Compact ultra-wideband balun filter and its quasi-Yagi antenna application

In this paper, a compact quasi-Yagi antenna with ultra-wideband balun filter is presented. The proposed balun filter is constructed with composite microstrip and slotline resonators. With the excited three resonant modes of slotline resonator and two additional resonant modes of microstrip lines, the balun filter with ultra-wideband response can be realized. Thus, with this proposed ultra-wideband balun filter, the designed quasi-Yagi antenna presents an impedance bandwidth from 5.95 to 10.63 GHz with return loss |S₁₁|> 10 dB, and the antenna gain about 1.8-6.2 dBi of the interested passband can be achieved.