Folded monopole antenna for use with portable communications devices

摘要

An antenna arrangement of sufficiently small size to be accommodated in the housing of a portable communications device includes a pair of spaced folded monopole antennas. Each antenna includes a first printed circuit board having a conducting surface that forms a ground plane. Mounted on the first circuit board is a second printed circuit board having a right-angled strip of conducting material, which forms a folded monopole radiating element. The folding of the monopole reduces its height, to thereby enable it to fit into small casings and the like. To compensate for the effects of the folded monopole on the electrical match, frequency bandwidth and electromagnetic fields, a shunt inductance is introduced between the monopole and the ground plane. The antennas are mounted within cavities that can be lined or coated with metallic material, to improve the radiation patterns of the antennas and isolate them from the electronic components of the communications system.