MULTI-TARGET DATA PROCESSING FOR MULTI-STATIC AND MULTI-CHANNEL PASSIVE RADARS

• US 20130076558A1
• Filed: 08/28/2012
• Published: 03/28/2013
• Est. Priority Date: 07/09/2009
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: De Gramont, Emmanuel, Greverie, Wilfried, Klein, Mathieu, Deltour, Jean Claude, Allam, Sbastien
• Granted Patent: US 8,654,007 B2
• Time in Patent Office: Days
• US Class Current: 342/107
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/726 Multiple target tracking
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence

Abstract

The present invention relates to the general field of radar tracking applied to multi-static radar systems. It consists of a method for coherently merging the individual tracks generated from the various bistatic bases that make up the system so as to generate and maintain global tracks so that an object detected by a single bistatic base is represented by the corresponding track and an object detected by a number of bistatic bases and giving rise to the creation of a number of individual tracks is represented only by a single global track.

Claims

1. A tracking method for multi-static and multi-channel radar systems, said method creating global merged tracks by associating the individual blips generated by the various reception channels of the various bistatic bases that make up the system, comprising:

a first upstream merging step for generating, for each bistatic base, merged blips by associating individual blips relating to one and the same target, generated over time by the various reception channels of the bistatic base concerned, the merged blips produced being associated over time to form individual tracks, each individual track characterizing the trend of a given target;

a second downstream merging step for generating global tracks by associating the merged blips that make up the individual tracks generated by various bistatic bases and relating to one and the same target, and by merging the measurements forming the various merged blips to form global measurements used as observation vectors to maintain the global tracks formed, so that each object detected is represented only by a single global track.

2. The method as claimed in claim 1, wherein each merged blip j being characterized by a measurement vector y_j=(r_b, v_b, θ

), the first upstream merging step implements an operation to form individual tracks which itself comprises, for each measurement instant;

a first blip merging step for associating the individual blips of the various reception channels of each bistatic base which exhibit, for a given measurement instant, measurement vectors y_j that are close to one another and forming merged blips;

a second step for constructing individual tracks from the merged blips, an individual track being formed by the succession over time of the merged blips relating to one and the same target.

3. The method as claimed in claim 1, wherein the blip merging step itself comprises the following modules:

a first blip aggregation module which associates the individual blips of various reception channels of each bistatic base which exhibit, for a given measurement instant, measurement vectors y_j that are close to one another and forms merged blips;

a second module for merging the aggregated individual blips which generates, for each aggregate, a single resultant measurement vector y forming a merged blip, this measurement vector being made up from the measurement vectors y_j of the aggregated individual blips, the merged blip being used to form a given individual track;

a third module which checks the state of the individual tracks formed to determine the likelihood of the individual track concerned on the basis of the number of individual blips forming the aggregate from which the merged blips forming the track originate.

4. The method as claimed in claim 3, wherein the first blip aggregation module associates two individual blips p₁ and p₂, the measurement vectors y₁ and y₂ of which satisfy the proximity criterion consisting of the following three simultaneous equalities:

5. The method as claimed in claim 3, wherein the second merging module generates, for each aggregate, a measurement vector y(r_b, v_b, az) from the measurement vectors y_j(r_b, v_b, az) of the blips forming the aggregate, y being defined by the following equalities:

6. The method as claimed in claim 1, wherein the second downstream merging step cyclically implements, for each measurement instant, the following processing modules:

a module for initializing new global tracks from the individual tracks not yet associated deriving from the various bistatic bases;

a module for associating the individual tracks with the global tracks already formed, the association being made if, for the instant concerned, the measurement vector y associated with the individual track is statistically close to the predicted observation vector representing the state of the global track for that instant;

a locating module merging the bistatic distance measurements deriving from the individual tracks contributing to the global tracks;

tracking module;

a management module, responsible for sequencing the other modules and managing the state of the global tracks formed to determine the likelihood of the existing global tracks and for continuing or stopping the maintaining of these tracks, the decision to continue or stop being dependent on the number of merged blips associated with this global track at each of the measurement instants and on the variation of this number over time.

7. The method as claimed in claim 6, wherein the module for initializing new global tracks comprises five steps:

a first step which tests the azimuth consistency of the candidate individual tracks;

a second step which tests the distance consistency of the candidate individual tracks;

a third step which tests the speed consistency of the candidate individual tracks;

a fourth step which proceeds with the initialization of a global track;

a fifth step which consists in aggregating, with the initialized global track, individual tracks coming from the bistatic bases not involved in the initialization of the global track.

8. The method as claimed in claim 6, wherein the second step consists in defining the zone of intersection of the location ellipsoids as a juxtaposition of blocks, the characteristics of which are exploited to represent the position of the target, by a mean value and a covariance matrix.

9. The method as claimed in claim 6, wherein the module for associating the individual tracks with the global tracks implements the calculation of the statistical distance γ

separating a global track i and an individual track j of a bistatic base b, the calculation of γ

being performed on the basis of the bistatic distance, bistatic speed and azimuth components deriving from the association-candidate individual track and the projection y of the state x of the global track in the bistatic base of the candidate individual track.

10. The method as claimed in claim 6, wherein the tracking module proceeds, for each measurement instant k, with the prediction {tilde over (x)}_k of the components of the state vector x corresponding to each global track based on the estimation {circumflex over (x)}_k-1 of the components of the state vector x at the instant k−

1, this estimation itself being performed on the basis of the observation vector y_k-1 generated by means of the measurements relating, for the instant k−

1, to the individual tracks associated with the global track concerned and the prediction {tilde over (x)}_k-1 of the components of the state vector x at the instant k−

1, the components of the observation vector consisting of the result of the merging of the bistatic distances of each individual track, generated in the locating module for the global tracks of the downstream merging step and for the bistatic speeds of the same individual tracks obtained on completion of the upstream merging step.

11. The method as claimed in claim 6, wherein the tracking module proceeds, for each measurement instant k, with the prediction {tilde over (x)}_k of the components of the state vector x corresponding to each global track based on the estimation {tilde over (x)}_k-1 of the components of the state vector x at the instant k−

1, this estimation itself being performed on the basis of the observation vector y_k-1 generated by means of the measurements relating, for the instant k−

1, to the individual tracks associated with the global track concerned and the prediction {tilde over (x)}_k-1 of the components of the state vector x at the instant k−

1, the components of the observation vector consisting of the result of the merging of the bistatic distances of each individual track, generated in the locating module for the global tracks of the downstream merging step and for the bistatic speeds of the same individual tracks obtained on completion of the upstream merging step, the estimation {circumflex over (x)}_k and the prediction {tilde over (x)}_k-1 of the observation vector x being determinated by means of an extended Kalman filter.