Broadband low-profile antennas for wireless applications

Two novel broadband low-profile antennas are developed for the mobile terminals of wireless applications. The first one is a quasiplanar antenna which has a height of 0.06l0, where l0 is the free-space wavelength at the centre frequency. The second one is a planar antenna which has a height of 0.056l0. It is demonstrated that the quasiplanar antenna can achieve a bandwidth for VSWR , 2 of more than 45%, while the planar antenna realises a bandwidth of more than 40%. More importantly, over these bandwidths the broadband low-profile antennas have a quite constant omnidirectional radiation pattern with a peak gain of around 1 dBi. The antennas are designed on a commonly used RT/Duroid substrate; hence it is easy to integrate with RF front-end circuits. The antenna structures are described and the simulation and experimental results are presented.