Low profile tri-filar, single feed, helical antenna

• US 6,738,026 B1
• Filed: 12/09/2002
• Issued: 05/18/2004
• Est. Priority Date: 12/09/2002
• Status: Expired due to Fees

• Current Assignee: Centurion Industries Incorporated (Laird Limited)
• Original Assignee: Centurion Industries Incorporated (Laird Limited)
• Inventors: Rossman, Court Emerson, McKivergan, Patrick Daniel
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): DINH, TRINH VO
• Application Number:
  US10/314,685
• Publication Number:
  US 20040108964A1
• Time in Patent Office: 526 Days
• Field of Search: H01/Q.136, H01/Q 2.100, 343/895, 343/893, 343/806, 343/853, 343/700.MS
• US Class Current: 343/895
• CPC Class Codes: H01Q 1/362 for broadside radiating helical antennas
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 9/42 with folded element, the folded parts being spaced apart a small fraction of the operating wavelength

Abstract

A low-profile, tri-filar, helix antenna with linear polarization or circular polarization (CP) includes a single feed without an internal feed network. The antenna includes three metal, bent, quarter-wave monopoles positioned at 0°, 120°, and 240° on a top surface of the antenna. One of the monopoles is directly fed, and the other two are parasitically coupled to the fed monopole. Metal perturbations on the parasitic monopoles control their coupling phase to the fed monopole, and determine the antenna'"'"'s polarization. Without metal perturbations, the parasitic monopoles are linear polarized and both monopoles are coupled to the fed monopole at ±120. With metal perturbations, the parasitic monopoles are CP polarized and coupled at +120 degrees to the fed monopole. Various perturbations, capacitive and inductive shunts options are possible. The three monopoles are supported by a dielectric substrate, or they are freestanding.

Claims

1. A helix antenna, comprising:

a generally flat and electrically non-conductive antenna top-surface;

said top-surface having an outer perimeter and a central axis;

first, second and third metal monopole antenna elements generally equally spaced on said top surface at generally 120-degree intervals;

said first, second and third monopole antenna elements each having relatively closely spaced and parasitically-coupled first end portions that relatively closely surrounding said central axis;

said first, second and third monopole elements each having second end portions relatively closely adjacent to said outer perimeter; and

antenna feed means connected only to said second end portion of said first monopole element.

2. The helix antenna of claim 1 wherein about one-half of feed-energy presented to said antenna feed means is transmitted into space from said first monopole element, and about one-half of said feed-energy is parasitically coupled to said second and third monopole elements.

3. The helix antenna of claim 1 wherein said first, second and third monopole antenna elements are quarter wave monopole elements.

4. The helix antenna of claim 1 wherein a parasitic-coupling is about −

6 dB.

5. The helix antenna of claim 1 wherein a parasitic coupling acts as a feed network to said second and third monopole elements, and including:

inductive shunt means connected intermediate said antenna feed means and said second end portion of said first monopole element.

6. The helix antenna of claim 1 wherein said perimeter of said top-surface is selected from a group consisting of a hexagon perimeter, a circle perimeter, a circle-like perimeter, and a perimeter having 6×

N surfaces, where N is an integer that is larger than 1.

7. The helix antenna of claim 1 wherein said top-surface has a dielectric constant of about 3.1.

8. The helix antenna of claim 1 wherein said second end portion of each of said first, second and third monopole elements includes a shaped metal portion constructed and arranged to provide an electrical function selected from a group consisting of capacitive reactance and/or inductive reactance.

9. The helix antenna of claim 1 wherein said perimeter of said top-surface has a major dimension that is less than about 0.2 wavelengths in free space of an operating frequency of the antenna, and wherein said top-surface is selected from a group consisting of a multi-sided perimeter, a circle perimeter and circle-like perimeter.

10. The helix antenna of claim 1, including:

a single metal ground plane member cooperating with each of said first, second and third monopole elements.

11. The helix antenna of claim 1 wherein said second and third monopole elements are parasitically coupled to said first monopole element at plus 120-degrees, to thereby provide a linear polarized helix antenna.

12. The helix antenna of claim 1 wherein said second monopole element is parasitically coupled to said first monopole element at plus 120-degrees and said third monopole element is parasitically coupled to said first monopole element at minus 120-degrees, to thereby provide a circular polarized helix antenna.

13. The helix antenna of claim 1 wherein at least one of said second and third monopole elements includes a metal perturbation, such that one of said second and third monopole elements is coupled to said first monopole element at plus 120-degrees and such that another of said second and third monopole elements is coupled to said first monopole element at minus 120-degrees, to thereby provide a circular polarized helix antenna.

14. The helix antenna of claim 1 wherein each of said first, second and third monopole elements includes a bent portion located intermediate said first and second end portions.

15. The helix antenna of claim 1 wherein said first, second and third monopole elements define generally identical metal patterns on said top-surface.

16. A helix antenna, comprising:

an electrically non-conductive body member having a generally hexagonal generally flat top-surface, and having six generally equal size side walls that extend generally perpendicularly downward from said top-surface;

said top-surface having a central axis;

a first quarter wave monopole element having a first straight metal portion on said top-surface adjacent to a first of said side walls, having a bent metal portion on said top-surface adjacent to a portion of a second of said side walls, and having a second straight metal portion on said top-surface extending from said portion of said second side wall toward said central axis so as to position an end of said second straight metal portion generally adjacent to said central axis;

a second quarter wave monopole element having a first straight metal portion on said top-surface adjacent to a third of said side walls, having a bent metal portion on said top-surface adjacent to a portion of a fourth of said side walls, and having a second straight metal portion on said top-surface extending from said portion of said fourth side wall toward said central axis so as to position an end of said second straight metal portion generally adjacent to said central axis

a third quarter wave monopole element having a first straight metal portion on said top-surface adjacent to a fifth of said side walls, having a bent metal portion on said top-surface adjacent to portion of a sixth of said side walls, and having a second straight metal portion on said top-surface extending from said portion of said sixth side wall toward said central axis so as to position an end of said second straight metal portion generally adjacent to said central axis;

said ends of said second straight metal portions of said first, second and third monopole elements having relatively closely physical spacing so as to be parasitically-couple said first, second and third monopole elements;

a first inductive shunt metal pattern on said sixth side wall connected to said first straight metal portion of said first monopole element;

a second inductive shunt metal pattern on said third side wall connected to said first straight metal portion of said second monopole element;

a third inductive shunt metal pattern on said forth side wall connected to said first straight metal portion of said third monopole element; and

antenna feed means connected only to said first inductive shunt metal pattern.

17. The helix antenna of claim 16 wherein about one-half of any feed-energy presented to said antenna feed means is transmitted into space from said first monopole element, and about one-half of said feed-energy is parasitically coupled to said second and third monopole elements.

18. The helix antenna of claim 16 wherein said parasitic-coupling is about minus 6 dB.

19. The helix antenna of claim 16 wherein said body member has a dielectric constant of about 3.1.

20. The helix antenna of claim 16 wherein said hexagonally-shaped top-surface has a vertex-to-vertex dimension of about one inch.

21. The helix antenna of claim 16, including:

a single metal ground plane member cooperating with said first, second and third quarter wave monopole elements.

22. The helix antenna of claim 16 wherein said second and third monopole elements are parasitically coupled to said first monopole element at plus 120-degrees, to thereby provide a linear polarized helix antenna.

23. The helix antenna of claim 16 wherein said second monopole element is parasitically coupled to said first monopole element at plus 120-degrees and said third monopole element is parasitically coupled to said first monopole element at minus 120-degrees, to thereby provide a circular polarized helix antenna.

24. The helix antenna of claim 16 wherein at least one of said second and third monopole elements includes a metal perturbation, such that one of said second and third monopole elements is parasitically coupled to said first monopole element at plus 120-degrees and said the other of said second and third monopole elements is parasitically coupled to said first monopole element at minus 120-degrees, to thereby provide a circular polarized helix antenna.

25. A method of making a single-feed, three-monopole, helix antenna, comprising the steps of:

providing three planar, metal and quarter-wave monopole antenna elements;

physically positioning said three monopole elements in a common plane at about 0-degrees, 120-degrees, and 240-degrees, respectively, about a central axis;

physically positioning said three monopole elements such that first end portions of each of said three monopoles are located physically adjacent to each other and to said central axis, and such that said three monopole elements are relatively strongly coupled;

connecting an antenna-feed to a second end of a first of said monopole elements;

such that said first monopole element is a directly-fed monopole element, and such that a second and a third monopole element are parasitically-fed from said first monopole element; and

providing that said relatively strong coupling between said three monopole elements results in about one-half of any feed energy that is applied to said antenna feed is radiated from said first monopole element into space, as a remaining portion of said feed energy is parasitically coupled to said second and third monopole elements.

26. The method of claim 25 including the steps of:

providing an inductive shunt; and

connecting said inductive shunt intermediate said antenna-feed and said second end of said first monopole element.

27. The method of claim 25 wherein said relatively strong coupling is capacitive coupling.

28. The method of claim 25 wherein said relatively strong coupling has a magnitude of about −

6 dB.

29. The method of claim 25 wherein said common plane is provided by an electrically non-conductive member having a relatively low dielectric constant.

30. The method of claim 25 wherein said common plane is provided by an electrically non-conductive member having a dielectric constant of about 3.1.

31. The method of claim 25 wherein said second and third monopoles are both ed at about positive 120 degrees to said first monopole element.

32. The method of claim 25 wherein said second monopole element is coupled to said first monopole element at about positive 120-degrees, and wherein said third monopole element is coupled to said first monopole element at about negative 120-degrees.

33. The method of claim 25 including the step of:

providing one or more metal perturbations on one or both of said second and third monopole elements in order to control a phase-of-coupling of said second and third monopole elements to said first monopole element.