Devices, systems, and methods for radar-based artificial reality tracking
The disclosed apparatus may include at least one transponder that (1) is located on a wearable device worn by a user and (2) retransmits signals received at the transponder after shifting frequencies of the received signals to a certain frequency range. The apparatus may also include at least one radar device that (1) transmits a frequency-modulated radar signal to the transponder and (2) receives signals whose frequencies are within the certain frequency range. In addition, the apparatus may include a processing device that (1) detects a signal returned to the radar device from the transponder, (2) calculates, based on the returned signal, a distance between the transponder and the radar device, and then (3) determines, based on the distance between the transponder and the radar device, a current physical location of at least a portion of the user. Various other apparatuses, systems, and methods are also disclosed.
1. A system comprising:
at least one transponder that:
is located on a wearable device worn by a user; and
retransmits signals received at the transponder after shifting frequencies of the received signals to a certain frequency range;
at least one radar device that:
transmits a frequency-modulated radar signal to the transponder; and
receives signals whose frequencies are within the certain frequency range; and
a processing device communicatively coupled to the radar device, wherein the processing device:
detects a signal returned to the radar device from the transponder in response to the frequency-modulated radar signal;
calculates, based at least in part on the returned signal, a distance between the transponder and the radar device; and
determines, based at least in part on the distance between the transponder and the radar device, a current physical location of at least a portion of the user.
2. The system of claim 1 , further comprising an additional wearable device that:
is worn by the user; and
secures the radar device.
3. The system of claim 1 , wherein the transponder shifts the frequencies of the received signals to the certain frequency range by mixing the received signals with a signal whose frequency is within the certain frequency range.
4. The system of claim 1 , wherein:
the wearable device secures a plurality of transponders; and
each of the plurality of transponders shifts frequencies of received signals to a different frequency range such that each of the plurality of transponders retransmits signals with a different carrier frequency.
5. The system of claim 4 , wherein the radar device comprises a separate communication channel for each different carrier frequency with which the plurality of transponders retransmit signals.
6. The system of claim 5 , wherein at least one separate communication channel comprises an oscillator tuned to a particular carrier frequency.
7. The system of claim 5 , wherein the processing device identifies a particular transponder within the plurality of transponders that transmitted the returned signal based at least in part on a communication channel in which the radar device received the returned signal.
8. The system of claim 4 , wherein the returned signal comprises a superposition of:
a carrier frequency with which the transponder retransmits signals; and
a beat frequency that is proportional to the distance between the transponder and the radar device.
9. The system of claim 8 , wherein the processing device calculates the distance between the transponder and the radar device by extracting the beat frequency from the returned signal.
10. The system of claim 9 , wherein the processing device extracts the beat frequency from the returned signal by:
mixing the returned signal with the frequency-modulated radar signal to produce a mixed signal;
passing the mixed signal through an envelope filter to produce a filtered signal; and
determining a frequency of the filtered signal.
11. The system of claim 1 , wherein:
the processing device further passes the current physical location of the portion of the user to an artificial reality system that provides virtual content to the user; and
the artificial reality system modifies at least one virtual component of the artificial reality system to account for the current physical location of the portion of the user.
12. A radar system comprising:
a wearable device that is worn by a user of an artificial reality system;
at least one transponder that:
is secured to the wearable device; and
retransmits signals received at the transponder after shifting frequencies of the received signals to a certain frequency range;
at least one radar device that:
transmits a frequency-modulated radar signal to the transponder; and
receives signals whose frequencies are within the certain frequency range; and
a processing device communicatively coupled to the radar device, wherein the processing device:
detects a signal returned to the radar device from the transponder in response to the frequency-modulated radar signal;
calculates, based at least in part on the returned signal, a distance between the transponder and the radar device; and
determines, based at least in part on the distance between the transponder and the radar device, a current physical location of at least a portion of the user.
13. The radar system of claim 12 , wherein the transponder shifts the frequencies of the received signals to the certain frequency range by mixing the received signals with a signal whose frequency is within the certain frequency range.
14. The radar system of claim 12 , wherein:
the wearable device secures a plurality of transponders; and
each of the plurality of transponders shifts frequencies of received signals to a different frequency range such that each of the plurality of transponders retransmits signals with a different carrier frequency.
15. The radar system of claim 14 , wherein the radar device comprises a separate communication channel for each different carrier frequency with which the plurality of transponders retransmit signals.
16. The radar system of claim 15 , wherein at least one separate communication channel comprises an oscillator tuned to a particular carrier frequency.
17. The radar system of claim 15 , wherein the processing device identifies a particular transponder within the plurality of transponders that transmitted the returned signal based at least in part on a communication channel in which the radar device received the returned signal.
18. The radar system of claim 12 , further comprising an additional wearable device that:
is worn by the user; and
secures the radar device.
19. The radar system of claim 18 , wherein:
the wearable device comprises an artificial reality glove; and
the additional wearable device comprises an artificial reality helmet.
20. A method comprising:
transmitting, from a radar device, a frequency-modulated radar signal to a transponder that:
is located on a wearable device worn by a user; and
retransmits signals received at the transponder after shifting frequencies of the received signals to a certain frequency range;
detecting a signal returned to the radar device from the transponder in response to the frequency-modulated radar signal;
calculating, based at least in part on the returned signal, a distance between the transponder and the radar device; and
determining, based at least in part on the distance between the transponder and the radar device, a current physical location of at least a portion of the user.