Raster scan radar with true motion memory

• US 4,833,475 A
• Filed: 01/27/1986
• Issued: 05/23/1989
• Est. Priority Date: 01/27/1986
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Pease, William M., Bauer, Arthur L. Jr.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Sotomayor, John B.
• Application Number:
  US06/823,168
• Time in Patent Office: 1,212 Days
• Field of Search: 342/184, 342/185, 342/25
• US Class Current: 342/185
• CPC Class Codes: G01S 7/24 the display being orientated or displaced in accordance with movement of object carrying the transmitting and receiving apparatus, e.g. true-motion radar
• CPC Class Codes: G01S 7/298 Scan converters

Abstract

A radar system having a raster scan memory storing scan-to-scan integrated true motion stabilized data. A scan converter generates x,y addresses along azimuth sweeps from the x,y coordinates of own-ship relative to an arbitrary true reference origin. Accordingly, as own-ship moves, the initial x,y coordinates for the azimuth sweeps are continuously being updated. For each x,y coordinate generated, the scan converter also generates a range address for reading corresponding video data stored in polar coordinates relative to own-ship. The x,y coordinates are coupled to a PROM which rolls over the x,y coordinates that are outside of the x,y address field of the memory thereby enabling the addressing of the memory for storing data derived from corresponding polar coordinate video data. Data in the memory is used to raster scan a visual display. The memory is organized into a plurality of planes wherein the data for each pixel of the display is derived from a plurality of bits that are scan-to-scan integrated. The transfer of data to the visual display is controlled such that the raster scanning can be initiated from any row and from any column of stored data.

Claims

1. The method of processing echo signals received at a moving ship, comprising the steps of:

digitizing said echo signals to provide echo data in polar coordinates relative to said moving ship;

converting said echo data to rectangular coordinates relative to a true origin wherein polar coordinate data corresponding to the same spatial location but received on different scans are provided with the same rectangular coordinates notwithstanding the distance moved by said moving ship between said differenct scans;

rolling said rectangular coordinates over to be within a fixed predetermined address field;

correlating said converted data with spatially corresponding data received on at least one prior scan;

storing said correlated data in a memory; and

refreshing a raster scan display with the data stored in said memory.

2. A marine shipboard radar system for mounting on own-ship which is moving, comprising:

means for receiving radar returns;

a first memory;

means responsive to said radar returned for storing in said first memory data in polar coordinates relative to the spatial position of own-ship;

means for generating rectangular coordinates and, synchronous to the generation of each of said rectangular coordinates, generating an address for reading corresponding data from said first memory, said rectangular coordinates having a true origin that remains fixed regardless of the spatial position of said own-ship wherein the same rectangular coordinates are generated for polar coordinate data received on different scans from the same spatial location notwithstanding movement of said own-ship between said different scans;

a raster scan display;

a second memory for storing image data in accordance with said rectangular coordinates for refreshing said raster scan display, said second memory having a predetermined rectangular address field;

means for rolling over said generated rectangular coordinates to stay within said address field of said second memory; and

means for correlating said data read out of said first memory with spatially corresponding image data in said second memory to modify the image data stored in said second memory.

3. A marine radar, comprising:

means mounted on a moving ship for receiving echo signals;

a first memory for storing in polar coordinates having said moving ship as origin data corresponding to said echo signals;

a scan converter for generating x, y coordinates and, synchronous to the generation of each of said x, y coordinates, for generating a range address for reading corresponding data from said first memory, said x, y coordinates having a fixed true origin independent of the distance traveled by said moving ship wherein the same x, y coorinates are generated for echo signals from the same spatial location on different scans notwithstanding movement of said moving ship in the interim between said different scans;

a raster scan display;

a second memory having storage locations corresponding to pixels on said visual display for refreshing said raster scan display, said second memory having a predetermined x, y address field;

means for rolling over said generated x, y coordinates at the x and y boundaries of said x, y address field of said second memory; and

means responsive to said generated x, y coordinates for correlating said data read out of said first memory with spatially corresponding data in said second memory and for writing modified data back into said second memory.

4. A marine shipboard radar system, comprising:

means for receiving echo signals;

a first memory;

means responsive to said echo signals for storing in said first memory data in polar coordinates relative to the location of own-ship which is moving;

means for generating a set of rectangular coordinates corresponding to the location of said own-ship, said set of rectangular coordinates being in a rectangular coordinate system having an arbitrary true reference for origin which remains fixed independent of how far own-ship moves;

means for generating sets of rectangular coordinates along azimuths in said rectangular coordinate system from said rectangular coordinate set of said own-ship and, synchronous to the generation of each of said sets of rectangular coordinates, for generating a corresponding range address for reading said data from said first memory, said rectangular coordinates being the same for echo signals received on different scans from the same spatial location notwithstanding the location of said own-ship being different for said different scans;

a raster scan display;

a second memory for storing data in accordance with said rectangular coordinate system for refreshing said raster scan display, said second memory having a predetermined rectangular address field;

means for rolling over said generated sets of rectangular coordinates at the boundaries of said second memory address field so that said rectangular coordinates fall within said second memory address field; and

means for correlating data read out of said first memory with spatial corresponding data stored in said second memory and for modifying data stored in said second memory in accordance with said correlation.

5. A marine radar for mounting on a moving ship, comprising:

means for providing radar return data in polar coordinates relative to the instantaneous spatial location of said moving ship;

means for converting said polar coordinate data to cartesian coordinates relative to a true origin that remains fixed independent of the distance traveled by said moving ship wherein polar coordinate data corresponding to the same spatial location on different scans are converted to the same cartesian coordinates notwithstanding movement of said moving ship in the interim between said different scans;

a raster scan display;

a memory for storing spatially corresponding image data in cartesian format for refreshing said raster scan display, said memory having a predetermined address field of cartesian coordinates;

means for rolling over the cartesian coordinates of said converting means to be within said predetermined address field of said memory while maintaining said true origin of said cartesian coordinates notwithstanding said ship moving outside the spatial region initially defined by said memory; and

means for correlating data from said converting means with said image data in said memory and modifying said image data in said memory in accordance with said correlation.

6. The marine radar recited in claim 5 further comprising means for determining said instantaneous spatial location of said moving ship relative to said true origin, said converting means being responsive to said determining means.

7. A shipboard radar for moving ship, comprising:

means for providing radar return data in polar coordinates relative to the instantaneous spatial position of said moving ship;

means for determining said instantaneous spatial position of said moving ship;

a raster scan display;

a memory for providing bit image data in rectangular format for refreshing said raster scan display;

a scan converter responsive to said determining means for providing rectangular coordinate memory addresses for said polar coordinate data, said rectangular coordinate addresses being provided relative to a true origin independent of the movement of said moving ship wherein polar coordinate data which is received on different scans from the same spatial position are provided with the same rectangular coordinate memory address notwithstanding said moving being in different spatial positions for said different scans, said scan converter comprising means for rolling over rectangular coordinate memory addresses to be within the addressable field of said memory; and

means for correlating scan converted data with bit image data stored in said memory and having the same rectangular coordinate memory address.