Split aperture monopulse antenna system

• US 8,593,334 B2
• Filed: 07/29/2011
• Issued: 11/26/2013
• Est. Priority Date: 07/29/2011
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Sego, Daniel Joseph, Whelan, David Arthur
• Primary Examiner(s): Keith, Jack W
• Assistant Examiner(s): BYTHROW, PETER M
• Application Number:
  US13/194,527
• Publication Number:
  US 20130027241A1
• Time in Patent Office: 851 Days
• Field of Search: 342/123, 342/149, 342/152, 342/153, 342/154
• US Class Current: 342/154
• CPC Class Codes: G01S 13/4445 amplitude comparisons monopulse, i.e. comparing the echo signals received by an antenna arrangement with overlapping squinted beams
• CPC Class Codes: G01S 13/4463 using phased arrays

Abstract

A method and apparatus for processing electromagnetic waves. Electromagnetic waves are transmitted in a selected direction toward a target object from a first array of antenna elements. Scattered electromagnetic waves generated from the electromagnetic waves are received at a first portion of a second array of antenna elements configured to receive the scattered electromagnetic waves in a first direction with respect to the selected direction and at a second portion of the second array of antenna elements configured to receive the scattered electromagnetic waves in a second direction with respect to the selected direction. First information in the scattered electromagnetic waves received by the first portion is subtracted from second information in the scattered electromagnetic waves received by the second portion to form difference data. An elevation angle is identified between a direction of the target object and the selected direction using the difference data.

Claims

1. A method for processing electromagnetic waves, the method comprising:

transmitting the electromagnetic waves in a selected direction toward a target object from a first array of antenna elements;

receiving scattered electromagnetic waves generated from the electromagnetic waves transmitted in the selected direction at a first portion of a second array of antenna elements configured to receive the scattered electromagnetic waves in a first direction with respect to the selected direction and at a second portion of the second array of antenna elements configured to receive the scattered electromagnetic waves in a second direction with respect to the selected direction;

subtracting, by a processor, first information in the scattered electromagnetic waves received by the first portion of the second array of antenna elements from second information in the scattered electromagnetic waves received by the second portion of the second array of antenna elements to form difference data;

generating the first information from first signals generated by the second array of antenna elements in response to the first portion of the second array of antenna elements being electronically steered to receive the scattered electromagnetic waves in the first direction;

generating the second information from second signals generated by the second array of antenna elements in response to the second portion of the second array of antenna elements being electronically steered to receive the scattered electromagnetic waves in the second direction; and

identifying an elevation angle between a direction of the target object and the selected direction using the difference data.

2. The method of claim 1 further comprising:

adding the first information and the second information to form summed data; and

identifying a presence of the target object using the summed data.

3. The method of claim 2, wherein the step of identifying the elevation angle for the target object using the difference data comprises:

identifying the elevation angle as a product of a slope constant and a ratio of the difference data to the summed data.

4. The method of claim 1 further comprising:

estimating a height of the target object using the elevation angle.

5. The method of claim 1, wherein the step of identifying the elevation angle comprises:

identifying a slope of a curve representing the difference data; and

identifying a product of the inverse of the slope of the curve and a ratio of the difference data to summed data.

6. The method of claim 5 further comprising:

determining a desired level of accuracy for an identification of the elevation angle; and

selecting the first direction and the second direction to obtain the desired level of accuracy for the identification of the elevation angle, wherein the first direction and the second direction have an offset from the selected direction of a substantially same magnitude in an elevation direction and wherein a level of accuracy for the identification of the elevation angle increases as the offset increases.

7. The method of claim 1, wherein the second array of antenna elements has a first length that is longer than a second length of the second array of antenna elements.

8. The method of claim 1, wherein the first array of antenna elements is the second array of antenna elements.

9. The method of claim 1, wherein the first array of antenna elements and the second array of antenna elements are selected from a two-dimensional array of antenna elements and a three-dimensional array of antenna elements.

10. The method of claim 1, wherein the first direction and the second direction have a substantially same azimuth angle as the selected direction.

20. The method of claim 1, wherein the steps of generating the first information and generating the second information include electronically steering, the electronically steering including at least one of controlling time delays and phase for signals.

21. The method of claim 1, wherein an electronic steering further controls an accuracy and a sensitivity of the first array of antenna elements and the second array of antenna elements.

22. The method of claim 1, wherein the steps of generating the first information and generating the second information include independently electronically steering the first portion of the second array of antenna elements and the second portion of the second array of antenna elements.

11. An apparatus comprising:

a first array of antenna elements configured to transmit electromagnetic waves toward a target object, wherein the electromagnetic waves are transmitted having a selected direction;

a second array of antenna elements, wherein a first portion of the second array of antenna elements is configured to receive scattered electromagnetic waves generated in response to transmitting the electromagnetic waves toward the target object in a first direction with respect to the selected direction; and

wherein a second portion of the second array of antenna elements is configured to receive the scattered electromagnetic waves in a second direction with respect to the selected direction; and

a signal processing module configured to subtract first information in the scattered electromagnetic waves received by the first portion of the second array of antenna elements from second information in the scattered electromagnetic waves received by the second portion of the second array of antenna elements to form difference data; and

identify an elevation angle between a direction of the target object and the selected direction using the difference data, wherein the first portion of the second array of antenna elements is configured to generate first signals in response to the first portion of the second array of antenna elements being electronically steered to receive the scattered electromagnetic waves in the first direction and wherein the second portion of the second array of antenna elements is configured to generate second signals in response to the second portion of the second array of antenna elements being electronically steered to receive the scattered electromagnetic waves in the second direction.

12. The apparatus of claim 11, wherein the signal processing module is further configured to add the first information and the second information to form summed data;

and

identify a presence of the target object using the summed data.

13. The apparatus of claim 11, further comprising:

a transceiver connected to the second array of antenna elements by a transmission medium, wherein the transceiver is configured to receive the first signals and the second signals from the second array of antenna elements and generate the first information from the first signals and the second information from the second signals.

14. The apparatus of claim 11, wherein the signal processing module is further configured to estimate a height of the target object using the elevation angle.

15. The apparatus of claim 11, wherein the first array of antenna elements is the second array of antenna elements.

16. The apparatus of claim 11, wherein the first direction and the second direction have a substantially same azimuth angle as the selected direction.

17. The apparatus of claim 11, wherein the first array of antenna elements and the second array of antenna elements are associated with a platform selected from one of an aircraft, an unmanned aerial vehicle, and a helicopter.

18. An apparatus comprising:

an array of antenna elements configured to transmit electromagnetic waves in a selected direction toward a target object, wherein a first portion of the array of antenna elements is electronically steered to receive scattered electromagnetic waves in a first direction with respect to the selected direction and a second portion of the array of antenna elements is electronically steered to receive the scattered electromagnetic waves in a second direction with respect to the selected direction in which the scattered electromagnetic waves are generated in response to transmitting the electromagnetic waves toward the target object;

a transceiver connected to the array of antenna elements by a transmission medium, wherein the transceiver is configured to generate first information from first signals received from the array of antenna elements in response to the first portion of the array of antenna elements receiving the scattered electromagnetic waves in the first direction and generate second information from second signals received from the array of antenna elements in response to the second portion of the array of antenna elements receiving the scattered electromagnetic waves in the second direction; and

a signal processing module configured to add the first information and the second information to form summed data;

subtract the first information from the second information to form difference data; and

identify an elevation angle between a direction of the target object and the selected direction using the difference data and the summed data.

19. The apparatus of claim 18, wherein the first direction and the second direction have a substantially same azimuth angle as the selected direction.