DETERMINING AN OBJECT DISTANCE USING RADIO FREQUENCY SIGNALS

1 . A computer-implemented method, comprising:

receiving, by an object-tracking device, a first radio signal pattern from a direction of the target object;

determining a time interval from the received radio signal pattern;

determining a velocity of the object-tracking device; and

computing, by the object-tracking device, a distance to the target object based on the time interval and the velocity of the object-tracking device.

2 . The method of claim 1 , further comprising directing a directional antenna toward the target object to receive radio signal patterns from the target object.

3 . The method of claim 1 , wherein the radio signal pattern includes a first signal pattern followed by a second signal pattern; and

wherein the time interval includes a difference between a first timestamp for the first signal pattern and a second timestamp for the second signal pattern.

4 . The method of claim 1 , wherein the time interval is determined from a signal frequency of the radio signal pattern.

5 . The method of claim 1 , further comprising:

computing a velocity of the target object, relative to a motion of the object-tracking device.

6 . The method of claim 1 , further comprising:

determining an adjusted time interval which accounts for the object-tracking device's motion; and

computing an absolute velocity of the target object, based on the computed distance to the target object and the adjusted time interval.

7 . The method of claim 6 , wherein computing the velocity involves:

determining that the object is stationary responsive to determining that the adjusted time interval matches a predetermined time interval.

8 . The method of claim 1 , wherein the radio signal includes one or more of:

an infrared signal transmitted by the target object;

a Wi-Fi signal transmitted by the target object; and

a light signal transmitted by the object-tracking device and reflected off the target object.

9 . A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for tracking a target object by a local object-tracking device, comprising:

receiving a first radio signal pattern from a direction of the target object;

determining a time interval from the received radio signal pattern;

determining a velocity of the object-tracking device; and

computing a distance to the target object based on the time interval and the velocity of the object-tracking device.

10 . The storage medium of claim 9 , further comprising directing a directional antenna toward the target object to receive radio signal patterns from the target object.

11 . The storage medium of claim 9 , wherein the radio signal pattern includes a first signal pattern followed by a second signal pattern; and

wherein the time interval includes a difference between a first timestamp for the first signal pattern and a second timestamp for the second signal pattern.

12 . The storage medium of claim 9 , wherein the time interval is determined from a signal frequency of the radio signal pattern.

13 . The storage medium of claim 9 , further comprising:

computing a velocity of the target object, relative to a motion of the object-tracking device.

14 . The storage medium of claim 9 , further comprising:

determining an adjusted time interval which accounts for the object-tracking device's motion; and

computing an absolute velocity of the target object, based on the computed distance to the target object and the adjusted time interval.

15 . The storage medium of claim 9 , wherein the radio signal includes one or more of:

an infrared signal transmitted by the target object;

a Wi-Fi signal transmitted by the target object; and

a light signal transmitted by the object-tracking device and reflected off the target object.

16 . An object-tracking apparatus for tracking a target object, the computer system comprising:

a radio receiver for receiving a first radio signal pattern from a direction of the target object; and

a distance-computing module for:

determining a time interval from the received radio signal pattern;

determining a velocity of the object-tracking apparatus; and

computing a distance to the target object based on the time interval and the velocity of the object-tracking apparatus.

17 . The object-tracking apparatus of claim 16 , wherein the object-tracking apparatus further comprises:

a directional antenna; and

an antenna-controlling module for directing a directional antenna toward the target object to receive radio signal patterns from the target object.

18 . The object-tracking apparatus of claim 16 , wherein the radio signal pattern includes a first signal pattern followed by a second signal pattern; and

wherein the time interval includes a difference between a first timestamp for the first signal pattern and a second timestamp for the second signal pattern.

19 . The object-tracking apparatus of claim 16 , wherein the distance-computing module determines the time interval from a signal frequency of the radio signal pattern.

20 . The object-tracking apparatus of claim 16 , further comprising:

a velocity-computing module configured to compute a velocity of the target object, relative to a motion of the object-tracking apparatus.

21 . The object-tracking apparatus of claim 16 , further comprising a velocity-computing module configured to:

determine an adjusted time interval which accounts for the motion of the object-tracking apparatus; and

compute an absolute velocity of the target object, based on the computed distance to the target object and the adjusted time interval.

22 . The object-tracking apparatus of claim 16 , wherein the radio signal includes one or more of:

an infrared signal transmitted by the target object;

a Wi-Fi signal transmitted by the target object; and

a light signal transmitted by the object-tracking apparatus and reflected off the target object.