Wireless communication with a medical implant

An apparatus for providing transdermal wireless communication in a selected direction, said apparatus comprising:

• medical implant circuitry;
• a transceiver coupled to the medical implant circuitry;
• a first metal surface disposed in a plane perpendicular to the selected direction, the first metal surface having an end portion, and a base portion, and
• a first planar radiating element tuned to a first frequency and disposed on a dielectric layer above the first metal surface, the first planar radiating element having
• a first reactive portion at a first end thereof,
• a second reactive portion at a second end thereof, and
• a first planar radiating strip extending between the first reactive portion and the second reactive portion;
• and
• a feed structure in electrical communication with the transceiver and the first planar radiating strip for providing the carrier signal to the first planar radiating strip.

An apparatus for providing wireless communication across the skin of a patient, the apparatus comprising:

• medical implant circuitry;
• a transceiver coupled to the medical implant circuitry;
• a feed configured to receive a signal from the transceiver;
• a planar radiating element coupled to the feed, the planar radiating element supporting an electric field distribution;
• and
• a grounded field stop disposed to block radiation from selected portions of the electric field distribution.

A method for providing transdermal communication, the method comprising:

• causing a current on an antenna implanted inside a patient, the antenna supporting an electromagnetic field having a near-field component and a far-field component;
• shielding the near-field component with a grounding structure, thereby trapping energy contained in the near-field component and reducing the extent to which the energy in the near-field component interacts with the patient;
• and
• allowing the propagation of the far-field component through the skin of the patient.

A method of providing wireless communication between a medical implant in a patient and a base station, the method comprising:

• causing an antenna on the medical implant to launch a wave having a first portion in a first direction and a second portion in a second direction, the first and second portions having differing magnitudes, wherein a portion of the first portion enters a biological waveguide defined by a peripheral layer of the body of the patient, the biological waveguide having a first permittivity that differs from the permittivity of the medium surrounding the base station;
• whereby the wave launched into the biological waveguide becomes a guided wave having an energy, and wherein as the guided wave propagates in the biological waveguide, a portion of the energy escapes the biological waveguide and enters the medium surrounding the base station;
• and
• wherein the ratio of energy escaping the biological waveguide to the energy remaining in the biological waveguide depends on the ratio between the permittivity of the biological waveguide and the permittivity of the medium surrounding the base station.

A method of determining a preferred patient orientation for establishing communication between a medical implant inside a patient and a base station outside the patient, the method comprising:

• following healing of an incision caused by implantation of a medical implant inside a patient, determining an angle between an implant axis of the implant and a patient axis of the patient;
• on the basis of the angle, determining an optimal orientation of the patient relative to the base station for establishing wireless communication between the medical implant and the base station;
• and
• providing, to the patient, information representative of the optimal orientation.

An apparatus for providing energy to first and second antennas, the apparatus comprising:

• a first section of a microstrip transmission line, the first section extending from a feedpoint along an axis;
• a first load for coupling to the first antenna, the first load being connected to a distal end of the first section;
• a second section of microstrip transmission line, the second section extending along the axis and having a proximal end connected to the first pair of microstrip transmission line stubs;
• and
• a second load connected to a distal end of the second section for coupling to the second antenna;
• wherein the lengths of the first and second sections are selected to cause an electromagnetic wave having a first frequency to encounter an impedance mismatch at the first load and an impedance match at the second load, and to cause an electromagnetic wave having a second frequency to encounter an impedance mismatch at the second load and an impedance match at the first load.

An apparatus for providing energy to first and second antennas, the apparatus comprising:

• a first section of a microstrip transmission line, the first section extending from a feedpoint along an axis;
• a first load for coupling to the first antenna, the first load being connected to a distal end of the first section;
• a second section of microstrip transmission line extending from the feedpoint and along a direction parallel to and offset from the axis;
• and
• a second load for coupling to the second antenna, the second section being connected to a distal end of the second section;
• wherein the lengths of the first and second sections are selected to cause an electromagnetic wave having a first frequency to encounter an impedance mismatch at the first load and an impedance match at the second load, and to cause an electromagnetic wave having a second frequency to encounter an impedance mismatch at the second load and an impedance match at the first load.