High-accuracy and low-power tracking system for mobile devices

A wireless link for establishing the position of a second device with respect to a first device, the wireless link comprising:

• a first transceiver circuit in the first device including
• a beacon generator to generate the beacon at a particular frequency and direction,
• an antenna to transmit the beacon and, where the second device lies within a range of directions of the beacon, receive the reflected beacon, and
• an injection-locked oscillator having an input coupled to the antenna to lock to the reflected beacon when the reflected beacon has a frequency value within a locking range of the oscillator;
• and
• a second transceiver circuit in the second device including a reflective antenna to receive a beacon of a beacon frequency from a first direction and reflect the beacon as a reflected beacon in the opposite direction.

A method of tracking a second electronic device with respect to a first electronic device, the method comprising:

• setting an oscillator signal for an injection-locked oscillator to a natural frequency value;
• transmitting a beacon at a beacon frequency value, the beacon frequency value different from the natural frequency value by an offset value;
• receiving a reflected beacon corresponding to the transmitted beacon when the second electronic device lies within a range of directions of the beacon;
• injecting the received reflected beacon into the injection-locked oscillator;
• and
• locking to the reflected beacon when the reflected beacon has a frequency value within locking range of the oscillator.