System for tracking radar targets in background clutter

• US 5,748,140 A
• Filed: 03/28/1996
• Issued: 05/05/1998
• Est. Priority Date: 03/28/1996
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Inventors: Schober, Michael B.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/627,813
• Time in Patent Office: 768 Days
• Field of Search: 342/90, 342/93, 342/97, 342/140, 342/160, 342/161, 342/162
• US Class Current: 342/90
• CPC Class Codes: G01S 13/52 Discriminating between fixed and moving objects or between objects moving at different speeds
• CPC Class Codes: G01S 13/726 Multiple target tracking

Abstract

A radar tracking system 100 adapted for use with existing radar tracking systems. The inventive system includes a radar target detection system 106, 108 for detecting radar targets in clutter using magnitude and angular position information obtained from return signals. A tracking algorithm 104 is used to track and update the positions of said targets with respect to the position of the radar system. The tracking algorithm includes a true target angle estimator 110 for maintaining accurate target angle information when the target is clutter and when the target is out of clutter. The tracking algorithm maintains accurate target distance information when the target is in clutter and when the target is out of clutter. In a specific embodiment, accurate distance information is maintained in a track file 122 where the amplitudes of return signals are stored once a target is detected by the detection system 100.

Claims

1. A radar system comprising:

means for detecting radar targets in clutter using magnitude and angular position information obtained from return signals and

means for tracking and updating the positions of said targets with respect to the position of the radar system, said means for tracking including angle means for extracting target angle information from clutter angle information when the target is in clutter.

2. The invention of claim 1 wherein said means for tracking includes a track file for filtering information about a target once a target is detected by said means for detecting.

3. The invention of claim 1 wherein said means for tracking includes means for accessing current range and Doppler information within a radar mainlobe beamwidth of the radar system.

4. The invention of claim 3 wherein said angle means includes means for decentroiding said angle values, said means for decentroiding having a system for factoring out angle information received from clutter returns from angle information received from target returns.

5. The invention of claim 4 wherein said angle means includes the following equation for factoring out angle information received from clutter returns from angle information received from target returns:

space="preserve" listing-type="equation">θ

.sub.new =((Po+P1)*θ

-Po*θ

o)/P1

where Po is the average power of the clutter, Pl is the power of a test signal such as a potential target return, θ

is the angular position of said test signal, θ

o is the average angle of said clutter returns, and θ

_new is decentroided angle information whose expected value is the actual angle of the target.

6. The invention of claim 4 wherein said means for decentroiding said angle values includes an accuracy means for determining the accuracy of decentroided angle information.

7. The invention of claim 6 wherein said accuracy means includes a system which computes variance as a function of angular separation distance between an estimated true target location and an estimated location of the clutter.

8. The invention of claim 7 wherein said estimated true target location is said decentroided angle information.

9. The invention of claim 7 wherein said estimated true target location is an averaged or smoothed angle value obtained from a track file.

10. The invention of claim 7 wherein said variance is computed using the following equation:

space="preserve" listing-type="equation">σ

.sub.θ

.sup.2 =(Po/P1)(θ

.sub.new -θ

o).sup.2 /(2(N-1))

where σ

₇₄ ² is the variance, Po is the average power of said clutter returns, P1 is the power of a test signal such as a potential target return, θ

_new is the estimated true target location and θ

o is the average angle of said clutter returns.

11. Method for tracking a radar target in clutter using a radar system comprising the steps of:

forming a range Doppler matrix (RD matrix);

determining from said RD matrix if said radar target is in the beam region of said radar system, is in clutter, or is in a noise only region of the RD matrix;

performing conventional detection and tracking algorithms if said target is in a noise only region of the RD matrix;

executing a tracking algorithm if said target is in the beam region of the radar system or is in clutter, said tracking algorithm including the steps of;

selecting locations in the RD matrix for testing and sampling clutter returns and potential target returns and providing clutter angle and magnitude information and target magnitude and angle information in response thereto;

applying a beam detection algorithm which utilizes said clutter angle and magnitude information and said target angle and magnitude information to detect said target;

decentroiding said target angle information for providing an accurate true target angle estimate;

updating any required filters and track files of said radar system with said accurate true target angle estimate, said target magnitude information and said clutter magnitude and angle information; and

repeating the above steps as necessary to track a target through regions of the RD matrix.