Compact UWB directional coupler with one notch-band

An ultra-wideband (UWB) parallel coupled-line directional coupler (DC) with one notch-band based on folded stepped impedance resonator (SIR) is investigated in this paper. The proposed UWB DC is comprised of one conventional microstrip directional coupler, two folded shunt quarter-wavelength short-circuited stubs and one SIR with metalized via hole to ground. The SIR is studied and employed to generate one desired notched band. The predicted results are compared with measured data and good agreement is reported.