DIGITAL RADAR SIMULATION SYSTEM

• US 3,764,719 A
• Filed: 09/01/1971
• Issued: 10/09/1973
• Est. Priority Date: 09/01/1971
• Status: Expired due to Term

• Current Assignee: Darold R. Dell
• Original Assignee: Darold R. Dell
• Inventors: Dell, Darold R.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US05/176,893
• Time in Patent Office: 769 Days
• Field of Search: 35/10.4
• US Class Current: 434/2
• CPC Class Codes: G01S 7/4052 by simulation of echoes
• CPC Class Codes: G01S 7/4082 using externally generated reference signals, e.g. via remote reflector or transponder
• CPC Class Codes: G09B 9/40 Simulation of airborne radar

Abstract

A digital radar simulation system having a main memory in which data words representative of the elevation and reflectance of discrete locations in a geographic area are stored in cartesian coordinate format. The main memory is continuously sampled to retrieve the data words of locations coming into the radar field of view of a simulated aircraft overflying the geographical area, which data words are placed in a field of view memory in cartesian coordinate format. Signals representative of the speed and heading of the simulated aircraft are used to control the selection of new data words so as to continuously update the field of view memory, so that the field of view memory will at all times contain the data words corresponding to the locations within the simulated aircraft field of view. The data words in the field of view memory are accessed out in a polar coordinate arrangement in the form of successive, discretely spaced radial scan lines and in the order of increasing range for each scan line with the origin of the polar coordinate system coinciding with the position of the simulated aircraft. The data words thus accessed from the field of view memory are suitably processed to produce a radar-like display on a cathode ray tube screen.

Claims

1. A digital radar simulation system comprising a main memory containing data words representative of the radar reflectance and elevation of an array of sub-areas of a geographic area, field of view memory means for accessing and storing the data words of a portion of the geographical area within the field of view of a simulated aircraft, and sequencing means for electronically accessing the data words in the field of view memory means in polar coordinate arrangement.

2. Apparatus according to claim 1 wherein said main memory comprises optically coded data storage means mounted to a movable support and optically sensitive means for scanning the storage means.

3. Apparatus according to claim 2 wherein the data words are arranged on perpendicular bits and tracks on said data storage means in cartesian coordinate format.

4. Apparatus according to claim 2 including buffer means between the optically sensitive means and the field of view memory means for the temporary storage of output signals.

5. Apparatus according to claim 1 wherein the data words are arranged in cartesian coordinate format in said field of view memory means and said field of view memory means includes updating means for entering data words corresponding to locations entering the field of view of a simulated aircraft while deleting data words corresponding to locations leaviNg the field of view of the simulated aircraft.

6. Apparatus according to claim 5 wherein said sequencing means comprises means for accessing the data words in a sector of the field of view memory means centered about a line corresponding to the instantaneous relative direction of the simulated aircraft, in the form of a plurality of successive radial scan lines originating from the instantaneous relative position of the simulated aircraft, the data words accessed being those adjacent the scan lines.

7. Apparatus according to claim 5 further comprising beam widening means for averaging the data words at varying azimuthal locations adjacent the scan lines to effect a blurring simulating radar beam widening.

8. A digital radar simulation system for simulating the radar display of an aircraft overflying a geographical area comprising:

a high density main memory storing digital data words representing the radar reflectance and altitude of an array of equally spaced geographic sub-areas disposed in cartesian coordinates, a field of view memory for storing a plurality of said digital data words in cartesian coordinate arrangement, means for non-destructively reading the data words in a region of the main memory disposed about the instantaneous position of said aircraft and for entering these data words in the field of view memory, sequencing means for electronically accessing data words from the field of view memory lying proximate to a plurality of successive radial scan lines originating from the instantaneous relative position of the aircraft, said scan lines forming a sector centered about a line corresponding to the instantaneous relative direction of the aircraft and processing means for processing the data words from the sequencing means for display on a cathode ray tube.

9. Apparatus according to claim 8 wherein said processing means comprises separating means for separating the data words into elevation and reflectance signals, means for digital-to-analog converting said elevation and reflectance signals, and a radar equation computer responsive to the analog signals.

10. Apparatus according to claim 8 wherein said main memory comprises optically coded data storage means mounted to a movable support and optically sensitive means for scanning the storage means.

11. Apparatus according to claim 10 wherein said optically coded data storage means comprises at least one cylindrical strip mounted to a rotating drum, one of the cartesian coordinate axes being parallel to the circumference of the drum, and means for moving the optically sensitive means in the direction of the other of said axes in response to the movement of said aircraft.

12. A method of simulating the radar display of a geographic area as viewed from an aircraft comprising the steps of storing data words representative of the radar reflectance and elevation of an array of sub-areas of the geographic area, reading and temporarily storing the data words of a region of the geographic area encompassing the location of the aircraft, sequentially electronically accessing those temporarily stored data words lying proximate to a plurality of successive radial scan lines originating from the instantaneous relative position of the aircraft, said scan lines forming a sector centered about a line corresponding to the instantaneous relative direction of the aircraft and processing the sequentially accessed data words for display on a cathode ray tube.

13. The method according to claim 12 wherein the step of storing comprises storing the data words on an optically coded storage medium and the step of reading comprises rotating the optically coated storage medium adjacent an optical sensor.

14. The method according to claim 12 wherein the data words are stored in a cartesian coordinate arrangement.

15. The method according to claim 14 wherein the step of processing includes averaging the radar reflectance component of a plurality of data words proximate to the scan line at a given range to producE a beam widening effect.

16. The method according to claim 15 wherein the step of processing includes separating the radar reflectance and elevation components of the data words, digital-to-analog converting the components and computing simulated radar signals from the components in accordance with the radar equation.

17. The method according to claim 14 wherein the step of reading and temporarily storing includes periodically updating the temporarily stored data words by deleting those data words corresponding to sub-areas leaving the field of view of the aircraft and substituting therefor data words corresponding to sub-areas entering the field of view of the aircraft.