Planar monopole antenna with dual frequency for UWB system

For an ultra-wideband (UWB) system, the antenna with wide bandwidth able to cover from 3.1 to 10.6 GHz is required. It has been already proposed several types of wideband antennas which cover whole frequency range. On the other hand, since UWB system covers from 3.1 to 10.6 GHz, it is necessary to suppress the interference from other systems using some of frequency band in 3.1-10.6 GHz. In this paper, the novel planar monopole antenna, which consists of two connected rectangular plates, is presented. The return loss characteristics, radiation pattern, and current distribution of the antenna are simulated by the FDTD method. The proposed planar monopole antenna's structure has dual frequency and broad bandwidth at both resonant frequencies. The return loss level at the eliminated frequency between both resonant frequencies is almost O dB. The radiation patterns at each resonant frequency are almost omni-directional. The current distributions at each frequency are similar to that of planar rectangular monopole, so the radiation patterns become omni-direction in horizontal plane at each resonant frequency. Therefore, wide bandwidth characteristics can be achieved.