CROSS-DIPOLE ANTENNA CONFIGURATIONS

• US 20110068992A1
• Filed: 07/21/2010
• Published: 03/24/2011
• Est. Priority Date: 08/03/2009
• Status: Active Grant

• Current Assignee: Venti Group, LLC
• Original Assignee: Venti Group, LLC
• Inventors: Payne, William Ernest
• Granted Patent: US 8,325,101 B2
• Time in Patent Office: Days
• US Class Current: 343/797
• CPC Class Codes: G06F 30/20 Design optimisation, verification or simulation optimisation, verification or simulation of circuit designs G06F30/30
• CPC Class Codes: H01Q 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 21/26 Turnstile or like antennas comprising arrangements of three or more elongated elements disposed radially and symmetrically in a horizontal plane about a common centre
• CPC Class Codes: H01Q 9/28 Conical, cylindrical, cage, strip, gauze, or like elements having an extended radiating surface; Elements comprising two conical surfaces having collinear axes and adjacent apices and fed by two-conductor transmission lines waveguide horns or mouths H01Q13/00; slot antennas H01Q13/00

Abstract

An apparatus has an improved antenna pattern for a cross dipole antenna. Such antennas desirably have an omnidirectional antenna pattern. Conventional cross dipole antennas exhibit nulls in their antenna patterns, which can cause antennas to deviate from a standard or specification. Applicant recognized and confirmed that the connection of a coaxial cable to the antenna arms is a cause of the nulls in the antenna pattern, and has devised techniques disclosed herein to compensate or cancel the effects of the connection. In one embodiment, the arms of the cross dipole antenna that are coupled to a center conductor of the coaxial cable remain of conventional length, but the arms of the cross dipole antenna that are coupled to a shield of the coaxial cable are lengthened by a fraction of the radius of the outer diameter of the coaxial cable.

Claims

1. An apparatus comprising a cross-dipole antenna, the cross-dipole antenna comprising:

a coaxial structure having a center conductor and an outer shield having an outer diameter with corresponding radius R;

a plurality of conductive arms comprising at least a first arm, a second arm, a third arm, and a fourth arm, wherein the plurality lie generally in a plane and are spaced apart from each other by about 90 degrees, such that a proximal end of each of the plurality of arms is arranged near a center point and wherein each of the plurality of arms extends generally outward at a distal end, wherein;

the first arm is electrically coupled to the center conductor at a proximal end and has a first predetermined effective electrical length;

the second arm is electrically coupled to the center conductor at a proximal end and has a second predetermined effective electrical length different from the first predetermined length;

the third arm is electrically coupled to the outer shield at a proximal end and has a third predetermined effective electrical length, wherein the third predetermined length is equal to the sum of the first predetermined effective electrical length and 0.3 to 1.2 times the radius R, the third arm extending opposite the first arm such that the third arm and the first arm form a first dipole; and

the fourth arm is electrically coupled to the outer shield at a proximal end and has a fourth predetermined effective electrical length, wherein the fourth predetermined effective electrical length is equal to the sum of the second predetermined effective electrical length and 0.15 to 1.5 times the radius R, the fourth arm extending opposite the second arm such that the fourth arm and the second arm form a second dipole;

wherein one or more of the first predetermined effective electrical length, the second effective electrical length, the third effective electrical length, or the fourth effective electrical length is physically shorter than its predetermined effective electrical length.

2. The apparatus of claim 1, wherein each of the first predetermined effective electrical length, the second predetermined effective electrical length, the third predetermined effective electrical length, and the fourth predetermined effective electrical length are fixed.

3. The apparatus of claim 1, wherein the coaxial structure comprises a coaxial cable feedline.

4. The apparatus of claim 1, wherein the plurality of conductive arms comprise traces of a printed circuit board.

5. The antenna of claim 1, wherein the third arm and the fourth arm are longer than the first arm and the second arm, respectively, by 0.3 to 1.2 times the radius R.

6. The apparatus of claim 1, wherein the third arm and the fourth arm are longer than the first arm and the second arm, respectively, by 0.42 to 0.78 times the radius R.

7. The apparatus of claim 1, wherein the third arm and the fourth arm are longer than the first arm and the second arm, respectively, by 0.48 to 0.72 times the radius R.

8. The apparatus of claim 1, wherein the third arm and the fourth arm are longer than the first arm and the second arm, respectively, by 0.54 to 0.66 times the radius R.

9. The apparatus of claim 1, wherein the third arm and the fourth arm are longer than the first arm and the second arm, respectively, by about 0.6 times the outer radius R.

10. The apparatus of claim 1, wherein the antenna further comprises one or more reflectors.

11. The apparatus of claim 1, wherein the cross-dipole antenna has a first polarization orientation, further comprising a second antenna having a second polarization orthogonal to the first polarization.

12. The apparatus of claim 11, wherein the cross dipole antenna has the horizontally-polarized orientation and the second antenna has the vertically-polarized orientation.

13. The apparatus of claim 11, wherein the second antenna comprises a monopole antenna.

14. The apparatus of claim 11, wherein the second antenna comprises a dipole antenna.

15. The apparatus of claim 11, wherein the cross dipole antenna has the horizontally-polarized orientation, and wherein the second antenna is spaced horizontally apart from the cross dipole antenna, wherein each of the cross dipole antenna and the second antenna are coupled to separate feedlines.

16. The apparatus of claim 11, further comprising:

one or more additional cross dipole antennas having the same polarization orientation as the cross dipole antenna; and

one or more additional antenna having the same polarization orientation as the second antenna, wherein the apparatus comprises an antenna array.

17. The apparatus of claim 11, further comprising a second cross dipole antenna as a third antenna, and further comprising a fourth antenna, wherein the second cross dipole antenna has the same polarization orientation as the cross dipole antenna, wherein the fourth antenna has the same polarization orientation as the second antenna, wherein the cross dipole antenna, the second antenna, the second cross dipole antenna, and the fourth antenna are arranged in a 2×

2 antenna array such that the second cross dipole antenna is diagonally across from the cross dipole antenna, and the fourth antenna is diagonally across from the second antenna.

18. The apparatus of claim 11, further comprising a tee joint having a first end, a second end, and a third end, wherein the first end is coupled to a feedline, wherein the cross dipole antenna is disposed at the second end, wherein the second antenna is disposed at the third end, and wherein the second antenna comprises a monopole antenna.

19. The apparatus of claim 1, wherein the one or more of the first predetermined effective electrical length, the second effective electrical length, the third effective electrical length, or the fourth effective electrical length is physically shorter than its predetermined effective electrical length via a miniaturization technique selected from at least one of a bent arm, a folded arm, a capacitive end loaded arm, a meander pattern loaded arm, an inductively loaded arm, or embedding in a high relative permittivity and/or permeability material.

20. An apparatus comprising a cross-dipole antenna, the cross-dipole antenna comprising:

a coaxial structure having a center conductor and an outer shield;

at least a first arm, a second arm, a third arm, and a fourth arm, wherein the arms lie generally in a plane and are spaced apart from each other by about 90-degrees, wherein a proximal end of each arm is arranged near a center point and wherein each arm extends generally outward at a distal end, wherein;

the first arm is electrically coupled to the center conductor at a proximal end;

the second arm is electrically coupled to the center conductor at a proximal end;

the third arm is electrically coupled to the outer shield at a proximal end, the third arm extending opposite the first arm such that the third arm and the first arm form a first dipole; and

the fourth arm is electrically coupled to the outer shield at a proximal end, the fourth arm extending opposite the second arm such that the fourth arm and the second arm form a second dipole;

wherein a radius of the outer shield of the coaxial structure is at least one-fiftieth a length of the shortest of the first arm, the second arm, the third arm, or the fourth arm, and wherein each of the first arm, the second arm, the third arm, and the fourth arm have different predetermined effective electrical lengths, as measured from a center of the coaxial structure, to compensate for distortion of the antenna pattern induced by the coaxial structure, wherein one or more of the first arm, the second arm, the third arm, or the fourth arm is physically shorter than its predetermined effective electrical length.

21. The apparatus of claim 20, wherein the radius of the outer shield of the coaxial structure is at least one-thirtieth of the shortest of the first arm, the second arm, the third arm, or the fourth arm.

22. The apparatus of claim 20, wherein each of the first predetermined length, the second predetermined length, the third predetermined length, and the fourth predetermined length are fixed.

23. The apparatus of claim 20, wherein the coaxial structure comprises a coaxial cable feedline.

24. The apparatus of claim 20, wherein the coaxial structure comprises a coaxial cable connector.

25. The apparatus of claim 20, wherein the first arm, the second arm, the third arm, and the fourth arm comprise traces of a printed circuit board.

26. The apparatus of claim 20, wherein the antenna further comprises one or more reflectors.

27. The apparatus of claim 20, wherein the cross-dipole antenna has a first polarization, further comprising a second antenna having a second polarization orthogonal to the first polarization.

28. The apparatus of claim 27, wherein the cross dipole antenna has the horizontally-polarized orientation and the second antenna has the vertically-polarized orientation.

29. The apparatus of claim 27, wherein the second antenna comprises a monopole antenna.

30. The apparatus of claim 27, wherein the second antenna comprises a dipole antenna.

31. The apparatus of claim 27, wherein the cross dipole antenna has the horizontally-polarized orientation, and wherein the second antenna is spaced horizontally apart from the cross dipole antenna, wherein each of the cross dipole antenna and the second antenna are coupled to separate feedlines.

32. The apparatus of claim 27, further comprising:

one or more additional cross dipole antennas having the same polarization orientation as the cross dipole antenna; and

one or more additional antenna having the same polarization orientation as the second antenna, wherein the apparatus comprises an antenna array.

33. The apparatus of claim 27, further comprising a second cross dipole antenna as a third antenna, and further comprising a fourth antenna, wherein the second cross dipole antenna has the same polarization orientation as the cross dipole antenna, wherein the fourth antenna has the same polarization orientation as the second antenna, wherein the cross dipole antenna, the second antenna, the second cross dipole antenna, and the fourth antenna are arranged in a 2×

2 antenna array such that the second cross dipole antenna is diagonally across from the cross dipole antenna, and the fourth antenna is diagonally across from the second antenna.

34. The apparatus of claim 27, further comprising a tee joint having a first end, a second end, and a third end, wherein the first end is coupled to a feedline, wherein the cross dipole antenna is disposed at the second end, wherein the second antenna is disposed at the third end, and wherein the second antenna comprises a monopole antenna.

35. The apparatus of claim 20, wherein the one or more of the first arm, the second arm, the third arm, or the fourth arm is physically shorter than its predetermined effective electrical length via a miniaturization technique selected from at least one of a bent arm, a folded arm, a capacitive end loaded arm, a meander pattern loaded arm, an inductively loaded arm, or embedding in a high relative permittivity and/or permeability material.

36. An apparatus comprising a cross-dipole antenna, the cross-dipole antenna comprising

a coaxial structure having a center conductor and an outer shield, the outer shield having an outer diameter and a corresponding radius R;

a first dipole comprising a first pair of arms; and

a second dipole comprising a second pair of arms;

wherein the arms of at least one pair of the first pair or the second pair have fixed asymmetric effective electrical lengths such that an arm coupled to the outer shield is longer than an arm coupled to the center conductor, as measured from a center of the coaxial structure, by 0.15 to 1.5 times the radius R, wherein at least one arm of the antenna has an effective electrical length shorter than its physical length.

37. The apparatus of claim 36, wherein the longer arm is longer than the shorter arm by 0.3 to 1.2 times the radius R.

38. The apparatus of claim 36, wherein the longer arm is longer than the shorter arm by 0.42 to 0.78 times the radius R.

39. The apparatus of claim 36, wherein the longer arm is longer than the shorter arm by 0.48 to 0.72 times the radius R.

40. The apparatus of claim 36, wherein the longer arm is longer than the shorter arm by 0.54 to 0.66 times the radius R.

41. The apparatus of claim 36, wherein the longer arm is longer than the shorter arm by about 0.6 times the radius R.

42. The apparatus of claim 36, wherein the radius of the outer shield of the coaxial structure is at least one-thirtieth of the shortest arm of the first dipole or the second dipole.

43. The apparatus of claim 36, wherein the coaxial structure comprises a coaxial cable feedline.

44. The apparatus of claim 36, wherein the coaxial structure comprises a coaxial cable connector.

45. The apparatus of claim 36, wherein the first dipole and the second dipole comprise traces of a printed circuit board.

46. The apparatus of claim 36, wherein the antenna further comprises one or more reflectors.

47. The apparatus of claim 36, wherein the cross-dipole antenna has a first polarization, further comprising a second antenna having a second polarization orthogonal to the first polarization.

48. The apparatus of claim 47, wherein the cross dipole antenna has the horizontally-polarized orientation and the second antenna has the vertically-polarized orientation.

49. The apparatus of claim 47, wherein the second antenna comprises a monopole antenna.

50. The apparatus of claim 47, wherein the second antenna comprises a dipole antenna.

51. The apparatus of claim 47, wherein the cross dipole antenna has the horizontally-polarized orientation, and wherein the second antenna is spaced horizontally apart from the cross dipole antenna, wherein each of the cross dipole antenna and the second antenna are coupled to separate feedlines.

52. The apparatus of claim 47, further comprising:

one or more additional cross dipole antennas having the same polarization orientation as the cross dipole antenna; and

one or more additional antenna having the same polarization orientation as the second antenna, wherein the apparatus comprises an antenna array.

53. The apparatus of claim 47, further comprising a second cross dipole antenna as a third antenna, and further comprising a fourth antenna, wherein the second cross dipole antenna has the same polarization orientation as the cross dipole antenna, wherein the fourth antenna has the same polarization orientation as the second antenna, wherein the cross dipole antenna, the second antenna, the second cross dipole antenna, and the fourth antenna are arranged in a 2×

2 antenna array such that the second cross dipole antenna is diagonally across from the cross dipole antenna, and the fourth antenna is diagonally across from the second antenna.

54. The apparatus of claim 47, further comprising a tee joint having a first end, a second end, and a third end, wherein the first end is coupled to a feedline, wherein the cross dipole antenna is disposed at the second end, wherein the second antenna is disposed at the third end, and wherein the second antenna comprises a monopole antenna.

55. The apparatus of claim 36, wherein the at least one arm is physically shorter than its predetermined effective electrical length via a miniaturization technique selected from at least one of a bent arm, a folded arm, a capacitive end loaded arm, a meander pattern loaded arm, an inductively loaded arm, or embedding in a high relative permittivity and/or permeability material.

56. A method for designing a cross-dipole antenna intended to be used for a signal having a wavelength λ

, wherein the cross-dipole antenna comprises a first arm, a second arm, a third arm, and a fourth arm, the method comprising;

generating a simulation model of the cross-dipole antenna, wherein the simulation model includes the first arm, the second arm, the third arm, the fourth arm and a coaxial structure to which the first arm, the second arm, the third arm, and the fourth arm are connected;

simulating the cross-dipole antenna via computer execution of the simulation model;

starting with a length aλ

for the first arm and the third arm, wherein a value for a is about 0.25, wherein the first arm is connected to a center conductor of the coaxial structure and the third arm is connected to a shield of the coaxial structure;

starting with a length bλ

for the second arm and the fourth arm, wherein a value for b is about 0.25, wherein the second arm is connected to a center conductor of the coaxial structure and the fourth arm is connected to a shield of the coaxial structure;

adjusting the value for a of the shorter arms and adjusting the value for b of the longer arms until a quadrature phase relationship is established among the arms, wherein a final value for a of the shorter arms is less than a final value for b of the longer arms, wherein the quadrature phase relationship is determined via computer execution of the simulation model;

increasing a length of the third arm relative to the first arm by a fraction x of a radius R of the coaxial structure;

increasing a length of the fourth arm relative to the second arm by the fraction x of the radius R of the coaxial structure; and

adjusting arm lengths of one or more of the first arm, the second arm, the third arm, and the fourth arm in response to simulation results.

57. The method of claim 56, wherein a value for x is between about 0.15 to about 1.5.

58. The method of claim 56, wherein a value for x is between about 0.3 to about 1.2.

59. The method of claim 56, wherein a value for x is between about 0.42 to about 0.78.

60. The method of claim 56, wherein a value for x is between about 0.48 to about 0.72

61. The method of claim 56, wherein a value for x is between about 0.54 to about 0.66.

62. The method of claim 56, further comprising adjusting at least one arm length for an antenna miniaturization technique in which a physical length of the arm length is shorter than an effective electrical length, wherein the miniaturization technique is selected from at least one of a bent arm, a folded arm, a capacitive end loaded arm, a meander pattern loaded arm, an inductively loaded arm, or embedding in a high relative permittivity and/or permeability material.