Broadband multi-element antenna

摘要

A broadband multi-element antenna is presented. The antenna comprises a monopole centrally disposed within a cavity of the body, and a plurality of antenna elements disposed at ninety degree increments about the periphery of the cavity. A plurality of isolation traps are connected between selected pairs of the antenna elements. The isolation traps are half-wavelength transmission lines which permit excitation of the respective plurality of elements by input signals which are of equal amplitude and 180 DEG out-of-phase but are short circuits between the respective pairs for in phase signals parasitically induced from the monopole. Additionally, switching traps are connected to respective ones of the antenna elements. The switching traps comprise quarter-wave transmission lines which are switchable to ground and selectively provide a short circuit of signals at the respective ones of the elements for changing the radiation pattern of the antenna.