A new ultra wideband tapered balun for improved ELEVEN antenna

A novel wideband tapered balun based on ELEVEN antenna is presented and carefully examined in this paper. The proposed balun consists of one patch which is printed both sides. By using two smooth intergrade structures, balanced-to-unbalanced ports impedance of 50Ω-180Ω is acquired. This balun-transformer achieves an impedance bandwidth from 2-18 GHz for VSWR<;1.8, also in the frequency band, transmission coefficient |S21|>;1.1dB is achieved.