Antenna configuration

Abstract

Power is transmitted to an implanted receiving coil oriented such that an axis of the receiving coil is parallel to skin of a subject. A transmitting coil is in a housing, which is placed against the skin. A central axis of the transmitting coil is perpendicular to the skin. A portion of the transmitting coil is over the receiving coil. A first distance, from the axis of the transmitting coil to a center of the receiving coil, is greater than a second distance, from the axis of the transmitting coil to an inner edge of the portion of the transmitting coil. The first distance is less than a third distance, from the axis of the transmitting coil to an outer edge of the portion of the transmitting coil. Circuitry powers the implant by driving current through the transmitting coil that induces current is the receiving coil.

1 - 63 . (canceled) 
     
     
         64 . Apparatus for use with a medical implant that comprises a receiving coil, the apparatus comprising:
 a flexible housing configured to be placed against skin of a subject;   a flexible transmitting coil disposed in the housing;   control circuitry configured to transmit power to the medical implant by driving a current through the transmitting coil that induces an induced current in the receiving coil;   a sensor coupled to the control circuitry, the sensor configured to determine an extent of divergence of (a) a resonance frequency of the transmitting coil when the transmitting coil is flexed from (b) a nominal resonance frequency of the transmitting coil, occurring in the absence of any forces applied to the transmitting coil, and configured to output a signal according to the determination; and   one or more electrical components, coupled to the control circuitry and configured to tune the resonance frequency of the transmitting coil in response to the determination of the sensor.   
     
     
         65 . The apparatus according to  claim 64 , wherein the control country is configured to set the frequency of the current output by the control circuitry to be between 1 and 20 MHz. 
     
     
         66 . The apparatus according to  claim 64 , wherein the flexible transmitting coil is configured to flex such that it can substantially conform to a lateral wall of a cylinder having a diameter between 8 and 50 cm. 
     
     
         67 . The apparatus according to  claim 64 , wherein the sensor comprises a phase detector, configured to (a) determine a phase difference between the phase of the current output by the control circuitry, and the phase of either a current or a voltage on at least one component of the transmitting coil, wherein the phase difference is due to flexing of the transmitting coil, and (b) output a signal according to the determination. 
     
     
         68 - 71 . (canceled) 
     
     
         72 . The apparatus according to  claim 64 , wherein at least one of the one or more electrical components is a variable capacitor, wherein the control circuitry is configured to vary a capacitance of the variable capacitor according to the signal output by the sensor, and wherein the resonance frequency of the transmitting coil varies according to the variation of the capacitance of the variable capacitor. 
     
     
         73 . The apparatus according to  claim 64 , further comprising a plurality of switches, each switch coupled to a respective one of the electrical components. 
     
     
         74 . The apparatus according to  claim 73 , wherein the control circuitry is configured to tune the resonance frequency of the transmitting coil, according to the signal output by the sensor, by activating at least one of the plurality of switches to facilitate or inhibit current flow through the respective electrical component. 
     
     
         75 . The apparatus according to  claim 74 , wherein the control circuitry is configured to dither the resonance frequency of the transmitting coil by repeatedly activating and deactivating the at least one of the plurality of switches to facilitate or inhibit current flow through the respective electrical component. 
     
     
         76 . (canceled) 
     
     
         77 . The apparatus according to  claim 73 , wherein the one or more electrical components is a plurality of inductors, coupled in series. 
     
     
         78 . (canceled) 
     
     
         79 . The apparatus according to  claim 77 , wherein a first one of the inductors has an inductance of 1.5-2.5 times an inductance of another one of the inductors. 
     
     
         80 - 81 . (canceled) 
     
     
         82 . The apparatus according to  claim 77 , wherein the control circuitry is configured such that when the extent of divergence of (a) the resonance frequency of the transmitting coil when the transmitting coil is flexed from (b) the nominal resonance frequency of the transmitting coil is reduced, current is allowed to pass through at least one of the inductors and current is inhibited from passing through at least another one of the inductors. 
     
     
         83 . The apparatus according to  claim 73 , wherein the one or more electrical components is a plurality of capacitors coupled in parallel. 
     
     
         84 . (canceled) 
     
     
         85 . The apparatus according to  claim 83 , wherein a first one of the capacitors has a capacitance of 1.5-2.5 times a capacitance of another one of the capacitors. 
     
     
         86 - 87 . (canceled) 
     
     
         88 . The apparatus according to  claim 83 , wherein the control circuitry is configured such that when the extent of divergence of (a) the resonance frequency of the transmitting coil when the transmitting coil is flexed from (b) the nominal resonance frequency of the transmitting coil is reduced, current is allowed to pass through at least one of the capacitors and current is inhibited from passing through at least another one of the capacitors. 
     
     
         89 - 96 . (canceled) 
     
     
         97 . The apparatus according to  claim 73 , wherein:
 the control circuitry is configured to activate the switches by applying a respective voltage of 30-300 volts to each switch,   the switches comprise transistors, acting as diodes, having respective capacitances that are dependent on the respective voltage applied to each switch.   
     
     
         98 . The apparatus according to  claim 97 , wherein the control circuitry is configured to apply the respective voltages to the respective switches at a voltage of 50-200 volts. 
     
     
         99 . The apparatus according to  claim 73 , wherein:
 the control circuitry is configured to activate the switches by applying a respective voltage of 30-300 volts to each switch, and   the switches comprise transistors, which behave in their off states as variable capacitors, having respective capacitances that are dependent on the respective voltage applied to each switch.   
     
     
         100 . The apparatus according to  claim 99 , wherein the control circuitry is configured to apply the respective voltages to the respective switches at a voltage of 50-200 volts. 
     
     
         101 . The apparatus according to  claim 64 , further comprising the medical implant. 
     
     
         102 . (canceled)