Radar video scan converter

• US 4,845,501 A
• Filed: 01/27/1986
• Issued: 07/04/1989
• Est. Priority Date: 01/27/1986
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Pope, Albert A., Pease, William M.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Sotomayor, John B.
• Application Number:
  US06/823,165
• Time in Patent Office: 1,254 Days
• Field of Search: 342/185, 342/184
• US Class Current: 342/185
• CPC Class Codes: G01S 7/298 Scan converters

Abstract

A marine radar system having a multi-plane video memory for storing scan-to-scan integrated video data used to raster scan the CRT. A scan converter generates cartesian or x,y addresses for the video memory and synchronous with the generation of each, x,y address, generates a range address for reading corresponding video data from an r,θ or polar memory. The x,y addresses are generated along azimuth sweeps by incrementing one coordinate by a pixel unit and the other coordinate by a trigonometric function. The unit coordinate and the trigonometric function are determined by the 45° octant in which the azimuth sweep is located. The pixel unit incremented coordinate is offset by one pixel unit from the origin of the azimuth sweep in alternate octants to address pixels along the octant boundaries and thereby avoid display artifacts.

Claims

1. In combination:

a visual display;

a memory having storage locations corresponding to pixels on said visual display;

means for generating addresses for storing data in said memory, said data corresponding to echo signals received by scanning a plurality of azimuths of a scan, said generating means generating at least one of said memory addresses a plurality of times during said scan;

means for providing composite data for said one memory address, said providing means comprising means for ORing all of the data corresponding with said one memory address which is received during said scan to provide said composite data; and

means responsive to said composite data for updating the contents of said one memory address in said memory after said one memory address is generated for the last time during said scan.

2. The combination recited in claim 1 wherein said generating means comprises means for determining the first time said one memory address is generated during said scan.

3. The combination recited in claim 2 wherein said generating means further comprises means for determining the last time said one memory address is generated during said scan.

4. In combination:

a first memory for storing, in range format, echo data received from an azimuth of a scan;

a visual display;

a second memory having storage location corresponding to pixels on said visual display;

a scan converter for generating addresses for said second memory and, synchronous with the generation of each of said second memory addresses, for generating an address for reading corresponding echo data out of said first memory;

said scan converter generating at least one of said second memory addresses a plurality of times during said scan;

means for providing composite data in response to each echo data read out of said first memory corresponding to said one address of said second memory during a scan; and

means responsive to said composite data for modifying the contents of said one memory address in said second memory.

5. The combination recited in claim 4 wherein said scan converter means comprises means for determining the first time said one second memory address is generated during said scan.

6. The combination recited in claim 4 wherein said scan converter comprises means for determining the last time said one second memory address is generated during said scan.

7. In combination:

a first memory for storing in range format radar return data received from an azimuth of a scan;

a visual display;

a second memory having storage locations corresponding to pixels on said visual display;

a scan converter for generating addresses for said second memory and synchronously with the generation of each of said second memory addresses, for generating an address for reading corresponding radar return data out of said first memory;

said scan converter comprising means for generating a first control signal the first time one of said second memory addresses is generated during a scan;

said scan converter further comprising means for generating a second control signal the last time said one memory address is generated during said scan;

means for providing resultant data in response to all of said return data read out of said first memory for said one second memory address during said scan;

means for reading the storage location in said second memory addressed by said one second memory address; and

means for writing data into said storage location of said one second memory address in accordance with said resultant data and said data read out of said second memory.

8. In combination:

a first memory for storing in range format radar return data received from an azimuth of a scan;

a visual display;

a second memory having a plurality of storage locations corresponding to pixels on said visual display;

a scan converter for generating addresses for said second memory and synchronous to the generation of each of said second memory addresses, for generating an address for reading corresponding radar return data from said first memory;

said scan converter comprising means for generating a first control signal the first time one pixel corresponding address for said second memory is generated during a scan and for generating a second control signal the last time said one pixel corresponding address for said second memory is generated during a scan;

a third memory having storage locations corresponding to predetermined ones of said storage locations of said second memory;

means responsive to said first control signal for writing said radar return data into said third memory; and

means responsive to said second control signal for modifying data stored in said second memory in accordance with said radar return data stored in said third memory.

9. The combination in accordance with claim 8 further comprising means responsive to the absence of said first control signal for reading data from said third memory, ORing it with radar return data read out of said first memory, and writing the result into said third memory.

10. The combination in accordance with claim 9 wherein said second memory has a plurality of said storage locations corresponding to at least one of said pixels and the data stored in said plurality of said storage locations corresponds to radar return data received for that pixel on a plurality of previous scans.

11. In combination:

a memory having storage locations addressable by x,y coordinate addresses;

a scan converter for converting data corresponding to echo signals received in polar coordinates from a plurality of azimuth angles of a scan into data signals having corresponding x,y coordinate addresses, said scan converter generating at least one of said x,y coordinate addresses a plurality of times during said scan;

said scan converter comprising means for generating a control signal the last time said one x,y coordinate address is generated during said scan;

means for ORing all of said data signals during said scan which correspond to said one x,y coordinate address to provide a composite signal for said one x,y coordinate address; and

means responsive to said control signal and said composite signal for modifying the contents of the storage location of said memory addressed by said one x,y coordinate address.

12. The combination recited in claim 11 further comprising a visual display and means for refreshing said visual display in raster scan format with data from said memory.

13. The combination recited in claim 11 wherein said scan converter comprises means for generating a range addresses corresponding to echo signals for each x,y coordinate address generated.

14. The combination recited in claim 11 wherein said scan converter further comprises means for generating a second control signal the first time said one x,y coordinate address is generated during said scan.

15. In combination:

means for polar scanning a region along a plurality of successive azimuth angles for radar return signals;

a first memory for storing said radar return signals corresponding to their range and received azimuth angle;

means for sequentially generating cartesian coordinate addresses along said azimuth angles;

means synchronized with the generation of each of said cartesian coordinate addresses for generating a range address for reading a corresponding radar return signal from said first memory;

means for generating a first control signal the first time one of said cartesian coordinate addresses is generated during a scan of said scanning means;

means for generating a second control signal the last time said one cartesian coordinate address is generated during said scan;

a second memory having storage locations addressable by said generated cartesian coordinate addresses;

means responsive to said first control signal and all of the radar return signals read from said first memory in synchronism with said one cartesian coordinate address during said scan for providing a resultant signal, said providing means comprising a third memory having storage locations corresponding to at least some of said storage locations of said second memory; and

means responsive to said second control signal for modifying the storage location of said second memory addressed by said one cartesian coordinate address in accordance with said resultant signal.

16. The method of generating x,y coordinates along successive azimuth sweeps of a polar scan having a plurality of sectors, comprising the step of:

offsetting the initial x,y coordinate of azimuth sweeps in predetermined ones of said plurality of sectors.

17. The method of generating x,y coordinates along successive azimuth sweeps through a plurality of sectors of a scan wherein the generation of said x,y coordinates along each of said azimuth sweeps is a function of its sector, comprising the step of:

offsetting in predetermined ones of said plurality of sectors the initial x,y coordinate from which x,y coordinates are generated along azimuth sweeps.

18. The method of generating x,y coordinates for scan converting polar coordinate data received along one azimuth sweep of a plurality of successive azimuth sweeps of a scan into cartesian coordinate format, comprising the steps of:

loading a first storage device with a first value corresponding to one of said x,y coordinates of the origin of said azimuth sweep;

loading a second storage device with a second value corresponding to the opposite of said one x,y coordinate of said origin of said azimuth sweep;

offsetting said first storage device by one coordinate unit; and

successively incrementing said first storage device by one coordinate unit while synchronously incrementing said second storage device by a value corresponding to a trigonometric function.

19. The method of generating cartesian coordinates for scan converting polar coordinate data received along one azimuth sweep of a plurality of successive azimuth sweeps of a scan, comprising the steps of:

loading one of said cartesian coordinates corresponding to the origin of said one azimuth sweep into a first register;

loading the opposite coordinate of said one cartesian coordinate corresponding to said origin of said one azimuth sweep into a second register;

offsetting by one coordinate unit said first register as a function of the octant of said scan in which said azimuth sweep is located, said offsetting being executed in alternate ones of said octants; and

repeatedly incrementing said first register by one coordinate unit while synchronously incrementing said second register by a trigonometric value.

20. The method recited in claim 19 wherein said trigonometric value is a function of said octant.

21. The method of generating sets of rectangular coordinates for scan converting to cartesian coordinates data received in polar coordinates along one azimuth of a plurality of successive azimuths of a polar scan, comprising the steps of:

offsetting a first register by one rectangular coordinate unit; and

successively incrementing said first register by said one rectangular coordinate unit while synchronously incrementing a second register by a trigonometric value as a function of the octant of said azimuth in said polar scan.

22. Apparatus for generating x,y coordinates for scan converting polar coordinate data received along an azimuth sweep of a plurality of successive azimuth sweeps of a 360°

scan to cartesian coordinates, comprising;

a first register for storing a value corresponding to one of said cartesian coordinates in first predetermined octants of said scan and for storing a value corresponding to the opposite cartesian coordinate in second predetermined octants of said scan;

a second register for storing a value corresponding to said opposite cartesian coordinate in said second predetermined octants and for storing said one cartesian coordinate in said first predetermined octants;

means for loading into said first register a value corresponding to the coordinate origin of said azimuth sweep of the octant dependent coordinate to be stored in said first register;

means for loading into said second register a value corresponding to the coordinate origin of said azimuth sweep of the octant dependent coordinate to be stored in said second register;

means for offsetting said first register by a coordinate unit in alternate octants; and

means for incrementing said first register by said coordinate unit while incrementing said second register by a trigonometric value of a coordinate unit as a function of the octant of said azimuth sweep.

23. The method of generating rectangular coordinates for scan converting polar coordinate data received from a plurality of successive azimuth sweeps of a radar scan, comprising the steps of:

offsetting in alternate octants of said scan one coordinate of a pair of rectangular coordinates corresponding to the origin of said azimuth sweeps; and

generating pairs of rectangular coordinates along said azimuth sweeps.

24. The method recited in claim 23 wherein said offsetting corresponds to one coordinate unit in a direction away from said azimuth sweep.

25. The method of generating rectangular coordinates for scan converting data received from a plurality of successive azimuth sweeps of a scan, comprising the steps of:

offsetting one coordinate of a pair of rectangular coordinates corresponding to the origin of one of said azimuth sweeps of said scan, said offsetting being a function of the sector of said one azimuth sweep; and

generating pairs of rectangular coordinates from said offset pair of coordinates along said azimuth sweep by sequentially incrementing said one coordinate by a coordinate unit and synchronously incrementing the opposite coordinate by a trigonometric fraction of a coordinate unit as a function of said sector.

26. The method recited in claim 25 wherein said offsetting is by one coordinate unit in predetermined ones of said sectors in a direction opposite said azimuth sweep and by zero coordinate units in alternate sectors of said predetermined sectors.

27. The method of generating rectangular coordinates for scan converting polar coordinate data received along a plurality of successive azimuth sweeps of a radar scan, comprising the steps of:

generating a pair of rectangular coordinates corresponding to the origin of one of said azimuth sweeps;

offsetting one coordinate of said pair of coordinates in response to said azimuth sweep being in predetermined sectors of said scan; and

generating pairs of rectangular coordinates from said offset along the azimuth of said azimuth sweep.

28. The method recited in claim 27 wherein said generating from said offset pair of coordinates is provided by sequentially incrementing said one coordinate by a coordinate unit and synchronously incrementing the opposite coordinate by a trigonometric value determined as a function of said sector.

29. The method recited in claim 27 wherein said sectors define 45°

octants.

30. The method of generating x,y coordinates for scan converting polar coordinate data received from a plurality of azimuth sweeps of a radar scan divided into eight 45°

octants, comprising the steps of;

offsetting as a function of the octant of said octants in which one of said azimuth sweeps is located one coordinate of a pair of rectangular coordinates corresponding to the origin of said one azimuth sweep; and

generating x,y coordinates along said one azimuth sweep from said offset pair of coordinates by incrementing said one coordinate by a coordinate unit and synchronously incrementing the opposite coordinate by a value trigonometrically corresponding to said coordinate unit as a function of said octant of said one azimuth sweep.

31. The method recited in claim 30 wherein the sign of incrementing said x and y coordinates is a function of said octant of said one azimuth sweep.

32. The method of generating rectangular coordinates for scan converting polar coordinate data received at a plurality of successive azimuth sweeps of a radar scan divided into sectors, comprising the steps of:

for each of said azimuths in a first sector of said sectors, offsetting one coordinate of a pair of coordinates corresponding to the origin of each of said azimuth sweeps in said first sector, said offsetting being equivalent to one coordinate unit;

for each of said azimuth sweeps in said first sector, generating pairs of coordinates along each of said azimuth sweeps in said first sector from said offset by incrementing said one coordinate by a coordinate unit while synchronously incrementing the opposite coordinate by a fraction of a coordinate unit as a function of a trigonometric value as a function of said first sector;

for each of said azimuth sweeps in a second sector bordering said first sector, generating pairs of coordinates along each of said azimuth sweeps in said second sector from a pair of coordinates respectively corresponding to the origin of said azimuth sweeps in said second sector.

33. The method of generating rectangular coordinates for scan converting polar coordinate data received from a plurality of azimuth sweeps of a radar scan divided into 45°

octants, comprising the steps of;

offsetting in alternate ones of said octants one of the coordinates of a pair of coordinates corresponding to the origin of each of said azimuth sweeps in said alternate octants; and

generating pairs of coordinates at the azimuths of said azimuth sweeps around said scan by incrementing from said origin offsets in said alternate octants and by incrementing in the other octants from pairs of coordinates corresponding to the origin of said respective azimuth sweeps in the octants other than said alternate octants.