Quadrifilar helix antenna
A quadrifilar helix antenna ( 1 ) comprising a first and a second set of helical antenna elements ( 2 a– 5 a, 2 b– 5 b ) symmetrically arranged around a longitudinal axis extending through the axial center of the antenna ( 1 ). The antenna ( 1 ) is excited from feeding points ( 2 c– 5 c ) in a local ground plane at the bottom ( 6 ) of the antenna. The helical antenna elements ( 2 a– 5 a ) of the first set are interconnected in respective top ends of the elements at the top ( 7 ) of the antenna. The bottom ends of the first set are in galvanic contact with the respective feeding points ( 2 c– 5 c ). The antenna is characterized in that the top ends of helical antenna elements ( 2 b– 5 b ) of the second set are arranged in an open circuit and remain unconnected. The bottom ends of the helical antenna elements ( 2 b– 5 b ) of the second set each includes a connection ( 2 d– 5 d ) to the local ground plane.
1. A quadrifilar helix antenna comprising a first and a second set of helical antenna elements symmetrically arranged around a longitudinal axis extending through the axial center of the antenna, wherein the antenna is excited from feeding points in a local ground plane at the bottom of the antenna, the helical antenna elements of the first set are interconnected in respective top ends of the elements at the top of the antenna and the bottom ends of the first set are in galvanic contact with the respective feeding points, wherein the bottom ends of the helical antenna elements of the second set each have a connection to the local ground plane and that the top ends of helical antenna elements of the second set are arranged in an open circuit and remain unconnected.
2. A quadrifilar helix antenna in accordance with claim 1 , wherein the first set of helices is enclosed by the second set of helices.
3. A quadrifilar helix antenna in accordance with claim 1 , wherein antenna elements in the first and second set are adjacent and arranged in pairs so that two-wire circuits are formed by an antenna element of the first set and a respective antenna element of the second set.
4. A quadrifilar helix antenna in accordance with claim 1 , wherein each pair of antenna elements are arranged in the direction of a ray extending through the longitudinal axis of the antenna.
5. A quadrifilar helix antenna in accordance with claim 1 , wherein the top ends of the first set of antenna elements are interconnected by a galvanic interconnection.
6. A quadrifilar helix antenna in accordance with claim 1 , wherein the first set of helical antenna elements are etched circuits on a first substrate formed as a first cylinder with a first diameter, the second set of helical antenna elements are etched circuits on a second substrate formed as a second cylinder with a second diameter that is larger than the first diameter, and wherein the second cylinder is arranged to embrace the first cylinder.
7. A quadrifilar helix antenna in accordance with claim 6 , wherein the etched circuits on the respective substrates are arranged to overlap in an area in the vertical direction of the antenna.
8. A quadrifilar helix antenna in accordance with claim 6 wherein the two cylinders or cones are separated by gas or vacuum.
9. A quadrifilar helix antenna in accordance with claim 6 wherein the two cylinders or cones are separated by a spacing distance material.
10. A quadrifilar helix antenna in accordance with claim 1 , wherein the first set of helical antenna elements are etched circuits on a first substrate formed as a first circular cone with first dimensions, the second set of helical antenna elements are etched circuits on a second substrate formed as a second circular cone with second dimensions that are larger than the first dimensions, and wherein the second cone is arranged to embrace the first cone.
11. A quadrifilar helix antenna in accordance with claim 1 , wherein the first set of helical antenna elements and the second set of helical antenna elements are etched circuits on one substrate so that the antenna elements are co-planar circuits.
12. A quadrifilar helix antenna in accordance with claim 1 , wherein the first and second set of helical antenna elements are self-supporting double helices.
13. A quadrifilar helix antenna in accordance with claim 12 , wherein the antenna elements are locked into position by means of spacing elements.