Simultaneous triple aperture radar

• US 4,825,213 A
• Filed: 01/12/1987
• Issued: 04/25/1989
• Est. Priority Date: 05/15/1981
• Status: Expired due to Term

• Current Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Original Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Inventors: Smrek, Walter J.
• Primary Examiner(s): TARCZA, THOMAS H
• Application Number:
  US07/012,765
• Time in Patent Office: 834 Days
• Field of Search: 342/25, 342/160, 342/162, 342/161
• US Class Current: 342/25.00B
• CPC Class Codes: G01S 13/9029 specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time
• CPC Class Codes: G01S 13/9092 combined with monopulse techniques

Abstract

An improved radar system and technique are disclosed for use in detecting and tracking moving or stationary targets within the antenna field of view. Precise correction of doppler induced location errors is provided by the use of raw sensor data. Return signals are doppler processed, phase shifted and compared in a manner which preserves the angle of arrival of a moving target irrespective of the boresight direction. Stationary target return signals are constructively combined so as to augment the target signal gain independent of the antenna boresight direction.

Claims

1. An airborne simultaneous triple synthetic aperture radar system comprising:

first, second and third antenna means linearly spaced on an aircraft, each of said antenna means being electrically connected to a dedicated receive channel processor,

first, second and third frequency filter means in electrical communication with said first, second and third antenna means, respectively,

means for phase shifting the output of said first filter means to effect clutter coincidence with the output of said second filter means,

means for phase shifting the output of said second filter means to effect clutter coincidence with the output of said third filter means,

signal reduction means for combining clutter coincided filter outputs to derive a residual signal from each pair of clutter coincided signals,

signal addition means for combining the two residual signals so obtained,

signal comparison means for comparing the combined residual signals to a threshold and generating a moving target detection indicator signal,

signal comparison means adapted to determine phase relationships between residual signals to define the electrical phase angle between them, and

data processing means for deriving the doppler position and angle off boresight of the moving target.

2. The apparatus as described in claim 1, wherein said antenna means include three physically separate antenna assemblies.

3. The apparatus as described in claim 1, wherein said antenna means include three component parts of a single antenna array.

4. The apparatus as described in claim 1, further including means for averaging each of the residual signals over time to define amplitude and phase imbalances in the antenna means and receive channel processors.

5. The apparatus as defined in claim 1, further including signal dividing means for extracting defined moving target information from the filter output signals, phase shifting means for effecting clutter coincidence between the non-moving target portion of each filter output signal, and signal summing means for combining phase coincided portions of adjacent filter output signals as to define the representative signal amplitude of objects not in motion relative to a motion compensation point.

6. The apparatus as described in claim 4, further including signal balancing means for processing said imbalances as to match phase and amplitude characteristics of each antenna means and receive channel processor combination.

7. The apparatus as defined in claim 5, further including means for combining the non-moving portions of each filter output signals to generate a ground map display.