Patent ID: 7353089

Claim:
A motorized cart controlled by a radio frequency signal comprising: a receiver configured to detect a signal emitted from a transmitter; a signal processor, in communication with the receiver, configured to determine a relative position of the transmitter based on a phase difference between the signal received on a first antenna and the signal received on a second antenna, and to generate first and second drive control signals from the signals received on the first and second antennas; and motor control circuitry, in communication with the signal processor, configured to drive a first drive motor based on the first drive control signal and drive a second drive motor based on the second drive control signal so as to move a location of the motorized cart, wherein the motorized cart maintains a predetermined distance from the transmitter, and further wherein the first and second drive control signals prevent the first and second drive motors from moving the cart when the cart is within a predetermined distance from the transmitter.