Dielectric-loaded antenna

摘要

A dielectric-loaded antenna for operation at frequencies over 200 MHz has a cylindrical ceramic core (12) with a relative dielectric constant greater than 5. The core (12) is formed with recesses in its cylindrical outer surface and the recesses are filled with conductive material thereby forming a three-dimensional antenna element structure having antenna elements (10A - 10D) inlaid in the ceramic material and with their outer surfaces flush with the outer surface of the core. The antenna is manufactured by forming the core from the ceramic material when in a green state, firing the core, metallising the core outer surface whereby conductive material enters the recesses as well as covering other parts of the core outer surface, and then machining the metallised core to an extent such that conductive material is left in the recesses but portions of the core between the recesses are exposed. The recesses are generally rectangular in cross-section such that the conductive antenna elements (10A - 10D) have well-defined edges of a predetermined thickness to provide low electrical resistance along the element sides where radio frequency currents are concentrated.