Velocity extraction

• US 20070013580A1
• Filed: 06/21/2005
• Published: 01/18/2007
• Est. Priority Date: 06/24/2004
• Status: Active Grant

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Integrated System Technologies Ltd. (BAE Systems Plc)
• Inventors: Finch, Derek, Deakin, Anthony
• Granted Patent: US 7,688,256 B2
• Time in Patent Office: Days
• US Class Current: 342/160
• CPC Class Codes: G01S 13/225 with cyclic repetition of a non-uniform pulse sequence, e.g. staggered PRF
• CPC Class Codes: G01S 13/227 with repetitive trains of uniform pulse sequences, each sequence having a different pulse repetition frequency
• CPC Class Codes: G01S 13/24 using frequency agility of carrier wave
• CPC Class Codes: G01S 13/5246 post processors for coherent MTI discriminators, e.g. residue cancellers, CFAR after Doppler filters
• CPC Class Codes: G01S 13/726 Multiple target tracking
• CPC Class Codes: G01S 7/2886 using I/Q processing

Abstract

A method of extracting a radial velocity characteristic of a target from coherent pulse bursts comprising the steps of applying to data a ‘best fit’ model of the echo returns from a target in the presence of clutter to obtain a residue (error) value and minimising the error value by a predetermined method to give the best fit value for the target radial velocity. The method enables more information to be retrieved from coherent bursts than conventional methods and therefore greatly enhances performance of radiation pulse echo detection.

Claims

1-16. -16. (canceled)

17. A method of extracting a radial velocity characteristic of a target from one or more coherent radiation pulse bursts comprising the steps of:

(a) receiving radiation echo returns of the pulse bursts from a remote scene;

(b) processing the echo returns into in-phase (I) and quadrature (Q) components;

(c) measuring returns at intervals to provide sampled data;

(d) applying a predetermined function to the I-Q returns;

(e) modifying the predetermined function to match the sampled data as a function of velocity; and

(f) determining the target radial velocity in dependence upon said modification step of the predetermined function.

18. A method as claimed in claim 17 wherein step (d) comprises fitting a curve to the I-Q returns and step (e) comprises optimising the fit to the sampled data as a function of velocity in a least squares fashion.

19. A method as claimed in claim 18 wherein a model of clutter return is provided for use in steps (d) and (e).

20. A method as claimed in claim 19 wherein the model of clutter return is a low order polynomial function in I and Q.

21. A method as claimed in claim 17 further comprising the step of extracting target amplitude from the sampled data.

22. A method as claimed in claim 17 further comprising the step of extracting range ambiguity from the sampled data.

23. A method as claimed in claim 17 further comprising the step of extracting target azimuth from the sampled data.

24. A method as claimed in claim 20 wherein the echo returns are measured at non-equi-spaced intervals.

25. A method as claimed in claim 24 wherein the pulse bursts are transmitted at a frequency which is changed between successive pulses.

26. A method as claimed in claim 24 wherein each pulse burst consists of multiple pulses transmitted at irregular intervals.

27. A method as claimed in claim 24 wherein the pulse bursts are internally coherent but mutually incoherent.

28. A method as claimed in claim 17 further comprising the step of carrying out conventional Moving Target Indication/Moving Target Detection filtering and target detection before applying a predetermined function, as in step (d), to the I-Q returns in which a target was detected.

29. A microprocessor programmed to carry out the method of claim 17.

30. A program element comprising program code operable to carry out a method as claimed in claim 17.

31. The program element of claim 30 on a carrier medium.

32. A data processing system adapted and arranged to carry out a method as claimed in claim 17 comprising:

(g) a transmitter;

(h) a receiver;

(i) an I and Q component splitter;

(j) an analog-to-digital converter, and

(k) processing means to fit a predetermined function to I and Q components according to steps (d) and (e).

33. A method as claimed in claim 17 wherein a model of clutter return is provided for use in steps (d) and (e).

34. A method as claimed in claim 33 wherein the pulse bursts are transmitted at a frequency which is changed between successive pulses.

35. A method as claimed in claim 33 wherein each pulse burst consists of multiple pulses transmitted at irregular intervals.

36. A method as claimed in claim 33 wherein the pulse bursts are internally coherent but mutually incoherent.