Patent ID: 7864157

Claim:
A device for sensing the movement of a human interface device HID, comprising: two or more base station transceivers that each transmit radio signals at different selected frequencies to the HID to trigger retransmission of responsive radio signals back from a corresponding pair of transceivers disposed in the HID, wherein the pair of transceivers disposed in the HID are each coupled to a respective antenna, the HID antennae being mounted at fixed locations spaced apart on the HID; each base station transceiver configured to transmit a corresponding first radio signal at a respective one of the selected frequencies for reception and retransmission by the corresponding HID transceiver; each base station transceiver further configured to receive and detect the corresponding retransmitted radio signal back from the corresponding HID transceiver; and processing means coupled to each of the base station transceivers for generating a respective output signal that changes logical state responsive to the received retransmitted radio signals received from the corresponding HID transceiver, so that the output signal of a first one of the base station transceivers exhibits a first frequency proportional to a distance between the first base station and a first corresponding HID transceiver; and the output signal of a second one of the base station transceivers exhibits a second frequency proportional to a distance between the second base station and a second corresponding HID transceiver; and second processing means for calculating movement of the HID based on the first and second output signals.