New Ultra-wideband Planar Antenna Research

Antennas are a kind of converters (or energy converters) between traveling wave and free space wave. They are the necessary components in the modern wireless systems. The miniature and wide band of the antennas become more and more important than before as the development of communication technology. There are not any differences in the radiation theories between the ultra-wide band antenna and the ordinary narrow band one, but the former is developed based on the latter. The main content of the subject on the ultra-wide band antenna is to explore the novel theories, techniques, and methods to research them in very broad band.This dissertation mainly researches the vivaldi slot antennas and bowtie antennas. Several novel planar antennas are proposed. Many technologies of them are discussed in theory, simulation and experiment.The first novel planar antenna is modified from a conventional vivaldi slot antenna. Placing each metal part on each side of dielectric-slab,modify the shape of antennas (remove a sector of 90°)and add round corners to the modified slot ,we gain a 10dB return loss bandwidth of 182%, from 0.23 to 5 GHz. Moreover, the radiation pattern of the proposed antenna gets more stable and its main beam is kept almost unchanged as the frequencies increase.The second planar antenna is modified from a conventional bowtie antenna. As above, we place each metal part on each side of dielectric-slab, which is convenience for fed and easy for the transition from unbalance to balance. By these means, we gain a 10dB return loss bandwidth of 176%, from 0.5 to 8 GHz.It is concluded from the results of this thesis that, planar antennas are fit for broadband working. And most of these antennas can be worked out by optimizing their geometry parameters. Planar antennas will place an important role in the miniature systems.