Dipole antennas and coaxial to microstrip transitions
View Patent ↗The invention relates in part to a folded dipole having a dipole axis and a pair of arms which together have a profile which is concave on one side and convex on the other when viewed along the dipole axis. The dipoles may be arranged as a dipole box around a central region, typically in a generally circular or square configuration. Further elements may be placed in the dipole box or in the gaps between dipole boxes. The antenna may be a single-band antenna, or a multi-band antenna with the further elements operating in a different frequency band to the dipole boxes. The further elements may be concentric dipole boxes. The invention is particularly suited for use in a cellular base station panel antenna. A novel coaxial to microstrip transition is also described.
1. A folded dipole comprising a fed dipole fed at a center of the fed dipole and a passive dipole being continuous from one end to the other end of the passive dipole, the fed dipole and passive dipole separated by a gap and connected at ends of the fed dipole and the ends of passive dipole, the folded dipole having an axis of propagation defining a dipole axis, the folded dipole comprising a pair of arms which together have a profile which is concave on one side and convex on the other when viewed along the dipole axis.
2. A folded dipole according to claim 1 wherein the arms are at least partially curved.
3. A folded dipole according to claim 2 wherein the arms have curved portions which have a substantially constant radius of curvature.
4. A folded dipole according to claim 2 wherein the aims are at least partially curved in a plane substantially orthogonal to the dipole axis.
5. A folded dipole according to claim 1 wherein the pair of arms meets at a corner.
6. A folded dipole according to claim 5 wherein the corner subtends an angle lying in the range of 80° to 100°.
7. A folded dipole according to claim 5 wherein each arm is substantially straight.
8. A folded dipole according to claim 5 wherein the corner is truncated.
9. A folded dipole according to claim 1 further comprising an input section coupled to a concave side of the pair of arms.
10. A folded dipole according to claim 1 wherein the pair of arms are formed of sheet material.
11. A folded dipole according to claim 10 wherein both arms are formed from the same sheet.
12. A folded dipole according to claim 1 further comprising a first feed leg coupled to one of the arms and a second feed leg coupled to the other arm.
13. An antenna comprising a ground plane; and a folded dipole according to claim 1 arranged with its dipole axis directed away from the ground plane.
14. A base station including an antenna according to claim 13 .
15. A communication system including a network of base stations according to claim 14 .
16. A dipole box comprising two or more folded dipoles arranged around a central region, each folded dipole comprising a fed dipole fed at a center of the fed dipole and a passive dipole being continuous from one end to the other end of the passive dipole, the fed dipole separated by a gap and connected at ends of the fed dipole and the ends of passive dipole, the folded dipole having a dipole axis and a pair of arms which together have a profile which is concave on one side and convex on the other when viewed in plan.
17. A dipole box according to claim 16 wherein each pair of arms has a curved portion with a centre of curvature which is located in the central region.
18. A dipole box according to claim 16 comprising four or more folded dipoles arranged around the central region.
19. A dipole box according to claim 18 wherein the dipoles are arranged as orthogonally opposed pairs.
20. A dipole box according to claim 19 wherein each pair of dipoles is oriented to radiate at about ±45° polarization with respect to vertical.