The present invention relates to communication antennas, and in particular, antennas which have an emitter element positioned in front of a reflector surface.
Crossed dipole antennas for generating linear or circular polarizations are known. A crossed dipole antenna is known from the article “A wide-band aerial system for circularly polarized waves, suitable for ionospheric research”, G. J. Phillips, IEE Proc., Vol. 98 III, 1951, p. 237-–239. Turnstile antennas are described in various U.S. patents. An example is shown in U.S. Pat. No. 2,086,976 from 1935. The antenna shown includes a mast on which multiple crossed antennas are positioned. There are also numerous textbooks which are concerned with turnstile antennas.
In order to improve the directional efficiency, the antenna elements are frequently positioned in front of a metallic reflector surface. This approach is known and is applied in the following two antennas. A dual polarized dipole antenna may be inferred from U.S. Pat. No. 6,313,809 (which essentially corresponds to German Published Application 198 60 121 A1) of the firm Kathrein. These dipole antennas are distinguished in that they include a number of individual dipole elements which are positioned in front of a reflector. The dipole elements are positioned as a dipole square in a top view and each dipole element is fed individually via a symmetrical line.
A double-polarized multirange dipole antenna may be inferred from U.S. Pat. No. 6,333,720 of the firm Kathrein.
The bandwidth of a dipole antenna may be improved by using thick dipoles or bowtie dipole structures. Such a broadband dipole antenna is described in the article entitled “Broad-band half-wave dipole”, M. C. Bailey, IEEE Trans. Antennas Prop., Vol. 32, 1984, p. 410–412. In addition, a broadband antenna having a thick dipole structure is cited in the Antenna Engineering Handbook, R. C. Johnson and H. Jasik, editors, 2nd Edition, McGraw Hill, 1984, on p. 28–11.
It is a problem of the antenna arrangements of the prior art, which are used in the field of communication and particularly mobile wireless communication, that the antennas are costly and heavy. This leads to expensive and complicated group antennas.
What is needed therefore, is a broadband dipole antenna which is simple and cost-effective. Further, what is needed is a dipole antenna which is suitable for installation in a group antenna.