Multistatic target detection and geolocation
Aspects of this invention are directed to the substantially improved detection and geolocation accuracy of targets (stationary or moving) by using the coherent data received at multiple airborne sensors. Further aspects are directed to aligning the (unknown) time-delayed and Doppler-shifted signals received at the multiple sensors relative to an arbitrary reference sensor, which depend on the unknown target position. This results in the target position and velocity vectors being simultaneously estimated and the detection peak enhanced by obtaining near coherent gain. Still further aspects are directed to the coherent generalized likelihood ratio test (GLRT) and the minimum variance distortionless response (MVDR) statistic for multistatic radar systems, conditioned on estimation of certain parameters that render the system coherent. Analytical and computer simulation results are presented to show substantially enhanced detection and geolocation of moving targets in clutter.
1. A multistatic radar system comprising:
a transmitter for transmitting a first signal at a first time to reflect off a target, the first signal reflecting off the target as a second signal at a second time;
a plurality of spatially separated receivers on corresponding geographically separated platforms, each of the receivers being configured to receive the second signal from the target as one of a corresponding plurality of third signals and at one of a corresponding plurality of third times; and
a signal processor for fusing the third signals and the third times from the receivers,
wherein the fusing of the third signals and the third times comprises:
aligning the third signals in time delay and Doppler shift using the corresponding plurality of third times; and
summing the resulting aligned third signals to detect or geolocate the target at the second time.
2. The multistatic radar system of claim 1 , wherein the summing of the resulting aligned third signals comprises non-coherently summing the resulting aligned third signals.
3. The multistatic radar system of claim 2 , wherein the aligning of the third signals in time delay and Doppler shift comprises generating and applying a non-coherent Generalized Likelihood Ratio Test (GLRT) statistic.
4. The multistatic radar system of claim 1 , wherein the summing of the resulting aligned third signals comprises coherently summing the resulting aligned third signals.
5. The multistatic radar system of claim 4 , wherein the aligning of the third signals in time delay and Doppler shift comprises generating and applying a coherent Generalized Likelihood Ratio Test (GLRT) statistic.
6. The multistatic radar system of claim 4 , wherein the aligning of the third signals in time delay and Doppler shift comprises generating and applying a coherent minimum variance distortionless response (MVDR) statistic.
7. The multistatic radar system of claim 1 , wherein the aligning of the third signals in time delay and Doppler shift comprises modeling location and velocity vectors of the target.
8. The multistatic radar system of claim 1 , wherein the fusing of the third signals and the third times comprises representing a state vector of the target in a centralized Cartesian coordinate system over all of the receivers.
9. The multistatic radar system of claim 1 , wherein the detection or geolocation of the target is decided when the summing of the resulting aligned third signals exceeds a threshold.
10. The multistatic radar system of claim 1 , wherein the target comprises a moving target in clutter, and the fusing of the third signals and the third times comprises detecting or geolocating the target in the clutter.
11. A method of detection and geolocation of a target by a multistatic radar system comprising a transmitter, a plurality of spatially separated receivers on corresponding geographically separated platforms, and a signal processor, the method comprising:
transmitting a first signal at a first time from the transmitter to the target, the first signal reflecting off the target as a second signal at a second time;
receiving the second signal in the receivers on the corresponding geographically separated platforms, each of the receivers receiving the second signal from the target as one of a corresponding plurality of third signals and at one of a corresponding plurality of third times; and
fusing the third signals and the third times from the receivers on the signal processor, comprising:
aligning the third signals in time delay and Doppler shift using the corresponding plurality of third times; and
summing the resulting aligned third signals to detect or geolocate the target at the second time.
12. The method of claim 11 , wherein the summing of the resulting aligned third signals comprises non-coherently summing the resulting aligned third signals.
13. The method of claim 12 , wherein the aligning of the third signals in time delay and Doppler shift comprises generating and applying a non-coherent Generalized Likelihood Ratio Test (GLRT) statistic.
14. The method of claim 11 , wherein the summing of the resulting aligned third signals comprises coherently summing the resulting aligned third signals.
15. The method of claim 14 , wherein the aligning of the third signals in time delay and Doppler shift comprises generating and applying a coherent Generalized Likelihood Ratio Test (GLRT) statistic.
16. The method of claim 14 , wherein the aligning of the third signals in time delay and Doppler shift comprises generating and applying a coherent minimum variance distortionless response (MVDR) statistic.
17. The method of claim 11 , wherein the aligning of the third signals in time delay and Doppler shift comprises modeling location and velocity vectors of the target.
18. The method of claim 11 , wherein the fusing of the third signals and the third times comprises representing a state vector of the target in a centralized Cartesian coordinate system over all the receivers.
19. The method of claim 11 , wherein the detection or geolocation of the target is decided when the summing of the resulting aligned third signals exceeds a threshold.
20. The method of claim 11 , wherein the target comprises a moving target in clutter, and the fusing of the third signals and the third times comprises detecting or geolocating the target in the clutter.