A highly selective UWB bandpass filter using stepped impedance stubs

We present a new ultra-wideband (UWB) band-pass filter (BPF) configuration with a stepped impedance short-circuited stub (SISS)-loaded triple-mode resonator (TMR) and stepped impedance radial stub (SIRS). The novel SISS-loaded TMR and SIRS improve the roll-off ratio at both ends. Even though this UWB BPF is based on a single resonator, the measured results show excellent in-band performance with a small insertion loss less than 0.6 dB and return loss greater than -16 dB. The proposed UWB BPF has sharp roll-off ratio of 96 and 43 dB/GHz, respectively, at the lower and upper edges of the pass-band, and a wide stop-band from 10.8 to 15.6 GHz with the rejection greater than 20 dB.