Target-tracking radar and method for responding to fluctuations in target SNR

1. A target-tracking radar comprising point-target determinator configured to:

determine whether a target can be considered a point target based on a signal-to-noise ratio (SNR) of received signals and off-boresight error estimates;

provide measurement-variance estimates generated from the SNR to a target-state estimator when the target is determined to be a point target; and

refrain from providing the measurement-variance estimates to the target-state estimator when the target is determined not to be a point target.

2. The target-tracking radar of claim 1 further comprising:

processing circuitry to generate the SNR based on the received signals and one of a measured, estimated or predetermined noise level; and

a monopulse error calculator to determine the off-boresight error estimates based on the received signals,

wherein the received signals comprise a sum signal, an azimuth delta signal and an elevation delta signal.

3. The target-tracking radar of claim 1 wherein the point-target determinator comprises:

a variable-threshold calculator to generate a variable threshold based on the SNR;

a glint detector to compare the variable threshold with the off-boresight error estimates; and

a Markov-chain counter to count a number of times that the off-boresight error estimates exceed the variable threshold based on an output from the glint detector.

4. The target-tracking of claim 3 wherein the output of the glint detector indicates when the off-boresight error estimates exceed the variable threshold.

5. The target-tracking radar of claim 3 wherein the point-target determinator further comprises:

a monopulse variance estimator to generate the measurement-variance estimates from the SNR; and

a point target classifier to provide the measurement-variance estimates to the target-state estimator when the Markov-chain counter indicates that the target is a point target.

6. The target-tracking radar of claim 5 wherein the point target classifier is further configured to refrain from providing the measurement-variance estimates to the target-state estimator when the Markov-chain counter indicates the target is not a point target.

7. The target-tracking radar of claim 5 further comprising a tracking controller to provide tracking control signals to control one or more antennas of the target-tracking radar,

wherein the target-state estimator is configured to calculate target position updates for use by the tracking controller to track the target with the one or more antennas.

8. The target-tracking radar of claim 7 wherein when the target is determined to be a point target, the target-state estimator is configured use the measurement-variance estimates to calculate the target position updates, and

wherein when the target is determined not to be a point target, the target-state estimator is configured to use residuals to calculate the target position updates.

9. The target-tracking radar of claim 8 wherein the target is a non-maneuvering target including one or a munition or a missile, and

wherein the target-tracking radar is configured to track a position of the target at range.

10. A method performed by a target-tracking radar for responding to fluctuations in target SNR for target tracking comprising:

determining, by a point-target determinator, whether a target can be considered a point target based on a signal-to-noise ratio (SNR) of received radar signals and off-boresight error estimates; and

providing, by the point-target determinator, measurement-variance estimates generated from the SNR to a target-state estimator when the target is determined to be a point target.

11. The method of claim 10 further comprising:

configuring the target-state estimator to use the measurement-variance estimates to generate target position updates.

12. The method of claim 11 further comprising:

refraining from providing the measurement-variance estimates to the target-state estimator when the target is determined not to be a point target; and

configuring the target-state estimator to use residuals to calculate the target position updates when the target is determined not to be a point target.

13. The method of claim 12 further comprising:

generating a variable threshold based on the SNR;

comparing the variable threshold with the off-boresight error estimates; and

counting a number of times that the off-boresight error estimates exceed the variable threshold based on the comparison of the variable threshold with the off-boresight error estimates.

14. The method of claim 13 further comprising:

generating the measurement-variance estimates from the SNR; and

providing the measurement-variance estimates to the target-state estimator when the counting indicates that the target is a point target.

15. A point target determinator comprising:

a variable-threshold calculator configured to generate a variable threshold based on a signal-to-noise ratio (SNR) of received radar signals;

a glint detector configured to compare the variable threshold with off-boresight error estimates;

a Markov-chain counter configured to count a number of times that the off-boresight error estimates exceed the variable threshold based on an output from the glint detector;

a monopulse variance estimator configured to generate measurement-variance estimates from the SNR; and

a point target classifier configured to provide the measurement-variance estimates to a target-state estimator based on an output of the Markov-chain counter indicating that the target is a point target.

16. The point target determinator of claim 15 wherein the output of the glint detector indicates when the off-boresight error estimates exceed the variable threshold, and

wherein the point target classifier is configured to refrain from providing the measurement-variance estimates to the target-state estimator when the target is determined not to be a point target.

17. The point-target determinator of claim 16 wherein when the target is determined to be a point target, the target-state estimator is configured to use the measurement-variance estimates to calculate the target position updates, and

wherein when the target is determined not to be a point target, the target-state estimator is configured to use filter residuals to calculate the target position updates.

18. A non-transitory computer-readable storage medium having instructions stored thereon which, when executed by one or more processors cause the one or more processors to determine whether a target is a point target by performing the following operations:

generating a variable threshold based on a signal-to-noise ratio (SNR) of received radar signals;

comparing the variable threshold with off-boresight error estimates;

counting a number of times that the off-boresight error estimates exceed the variable threshold based on an output from the comparing;

generating measurement-variance estimates from the SNR; and

providing the measurement-variance estimates to a target-state estimator based on an output of the counting indicating that the target is a point target.

19. The computer-readable storage medium of claim 18 wherein the instructions further configure the one or more processors to:

configure the target-state estimator to use the measurement-variance estimates to calculate the target position updates when the target is determined to be a point target; and

configure the target-state estimator to use residuals to calculate the target position updates when the target is determined not to be a point target.

20. A target-tracking radar comprising:

a point-target determinator;

a target-state estimator; and

a tracking controller configured to provide tracking control signals to control one or more antennas of the target-tracking radar,

wherein the target-state estimator is configured to calculate target position updates for use by the tracking controller to track the target with one or more antennas,

wherein the point-target determinator comprises:

a variable-threshold calculator configured to generate a variable threshold based on a signal-to-noise ratio (SNR) of received signals;

a glint detector configured to compare the variable threshold with off-boresight error estimates;

a Markov-chain counter configured to count a number of times that the off-boresight error estimates exceed the variable threshold based on an output from the glint detector;

a monopulse variance estimator configured to generate measurement-variance estimates from the SNR; and

a point target classifier configured to provide the measurement-variance estimates to a target-state estimator based on an output of the Markov-chain counter indicating that the target is a point target, and

wherein the output of the glint detector indicates when the off-boresight error estimates exceed the variable threshold, and

wherein the point target classifier is configured to refrain from providing the measurement-variance estimates to the target-state estimator when the target is determined not to be a point target.

21. The target tracking radar of claim 20 wherein when the target is determined to be a point target, the target-state estimator is configured to use the measurement-variance estimates to calculate the target position updates, and

wherein when the target is determined not to be a point target, the target-state estimator is configured to use filter residuals to calculate the target position updates.