Radar video detector and target tracker

• US 4,845,500 A
• Filed: 03/25/1988
• Issued: 07/04/1989
• Est. Priority Date: 03/25/1988
• Status: Expired due to Term

• Current Assignee: Sperry Marine Incorporated Charlottesville VA
• Original Assignee: Sperry Marine, Inc. (Northrop Grumman Corporation)
• Inventors: Corbett, James D., Cornett, Johnny A.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Hellner, Mark
• Application Number:
  US07/173,399
• Time in Patent Office: 466 Days
• Field of Search: 342/90, 342/91, 342/136, 342/139
• US Class Current: 342/90
• CPC Class Codes: G01S 13/72 for two-dimensional tracking, e.g. combination of angle and range tracking, track-while-scan radar
• CPC Class Codes: G01S 7/2927 by deriving and controlling a threshold value

Abstract

A system for detecting and tracking a multiplicity of targets averages radar video returns over small sectors for data smoothing and noise reduction, provides adaptive thresholding by determining noise levels in an area of interest and establishes a detection threshold in accordance with such noise level, stores the video data for reach target of interest so that multiple targets on the same bearing may be tracked, and reduces the probability of target swapping by adjusting the target window in accordance with target size and weighting the cells within the window.

Claims

1. An apparatus for detecting radar return video signals comprising:

means for receiving said video signals within predetermined range bins and angle sectors for providing signals representative of average amplitudes of a plurality of successive radar returns within cells of a matrix of cells formed by said range bins and said angle sectors, each range bin forming a row in said matrix and each angle sector forming a column;

means for storing said representative signals in memory units corresponding to said cells, thereby establishing memory stored signals;

means responsive to said memory stored signals for computing a mean value and a mean deviation value for said representative signals in at least one row of said matrix;

means coupled to said computing means and said memory means for subtracting a linear combination of said mean value and said mean deviation value from said memory stored signals, thereby establishing noise reduced signals; and

means responsive to said noise reduced signals for setting positive noise reduced signals to zero in cells not having at least one abutting cell with a positive noise reduced signal, abutting cells with positive noise reduced signals therein representing detected target units.

2. An apparatus for detecting radar return video signals in accordance with claim 1 further including means for establishing at least one detection window, each window commencing in range and angle at selected positions, extending in range for a plurality (m) range bins and extending angularly for a multiplicity (n) angle sectors, thereby establishing windows with m×

n cells therein.

3. An apparatus for detecting radar return video signals in accordance with claim 2 further including:

means for counting said detected target units in each window to provide a signal representative of a target size therein;

means for weighting said detected target units in accordance with row positions to obtain a row weighted signal for each row;

means for weighting said detected target units in accordance with column positions to obtain a column weighted signal for each column;

means for summing said row weighted signals, said column weighted signals, and signals in all cells to obtain a signal representative of a row weighted sum, a signal representative of a column weighted sum, and a signal representative of a total signal sum, respectively, for each window; and

means responsive to said signals representative of said row and column weighted sums and said signal representative of said total signal sum for dividing said signals representative of said row and column weighted sums by said signal representative of said total signal sum to obtain a signal representative of target position in each window.

4. An apparatus for detecting radar return video signals in accordance with claim 3 further including means responsive to said signal representative of said target size and said signals representative of said row and target position for adjusting each window size in accordance with said target size therein, thereby providing adjusted windows, and for centering targets within said adjusted windows.

5. An apparatus for detecting radar return video signals in accordance with claim 4 wherein said return video signals are detected by a radar system having a scanning antenna and means for determining angular locations of said targets in said windows relative to a predetermined angular reference further including:

means for determining speeds and headings of moving targets in said windows and providing signals representative thereof; and

means responsive to said speed and heading representative signals for providing predicted positions of said targets for subsequent antenna scans.

6. A method for detecting radar return video signals including the steps of:

receiving said video signals within predetermined range bins and angle sectors, said range bins and angle sectors forming cells in a range-angle matrix of cells;

averaging signal amplitudes of successive radar returns for each cell, to provide signals representative of average amplitudes in each cell;

storing said representative signals in memory units corresponding to said cells, thereby establishing memory stored signals;

computing a mean value and a mean deviation value for said representative signals in at least one row of said matrix in response to said memory stored signals;

subtracting a linear combination of said mean value and mean deviation value from said memory stored signals, thereby establishing noise reduced signals; and

setting positive noise reduced signals to zero in cells not having at least one abutting cell with a positive noise reduced signal, abutting cells with positive noise reduced signal, abutting cells with positive noise reduced signals therein representing detected target units.

7. A method for detecting radar return video signals in accordance with claim 6 further including the step of establishing at least one detection window, each window commencing in range and angle at selected positions, extending in range for a plurality (m) range bins and extending angularly (n) for a multiplicity (n) angle sectors, thereby establishing m×

n cells in a window.

8. A method for detecting radar return video signals in accordance with claim 7 further including the steps of:

counting said target units in each window to provide a signal for each window representative of a target size therein;

weighting said detected target units in accordance with row positions in said window to obtain a row weighted signal for each row;

weighting said detected target units in accordance with column positions in said windows to obtain a column weighted signal for each column;

summing said row weighted signals, said column weighted signals, and signals in all cells in each window to obtain a signal representative of a row weighted sum, a signal representative of a column weighted sum, and a signal representative of a total signal sum, respectively, for each window; and

dividing said row and column weighted sums of a window by said signal representative of said total sum to obtain a signal representative of target position in each window.

9. The method of claim 8 further including the steps of:

adjusting each window size in accordance with a target size therein thereby providing adjusted windows; and

centering targets within said adjusted windows.

10. The method of claim 9 further including the steps of:

determining speeds and headings of moving targets in said windows; and

calculating predicted positions of said targets at a subsequent time.