Low profile dual frequency dipole antenna structure

• US 6,961,028 B2
• Filed: 01/17/2003
• Issued: 11/01/2005
• Est. Priority Date: 01/17/2003
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Joy, Philip, Reasoner, Harold D.
• Primary Examiner(s): Lee, Wilson
• Application Number:
  US10/346,895
• Publication Number:
  US 20040140941A1
• Time in Patent Office: 1,019 Days
• Field of Search: 343/895, 343/795, 343/803, 343/817, 343/821, 343/725, 343/726, 343/727
• US Class Current: 343/895
• CPC Class Codes: H01Q 21/30 Combinations of separate antenna units operating in different wavebands and connected to a common feeder system
• CPC Class Codes: H01Q 5/371 Branching current paths
• CPC Class Codes: H01Q 9/16 with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole H01Q9/44 takes precedence

Abstract

An antenna includes a first dipole having first and second stripline radiating elements extending in opposite directions from a central feed point and along a generally rectangular outline of the antenna. The first dipole is operable to be resonant at a first frequency. The antenna also includes a second dipole having third and fourth stripline radiating elements extending in opposite directions from the central feed point and generally parallel to the first and second stripline radiating elements. The third and fourth stripline radiating elements generally follow and stay within the rectangular antenna outline. The second dipole is operable to be resonant at a second frequency. The antenna also includes a stripline balun electrically coupled to the central feed point and extending generally parallel with the first and second dipoles and along the rectangular antenna outline.

Claims

1. An antenna, comprising:

first dipole having first and second stripline radiating elements extending in opposite directions from a central feed point and along a first side of a generally rectangular outline of the antenna, the first dipole operable to be resonant at a first frequency;

second dipole having third and fourth stripline radiating elements extending in opposite directions from the central feed point and generally parallel to the first and second stripline radiating elements, the third and fourth stripline radiating elements generally following and staying within the rectangular antenna outline, and the second dipole operable to be resonant at a second frequency; and

a balun have a plurality of stripline segments and electrically coupled between the central feed point and a ground and extending generally parallel with the first and second dipoles and along the rectangular antenna outline.

2. The antenna, as set forth in claim 1, further comprising first and second decoupling elements coupled respectively to third and fourth stripline radiating elements.

3. The antenna, as set forth in claim 2, wherein the first and second decoupling elements generally extending along the first axis of the rectangular antenna outline.

4. The antenna, as set forth in claim 1, wherein the third stripline radiating element of the second dipole comprises:

first segment having a first predetermined length and extending from the central feed point parallel to the first stripline radiating element of the first dipole and terminating generally immediately beyond the first stripline radiating element of the first dipole;

second segment having a second predetermined length and coupled to the first segment at 90°

thereto and extending perpendicular to the first segment toward the first side of the rectangular antenna outline;

third segment having a third predetermined length and coupled to the second segment at 90°

thereto and extending along the first side of the rectangular antenna outline away from the central feed point and terminating at a second side of the rectangular antenna outline;

fourth segment having a fourth predetermined length coupled to the third segment at 90°

thereto and extending perpendicularly to the third segment along the second side of the rectangular antenna outline and terminating proximate to the stripline balun;

fifth segment having a fifth predetermined length coupled to the fourth segment at 90°

thereto and extending perpendicularly to the fourth segment toward the central feed point; and

the first through fifth predetermined lengths of the first through fifth segments total length equal to λ

₂/4, where λ

₂ is the resonant wavelength of the second dipole.

5. The antenna, as set forth in claim 1, wherein the fourth stripline radiating element of the second dipole comprises:

first segment having a first predetermined length and extending from the central feed point parallel to the first stripline radiating element of the first dipole and terminating generally immediately beyond the first stripline radiating element of the first dipole;

second segment having a second predetermined length and coupled to the first segment at 90°

thereto and extending perpendicular to the first segment toward the first side of the rectangular antenna outline;

third segment having a third predetermined length and coupled to the second segment at 90°

thereto and extending along a first side of the rectangular antenna outline away from the central feed point and terminating at a third side of the rectangular antenna outline;

fourth segment having a fourth predetermined length coupled to the third segment at 90°

thereto and extending perpendicularly to the third segment along the third side of the rectangular antenna outline and terminating proximate to the stripline balun;

fifth segment having a fifth predetermined length coupled to the fourth segment at 90°

thereto and extending perpendicularly to the fourth segment toward the central feed point; and

the first through fifth predetermined lengths of the first through fifth segments total length equal to λ

₂/4, where λ

₂ is the resonant wavelength of the second dipole.

6. The antenna, as set forth in claim 1, wherein the third and fourth stripline radiating elements of the second dipole generally following the rectangular antenna outline and bending at 90°

to follow the rectangular antenna outline if necessary.

7. The antenna, as set forth in claim 1, wherein the third stripline radiating element is a mirror image of the fourth stripline radiating element along the central feed point.

8. The antenna, as set forth in claim 1, wherein the antenna is symmetrical along a central axis at the central feed point bisecting the first and second dipoles.

9. The antenna, as set forth in claim 1, wherein the balun comprises:

a generally rectangular circuitous configuration coupled at one end to first and third radiating elements of the respective first and second dipoles, and second end to second and fourth radiating elements of the respective first and second dipoles; and

a channel formed by the balun stripline segments.

10. The antenna, as set forth in claim 9, wherein the balun is located proximate to the first and second dipoles within the generally rectangular antenna outline.

11. The antenna, as set forth in claim 1, wherein the balun comprises:

a first balun channel section extending generally perpendicularly to the first and second dipole radiating elements from the common feed point; and

a second balun channel section coupled to the first balun channel section, the second balun channel section extending generally parallel with the first and second dipole radiating elements.

12. An antenna structure, comprising:

a generally rectangular outline having a width, W, and a length, L, and a center axis bisecting the length of the rectangular outline;

a central feed point lying on the center axis of the rectangular outline;

first dipole coupled to the central feed point having first and second radiating elements extending opposite one another along the length of the rectangular outline for a total length less than L;

second dipole coupled to the central feed point having third and fourth radiating elements extending opposite one another along the length of the rectangular outline for a length equal to L, the third and fourth radiating elements further comprising short perpendicular segments extending along the width of the rectangular outline operable to extend a total length of third and fourth radiating elements to a predetermined desired length, the third and fourth radiating elements generally staying within the rectangular outline; and

a balun formed by stripline segments coupled to the central feed point, the balun stripline segments forming a narrow channel having a generally inverse T configuration.

13. The antenna structure, as set forth in claim 12, further comprising first and second decoupling elements coupled respectively to third and fourth radiating elements.

14. The antenna structure, as set forth in claim 13, wherein the first and second decoupling elements generally extending along the length of the rectangular outline.

15. The antenna structure, as set forth in claim 12, wherein the third radiating element of the second dipole comprises:

first segment having a first predetermined length and extending from the central feed point parallel to and adjacent the first radiating element of the first dipole and terminating generally immediately beyond the first radiating element of the first dipole;

second segment having a second predetermined length and coupled to the first segment at 90°

thereto and extending perpendicular to the first segment toward the rectangular outline;

third segment having a third predetermined length and coupled to the second segment at 90°

thereto and extending along a first side of the rectangular outline away from the central feed point and terminating at a second side of the rectangular outline;

fourth segment having a fourth predetermined length coupled to the third segment at 90°

thereto and extending perpendicularly to the third segment along the second side of the rectangular antenna outline and terminating proximate to the balun;

fifth segment having a fifth predetermined length coupled to the fourth segment at 90°

thereto and extending perpendicularly to the fourth segment toward the central feed point; and

the first through fifth predetermined lengths of the first through fifth segments total length equal to λ

₂/4, where λ

₂ is the resonant wavelength of the second dipole.

16. The antenna structure, as set forth in claim 12, wherein the fourth stripline radiating element of the second dipole comprises:

first segment having a first predetermined length and extending from the central feed point parallel to and adjacent the first radiating element of the first dipole and terminating generally immediately beyond the first radiating element of the first dipole;

second segment having a second predetermined length and coupled to the first segment at 90°

thereto and extending perpendicular to the first segment toward the rectangular outline;

third segment having a third predetermined length and coupled to the second segment at 90°

thereto and extending along a first side of the rectangular outline away from the central feed point and terminating at a third side of the rectangular outline;

fourth segment having a fourth predetermined length coupled to the third segment at 90°

thereto and extending perpendicularly to the third segment along the third side of the rectangular antenna outline and terminating proximate to the balun;

fifth segment having a fifth predetermined length coupled to the fourth segment at 90°

thereto and extending perpendicularly to the fourth segment toward the central feed point; and

the first through fifth predetermined lengths of the first through fifth segments total length equal to λ

₂/4, where λ

₂ is the resonant wavelength of the second dipole.

17. The antenna structure, as set forth in claim 12, wherein the third radiating element is a mirror image of the fourth radiating element along the center axis.

18. The antenna structure, as set forth in claim 12, wherein the antenna is symmetrical along the center axis.

19. The antenna structure, as set forth in claim 12, wherein the antenna structure comprises lengths of conductive stripline formed on a dielectric substrate.

20. The antenna structure, as set forth in claim 12, wherein the balun stripline segments form a generally continuous rectangular stripline coupled at one end to first and third radiating elements of the respective first and second dipoles, and second end to second and fourth radiating elements of the respective first and second dipoles.

21. The antenna structure, as set forth in claim 20, wherein the balun is located proximate to the first and second dipoles within the generally rectangular antenna outline.

22. The antenna structure, as set forth in claim 12, wherein the balun comprises:

a first balun channel section extending generally perpendicularly to the first and second dipole radiating elements from the common feed point; and

a second balun channel section coupled to the first balun channel section, the second balun channel section extending generally parallel with the first and second dipole radiating elements.

23. A method of forming an antenna structure, comprising:

defining a generally rectangular outline having a width, W, and a length, L, and a center axis bisecting the length of the rectangular outline;

providing a central feed point lying on the center axis of the rectangular outline;

forming a first dipole coupled to the central feed point having first and second radiating elements extending opposite one another along the length of the rectangular outline for a total length less than L;

forming a second dipole coupled to the central feed point having third and fourth radiating elements extending opposite one another along the length of the rectangular outline for a length equal to L, the third and fourth radiating elements further comprising short perpendicular segments extending along the width of the rectangular outline operable to extend a total length of third and fourth radiating elements to a predetermined desired length, the third and fourth radiating elements generally staying within the rectangular outline; and

forming a balun having stripline segments coupled to the central feed point and forming a narrow channel therebetween.

24. The method, as set forth in claim 23, further comprising forming first and second decoupling elements coupled respectively to third and fourth radiating elements.

25. The method, as set forth in claim 23, wherein forming the third radiating element of the second dipole comprises:

forming a first segment having a first predetermined length and extending from the central feed point parallel to and adjacent the first radiating element of the first dipole and terminating generally immediately beyond the first radiating element of the first dipole;

forming second segment having a second predetermined length and coupled to the first segment at 90°

thereto and extending perpendicular to the first segment toward the rectangular outline;

forming a third segment having a third predetermined length and coupled to the second segment at 90°

thereto and extending along a first side of the rectangular outline away from the central feed point and terminating at a second side of the rectangular outline;

forming a fourth segment having a fourth predetermined length coupled to the third segment at 90°

thereto and extending perpendicularly to the third segment along the second side of the rectangular antenna outline and terminating proximate to the balun;

forming a fifth segment having a fifth predetermined length coupled to the fourth segment at 90°

thereto and extending perpendicularly to the fourth segment toward the central feed point; and

whereby the first through fifth predetermined lengths of the first through fifth segments total length equals to λ

₂/4, where λ

₂ is the resonant wavelength of the second dipole.

26. The method, as set forth in claim 23, wherein forming the fourth stripline radiating element of the second dipole comprises:

forming a first segment having a first predetermined length and extending from the central feed point parallel to and adjacent the first radiating element of the first dipole and terminating generally immediately beyond the first radiating element of the first dipole;

forming a second segment having a second predetermined length and coupled to the first segment at 90°

thereto and extending perpendicular to the first segment toward the rectangular outline;

forming a third segment having a third predetermined length and coupled to the second segment at 90°

thereto and extending along a first side of the rectangular outline away from the central feed point and terminating at a third side of the rectangular outline;

forming a fourth segment having a fourth predetermined length coupled to the third segment at 90°

thereto and extending perpendicularly to the third segment along the third side of the rectangular antenna outline and terminating proximate to the balun;

forming a fifth segment having a fifth predetermined length coupled to the fourth segment at 90°

thereto and extending perpendicularly to the fourth segment toward the central feed point; and

whereby the first through fifth predetermined lengths of the first through fifth segments total length equals to λ

₂/4, where λ

₂ is the resonant wavelength of the second dipole.

27. The method, as set forth in claim 23, comprises forming the antenna structure using lengths of conductive stripline formed on a dielectric substrate.

28. The method, as set forth in claim 23, comprises etching a dielectric substrate to form lengths of conductive stripline for the antenna structure.

29. The method, as set forth in claim 23, wherein forming the balun comprises forming a generally continuous rectangular stripline coupled at one end to first and third radiating elements of the respective first and second dipoles, and second end to second and fourth radiating elements of the respective first and second dipoles.

30. The method, as set forth in claim 23, wherein forming a balun comprises:

forming a first balun channel section extending generally perpendicularly to the first and second dipole radiating elements from the common feed point; and

forming a second balun channel section coupled to the first balun channel section, the second balun channel section extending generally parallel with the first and second dipole radiating elements.