Abstract:Based on the electromagnetic coupled microstrpslotline transition, a novel ultra-wideband (UWB) bandpass filter with compact size and a tunable notched band is presented in this paper. By loading a short ended stepped impedance resonator coupled with the slotline, a tunable notched band is produced. Moreover, To obtain wide stopband, three microstrip lines with a fan shape are setted on input and output feedlines. The centel frequency of this filter is 6.85 GHz, and the measured 3 dB bandwidth from 1.95 GHz to 13.15 GHz which makes the FBW to 148%. A good agreement is achieved between simulation and measurement.