This invention relates to a broad band antenna and, more particularly, to broad band broadcast antenna capable of broadcasting for example television signals in circular polarization.
Although, horizontally polarized television broadcasting has been almost exclusively used in the U.S.A., it appears from said recent test results, that circularly polarized broadcasting might well improve television reception in large metropolitan areas. The FCC has just recently approved circular polarization for television broadcasting. While circular polarization has been known for some time, one of the major difficulties in providing circular polarization for television is the broad bandwidth required. This is particularly true at the low VHF frequencies where the percentage bandwidth is quite large.
In radio or television broadcasting, it is particularly desirable in many installations to broadcast an omnidirectional pattern so that all receivers at a given radial distance from the broadcaster's antenna receive essentially the same signal strength. Often the broadcasting antennas are mounted or are required to be mounted to a triangular tower which may serve as the support for other antennas. It is therefore desirable for the sake of cost to provide antennas which have a beam width and a structure such that when one is mounted to each side of a typical triangular tower essentially omnidirectional radiation takes place. When there is a requirement for the provision of circularly polarized radiation, additional problems are encountered in mounting the antennas to the reflective towers.