Helical antenna for frequencies in exess of 200MHZ

摘要

A UHF antenna has an electrically insulative cylindrical core of a solid material having a relative dielectric constant greater than 5, and a three-dimensional antenna element structure disposed on or adjacent the outer cylindrical surface of the core. The antenna element structure is coupled to a coaxial feeder passing axially through the core. To reduce the effect of unwanted resonant modes associated with the resonant length of the feeder inside the core, the core is spaced from the outer conductor of the feeder by an intervening layer of insulative material having a relative dielectric constant which is much lower that that of the core material.