Human proximity sensor using short-range radar

1. A method performed by a user equipment to detect a proximity of human tissue, the method comprising:

determining a mutual coupling signal associated with a transmit antenna and a receive antenna of the user equipment;

determining a mutual coupling difference between the mutual coupling signal and a reference mutual coupling signal;

determining a beat signal difference between a current beat signal and a previous beat signal;

determining an amount of micro-motion that is present within a near field of the user equipment based at least in part on the beat signal difference;

determining whether human tissue is present within the near field of the user equipment based on the mutual coupling difference and the amount of micro-motion;

determining an amount of radio frequency exposure associated with the human tissue based on determining that the human tissue is present within the near field of the user equipment; and

reducing the amount of radio frequency exposure associated with the human tissue based on determining that the amount of radio frequency exposure exceeds a maximum permissible exposure.

2. The method of claim 1 , wherein the reference mutual coupling signal is determined when human tissue is absent from the near field of the user equipment.

3. The method of claim 1 , wherein the near field is at least 4 centimeters away from a nearest outer surface of the user equipment.

4. The method of claim 1 , wherein the maximum permissible exposure comprises 1 milliwatt per square centimeter.

5. The method of claim 1 , further comprising:

determining that the human tissue is present in the near field based on determining that the amount of micro-motion that is present within the near field exceeds a threshold.

6. The method of claim 1 , further comprising:

determining that the human tissue is absent in the near field based on determining that the amount of micro-motion that is present within the near field fails to exceed a threshold.

7. The method of claim 1 , wherein determining the amount of micro-motion that is present within the near field of the user equipment comprises:

determining an amount of noise associated with the near field when the human tissue is absent; and

determining a rise over noise based on the beat signal difference and the amount of noise.

8. The method of claim 7 , further comprising:

based on determining that the rise over noise is approximately 1, determining that the human tissue is absent in the near field.

9. The method of claim 7 , further comprising:

based on determining that the rise over noise is greater than 1, determining that the human tissue is present in the near field.

10. A user equipment comprising:

a memory;

at least one transceiver; and

at least one processor communicatively coupled to the memory and the at least one transceiver, the at least one processor configured to:

determine a mutual coupling signal associated with a transmit antenna and a receive antenna of the user equipment;

determine a mutual coupling difference between the mutual coupling signal and a reference mutual coupling signal;

determine a beat signal difference between a current beat signal and a previous beat signal;

determine an amount of micro-motion that is present within a near field of the user equipment based at least in part on the beat signal difference;

determine whether human tissue is present within the near field of the user equipment based on the mutual coupling difference and the amount of micro-motion;

determine an amount of radio frequency exposure associated with the human tissue based on determining that the human tissue is present within the near field of the user equipment; and

reduce the amount of radio frequency exposure associated with the human tissue based on determining that the amount of radio frequency exposure exceeds a maximum permissible exposure.

11. The user equipment of claim 10 , wherein the reference mutual coupling signal is determined when human tissue is absent from the near field of the user equipment.

12. The user equipment of claim 10 , wherein the near field is at least 4 centimeters away from a nearest outer surface of the user equipment.

13. The user equipment of claim 10 , wherein the maximum permissible exposure comprises 1 milliwatt per square centimeter.

14. The user equipment of claim 10 , wherein the at least one processor is further configured to:

determine that the human tissue is present in the near field based on determining that the amount of micro-motion that is present within the near field exceeds a threshold.

15. The user equipment of claim 10 , wherein the at least one processor is further configured to:

determine that the human tissue is absent in the near field based on determining that the amount of micro-motion that is present within the near field fails to exceed a threshold.

16. The user equipment of claim 10 , wherein the at least one processor is further configured to:

determine an amount of noise associated with the near field when the human tissue is absent; and

determine a rise over noise based on the beat signal difference and the amount of noise.

17. The user equipment of claim 16 , wherein the at least one processor is further configured to:

determine that the human tissue is absent in the near field based on determining that the rise over noise is approximately 1.

18. The user equipment of claim 16 , wherein the at least one processor is further configured to:

determine that the human tissue is present in the near field based on determining that the rise over noise is greater than 1.

19. An apparatus comprising:

means for determining a mutual coupling signal associated with a transmit antenna and a receive antenna of the apparatus;

means for determining a mutual coupling difference between the mutual coupling signal and a reference mutual coupling signal;

means for determining a beat signal difference between a current beat signal and a previous beat signal;

means for determining an amount of micro-motion that is present within a near field of the apparatus based at least in part on the beat signal difference;

means for determining whether a human tissue is present within the near field of the apparatus based on the mutual coupling difference and the amount of micro-motion;

means for determining an amount of radio frequency exposure associated with the human tissue based on determining that the human tissue is present within the near field of the apparatus; and

means for reducing the amount of radio frequency exposure associated with the human tissue based on determining that the amount of radio frequency exposure exceeds a maximum permissible exposure.

20. The apparatus of claim 19 , wherein the reference mutual coupling signal is determined when human tissue is absent from the near field of the apparatus.

21. The apparatus of claim 19 , wherein the near field is at least 4 centimeters away from a nearest outer surface of the apparatus.

22. The apparatus of claim 19 , wherein the maximum permissible exposure comprises 1 milliwatt per square centimeter.

23. The apparatus of claim 22 , further comprising:

means for determining that the human tissue is present in the near field based on determining that the amount of micro-motion that is present within the near field exceeds a threshold.

24. The apparatus of claim 19 , further comprising:

means for determining that the human tissue is absent in the near field based on determining that the amount of micro-motion that is present within the near field fails to exceed a threshold.

25. The apparatus of claim 19 , wherein determining the amount of micro-motion that is present within the near field of the apparatus comprises:

means for determining an amount of noise associated with the near field when the human tissue is absent; and

means for determining a rise over noise based on the beat signal difference and the amount of noise.

26. The apparatus of claim 25 , further comprising:

means for determining that the human tissue is absent in the near field based on determining that the rise over noise is approximately 1.

27. The apparatus of claim 25 , further comprising:

means for determining that the human tissue is present in the near field based on determining that the rise over noise is greater than 1.

28. A non-transitory computer-readable storage medium to store instructions executable by one or more processors to:

determine a mutual coupling signal associated with a transmit antenna and a receive antenna of a user equipment;

determine a mutual coupling difference between the mutual coupling signal and a reference mutual coupling signal;

determine a beat signal difference between a current beat signal and a previous beat signal;

determine an amount of micro-motion that is present within a near field of the user equipment based at least in part on the beat signal difference;

determine whether human tissue is present within the near field of the user equipment based on the mutual coupling difference and the amount of micro-motion;

determine an amount of radio frequency exposure associated with the human tissue based on determining that the human tissue is present within the near field of the user equipment; and

reduce the amount of radio frequency exposure associated with the human tissue based on determining that the amount of radio frequency exposure exceeds a maximum permissible exposure.

29. The non-transitory computer-readable storage medium of claim 28 , wherein the instructions are further executable by the one or more processors to:

determine that the human tissue is present in the near field based on determining that the amount of micro-motion that is present within the near field exceeds a threshold.

30. The non-transitory computer-readable storage medium of claim 28 , wherein the instructions are further executable by the one or more processors to:

determine an amount of noise associated with the near field when the human tissue is absent; and

determine a rise over noise based on the beat signal difference and the amount of noise.