAR averaged over a time period of 6 minutes or less in any one gram of tissue of the patient excluding the patient's extremities, and wherein the predetermined threshold is 8 W / kg.

35. 35. The device of any one of claims 1 to 34, wherein the SAR parameter comprises a peak spatial average SAR averaged over a time period of 6 minutes or less in any 10 grams of tissue in the patient's extremity, and wherein the predetermined threshold is 20 W / kg.

36. 36. The device of any one of claims 1 to 35, wherein the SAR parameter comprises an average SAR averaged over the patient's whole body over a period of no more than 6 minutes, and wherein the predetermined threshold is 0.4 W / kg.

37. 1. A device for use with an implant implanted in a first anatomical region of a patient, comprising: a carrier configured to be disposed on a surface, the carrier having a first region and a second region that do not overlap one another; an antenna carried by the carrier, the antenna comprising a conductive material having a first length in a first configuration with one or more loops in the first region and a second length in a second configuration with one or more loops in the second region; the first configuration and the second configuration have different amounts of the conductive material; The device, wherein the antenna is configured to generate a magnetic field configured to power the implant when the carrier is positioned on the surface and near the patient such that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with a second anatomical region of the patient, and wherein the magnetic field is configured to prevent a specific absorption rate (SAR) parameter in the patient from exceeding a predetermined threshold when powering the implant.

38. 38. The device of claim 37, wherein the magnetic field has a component configured to extend through the antenna of the implant in a direction substantially perpendicular to a radial dimension of the antenna of the implant.

39. 39. The device of claim 38, wherein the component of the magnetic field is substantially perpendicular to the surface.

40. 40. The device of claim 38 or 39, wherein the component of the magnetic field is configured to extend through the implant antenna in a direction substantially perpendicular to a radial dimension of the implant antenna over a range of head nod angles, head axial angles, head positions, and / or head rotations.

41. A device according to any preceding claim, wherein the average strength of the components of the magnetic field is at least 2 A / m within a volume of at least 25 cubic centimetres.

42. 42. The device of any one of claims 1-41, wherein the magnetic field is configured to deliver between about 5 mW and about 50 mW of power to the implant when the carrier is positioned on the surface and near the patient such that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with the second anatomical region of the patient.

43. The device of any one of claims 1 to 42, wherein the first anatomical region comprises the patient's head.

44. The device of any one of claims 1 to 43, wherein the second anatomical region is located below the patient's head.

45. The device of any one of claims 1 to 44, wherein the second anatomical region comprises the neck and / or back of the patient.

46. 46. ​​The device of any one of claims 1 to 45, wherein the second anatomical region has a larger volume and / or is less rounded than the first anatomical region.

47. 47. The device of any one of claims 1 to 46, wherein the second anatomical region is positioned closer to the carrier than the first anatomical region along a direction substantially perpendicular to the surface.

48. 48. The device of any one of claims 1 to 47, wherein the first region of the antenna comprises a conductive material of a first density and the second region of the antenna comprises a conductive material of a second density.

49. 49. The device of claim 48, wherein the first density is greater than the second density.

50. The device of any one of claims 1 to 49, wherein the second length forms a single loop.

51. The device of any one of claims 1 to 50, wherein the first length forms at least a first loop and a second loop.

52. 52. The device of claim 51, wherein the second loop is disposed within an inner region defined by the first loop.

53. 53. The device of claim 51 or 52, wherein the first loop is electrically connected in series with the second loop.

54. 54. The device of any one of claims 1 to 53, wherein the first configuration and the second configuration differ in at least one of length, number of loops, or loop size.

55. A device according to any preceding claim, wherein the first region of the carrier receives a greater amount of magnetic flux from the antenna than the second region of the carrier.

56. The antenna includes a transition region, the transition region comprising: a first segment configured to carry a radio frequency (RF) current in a first direction, the first segment including a first end of the first length and a first end of the second length; a second segment including a second end of the first length and a second end of the second length configured to conduct a radio frequency (RF) current in a second direction opposite the first direction; 56. The device of any one of claims 1 to 55, wherein at least a portion of the first segment and at least a portion of the second segment overlap along a thickness of the antenna in the transition region.

57. 57. The device of claim 56, wherein the first segment and the second segment are disposed at an angle of less than about 30 degrees relative to each other in a plane substantially perpendicular to the thickness direction.

58. 58. The device of claim 56 or 57, wherein the first segment and the second segment are aligned along a thickness direction of the carrier.

59. The device of any one of claims 1 to 58, further comprising at least one capacitor electrically connected to the conductive material.

60. 60. The device of claim 59, wherein the at least one capacitor is electrically connected in series with the conductive material.

61. A device according to any preceding claim, wherein the first region of the carrier is substantially coplanar with the second region.

62. A device according to any preceding claim, wherein the surface is a surface on which the patient lies while sleeping.

63. 63. The device of any preceding claim, wherein the first region is located on one side of a center line of the carrier and the second region is located on the other side of the center line of the carrier.

64. 64. The device of claim 63, wherein the direction of current flow through the antenna reverses at the centerline.

65. 65. The device of claim 63 or 64, wherein the centerline substantially bisects the carrier.

66. 66. A device according to any preceding claim, wherein the antenna has a large quadrupole moment and a small dipole moment so as to produce an electromagnetic field with less electromagnetic radiation at a greater distance from the antenna.

67. 67. The device of any one of claims 1 to 66, wherein the SAR parameter comprises a peak spatial average SAR averaged over a time period of 30 minutes or less in any one gram of tissue of the patient excluding the patient's extremities, and wherein the predetermined threshold is 1.6 W / kg.

68. 68. The device of any one of claims 1 to 67, wherein the SAR parameter comprises a peak spatial average SAR averaged over any 10 grams of tissue in the patient's extremity within a 30 minute time period, and wherein the predetermined threshold is 4 W / kg.

69. 69. The device of any one of claims 1 to 68, wherein the SAR parameter comprises an average SAR averaged over the patient's whole body over a period of no more than 30 minutes, and wherein the predetermined threshold is 0.08 W / kg.

70. 70. The device of any one of claims 1 to 69, wherein the SAR parameters comprise peak spatial average SAR averaged over a time period of 6 minutes or less in any one gram of tissue of the patient excluding the patient's extremities, and wherein the predetermined threshold is 8 W / kg.

71. 71. The device of any one of claims 1 to 70, wherein the SAR parameters comprise peak spatial average SAR averaged over any 10 grams of tissue in the patient's extremity over a time period of 6 minutes or less, and wherein the predetermined threshold is 20 W / kg.

72. 72. The device of any one of claims 1 to 71, wherein the SAR parameter comprises an average SAR averaged over the patient's whole body over a period of no more than 6 minutes, and wherein the predetermined threshold is 0.4 W / kg.

73. 1. A device for use with an implant implanted in a first anatomical region of a patient, comprising: a carrier configured to be disposed on a surface, the carrier having a first side and a second side opposite the first side; and an antenna carried by the carrier; the carrier includes a first region located between the first side and a centerline and a second region located between the second side and the centerline, wherein current flows in a first direction through the first region and in a direction opposite to the first direction through the second region such that current flow through the antenna reverses at the centerline; 1. A device comprising: a carrier having an antenna comprising a conductive material that forms at least two first loops in the first region of the carrier and a second loop in the second region of the carrier; wherein when the carrier is positioned on the surface and near the patient such that the first region of the carrier is aligned with the first anatomical region and the second region of the carrier is aligned with a second anatomical region of the patient, the antenna generates a magnetic field configured to power the implant; and wherein when the magnetic field is powering the implant, a specific absorption rate (SAR) parameter in the patient does not exceed a predetermined threshold.

74. 74. The device of claim 73, wherein the antenna is configured to generate a magnetic field having a component substantially aligned with a width dimension of the antenna.

75. 75. The device of claim 74, wherein the component of the magnetic field is substantially perpendicular to the surface.

76. 76. The device of claim 74 or 75, wherein the component of the magnetic field is configured to extend through the antenna of the implant in a direction substantially perpendicular to a radial dimension of the antenna over a range of head nod angles, head axial angles, head positions, and / or head rotations.

77. 77. A device according to any preceding claim, wherein the component has an average intensity at the implant of at least 2 A / m when the magnetic field is powering the implant.

78. 78. The device of any one of claims 1 to 77, wherein the components have an average intensity of at least 2 A / m over a volume of at least 25 cubic centimeters when the magnetic field is powering the implant.

79. 79. The device of any one of claims 1 to 78, wherein at least two of the first loops are electrically connected in series to the second loop.

80. 80. The device of any one of claims 1 to 79, wherein at least two of the first loops are electrically connected in series with each other.

81. 81. The device of any one of claims 1 to 80, wherein each of at least two of the first loops is configured to carry current in a first direction and the second loop is configured to carry current in a second direction opposite to the first direction.

82. The device of any one of claims 1 to 81, wherein the at least two first loops comprise a major loop and a minor loop.

83. 83. The device of claim 82, wherein the major loop circumscribes a first area and the minor loop circumscribes a second area that is smaller than the first area.

84. 84. The device of any one of claims 81 to 83, wherein the at least two first loops include a major loop and at least two minor loops.

85. 85. The device of claim 84, wherein the at least two minor loops are spaced apart along a length of the carrier, the length of the carrier being substantially perpendicular to the width of the carrier.

86. 86. The device of claim 84 or 85, wherein the at least two minor loops encircle substantially equal areas.

87. 87. A device according to any preceding claim, wherein the first region of the carrier has a greater amount of magnetic flux from the antenna than the second region of the carrier.

88. the first region of the antenna comprises a first length of conductive material, the second region of the antenna comprises a second length of conductive material, the antenna further comprising a transition region, the transition region comprising: a first segment configured to carry a current in a first direction, the first segment including a first end of a first length and a first end of a second length; a second segment configured to conduct current in a second direction, the second segment including a second end of the first length and a second end of the second length; 88. The device of any one of claims 1 to 87, wherein at least a portion of the first segment and at least a portion of the second segment overlap along a thickness of the antenna in the transition region.

89. 89. The device of claim 88, wherein the first segment and the second segment are disposed at an angle of less than about 30 degrees relative to one another in a plane substantially perpendicular to the thickness direction.

90. 90. The device of claim 88 or 89, wherein the first segment and the second segment are aligned along a thickness direction of the carrier.

91. A device according to any preceding claim, wherein the antenna is configured to operate at a frequency of about 6.78 MHz.

92. 92. A device according to any preceding claim, wherein the antenna comprises a capacitor electrically connected to the conductive material to produce a real input impedance of the antenna at the operating frequency.

93. 93. The device of any one of claims 1 to 92, wherein the antenna comprises a capacitor electrically connected in series with the conductive material.

94. 94. The device of any one of claims 1 to 93, wherein the antenna comprises a capacitor electrically connected in parallel with the conductive material.

95. 95. The device of any one of claims 92 to 94, wherein the capacitor has a capacitance of about 500 pF to about 2000 pF.

96. 96. The device of any one of claims 92 to 95, wherein the capacitor has a variable capacitance.

97. 97. The device of any one of claims 92 to 96, wherein the antenna comprises a plurality of capacitors electrically connected in series with the conductive material.

98. 98. The device of claim 97, wherein adjacent ones of the plurality of capacitors are spaced apart along the length of the conductive material.

99. 99. The device of claim 97 or 98, wherein the plurality of capacitors comprises from about 8 to about 15 capacitors.

100. 100. The device of any one of claims 97 to 99, wherein at least two of the plurality of capacitors have different capacitances.

101. A device according to any preceding claim, wherein the maximum voltage of the antenna is 600V or less.

102. 102. A device as claimed in any one of claims 97 to 101, wherein the voltage across a length of the conductive material between a first pair of capacitors of the plurality of capacitors is substantially equal to the voltage between a second pair of capacitors of the plurality of capacitors.

103. The device of any one of claims 1 to 102, wherein the first anatomical region is the patient's head.

104. The device of any one of claims 1 to 103, wherein the second anatomical region is the patient's neck.

105. The device of any one of claims 1 to 104, wherein the second anatomical region is the patient's back.

106. 106. The device of any one of claims 1 to 105, wherein the second anatomical region has a greater soft tissue to bone ratio than the first anatomical region.

107. 107. The device of any one of claims 1 to 106, wherein the second anatomical region is positioned closer to the carrier than the first anatomical region along a dimension substantially perpendicular to the surface.

108. A device according to any preceding claim, wherein the carrier comprises a fabric.

109. A device according to any preceding claim, wherein the carrier comprises perforated material.

110. A device according to any preceding claim, wherein the carrier comprises a foam material.

111. The device of any one of claims 1 to 110, wherein the carrier comprises at least two layers.

112. 112. The device of claim 111, wherein the at least two layers comprise different materials.

113. 113. The device of claim 111 or 112, wherein the conductive material is disposed between the at least two layers.

114. The device of any one of claims 1 to 113, wherein the carrier comprises a conductive material.

115. A device according to any preceding claim, wherein the carrier comprises a ferromagnetic material.

116. A device according to any preceding claim, wherein the antenna comprises a substrate carrying the conductive material, the substrate being carried by the carrier.

117. 117. The device of claim 116, wherein the substrate comprises polyimide.

118. A device according to any preceding claim, wherein the antenna has a large quadrupole moment and a small dipole moment such that electromagnetic radiation generates a small electromagnetic field at a distance from the antenna.

119. 119. The device of any one of claims 1 to 118, wherein the SAR parameters comprise peak spatial average SAR averaged over a time period of 30 minutes or less in any one gram of tissue of the patient excluding the patient's extremities, and wherein the predetermined threshold is 1.6 W / kg.

120. 120. The device of any one of claims 1 to 119, wherein the SAR parameter comprises a peak spatial average SAR averaged over any 10 grams of tissue in the patient's extremity over a time period of 30 minutes or less, and wherein the predetermined threshold is 4 W / kg.

121. 121. A device according to any preceding claim, wherein the SAR parameter comprises an average SAR averaged over the patient's whole body over a period of no more than 30 minutes, and wherein the predetermined threshold is 0.08 W / kg.

122. 122. The device of any one of claims 1 to 121, wherein the SAR parameters include peak spatial average SAR averaged over a time period of 6 minutes or less in any 1 gram of tissue excluding the patient's extremities, and wherein the predetermined threshold is 8 W / kg.

123. 123. The device of any one of claims 1 to 122, wherein the SAR parameter comprises a peak spatial average SAR averaged over any 10 grams of tissue in the patient's extremity over a time period of 6 minutes or less, and wherein the predetermined threshold is 20 W / kg.

124. 124. A device according to any one of claims 1 to 123, wherein the SAR parameter comprises an average SAR averaged over the whole body of the patient over a period of no more than 6 minutes, and wherein the predetermined threshold is 0.4 W / kg.

125. The neuromodulation system An external system, An external device comprising a device according to any one of claims 1 to 124, wherein the carrier of the external device is configured to be placed extracorporeally between a patient and a surface on which the external device is placed; a control unit electrically connected to an antenna of the external device, the control unit configured to supply a radio frequency (RF) current to the antenna so that the antenna generates a magnetic field; 1. A neuromodulation system comprising: an implantable neuromodulation device configured to be implanted in a first anatomical region of the patient, the implantable neuromodulation device comprising a second antenna and a lead extending from the second antenna and carrying an electrode, the second antenna configured to inductively couple with an antenna of the external device when positioned within a magnetic field generated by the antenna of the external device to induce a radio frequency (RF) current in the second antenna.

126. 126. The neuromodulation system of claim 125, wherein the implantable neuromodulation device does not include a battery.

127. A neuromodulation system according to any one of claims 1 to 126, wherein the radio frequency (RF) current induced in the second antenna is supplied to the electrode carried by the lead.

128. 128. The neuromodulation system of any one of claims 1 to 127, wherein the implantable neuromodulation device is configured to deliver electrical stimulation energy from the electrodes to tissue in the first anatomical region of the patient.

129. 129. The neuromodulation system of claim 128, wherein the tissue is the patient's hypoglossal nerve.

130. 130. The neuromodulation system of claim 128 or 129, wherein the tissue is the patient's genioglossus muscle.

131. 131. A neuromodulation system according to any one of claims 1 to 130, wherein the control unit comprises a variable matching circuit.

132. 132. The neuromodulation system of claim 131, wherein the variable matching circuit is configured to change the impedance presented to the antenna of the external device.

133. 133. The neuromodulation system of claim 131 or 132, wherein the variable matching circuit is configured to optimize the impedance presented to the antenna of the external device.

134. 134. The neuromodulation system of any one of claims 131 to 133, wherein the variable matching circuit comprises a plurality of capacitors and a plurality of switches.

135. 135. The neuromodulation system of any one of claims 131 to 134, wherein the variable matching circuit is configured to selectively activate or deactivate each of the plurality of capacitors via the plurality of switches.

Images