Patent ID: 8547335

Claim:
An input device for use with a computer system, the input device comprising: a pad comprising: a first antenna providing power to a portable unit; a radio frequency transmitter; a radio frequency receiver; a data link transferring data between the pad and the computer system; and an array of antennas transmitting and receiving radio frequency signals for tracking a location of the portable unit, wherein a phase and power of signals received in each array element of the antenna array depends on said signal's relative position from the portable unit; wherein a location of the portable unit in three-dimensional space relative to the pad is calculated by a processor device interpreting the radio frequency signals transmitted from the portable unit to the antenna array as coordinates in three-dimensional space; wherein the processor device uses the coordinates to update a corresponding position and movement of a cursor displayed on a screen of the computer system; and the portable unit operating without a battery within radio frequency range of the array of antennas, said portable unit comprising: memory storing an identifier; a second antenna; and electronic circuitry operably coupled with the second antenna.