MULTIFILAR HELIX ANTENNA

Abstract

The invention relates to a multifilar helix antenna (1) comprising a wave feed and polarizing section (2) comprising a cover portion (3) comprising a through opening (4). The antenna (1) comprises a helix radiator (5) comprising three or more resonant helical elements (6) evenly distributed about an imaginary circle. Each helical element (6) extends in a longitudinal direction (Z) from the feed and polarizing section (2) through the opening (4) in the cover portion (3) and wound to form the helix radiator (5). Each helical element (6) comprises one or a plurality of wave perturbations (7) separated in the longitudinal direction (Z) and that each set of perturbations are positioned at the same level in the longitudinal direction (Z) to yield an equivalent array of stacked helical radiators, wherein the cover portion (3) comprises a rotationally symmetric corrugated assembly (8).

Claims

1. A multifilar helix antenna comprising a wave feed and polarizing section comprising a cover portion comprising a through opening, the antenna comprising a helix radiator comprising three or more resonant helical elements evenly distributed about an imaginary circle, each helical element extending in a longitudinal direction (Z) from the feed and polarizing section through the opening in the cover portion and wound to form the helix radiator, characterized in that each helical element comprises one or a plurality of wave perturbations separated in the longitudinal direction (Z) and that each set of perturbations are positioned at the same level in the longitudinal direction (Z) to yield an equivalent array of stacked helical radiators, wherein the cover portion comprises a rotationally symmetric corrugated assembly.

2. The antenna according to claim 1, wherein the wave feed and polarizing section comprises as many taps as there are helical elements with corresponding angles of electrical phasing with equal amplitude over a desired significant bandwidth.

3. The antenna according to claim 1, wherein the helix radiator is trifilar.

4. The antenna according to claim 1, wherein the helix radiator is hexifilar.

5. The antenna according to claim 1, wherein the helix radiator is quadrifilar.

6. The antenna according to claim 1, wherein each helical element is an all-metal self-supporting structure.

7. The antenna according to claim 1, wherein each helical element is a metallic pattern on a common dielectric sheet.

8. The antenna according to claim 1, wherein the perturbation comprises a wave impedance discontinuity.

9. The antenna according to claim 1, wherein the perturbation is an indentation in the helical element.

10. The antenna according to claim 1, wherein the perturbation is a protrusion on the helical element.

11. The antenna according to claim 1, wherein the perturbation is a different material in the helical element compared to the main material in the helical element.

12. The antenna according to claim 1, wherein the helical elements are electrically connected at the far end of the helix radiator in the longitudinal direction with relation to the cover portion.

13. The antenna according to claim 1, wherein the helical elements are disconnected on the far end of the helix radiator in the longitudinal direction with relation to the cover portion.

14. The antenna according to claim 1, wherein the helical elements are wound equidistant with relation to each other and in the same cylindrical or conical plane.

15. The antenna according to claim 1, wherein the corrugated assembly comprises a recessed portion in the cover portion or in connection to the cover portion for decreasing back-radiation coupling into the feed and polarizing section.

16. The antenna according to claim 15, wherein the recessed portion is arranged in a circularly symmetric manner about the helix radiator.

17. The antenna according to claim 15, wherein the recessed portion comprises at least two parts arranged in a radial direction (R) about the helix radiator, wherein the radial direction (R) is a direction perpendicular to the longitudinal direction (Z), or wherein the recessed portions are arranged in a direction having a component in the radial direction (R) and a component in the longitudinal direction (Z).

18. The antenna according to claim 1, wherein the antenna comprises a dielectric radome covering the helix radiator.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0039] The invention will below be described in connection to a number of drawings, in which:

[0040] FIG. 1 shows a schematic view over a satellite, Sat, 101 and the earth 102 approximated as a circle and a ground station, Gnd Stn, 103, for the calculations in background art.

[0041] FIG. 2 schematically shows a perspective view of one example of a trifilar helix antenna according to the invention, and in which;

[0042] FIG. 3 shows a trifilar helix antenna according to FIG. 1 with a radome.

DETAILED DESCRIPTION OF DRAWINGS

[0043] In the figures, like items are denoted with the same numbers.

[0044] FIG. 1 shows a schematic view over a satellite, Sat, 101 and the earth 102 approximated as a circle and a ground station, Gnd Stn, 103, for the calculations in background art.

[0045] FIG. 2 schematically shows a perspective view of one example of a trifilar helix antenna 1 according to the invention.

[0046] In FIG. 2 the multifilar helix antenna 1 comprises a wave feed and polarizing section 2 comprising a cover portion 3 comprising a through opening 4. The antenna 1 comprises a helix radiator 5 comprising three resonant helical elements 6 evenly distributed about an imaginary circle. Each helical element 6 extends in a longitudinal direction Z from the feed and polarizing section 2 through the opening 4 in the cover portion 3 and wound to form the helix radiator 5. Each helical element 6 comprises one or a plurality of wave perturbations 7 separated in the longitudinal direction Z and that each triple of perturbations are positioned at the same level in the longitudinal direction Z to yield an equivalent array of stacked helical radiators, wherein the cover portion 3 comprises a rotationally symmetric corrugated assembly 8.

[0047] The wave feed and polarizing section 2 comprises as many taps as there are helical elements 6 with corresponding angles of electrical phasing with equal amplitude over a desired significant bandwidth.

[0048] In FIG. 2 each helical element 6 is an all-metal self-supporting structure. However, according to another example, not shown, each helical element 6 is a metallic pattern on a common dielectric sheet.

[0049] In FIG. 2 the perturbation 7 comprises a wave impedance discontinuity in the form of a protrusion 10 on the helical element 6. According to another example, not shown, the perturbation 7 is an indentation in the helical element 6. According to one example, the perturbation 7 is a different material in the helical element 6 compared to the main material in the helical element 6.

[0050] In FIG. 2 the helical elements 6 are electrically connected at the far end 13 of the helix radiator 5 in the longitudinal direction with relation to the cover portion. However, another example, not shown, the helical elements 6 are disconnected on the far end 13 of the helix radiator 5 in the longitudinal direction with relation to the cover portion 3.

[0051] In FIG. 2 the helical elements 6 are wound equidistant with relation to each other and in the same cylindrical plane. However in another example the helical elements 6 are wound equidistant with relation to each other and in the same conical plane.

[0052] In FIG. 2 the corrugated assembly 8 comprises two recessed portions 9 in the cover portion 3 for decreasing back-radiation coupling into the feed and polarizing section 2. The recessed portions 9 are arranged in a circularly symmetric manner about the helix radiator 5.

[0053] According to one example, not shown, the recessed portion 9 comprises at least two parts arranged in a radial direction R about the helix radiator 5. The radial direction R is a direction perpendicular to the longitudinal direction Z. In FIG. 2, the recessed portions are arranged in a direction having a component in the radial direction R and a component in the longitudinal direction Z, i.e. the plane in which the recessed portions are positioned are at an angle to the longitudinal direction and may be in the form of a cone shape or any other suitable shape.

[0054] In FIG. 2 the cover portion 3 comprises a reflection portion 14 in the form of a cone. The reflection portion 14 is designed to reflect unwanted and leaked waves in a direction away from the antennas intended direction of use. The reflection portion 14 is designed dependent on desired performance and may thus have any suitable shape and for, for example, conical, cylindrical and curved.

[0055] FIG. 3 shows a trifilar helix antenna according to FIG. 2 with a radome 11. The radome 11 is dielectric and covers the helix radiator 5. The radome 11 may comprise support units 12 for supporting the helix radiator 5. The support units 12 is advantageously positioned in connection to the perturbations 7 since other parts of the helix radiator is then not affected impedance wise of any connection to the support units 12.