TRANSMISSION ANTENNA DEVICE AND BROADCAST TOWER

摘要

PROBLEM TO BE SOLVED: To provide a transmission antenna system that is suitable to be mounted on a limited installation space at the upper part of a broadcast tower. SOLUTION: Antenna units 10 that are placed within a horizontal plane in a torus shape to form a multi-plane synthetic antenna are structured such that a plate-shaped main reflecting plate 12 is provided in parallel with an antenna element 11 at the rear side of the antenna element 11 provided with a radiation element of a loop shape or a dipole shape and a sub reflecting mirror 13 is provided nearly perpendicularly to both ends of the main reflecting plate in a direction of an antenna horizontal plane so as to enhance the directivity characteristic by suppressing side lobes and back lobes and to narrow the lateral width as the antenna units at the same time thereby making the size of the units compact. Furthermore, the transmission antenna system is structured such that a protection cover 14 to cover the antenna element 11 is provided via the sub reflecting mirror so as to relieve a wind pressure load of the broadcast tower.