Phased array antenna with wide null

• US 5,343,211 A
• Filed: 01/22/1991
• Issued: 08/30/1994
• Est. Priority Date: 01/22/1991
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: General Electric Company
• Inventors: Kott, Michael A.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US07/644,358
• Time in Patent Office: 1,316 Days
• Field of Search: 342/379, 342/381, 342/384, 342/424
• US Class Current: 342/379
• CPC Class Codes: G01S 7/2813 Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays specially adapted to secondary radar systems G01S13/762; aerials or aerials systems H01Q21/29, H01Q25/00
• CPC Class Codes: H01Q 3/2611 Means for null steering; Adaptive interference nulling

Abstract

An antenna subject to standoff sidelobe barrage jamming exhibits a null in its sidelobe structure at a selectable elevation angle for all azimuth angles of interest. The null can be set to the elevation angles corresponding to the angle of the standoff jammers. The null is generated with the aid of an interferometer associated with each column of the antenna array. The interferometer produces a pattern having a plurality of lobes. The interferometer pattern is phased and amplitude adjusted relative to the antenna pattern of its associated column line array so that subtraction of the patterns causes one or more sidelobe of the antenna pattern to be at least partially canceled. An azimuth beamformer combines the elevation patterns of a plurality of column arrays, each connected to its own interferometer, to produce a pencil beam with a sidelobe structure exhibiting a null at the particular elevation angle.

Claims

1. A phased-array antenna system, comprising:

a line array of antenna elements;

line array feed means coupled to said elements of said line array for producing a scannable directive antenna array beam and plural sidelobes;

interferometer means including at least two additional antenna elements, said additional antenna elements being mutually spaced and fed by difference feed means connected to at least two of said additional antenna elements for feeding said two of said antenna elements in phase opposition, so as to produce an interferometer beam defining a plurality of lobes;

interconnection means coupled to said line array feed means and to said interferometer means for feeding said line array feed means and said interferometer means in phase opposition; and

phase control means coupled to said interferometer means for adjusting the locations of said plurality of lobes, whereby one of said plurality of lobes of said interferometer means may be superposed upon one of said plural sidelobes for cancellation of at least a portion thereof.

2. An antenna system according to claim 1 further comprising subtracting means coupled to said difference feed means and to said line array feed means for causing said at least one of said lobes of said interferometer means to substantially reduce the magnitude of at least one of said sidelobes.

3. A jammer resisting antenna arrangement, comprising:

a first line array of first antenna elements with a first element-to-element spacing, aid lien array being oriented with its array direction vertical;

first elevation beamforming means including plural distal ports coupled to said first antenna elements of said first line array, and also including a combined port, for generating at said combined port at least one beam which is directive in elevation and which can be scanned in elevation, which beam is associated with a plurality of sidelobes;

first interferometer means including at least second and third antenna elements vertically arrayed with a second element-to-element spacing greater than said first element-to-element spacing, said second and third antenna elements being fed in phase opposition for generating an elevation radiation pattern including a plurality of lobes of substantially equal amplitude;

a second line array of fourth antenna elements with said first element-to-element spacing, said second line array being oriented with its array direction vertical;

second elevation beamforming means including plural distal ports coupled to said fourth antenna elements of said second line array, and also including a combined port, for generating at said combined port at least one beam which is directive in elevation and which can be scanned in elevation, which beam is associated with a plurality of sidelobes;

second interferometer means including at least fifth and sixth antenna elements vertically arrayed with said second element-to-element spacing, said fifth and sixth antenna elements being fed in phase opposition for generating an elevation radiation pattern including a plurality of lobes of substantially equal amplitude;

first subtracting means coupled to said combined port of said first elevation beamforming means and to said first interferometer means for combing the beams formed by said first elevation beamforming means and said first interferometer means in a manner providing cancellation of at least a portion of one of said sidelobes generated by said first beamforming means by one of said lobes of substantially equal amplitude generated by said first interferometer means;

second subtracting means coupled to said combined port of said second elevation beamforming means and to said second interferometer means for combining the beam formed by said second elevation beamforming means and said second interferometer means in a manner providing cancellation of at least a portion of one of said sidelobes generated by said second beamforming means by one of said lobes of substantially equal amplitude generated by said second interferometer means; and

azimuth beamforming means including at least first and second separated ports coupled to said first and second subtracting means, respectively, and also including a combined port, said azimuth beamforming means including phase shifters interconnected between said separated ports and said combined port for generating a directive beam scannable in azimuth, whereby said directive beam is scannable in both azimuth and elevation and is associated with sidelobes having a null at a predetermined elevation angel.

4. A jammer resisting antenna arrangement, comprising:

a first line array of first antenna elements with a first element-to-element spacing, said line array being oriented with its array direction horizontal;

first azimuth beamforming means including plural distal ports coupled to said first antenna elements of said first line array, and also including a combined port, for generating at said combined port at lest one beam which is directive in azimuth and which can be scanned in azimuth, which beam is associated with a plurality of sidelobes;

first interferometer means including at least second and third antenna elements horizontally arrayed with a second element-to-element spacing greater than said first element-to-element spacing, said second and third antenna elements being fed in phase opposition for generating an azimuth radiation pattern including a plurality of lobes of substantially equal amplitude;

a second line array of fourth antenna elements with said first element-to-element spacing, said second line array being oriented with its array direction horizontal;

second elevation beamforming means including plural distal ports coupled to said fourth antenna elements of said second line array, and also including a combined port, for generating at said combined port at least one beam which is directive in azimuth and which can be scanned in azimuth, which beam is associated with a plurality of sidelobes;

second interferometer means including at least fifth and sixth antenna elements horizontally arrayed with said second element-to-element spacing, said fifth and sixth antenna elements being fed in phase opposition for generating an azimuth radiation pattern including a plurality of lobes of substantially equal amplitude;

first subtracting means coupled to said combined port of said first azimuth beamforming means and to said first interferometer means for combining the beams formed by said first azimuth beamforming means and said first interferometer means in a manner providing cancellation of at least a portion of one of said sidelobes generated by said first beamforming means by one of said lobes of substantially equal amplitude generated by said first interferometer means;

second subtracting means coupled to said combined port of said second azimuth beamforming means and to said second interferometer means for combining the beam formed by said second azimuth beamforming means and said second interferometer means in a manner providing cancellation of at least a portion of one of said sidelobes generated by said second beamforming means by one of said lobes of substantially equal amplitude generated by said second interferometer means; and

elevation beamforming means including at least first and second separated ports coupled to said first and second subtracting means, respectively, and also including a combined port, said elevation beamforming means including phase shifters interconnected between said separated ports and said combined port for generating a directive beam scannable in elevation, whereby said directive beam generated by said elevation beamforming means is scannable in both azimuth and elevation and is associated with sidelobes having a null at a predetermined azimuth angle.