System and method for powering, controlling, and communicating with multiple inductively-powered devices

• US 6,263,247 B1
• Filed: 11/09/1999
• Issued: 07/17/2001
• Est. Priority Date: 06/09/1998
• Status: Expired due to Term

• Current Assignee: North Carolina State University (University of North Carolina System)
• Original Assignee: North Carolina State University (University of North Carolina System)
• Inventors: Nagle, H. Troy, Kelley, Arthur W., Mueller, Jeffrey S., Gyurcsik, Ronald S.
• Primary Examiner(s): Schaetzle, Kennedy
• Application Number:
  US09/436,680
• Time in Patent Office: 616 Days
• Field of Search: 607/60, 607/2, 607/18, 607/32, 607/33, 607/61, 607/59, 600/301, 600/407, 600/483, 600/509, 600/513, 128/903, 332/149, 332/178, 340/10.34, 340/825.69, 340/825.63, 340/870.18, 340/870.01, 340/870.32, 340/573.1, 340/870.11
• US Class Current: 607/60
• CPC Class Codes: A61N 1/3787 from an external energy source
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/402 the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge

Abstract

Magnetic Vector Steering (MVS) and Half-Cycle Amplitude Modulation (HCAM) are novel techniques which enhance the powering and control of multiple arbitrarily oriented implant devices. Together, these techniques enable arbitrarily oriented implants to receive power and command, programming, and control information in an efficient manner that preserves battery life and transmission time while reducing overall implant device bulk. By steering the aggregate magnetic field from a near-orthogonal set of AC-energized coils, selected implants can be powered or communicated with at desired times. Communication with individual implants can also be enhanced through half-cycle amplitude modulation—a technique that allows bit rates up to twice the energizing frequency. Unlike prior art systems, power and data transfer can be realized over the same frequency channel.

Claims

1. A system for inductively powering, controlling, and communicating with a plurality of biomedical implants comprising:

(a) a plurality of inductively powered biomedical implants positioned about a region of interest;

(b) an external coil assembly for the purpose of directing a magnetic field toward an implant of interest; and

(c) half-cycle amplitude modulation means coupled to said external coil assembly for transmitting data at up to twice the coil assembly power carrier frequency;

wherein said external coil assembly targets individual inductively powered implants using a steerable magnetic vector to direct the magnetic field of the energizing coil assembly to the inductively powered implant of interest.

2. The system of claim 1 wherein said external coil assembly comprises:

(a) an energizing coil for inductively powering said implants;

(b) magnetic field sensing means coupled to said energizing coil for determining the strength and phase of said energizing coil'"'"'s magnetic field;

(c) a pulse width modulation phasing circuit having;

(i) gain compensation means for maintaining a prescribed current within said energizing coil; and

(ii) phase compensation means for maintaining a fixed phase delay between said energizing coil and a clock source; and

(d) a power amplifier coupled to said pulse width modulation phasing circuit for amplifying the pulse width modulation phasing circuit output signal in order to drive said energizing coil.

3. The system of claim 2 wherein one or more energizing coils are linked together such that said implants may be arbitrarily oriented about said region of interest, and are powered by said one or more energizing coils at the same frequency and phase or phase ±

II.

4. The system of claim 3 wherein said half-cycle amplitude modulation means comprises:

(a) an energizing circuit comprised of said energizing coil coupled to a resonating capacitance driven by an AC power source, wherein said energizing coil is tap-able;

(b) a second inductive coil coupled to a tap point on the tap-able energizing coil, said second inductive coil having an effective inductance equivalent to a tapped section of the tap-able energizing coil;

(c) a first bi-lateral switch coupled to the tap-able energizing coil;

(d) a second bi-lateral switch coupled to the second inductive coil;

(e) modulation control means coupled to said switches for current steering; and

(f) current sensing means coupled to said modulation control means for detecting zero crossings of the energizing current waveform, such that bit transitions occur with every half-cycle of a power carrier reference signal when the magnetic field is modulated at instants when the energizing coil current is zero.