Passive radar for presence and motion detection
A passive detector ( 10 ) includes a receiver ( 11 ) configured to collect passive radiation ( 12 ) in an environment, where detailed information about a portion of the passive radiation is estimated as a baseline of the passive energy. The passive energy is generated by a passive source unrelated to the detector. A monitor ( 24 ) is configured to measure a fluctuation in the baseline. A decision module ( 34 ) is coupled to the monitor to determine whether the fluctuation represents a presence or motion in the environment. Detection methods are also disclosed.
1. A passive detector, comprising:
a receiver configured to collect passive radiation in an environment, where detailed information about a portion of the passive radiation is used to determine a baseline energy of passive energy generated by a passive source comprising a multi-channel wireless communications network signal unrelated to the detector;
a channel estimation module configured to estimate a strongest channel to be monitored in the baseline energy of the multi-channel wireless communications network signal;
a monitor configured to measure a fluctuation in the baseline energy of the strongest channel; and
a decision module coupled to the monitor to determine whether the fluctuations in the estimated strongest channel represent a presence or motion in the environment in reliance on a comparison of a computed decision variable to a threshold to determine if statistical fluctuations measured in said baseline energy of the strongest channel represent said presence of motion,
wherein the passive detector estimates the channel energy deviation of said estimated strongest channel over time.
2. The detector as recited in claim 1 , wherein the portion of the passive energy includes a mid-amble of a Global System for Mobile Communications (GSM) standard wireless communications network signal.
3. The detector as recited in claim 1 , wherein the decision module compares the decision variable to a threshold to determine if the fluctuation represents motion or a presence in the environment.
4. The detector as recited in claim 1 , wherein the decision module outputs a signal in accordance with a detected presence or motion.
5. The detector as recited in claim 1 , wherein the passive energy is collected from a nearby energy source unrelated to the detector.
6. The detector as recited in claim 1 , wherein the fluctuation is employed to measure the Doppler effect.
7. A passive motion detector, comprising:
a receiver configured to collect a wireless communications signal from an environment and estimate a baseline energy from an expected or periodic portion of the wireless communication signal, the baseline energy being generated by a passive source comprising a multi-channel wireless communications network signal unrelated to the detector, the receiver including a channel estimation module configured to estimate a strongest channel to be monitored in the baseline energy;
a channel estimation monitor configured to measure statistical fluctuations in the baseline energy of the strongest channel; and
a decision module coupled to the monitor and configured to determine whether the fluctuations in the estimated strongest channel represent a presence or motion in the environment in reliance on a comparison of a computed decision variable to a threshold to determine if statistical fluctuations measured in said baseline energy of the strongest channel represent said presence of motion.
8. The detector as recited in claim 7 , wherein the wireless communications signal includes a Global System for Mobile Communications (GSM) standard wireless communications network signal.
9. The detector as recited in claim 7 , wherein the expected or periodic portion of the communications signal includes a mid-amble of the GSM signal.
10. The detector as recited in claim 7 , wherein the decision module outputs a signal in accordance with a detected presence or motion.
11. The detector as recited in claim 7 , wherein the expected or periodic portion of the communications signal is collected from a base station.
12. A method for determining presence or motion in an environment in a passive detector, the method comprising:
estimating, by a channel estimator, a strongest channel from existing passive radiation in an environment wherein the passive radiation is generated by an unrelated passive source comprising a multi-channel wireless communication network signal;
monitoring, by a decision module, fluctuations in the passive radiation of the strongest channel of a multi-channel wireless communication network signal; and
determining, by the decision module, whether the fluctuations represent a presence or motion in the environment, and
wherein said determination is made in accordance with a decision variable which is computed based upon a statistical fluctuation in an energy deviation in said strongest channel of said multi-channel wireless communication network signal.
13. The method as recited in claim 12 , wherein the passive energy includes a mid-amble of a Global System for Mobile Communications (GSM) standard wireless communications network signal.
14. The method as recited in claim 12 , further comprising comparing the decision variable to a threshold to determine if the fluctuation represents motion or a presence in the environment.
15. The method as recited in claim 14 , further comprising adjusting detection sensitivity by adjusting the threshold.
16. The method as recited in claim 12 , further comprising outputting a signal in accordance with a detected presence or motion.
17. The method as recited in claim 12 , wherein the fluctuations are employed to measure the Doppler effect.