Method and system for locating signal emitters using cross-correlation of received signal strengths
View Patent ↗A method and system for determining a location of a first device that emits a signal: provide at least three sensors separated and spaced apart from each other; at each of the sensors, receive the signal emitted by the first device; determine the received signals for each of the sensors; determine cross-correlations of the received signals for pairs of the sensors; and determine the location of the first device from the magnitudes of the cross-correlations of the received signals.
1. A method of determining a location of a first device that emits a signal, comprising:
providing at least three sensors separated and spaced apart from each other;
at each of the sensors, receiving the signal emitted by the first device;
acquiring the received signals for each of the sensors;
determining magnitudes of cross-correlations between the received signals for pairs of the sensors; and
determining the location of the first device from the magnitudes of the cross-correlations of the received signals.
2. The method of claim 1 , further comprising calculating ratios of peak powers of the cross-correlations of the received signals.
3. The method of claim 1 , wherein determining the location of the first device from the cross-correlations comprises:
determining cross-correlation ratios of pairs of the cross-correlations, wherein in each of the pairs of cross-correlations, a pair of sensors for a first one of the cross-correlations in the pair of cross-correlations includes a same sensor as a pair of sensors for a second one of the cross-correlations in the pair of cross-correlations;
determining peak probability curves for each of the cross-correlation ratios; and
determining the emitter location as an area where the curves intersect.
4. The method of claim 1 , wherein determining the location of the first device from the cross-correlation comprises:
determining cross-correlation ratios of pairs of the cross-correlations, wherein in each of the pairs of cross-correlations, a pair of sensors for a first one of the cross-correlations in the pair of cross-correlations includes a same sensor as a pair of sensors for a second one of the cross-correlations in the pair of cross-correlations;
determining a cross-correlation ratio likelihood map for each of the cross-correlation ratios;
determining a composite likelihood map from a set comprising all of the cross-correlation ratio likelihood maps;
determining the emitter location as an area on the composite likelihood map with greatest likelihood.
5. The method of claim 1 , further comprising calculating ratios of the cross-correlations at a time offset corresponding to a time difference between a point at coordinates x, y on a two-dimensional probability plot, and a corresponding pair of sensors,
X
12
τ
(
x
,
y
)
X
13
τ
(
x
,
y
)
,
where τ(x,y) is the time offset at coordinates x, y,
where X 12 τ(x,y) is the cross correlation for a first pair of sensors at the time offset τ(x,y), and
where X 13 τ(x,y) is the cross correlation for a second pair of sensors at the time offset τ(x,y).
6. The method of claim 1 , further comprising synchronizing the sensors to have a common sense of time.
7. The method of claim 1 , further comprising applying Doppler correction to the received signals.
8. The method of claim 1 , further comprising:
at each of the sensors, receiving a second signal emitted by a second device, the second signal being transmitted at a same time and on a same frequency as the signal emitted by the first device; and
determining the location of the second device from the magnitudes of the cross-correlations of the received signals.
9. The method of claim 1 , wherein the signal is an acoustic signal.
10. The method of claim 1 , wherein the signal is an electromagnetic signal.
11. A system for determining a location of a first device that emits a signal, the system comprising:
at least three sensors separated and spaced apart from each other, each of the sensors including a receiver adapted to receive the signal emitted by the first device and to acquire the received signals for each of the sensors;
a network connecting the sensors and adapted to communicate data from the sensors;
means for determining magnitudes of the cross-correlations of the received signals for pairs of the sensors; and
means for determining the location of the first device from the magnitudes of the cross-correlations of the received signals.
12. The system of claim 11 , further comprising a processor, wherein the means for determining the magnitudes of the cross-correlations of the received signals comprises the processor.
13. The system of claim 12 , wherein the means for determining the location of the first device from the magnitudes of the cross-correlations of the received signals comprises the processor.
14. The system of claim 12 , wherein the processor is included in one of the sensors.
15. The system of claim 14 , wherein the means for determining the location of the first device from the magnitudes of the cross-correlations of the received signals comprises the processor.
16. The system of claim 14 , wherein the means for determining the location of the first device from the magnitudes of the cross-correlations of the received signals comprises a second processor external to the sensors and connected to the sensors by the network.
17. The system of claim 12 , wherein the processor is external to the sensors and is connected to the sensors by the network.
18. The system of claim 17 , wherein the means for determining the location of the first device from the magnitudes of the cross-correlations of the received signals comprises the processor.
19. The system of claim 11 , further comprising means for calculating ratios of peak powers of the cross-correlations of the received signals.
20. The system of claim 11 , wherein the means for determining the location of the first device from the cross-correlations comprises:
means for determining cross-correlation ratios of pairs of the cross-correlations, wherein in each of the pairs of cross-correlations, a pair of sensors for a first one of the cross-correlations in the pair of cross-correlations includes a same sensor as a pair of sensors for a second one of the cross-correlations in the pair of cross-correlations;
means for determining peak likelihood curves for each of the cross-correlation ratios; and
means for determining the emitter location as an area where the curves intersect.
21. The system of claim 11 , wherein the means for determining the location of the first device from the cross-correlations comprises:
means for determining cross-correlation ratios of pairs of the cross-correlations, wherein in each of the pairs of cross-correlations, a pair of sensors for a first one of the cross-correlations in the pair of cross-correlations includes a same sensor as a pair of sensors for a second one of the cross-correlations in the pair of cross-correlations;
means for determining a cross-correlation ratio likelihood map for each of the cross-correlation ratios;
means for determining a composite likelihood map from a set comprising all of the cross-correlation ratio likelihood maps;
means for determining the emitter location as an area on the composite likelihood map with greatest likelihood.
22. The system of claim 11 , further comprising means for calculating ratios of the cross-correlations at a time offset corresponding to a time difference between a point at coordinates x, y on a two-dimensional likelihood plot, and a corresponding pair of sensors,
X
12
τ
(
x
,
y
)
X
13
τ
(
x
,
y
)
,
where τ(x,y) is the time offset at coordinates x, y,
where X 12 τ(x,y) is the cross correlation for a first pair of sensors at the time offset τ(x,y), and
where X 13 τ(x,y) is the cross correlation for a second pair of sensors at the time offset τ(x,y).