Resonated notch antenna

• US 5,467,099 A
• Filed: 11/24/1993
• Issued: 11/14/1995
• Est. Priority Date: 04/20/1993
• Status: Expired due to Fees

• Current Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Original Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Inventors: Bonebright, Mark E., Glabe, John R.
• Primary Examiner(s): Hajec, Donald
• Assistant Examiner(s): Wigmore, Steven
• Application Number:
  US08/158,057
• Time in Patent Office: 720 Days
• Field of Search: 343/741, 343/767, 343/792.5, 343/795, 343/797, 343/749, 343/752
• US Class Current: 343/767
• CPC Class Codes: H01Q 13/08 Radiating ends of two-conductor microwave transmission lines, e.g. of coaxial lines, of microstrip lines
• CPC Class Codes: H01Q 21/067 using endfire radiating aerial units transverse to the plane of the array

Abstract

Resonant, end fire antennae that operate over broad frequency bands with a boosted gain at a preferred frequency, that can be incorporated into arrays, and that have low RF cross-sections are constructed from a transmission line, usually a piece of coaxial cable that if it is not self supporting, is mounted on or in a lightweight structural material with an outer end with a sheath or stripline the shape of half of a notch. The other half of the notch is formed from a conductor electrically connected to the center conductor of the coaxial cable. The cable and conductor are variably spaced to transition the characteristic impedance of the cable to that of free space. The transmission line and the conductor each have a quarter wavelength tuning stub connected thereto to boost the gain of the antenna at a predetermined frequency. The conductor and the sheath are terminated either with ground connections or by inductive loads.

Claims

1. An antenna element including:

a transmission line (36) having;

an outer conductive layer (60);

a conductive member (58) adjacent said outer conductive layer; and

dielectric spacing means (62) between said outer conductive layer and said conductive member, said transmission line further having;

a first transmission line end (34) for connection to RF means;

a second transmission line end (72);

a transmission line connecting portion (42 &

     44) extending from said first transmission line end; and

a transmission line notch portion (46) extending from said second transmission line end to said transmission line connecting portion; and

a conductor (50) having;

a first conductor end (78);

a second conductor end (72);

a conductor connecting portion (52 &

     54) extending from said first conductor end; and

a conductor notch portion (56) extending from said second conductor end to said conductor connecting portion, said transmission line notch portion is shaped in a first curve extending from said second transmission line end and said conductor notch portion is shaped in a second curve that is generally a mirror image of said first curve extending from said second conductor end, an RF energy field is set up across said transmission line notch portion and said conductor notch portion, said conductive member at said second transmission line end being electrically connected to said second conductor end so that said transmission line notch portion of said outer conductive layer and said conductor notch portion of said conductor form an RF active notch structure (from 72 to

     74) for radiating said RF energy field in a direction away from said RF active notch structure and for transitioning the characteristic impedance of said transmission line to that of air, and a portion of said conductor notch portion and a portion of said transmission line notch portion forming a parallel line transmission line therebetween.

2. The antenna element as defined in claim 1 further including:

a first resonant stub connected to said portion of said conductor notch portion; and

a second resonant stub connected to said portion of said transmission line notch portion, whereby the gain of said antenna element is boosted at the resonant frequency area of said resonant stubs.

3. The antenna element as defined in claim 2 wherein-said transmission line notch portion (228) and said conductor notch portion (230) define a center line (33) of said antenna element, each being spiraled about said connection of said conductive member and said second conductor end in the same direction about said center line, whereby said antenna element spirals about 90°

to produce circular polarization.

4. The antenna element as defined in claim 2 wherein said outer conductive layer has a predetermined effective electrical width and said conductor has a similar predetermined effective electrical width.

5. The antenna element as defined in claim 2 wherein said outer conductive layer is connected to said first conductor end near said first transmission line end.

6. The antenna element (180) as defined in claim 2 wherein said transmission line notch portion and said conductor notch portion include:

generally mirror image similar curved conductive strips (168 &

     172) extending from said second transmission line end and said second conductor end to produce exponentially varying impedance that gradually matches the characteristic impedance of said transmission line to that of free space.

7. The antenna element as defined in claim 2 wherein said notch structure includes:

a center line generally oriented equally spaced from said transmission line notch portion and said conductor notch portion, said transmission line connecting portion being comprised of;

a first subportion (42) extending adjacent said first end outwardly perpendicular to said center line; and

a second subportion (44) connected to said first subportion spaced from said first end and extending generally parallel to said center line, and said conductor connecting portion being comprised of;

a third subportion (52) extending adjacent said first end outwardly perpendicular to said center line and in general alignment with said first subportion; and

a fourth subportion (54) connected to said third subportion spaced from said first end and extending generally parallel to said center line and said second subportion.

8. The antenna element as defined in claim 2 wherein said transmission line has:

at least one load there on at said transmission line connecting portion thereof, and wherein said conductor has;

at least one load there on at said conductor connecting portion thereof.

9. The antenna element as defined in claim 2 wherein said outer conductive layer of said transmission line notch portion is comprised of:

at least one conductive transmission line planar sheet (168) defining a transmission line portion of said notch structure, wherein said conductive member of said transmission line notch portion includes;

at least one conductive planar strip (177) positioned parallel to said at least one conductive transmission line planar sheet and closely spaced thereto, and wherein said conductor notch portion includes;

at least one conductive conductor planar sheet (172) defining a conductor portion of said notch structure.

10. The antenna element as defined in claim 2 further including:

a planar dielectric layer for supporting said transmission line and said conductor in a plane, said planar dielectric layer having;

first and second opposite parallel sides, and wherein said conductive layer of said transmission line notch portion is a first conductive transmission line conductor sheet mounted on said first side of said planar dielectric layer, said element further including;

a second conductive transmission line planar sheet positioned on said second side of said planar dielectric layer, each conductive transmission line planar sheet having;

a transmission line edge defining a transmission line portion of said notch structure, wherein said conductive member of said transmission line notch portion includes;

at least one conductive planar strip parallel to said conductive transmission line planar sheets and closely spaced therebetween, and wherein said conductor notch portion includes;

first and second conductive conductor planar sheets positioned on said first and second opposite parallel sides of said planar dielectric layer respectively, each conductive conductor planar sheet having;

a conductor edge defining a conductor portion of said notch structure.

11. An antenna (80) including:

a first antenna element (82) having;

a transmission line having;

an conductive layer (108);

a conductive member within said conductive layer; and

dielectric spacing means (188) between said conductive layer and said conductive member, said transmission line further having;

a first transmission line end (92) for connection to RF means;

a second transmission line end (128);

a transmission line connecting portion extending from said first transmission line end (96); and

a transmission line notch portion (108) extending from said second transmission line end to said transmission line connecting portion; and

a conductor having;

a second conductor end (128); and

a conductor notch portion (120) extending from said second conductor end, said transmission line notch portion is shaped in a first curve extending from said second tramsmission line end and said conductor notch portion is shaped in a second curve that is generally a mirror image of said first curve extending from said second conductor end, an EF energy field is set up across said transmission line notch portion and said conductor notch portion, said conductive member at said second transmission line end being electrically connected to said second conductor end so that said transmission line notch portion of said conductive layer and said conductor notch portion of said conductor form an RF active notch structure for radiating said RF energy field in a direction away from said RF active notch structure and for transitioning the characteristic impedance of said transmission line to that of air; and

a second antenna element (82) having;

a transmission line having;

a conductive layer;

a conductive member within said conductive layer; and

dielectric spacing means between said conductive layer means and said conductive member, said transmission line further having;

a first transmission line end for connection to RF means;

a second transmission line end;

a transmission line connecting portion extending from said first transmission line end; and

a transmission line notch portion extending from said second transmission line end to said transmission line connecting portion; and

a conductor having;

a second conductor end; and

a conductor notch portion extending from said second conductor end, said transmission line notch portion is shaped in a first curve extending from said second transmission line end and said conductor notch portion is shaped in a second curve that is generally a mirror image of said first curve extending from said second conductor end, an RF energy field is set up across said transmission line notch portion and said conductor notch portion, said conductive member at said second transmission line end being electrically connected to said second conductor end so that said transmission line notch portion of said conductive layer and said conductor notch portion of said conductor form an RF active notch structure for radiating said RF energy field in a direction away from said RF active notch structure and for transitioning the characteristic impedance of said transmission line to that of air, said first and second antenna elements being positioned generally at right angles to each other with said notch structures adjacent.

12. The antenna as defined in claim 11 wherein each antenna element includes:

a first resonant stub connected to said portion of said conductor notch portion; and

a second resonant stub connected to said portion of said transmission line notch portion, whereby the gain of said antenna is boosted at the resonant frequency area of said stubs.

13. The antenna as defined in claim 12 wherein said conductive layers of said antenna elements have a predetermined effective electrical width and said conductors of said antenna elements have a similar predetermined effective electrical width.

14. The antenna as defined in claim 12 wherein said conductive layer of each antenna element is isolated from said first conductor end near said first transmission line end.

15. The antenna as defined in claim 12 wherein said transmission line notch portion and said conductor notch portion of each of said antenna elements is curved, extending from said second transmission line end and said second conductor end to smoothly transition the impedance of said transmission line to that of air.

16. The antenna as defined in claim 12 wherein said transmission line notch portion and said conductor notch portion of each of said antenna elements are formed in generally similar curves extending from said second transmission line end and said second conductor end, and wherein said notch structure of each of said antenna elements has:

a center line generally oriented equally spaced from said transmission line notch portion and said conductor notch portion, said center lines of said antenna elements being coextensive.

17. The antenna as defined in claim 12 wherein said transmission line of each of said antenna elements has:

at least one distributed ferrite load thereabout at said transmission line connecting portion thereof, and wherein said conductor of each of said antenna elements has;

at least one distributed ferrite load there about at said conductor connecting portion thereof.

18. The antenna as defined in claim 12 wherein said conductive layer of said transmission line notch portion of each of said antenna elements includes:

at least one conductive transmission line planar sheet having;

a first inner edge defining a transmission line edge defining a transmission line portion of said notch structure, wherein said conductive member of said transmission line notch portion of each of said antenna elements includes;

at least one conductive planar strip positioned parallel to said at least one conductive transmission line planar sheet and closely spaced therefrom, and wherein said conductor notch portion of each of said antenna elements includes;

at least one conductive conductor planar sheet having;

a second inner edge defining a conductor portion of said notch structure.

19. The antenna as defined in claim 12 wherein each of said antenna elements further includes:

a planar dielectric layer for supporting said transmission line and said conductor in a plane, said planar dielectric layer having;

opposite parallel sides, and wherein said conductive layer of said transmission line notch portion of each of said antenna elements is a covering including;

a pair of conductive transmission line planar sheets positioned on said opposite parallel sides of said planar dielectric layer, each conductive transmission line planar sheet having;

a first inner edge defining a transmission line portion of said notch structure, wherein said conductive member of said transmission line notch portion of each of said antenna elements includes;

at least one conductive planar strip parallel to said conductive transmission line planar sheets and closely spaced therebetween, and wherein said conductor notch portion of each of said antenna elements include;

a pair of conductive conductor planar sheets positioned on said opposite parallel sides of said planar dielectric layer, each conductive conductor planar sheet having;

a second inner edge generally facing said first inner edge and defining a conductor portion of said notch structure.

20. The antenna as defined in claim 12 including:

a plurality of said first and second antenna elements formed into an array.

21. The antenna as defined in claim 12 further including:

a control network connected to said first transmission line ends to control the polarization of the antenna pattern of said antenna.

22. An antenna element (30) including:

a coaxial cable (36) having;

a conductive sheath (60);

a center conductor (58);

a first cable end (34) for connection to RF means;

a second cable end (72);

a cable connecting portion (42 &

     46) extending from said first cable end; and

a cable notch portion (46) extending from said second cable end to said cable connecting portion including;

a resonant stub (49) connected to said conductive sheath; and

a wire (50) having;

a first wire end (78);

a second wire end (72);

a wire connecting portion (52 &

     54) extending from said first wire end; and

a wire notch portion (56) extending from said second wire end to said wire connecting portion including;

a resonant stub (57) connected to said wire, said coaxial cable notch portion is shaped in a first curve extending from said second coaxial cable end and said wire notch portion is shaped in a second curve that is generally a mirror image of said first curve extending from said second wire end, an RF energy field is set up across said coaxial cable notch portion and said wire notch portion, said center conductor at said second cable end being electrically connected to said second wire end so that said cable notch portion of said coaxial cable and said wire notch portion of said wire form an RF active notch structure for radiating said RF energy field in a direction away from said RF active notch structure and for transitioning the characteristic impedance of said coaxial cable to that of air.

23. The antenna element as defined in claim 22 further including:

dielectric means for supporting said coaxial cable, said wire, and said resonant stubs generally in a plane.

24. The antenna element as defined in claim 22 wherein said cable notch portion and said wire notch portion are formed in mirror image curves extending from said second cable end and said second wire end shaped to exponentially transition the characteristic impedance of said coaxial cable to that of air.

25. The antenna element as defined in claim 22 wherein said RF active notch structure has:

a center line generally oriented equally spaced from said cable notch portion and said wire notch portion, said cable connecting portion having;

a first shape;

a first cable subportion (42) extending adjacent said first cable end outwardly perpendicular to said center line; and

a second cable subportion (44) connected to said first cable subportion spaced from said first cable end and extending parallel to said center line of said notch portion thereof, and said wire connecting portion having;

a second shape that is the mirror image of said first shape;

a first wire subportion (52) extending adjacent said first wire end outwardly perpendicular to said center line; and

a second wire subportion (54) connected to said first wire subportion spaced from said first wire end and extending parallel to said center line of said notch portion thereof.

26. The antenna element as defined in claim 25 wherein said cable has:

at least one distributed ferrite load there about at said cable connecting portion thereof, and wherein said wire has;

at least one distributed ferrite load there about at said wire connecting portion thereof.

27. The antenna element as defined in claim 26 wherein said conductive sheath of said cable notch portion includes:

at least one conductive planar sheet adjacent said cable notch portion having;

a first edge defining a portion of said notch structure, and wherein said wire notch portion includes;

at least one conductive conductor planar sheet having;

a second edge generally facing said first edge and defining a portion of said notch structure.

28. The antenna element as defined in claim 22 wherein said cable notch portion and said wire notch portion have a small difference in electrical length.

29. The antenna element as defined in claim 22 wherein said conductive sheath is isolated from direct electrical connection with said center conductor at said second cable end.

30. An antenna (250) including:

a first planar antenna element (252) comprised of;

a dielectric panel (258) having;

a first side (266);

a second side (268);

a first side edge (280) extending between said first and second sides;

a second side edge (282) extending between said first and second sides; and

a third edge (264) extending between said first and second sides and said first and second side edges;

a first conductive strip (270) on said dielectric panel having;

a first portion having;

a first end (286) for connection to RF means; and

a second end (290) spaced from said first end; and

a second portion (292) extending from said second end of said first portion toward said third side edge, said second portion of said first conductive strip including;

a first curved edge portion (292); and

a second portion end (296);

a second conductive strip (271) on said dielectric panel having;

a first portion having;

a first end; and

a second end spaced from said first end; and

a second portion extending from said second end of said first portion toward said third side edge, said second portion of said second conductive strip including;

a second curved edge portion (293) generally facing said first curved edge portion and defining a notch for interacting with RF radiation therebetween; and

a second portion end (297) closely spaced from said first conductive strip second portion end; and

a conductor (288) positioned adjacent said first conductive strip, electrically insulated therefrom and having;

a first end (288a) for connection to RF means; and

a second end (300) that extends beyond said first conductive strip second portion end to said second conductive strip second portion end and is electrically connected thereto.

31. The antenna as defined in claim 30 wherein said second portion of said first conductive strip includes:

a first transmission line subportion (generally at

     295) extending from said first curved edge portion to said second portion end thereof, and wherein said second portion of said second conductive strip includes;

a second transmission line subportion (generally at

     295) extending from said second curved edge portion to said second portion end thereof.

32. The antenna as defined in claim 31 further including:

a first resonant stub connected to said first transmission line subportion; and

a second resonant stub connected to said second transmission line subportion.

33. The antenna as defined in claim 32 wherein said antenna has a bandwidth of frequencies for which said antenna is effective, said first and second resonant stubs having electrical lengths that are a quarter wave of at least one of the frequencies in said bandwidth.

34. The antenna as defined in claim 32 further including:

a third conductive strip (271) on said second side that is a mirror image of said first conductive strip and is electrically connected at spaced intervals that straddle said conductor; and

a fourth conductive strip (273) on said second side that is a mirror image of said second conductive strip and is electrically connected at spaced intervals thereto.

35. The antenna as defined in claim 34 wherein said first and third conductive strips are electrically connected along said first side edge, and said second and fourth conductive strips are electrically connected along said second side edge.

36. The antenna as defined in claim 35 further including:

RF absorbing material positioned on at least one of said first and third conductive strips adjacent said first side edge and on at least one of said second and fourth conductive strips adjacent said second side edge.

37. The antenna as defined in claim 32 further including:

a third conductive strip (271) on said second side that is a mirror image of said first conductive strip and is electrically connected at spaced intervals that straddle said conductor; and

a fourth conductive strip (273) on said first side that is a mirror image of said second conductive strip and is electrically connected at spaced intervals thereto.