3. UWB antenna in radio frequency range

Planar microwave circuitry has generated attractive radiating structures with high gain, low weight, reliability, ease of manufacturing and integration such as the Vivaldi antennas [36, 37], and the tapered slot antenna [38] for UWB antennas. The printed planar log-periodic dipole (LPDA) is the most suitable solution microwave frequencies [39]. LPDAs have a lot of advantages, such as directive radiation pattern, linear polarization and low cross polarization ratio over a wide frequency range [5]. At the beginning, coaxial cable was used for feeding the printed LPDAs at the radio and the TV frequency bands; however, it was found that the performance became worse when frequency increases. Due to huge increase in data traffic, there is a requirement for wireless networks which support both data and voice transfer simultaneously for short-range wireless communication systems [1, 2].
