Vector measuring aerial arrays for magnetic induction communication systems

• US 6,134,420 A
• Filed: 01/22/1998
• Issued: 10/17/2000
• Est. Priority Date: 11/01/1996
• Status: Expired due to Fees

• Current Assignee: Plantronics, Inc. (HP Inc.)
• Original Assignee: Plantronics, Inc. (HP Inc.)
• Inventors: Huddart, David, Flowerdew, Peter M.
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US09/010,807
• Time in Patent Office: 999 Days
• Field of Search: 343/867, 343/788, 455/41, 455/129, 455/269, 455/562, 455/274, 455/517
• US Class Current: 455/41.1
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H04B 5/22 Capacitive coupling
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/263 Multiple coils at either side
• CPC Class Codes: H04B 5/266 One coil at each side, e.g. with primary and secondary coils
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04B 7/04 using two or more spaced independent antennas
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity

Abstract

A wireless communication system automatically aligns a magnetic induction field to establish a two-way communication link between a stationary base unit located, for example, at a user'"'"'s work station, and a remote unit worn by the user, for example, as a headset or body pack. At any point in time, the base unit and the remote unit have an arbitrary relative orientation to each other. The base unit senses this orientation, then aligns the magnetic induction field to maintain the communication link with the remote unit. In one embodiment, the base unit preferably includes an aerial array having a number of mutually orthogonal windings. Each winding produces a signal when a magnetic induction field generated by the remote unit passes through the base unit. A selector module selects the longitudinal axis of the winding with the strongest signal as an approximation of a direction vector defining the orientation of the magnetic induction field relative to the base unit. In another embodiment, the base unit preferably includes an aerial array comprising three orthogonal windings disposed about a spherical core. A selector module selects one or more windings for transmitting a magnetic field that rotates in a plane orthogonal, i.e., "crossed field," to the direction vector defining the orientation of the received field relative to the base unit.

Claims

1. A magnetic inductive communication system that maintains a communication link between a base unit and a remote unit having a relative orientation to each other that changes over time, comprising:

a remote unit having at least one aerial for transmitting a first magnetic induction field and for receiving a second magnetic induction field, and

a base unit including;

a multi-axis aerial array for transmitting the second magnetic induction field and for receiving the first magnetic induction field, the multi-axis aerial array having a plurality of windings, each producing a first signal in response to the first magnetic induction field that represents at least one component of a direction vector defining an orientation of the first magnetic induction field in 3-dimensional space;

a selector module having a plurality of inputs and outputs, the selector module inputs coupled to the windings for selecting at least one of the plurality of windings to transmit the second magnetic induction field along the direction vector; and

a drive module having a plurality of inputs and outputs, the drive module inputs coupled to the selector module outputs for receiving the first signals of the selected windings, the drive module outputs coupled to the windings for generating a second signal in at least one winding, the second signal proportional to the first signal of the winding for generating the second magnetic induction field having substantially the same orientation as the first magnetic induction field.

2. The system of claim 1, wherein the longitudinal axis of the winding receiving the strongest first signal in response to first magnetic induction field is selected by the selector module as an approximation to the direction vector defining the orientation of the first magnetic induction field in 3-dimensional space.

3. The system of claim 1, wherein the second magnetic induction field rotates in a plane substantially orthogonal to the direction vector, and the second magnetic field induces a signal in a first winding in the remote unit that is located proximate to and orthogonal with a second winding.

4. The system of claim 3, wherein the first winding receives the second magnetic induction field and the second winding transmits the first magnetic induction field.

5. The system of claim 3, wherein the windings in the remote unit are mutually orthogonal and wound on a single permeable core to form a dual-axis aerial array.

6. The system of claim 1, wherein the remote unit includes a single winding that receives and transmits the first and second magnetic induction fields, respectively.

7. The system of claim 1, wherein the remote unit includes a single-axis aerial having a first winding for receiving the first magnetic induction field and a second winding, co-axial with the first winding, for transmitting the second magnetic field.

8. The system of claim 1, wherein the remote unit includes two mutually orthogonal solenoid aerials each having a single winding.

9. The system of claim 1, wherein the first magnetic induction field is a quasi-static field.

10. The system of claim 1, wherein the multi-axis aerial array comprises three mutually orthogonal single-axis solenoid aerials each having a single winding.

11. The system of claim 1, wherein the multi-axis aerial array comprises three mutually orthogonal windings wound on a single permeable core.

12. The system of claim 11, wherein the permeable core is spherical.

13. A magnetic inductive communication system that maintains a communication link between a base unit and a remote unit having a relative orientation to each other that changes over time, comprising:

a remote unit including at least one aerial for transmitting a first magnetic induction field and for receiving a second magnetic induction field, and

a base unit including;

a tri-axis aerial array for transmitting the second magnetic induction field and for receiving the first magnetic induction field, the tri-axis aerial array including at least three mutually orthogonal windings disposed about a spherical, permeable core, at least one winding producing a first signal in response to the first magnetic induction field that represents at least one component of a direction vector defining the orientation of the first magnetic induction field in 3-dimensional space;

selector module having a plurality of inputs and outputs, the selector module inputs coupled to the windings for selecting the winding receiving a strongest first signal to transmit the second magnetic induction field along the direction vector; and

a drive module having a plurality of inputs and outputs, the drive module inputs coupled to the selector module outputs for receiving the first signal of the winding having the strongest first signal, the drive module outputs coupled to the windings for generating a second signal in at least one winding, the second signal proportional to the first signal for generating the second magnetic induction field having substantially the same orientation as the first magnetic induction field.

14. A method of maintaining a communication link between a base unit and a remote unit having a relative orientation to each other that changes over time, comprising the steps of:

generating a first magnetic induction field and receiving a second magnetic induction field from at least one aerial in a remote unit;

producing a signal, in at least one aerial in a base unit in response to the first magnetic induction field, that represents at least one component of a direction vector defining an orientation of the first magnetic induction field in 3-dimensional space;

selecting, in response to the produced signal, at least one aerial in the base unit to transmit the second magnetic induction field along the direction vector; and

transmitting the second magnetic induction field from the selected aerial in the base unit, the second magnetic induction field having substantially the same orientation as the first magnetic induction field for establishing the magnetic induction duplex link with the remote unit.

15. The method of claim 14, wherein selecting at least one aerial comprises selecting the aerial in the base unit receiving the strongest signal in response to the first magnetic induction field as an approximation to the direction vector.

16. The method of claim 14, wherein generating from the base unit a second magnetic induction field comprises generating a field that rotates in a plane substantially orthogonal to the direction vector and that induces in the remote unit a signal in a first aerial located proximate to, and orthogonal with, a second aerial for transmitting the first magnetic induction field.