Generalized inner product method and apparatus for improved detection and discrimination

• US 20100245157A1
• Filed: 08/25/2009
• Published: 09/30/2010
• Est. Priority Date: 03/30/2009
• Status: Active Grant

• Current Assignee: United States Air Force (Government of the United States of America)
• Original Assignee: United States Air Force (Government of the United States of America)
• Inventors: Wicks, Michael C., Zhang, Yuhong
• Granted Patent: US 7,916,068 B2
• Time in Patent Office: Days
• US Class Current: 342/162
• CPC Class Codes: G01S 13/5248 combining a coherent MTI processor with a zero Doppler processing channel and a clutter mapped memory, e.g. MTD (Moving target detector), area MTI G01S13/538

Abstract

Method and apparatus for improving the detection and discrimination of slow moving or stationary range-Doppler spread objects on or in close proximity to the ground (or sea surface). Invention detects, discriminates and separates radar returns from interference including ground clutter discretes via a coherent process for separating target returns from the myriad of received signals. Thus the method and apparatus improves the probability of detecting and declaring the presence or absence of an object at the same time that the probability of false declaration decreases. The method and apparatus may be applied to the processing of any over resolved object, including airborne radar.

Claims

1. Apparatus for detecting and discriminating fixed and slow moving objects in clutter, comprising:

a radar receive channel capable of receiving a radar pulse;

a preprocessor for

converting said radar pulse to an intermediate frequency pulse;

sampling said intermediate frequency pulse to yield a digital representation thereof;

processing said digital representation so as to extract range-pulse data; and

recording said digital representation over one coherent processing interval;

a buffer memory for storing said recorded digital representation as a range-pulse data matrix;

a weighted discrete Fourier transformer for converting said range-pulse data matrix to a range-Doppler data matrix;

a pre-store memory for maintaining a database of target templates;

a range-Doppler index calculator for calculating the range-Doppler indices for each said target template;

a generalized inner product tester for composing and outputting an image formed from said range-Doppler indices and said range-Doppler data matrix; and

a detector/discriminator for determining the existence of a target and its geometric parameters from said image.

2. The apparatus of claim 1, wherein said generalized inner product tester further comprises:

means for separating said range-Doppler data matrix into;

range-Doppler data corresponding to a coherent processing interval under test; and

historical range-Doppler data lacking target detections;

means for forming a data vector under test from;

said range-Doppler data corresponding to a coherent processing interval under test; and

range-Doppler indices for each said target template;

a memory buffer for storing said formed data vector;

means for forming a training data vector from;

said historical range-Doppler data lacking target detections; and

range-Doppler indices for each said target template;

a memory buffer for storing said formed training data vector;

a covariance estimator for forming a covariance matrix from said formed training data vector;

means for computing a generalized inner product from said covariance matrix and said data vector under test; and

a memory buffer for storing said computed generalized inner product.

3. The apparatus of claim 2, wherein said extracted range-pulse data, received in one coherent processing interval for K range cells, is represented by the matrix:

X=[x₁ x₂ . . . x_K];

where

4. The apparatus of claim 3 wherein said database of target templates stored in said pre-store memory comprises:

a plurality of target templates further comprising the structure and shape of each target of interest;

a plurality of standardized target templates comprising circular ring templates and circular disk templates;

wherein each of said plurality of targets is large enough so as to cause a range-Doppler spectrum to be spread over multiple range-Doppler cells.

5. The apparatus of claim 4, wherein said database of target templates stored in said pre-store memory comprises said range-Doppler indices of each of said plurality of target templates and standardized target templates.

6. The apparatus of claim 5, wherein said range-Doppler index calculator further comprises means for calculating said range-Doppler indices for each target template in real-time or off-line.

7. The apparatus of claim 6, wherein said range-Doppler indices comprise:

target parameters comprising position, size, orientation, and radial speed; and

radar and platform parameters comprising wavelength, speed, and altitude.

8. The apparatus of claim 7 for detecting and discriminating fixed and slow moving objects in clutter comprises a mobile radar.

9. The apparatus of claim 8, wherein said mobile radar comprises an airborne radar.

10. The apparatus of claim 9, wherein said airborne radar is a coherent, pulse-Doppler radar.

11. Method for detecting and discriminating fixed and slow moving objects in clutter, comprising the steps of:

receiving a radar pulse;

preprocessing said radar pulse, said preprocessing further comprising the steps of;

converting said radar pulse to an intermediate frequency pulse;

sampling said intermediate frequency pulse to yield a digital representation thereof;

processing said digital representation so as to extract range-pulse data; and

recording said digital representation over one coherent processing interval;

storing said recorded digital representation as a range-pulse data matrix in a buffer memory;

converting said range-pulse data matrix to a range-Doppler data matrix through a weighted discrete Fourier transformer;

maintaining a database of target templates in a pre-store memory;

calculating the range-Doppler indices for each said target template in a range-Doppler index calculator;

composing and outputting an image formed from said range-Doppler indices and said range-Doppler data matrix by performing a generalized inner product test; and

determining the existence of a target and its geometric parameters from said image using a detector/discriminator.

12. The method of claim 11, wherein said step of performing a generalized inner product test further comprises the steps of:

separating said range-Doppler data matrix into;

range-Doppler data corresponding to a coherent processing interval under test; and

historical range-Doppler data lacking target detections;

forming a data vector under test from;

said range-Doppler data corresponding to a coherent processing interval under test; and

range-Doppler indices for each said target template;

storing said formed data vector in a memory buffer;

forming a training data vector from;

said historical range-Doppler data lacking target detections; and

range-Doppler indices for each said target template;

storing said formed training data vector in a memory buffer;

forming a covariance matrix from said formed training data vector by performing a covariance estimation;

computing a generalized inner product from said covariance matrix and said data vector under test; and

storing said computed generalized inner product in a memory buffer.

13. The method of claim 12, wherein said extracted range-pulse data, received in one coherent processing interval for K range cells, is represented by the matrix:

X=[x₁ x₂ . . . x_K];

where

14. The method of claim 13 wherein said database of target templates stored in said pre-store memory comprises:

a plurality of target templates further comprising the structure and shape of each target of interest;

a plurality of standardized target templates comprising circular ring templates and circular disk templates;

wherein each of said plurality of targets is large enough so as to cause a range-Doppler spectrum to be spread over multiple range-Doppler cells.

15. The method of claim 14, wherein said database of target templates stored in said pre-store memory comprises said range-Doppler indices of each of said plurality of target templates and standardized target templates.

16. The apparatus of claim 15, wherein said step of calculating range-Doppler indices further comprises the step of calculating said range-Doppler indices for each target template in real-time or off-line.

17. The method of claim 16, wherein said range-Doppler indices comprise:

target parameters comprising position, size, orientation, and radial speed; and

radar and platform parameters comprising wavelength, speed, and altitude.

18. The method of claim 17 wherein said radar is a mobile radar.

19. The method of claim 18, wherein said mobile radar is an airborne radar.

20. The method of claim 19, wherein said airborne radar is a coherent, pulse-Doppler radar.