Detection system

• US 5,504,486 A
• Filed: 12/02/1993
• Issued: 04/02/1996
• Est. Priority Date: 12/02/1993
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Corporation (Martin Marietta Corporation)
• Inventors: Bushman, Boyd B.
• Primary Examiner(s): Eldred, J. Woodrow
• Application Number:
  US08/161,554
• Time in Patent Office: 852 Days
• Field of Search: 342/90, 342/139, 342/160
• US Class Current: 342/90
• CPC Class Codes: G01S 13/02 Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
• CPC Class Codes: G01S 13/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S13/46
• CPC Class Codes: G01S 13/52 Discriminating between fixed and moving objects or between objects moving at different speeds
• CPC Class Codes: G01S 7/412 based on a comparison between measured values and known or stored values
• CPC Class Codes: G01S 7/414 Discriminating targets with respect to background clutter

Abstract

A detection system will detect targets against a fixed background if the target is of a type emitting a gaseous plume. The detection system directs electromagnetic energy, preferably radio frequency signals, toward the fixed background in an area of suspected target activity. The detection system has a receiver which detects reflected electromagnetic energy from the fixed background. The system will identify anomalous variations in range. The variations occur as a result of refraction of the electromagnetic energy wave passing through the gaseous exhaust stream. This indicates a probable target which is creating exhaust plume.

Claims

1. A method for detecting targets against a fixed background wherein each of said targets emits a gaseous exhaust plume, said method comprising the steps of:

directing electromagnetic energy at a fixed background in an area of suspected target activity;

detecting reflected electromagnetic energy from said fixed background;

identifying anomalous variations in range to selected points within said fixed background within said area which occur as a result of refraction of said electromagnetic energy passing through a gaseous exhaust plume; and

identifying a probable target location utilizing said selected points within said fixed background within said area.

2. The method for detecting targets against a fixed background according to claim 1 wherein said step of directing electromagnetic energy at a fixed background in an area of suspected target activity comprises the step of activating a radar system to direct radio frequency energy at a fixed background in an area of suspected target activity.

3. The method for detecting targets against a fixed background according to claim 1 wherein said step of detecting reflected electromagnetic energy from said fixed background comprises the step of detecting reflected electromagnetic energy from said fixed background at a plurality of successive instants.

4. The method for detecting targets against a fixed background according to claim 3 where said step of identifying anomalous variations in range to selected points within said fixed background in an area which occur as a result of refraction of said electromagnetic energy passing through a gaseous exhaust plume comprises the step of subtracting from said reflected electromagnetic energy received at a selected instant each portion thereof which is unchanged from electromagnetic energy received at a preceding instant.

5. A method for detecting targets against a fixed background wherein each of said targets emits a gaseous exhaust plume, said method comprising the steps of:

directing radio frequency electromagnetic energy at a fixed background in an area of suspected target activity;

detecting reflected electromagnetic energy from said fixed background at a plurality of successive instants;

identifying anomalous variations in range to selected points within said fixed background within said area which occur as a result of refraction of said electromagnetic energy passing through a gaseous exhaust plume by subtracting from said reflected electromagnetic energy received at a selected instant each portion thereof which is unchanged from electromagnetic energy received at a preceding instant; and

identifying a probable target location utilizing said selected points within said fixed background within said area.

6. A radar system for detecting low altitude targets against a fixed background wherein each of said low altitude targets emits a gaseous exhaust plume, said radar system comprising:

a transmitter for directing radio frequency electromagnetic energy at a fixed background in an area of suspected target activity;

a receiver for detecting reflected electromagnetic energy from said fixed background; and

a filter for identifying anomalous variations in range to selected points within said fixed background within said area which occur as a result of refraction of said electromagnetic energy passing through a gaseous exhaust plume wherein a low altitude target emitting a gaseous exhaust plume may be detected.

7. The radar system according to claim 6 further including a display for displaying a range and bearing to said selected points within said fixed background.

8. The radar system according to claim 7 wherein said receiver comprises a receiver for detecting radio frequency electromagnetic energy for detecting reflected radio frequency electromagnetic energy from said fixed background at a plurality of successive instants.

9. The radar system according to claim 8 wherein said filter comprises a means for subtracting from said reflected electromagnetic energy received at a selected instant each portion thereof which is unchanged from electromagnetic energy received at a preceding instant.