Abstract
Small size antennas with the circular polarization are required for ITS antenna of mobile communication. We developed a circularly polarized modified transmission line antenna(MTLA) using closed-spaced parasitic spiral element for a mobile communication. The properties of this antenna regarding to the axial ratio ,gain and radiation pattern are analyzed by means of the moment method. Various type of spiral element length are analyzed. As the results, we obtain that the axial ratio(≦3) is 20% and the gain is about 6dB. Moreover, it is concluded that the MTLA with a spiral element provides wide-band and dual-mode(vertical, circular polarization) mobile communication antenna.
