Antenna structure of a circular-polarized antenna for a vehicle
View Patent ↗A turnstile antenna has two dipoles which have a galvanic contact at the crossing point. The dipoles are arranged in a geometrically asymmetrical manner with respect to the crossing point. The turnstile antenna can be arranged either in a free space or over a metal plate.
1. An antenna structure of a circular-polarized antenna that can be arranged on an electrically conductive surface, the antenna structure comprising:
a first λ/2 dipole,
a second λ/2 dipole,
a crossing point for the first and second λ/2 dipoles to form a crossed dipole;
said λ/2 dipoles forming said crossed dipole being electrically conductively connected at said crossing point and, in relation to said crossing point, having a geometric asymmetry in at least one longitudinal direction of said λ/2 dipoles to form respective dipole limbs of different lengths from said crossing point, to thereby set a desired phase shift;
said antenna structure having only one feed point, positioned at one end of one of said λ/2 dipoles; and
wherein each one of said λ/2 dipoles includes at least one extending parallel to a plane and at least one leg extending at an angle with respect to the plane.
2. The antenna structure according to claim 1 , wherein said first λ/2 dipole is bent in a U shape and said second λ/2 dipole is bent in a U shape.
3. The antenna structure according to claim 2 , wherein said crossing λ/2 dipoles bent in a U shape comprise a punched and bent sheet metal material.
4. The antenna structure according to claim 2 , wherein a height and hence said limb length of said four limbs of said λ/2 dipoles bent in a U shape matches a curvature of the electrically conductive surface, to thereby obtain a horizontal crossing plane for the crossing λ/2 dipoles.
5. The antenna structure according to claim 1 , wherein said crossing λ/2 dipoles are disposed on a printed circuit board material.
6. The antenna structure according to claim 1 , wherein the electrically conductive surface is a vehicle roof.
7. The antenna structure according to claim 1 , wherein the circular-polarized antenna has an SDARS antenna for satellite communication frequencies fSDARS in a range 2.320 GHz≦fSDARS≦2.345 GHz.
8. The antenna structure according to claim 7 , wherein the SDARS antenna is disposed on an electrically conductive top of a shielding chamber of an antenna circuit board, and the shielding chamber encloses at least one of an antenna matching circuit, a tuner, or an amplifier.
9. The antenna structure according to claim 1 , wherein the circular-polarized antenna has a GPS antenna for satellite navigation frequencies fGPS in a range 1.574 GHz≦fGPS≦1.577 GHz.
10. The antenna structure according to claim 9 , wherein the GPS antenna is arranged on an electrically conductive top of a shielding chamber of an antenna circuit board, and the shielding chamber encloses at least one of an antenna matching circuit, a tuner, or an amplifier.
11. The antenna structure according to claim 1 , wherein a limb of one of said λ/2 dipoles is connected to a matching network and a coaxial feed line or to a receiver or transceiver.