Dual polarisation slot antenna for broad band propagation

摘要

The dual polarisation slot spiral structure has a dielectric substrate with a metallised surface (25). A set of spiral slots (21 to 24) are etched in the metallic surface. The slots form two polarisation sets each having a log periodic spiral winding. The arrangement has a rotation symmetry such that a 90 degree rotation about a central point does not modify the structure of the antenna. Each slot is outside the central supply regions, and has several successive sections. The inverted structure allows a low impedance antenna to be produced. The surface is preferably planar.