Methods and apparatus for detecting presence of an object in an environment

1. A method for detecting presence of an object in an environment, comprising:

receiving a Doppler signal during a frame in frequency domain;

separating the Doppler signal in the frequency domain into a plurality of sub-band signals;

determining a plurality of sub-band signal energies corresponding to the plurality of sub-band signals;

determining whether motion of the object is detected in accordance with one of the plurality of sub-band signal energies and a baseline energy; and

responsive to a determination that motion of the object is detected, setting a flag of object presence.

2. The method of claim 1 , wherein determining whether motion of the object is detected includes:

determining that motion of the object is detected when at least one of the plurality of sub-band signal energies is equal to or greater than a threshold; or

determining that motion of the object is not detected when none of the plurality of sub-band signal energies is equal to or greater than the threshold,

wherein the threshold is determined based on the baseline energy.

3. The method of claim 2 , wherein the threshold is a first threshold, and the first threshold is determined based on the baseline energy and a second threshold.

4. The method of claim 1 , wherein determining whether motion of the object is detected includes:

determining that motion of the object is detected when at least two of the plurality of sub-band signal energies are equal to or greater than a threshold; or

determining that motion of the object is not detected when less than two of the plurality of sub-band signal energies is equal to or greater than the threshold,

wherein the threshold is determined based on the baseline energy.

5. The method of claim 4 , wherein the at least two of the plurality of sub-band signal energies are signal energies of sub-bands that include at least two adjacent sub-bands.

6. The method of claim 4 , wherein the threshold is a first threshold, and the first threshold is determined based on the baseline energy and a second threshold.

7. The method of claim 1 , wherein receiving a Doppler signal in the frequency domain includes:

receiving a Doppler signal in time domain; and

transforming the Doppler signal in the time domain to the Doppler signal in the frequency domain using a short-time Fourier transform (STFT) or a filter bank.

8. The method of claim 1 , wherein:

the baseline energy includes a plurality of sub-band baseline energies corresponding to the plurality of sub-band signals, and

determining whether motion of the object is detected includes:

determining whether motion of the object is detected in accordance with the plurality of sub-band signal energies and the plurality of sub-band baseline energies.

9. The method of claim 1 , further comprising:

responsive to a determination that motion of the object is not detected, updating the baseline energy in accordance with the one of the plurality of sub-band signal energies.

10. The method of claim 1 , wherein the presence of the object includes presence of an inanimate object, a human, or an animal.

11. A method for detecting presence of an object in an environment, comprising:

receiving a Doppler signal in time domain;

determining whether motion of the object is detected in accordance with the Doppler signal in the time domain and a first baseline energy;

responsive to a determination that motion of the object is detected in accordance with the Doppler signal in the time domain and the first baseline energy, setting a first flag of object motion;

transforming the Doppler signal in the time domain to a Doppler signal in frequency domain;

determining whether motion of the object is detected in accordance with the Doppler signal in the frequency domain and a second baseline energy;

responsive to a determination that motion of the object is detected in accordance with the Doppler signal in the frequency domain and the second baseline energy, setting a second flag of object motion; and

setting a flag of object presence based on the first flag of object motion and the second flag of object motion.

12. The method of claim 11 , wherein transforming the Doppler signal in the time domain to a Doppler signal in the frequency domain includes:

transforming when a criterion is met, and the criterion includes:

the first flag is not set;

the first flag is set; or

the first flag is set and a signal energy of the Doppler signal in the time domain is less than a threshold.

13. An apparatus for detecting presence of an object in an environment, the apparatus comprising:

a memory storing instructions; and

a processor configured to execute the instructions to cause the apparatus to:

receive a Doppler signal during a frame in frequency domain;

separate the Doppler signal in the frequency domain into a plurality of sub-band signals;

determine a plurality of sub-band signal energies corresponding to the plurality of sub-band signals;

determine whether motion of the object is detected in accordance with one of the plurality of sub-band signal energies and a baseline energy; and

responsive to a determination that motion of the object is detected, set a flag of object presence.

14. The apparatus of claim 13 , wherein the processor is configured to execute the instructions to cause the apparatus to determine whether motion of the object is detected by:

determining that motion of the object is detected when at least one of the plurality of sub-band signal energies is equal to or greater than a threshold; or

determining that motion of the object is not detected when none of the plurality of sub-band signal energies is equal to or greater than the threshold,

wherein the threshold is determined based on the baseline energy.

15. The apparatus of claim 13 , wherein the processor is configured to execute the instructions to cause the apparatus to determine whether motion of the object is detected by:

determining that motion of the object is detected when at least two of the plurality of sub-band signal energies are equal to or greater than a threshold; or

determining that motion of the object is not detected when less than two of the plurality of sub-band signal energies is equal to or greater than the threshold,

wherein the threshold is determined based on the baseline energy.

16. The apparatus of claim 15 , wherein the at least two of the plurality of sub-band signal energies are signal energies of sub-bands that include at least two adjacent sub-bands.

17. The apparatus of claim 15 , wherein the threshold is a first threshold, and the first threshold is determined based on the baseline energy and a second threshold.

18. The apparatus of claim 13 , wherein the processor is configured to execute the instructions to cause the apparatus to receive the Doppler signal in frequency domain by:

receiving a Doppler signal in time domain; and

transforming the Doppler signal in the time domain to the Doppler signal in the frequency domain using a short-time Fourier transform (STFT) or a filter bank.

19. The apparatus of claim 13 , wherein:

the baseline energy includes a plurality of sub-band baseline energies corresponding to the plurality of sub-band signals, and

the processor is configured to execute the instructions to cause the apparatus to determine whether motion of the object is detected by:

determining whether motion of the object is detected in accordance with the plurality of sub-band signal energies and the plurality of sub-band baseline energies.

20. The apparatus of claim 13 , wherein the processor is further configured to execute the instructions to cause the apparatus to:

responsive to a determination that motion of the object is not detected, add the plurality of sub-band signal energies to the baseline energy using a moving average.