Double spiral antenna
View Patent ↗An antenna comprises a first antenna element, which has a first helix, and a second antenna element, which has a second helix. The first and the second antenna elements each have a feed point at an outer end of the corresponding helix and an open end at an inner end of the corresponding helix. A symmetrical helix antenna according to the invention can be integrated in a comparatively simple manner in an existing system, for example in a hearing aid. By integrating the antenna in a plastic housing, the antenna cannot be seen at all from the outside. The antenna is comparatively small in relation to conventional antennas.
1. An antenna for wireless data transmission, comprising:
a first radiator that comprises a first spiral with a first feed point at an outer end of the first spiral and an open-circuit end at an inner end of the first spiral and functions as a first arm of a dipole antenna; and
a second radiator that comprises a second spiral with a second feed point at an outer end of the second spiral and an open-circuit end at an inner end of the second spiral and functions as a second arm of the dipole antenna,
wherein the first radiator and the second radiator are configured to:
have a spatial gap between the first and the second radiators minimum in a range between 0.3 and 0.5 times a diameter of one of the first and the second spirals,
be coiled identically,
lie in a same plane or on a same material surface,
have a gap between the first feed point and the second feed point minimum of 5*10 −3 times a freespace wavelength at an operating frequency of the antenna.
2. The antenna as claimed in claim 1 , wherein the gap between the first feed point and the second feed point is in a range between 0.4 and 0.6 times a diameter of one of the first spiral and the second spiral.
3. The antenna as claimed in claim 1 , wherein a gap between a center of gravity of the first spiral and a center of gravity of the second spiral is greater than a hypotenuse of a right-angled triangle in which a first cathete has a length equal to half diameter of the first spiral and a second cathete has a length equal to half diameter of the second spiral.
4. The antenna as claimed in claim 3 , wherein the center of gravity of the first spiral and the center of gravity of the second spiral are geometric centers of gravity of lines which follow a course of the first spiral and a course of the second spiral respectively.
5. The antenna as claimed in claim 1 , wherein:
the first spiral comprises a first spiral substrate area and a first spiral axis,
the second spiral has a second spiral substrate area and a second spiral axis,
a parallel projection of the first spiral substrate area in a direction of the first spiral axis does not intersect with the second spiral substrate area, and
a parallel projection of the second spiral substrate area in a direction of the second spiral axis does not intersect with the first spiral substrate area.
6. The antenna as claimed in claim 1 , wherein the first radiator and the second radiator are electrically conductive.
7. The antenna as claimed in claim 1 , wherein the first radiator and the second radiator are radiating slots.
8. The antenna as claimed in claim 1 , wherein electrical characteristics at the first feed point and the second feed point are essentially symmetrical in relation to a reference potential.
9. The antenna as claimed in claim 1 , wherein the first radiator and the second radiator are arranged on a surface of a dielectric material.
10. The antenna as claimed in claim 9 , wherein the surface of the dielectric material is domed.
11. The antenna as claimed in claim 1 , wherein the first radiator and the second radiator are integrated into a housing that comprises a dielectric material and houses an electronic circuit.
12. The antenna as claimed in claim 11 , wherein the housing is a part of a behind-the-ear hearing aid.
13. The antenna as claimed in claim 1 , wherein the operating frequency of the antenna is in a range between 500 MHz and 6 GHz.
14. The antenna as claimed in claim 1 , wherein a maximum dimension of the antenna is 10 cm.
15. The antenna as claimed in claim 1 , wherein a maximum dimension of the antenna is less than one fifth of the freespace wavelength at the operating frequency of the antenna.
16. The antenna as claimed in claim 1 , wherein the antenna is used to wirelessly transmit data to a hearing aid.