Analysis And Design Of Wideband Antennas

The sizes and weights of wireless communication devices have rapidly been reduceddue to the development of modern integrated circuit technology and the requirements ofthe users. Meanwhile, it is envisaged that next generation wireless communication deviceswill require the capability to tune to a number of frequency bands for cellular applications,wireless local area networks (WLAN) and other wireless communications. Therefore, moreand more investigations are contributed to miniaturization and bandwidth-widening ofcommunication devices. On the other hand, the Ultra-Wideband (UWB) techniques haverecently received a lot of attention as the UWB systems have the features of largecommunication capacity, small average power density and good anti-interferencecapability.This dissertation mainly focuses on novel antenna bandwidth-widening techniques.The main contributions of the dissertation are listed as below:1. Propose new DRA antenna designs and equivalent circuit model. Two novelwideband DRAs are proposed. Meanwhile, an equivalent circuit model is proposed for thecomplicated three-resonance DRA with the Maquart mothod.2. Propose new UWB antenna designs. First, a novel combination of a dielectricresonator antenna (DRA) and a monopole antenna for UWB applications is proposed. Then,a balanced UWB antenna consisting of two planar monopole antennas and a tapered balunis proposed. Regarding the proposed balanced UWB antenna, it is found that less currentflows on the ground plane as compared to the unbalanced antenna so that improvedradiation efficency and ability of less sensitive to the perturbation of the ground plane areobtained.3. Propose new bandwidth-widening techniques for straight F-antennas for furtherpotential applications. Two novel straight F-antennas are presented, one of which is adual-band design for wireless local area network (WLAN) applications operating in the2.4GHz and 5.2/5.8GHz bands, and the other is a wideband design for WLAN systems atthe 5.2/5.8GHz bands and UWB systems at the 3.1GHz-5GHz band.