In this paper, a microstrip dual-band bandpass filter (DB-BPF) with a controllable bandwidth is designed and simulated at 3.7GHz and 7.4GHz. The DB-BPF is composed of an open stub, stepped impedance resonator (SIR) and a pair of shunt open stubs with good results of transmission and reflection characteristics. The transmission coefficient (S21) in the first band is 0.41dB with 3dB bandwidth of 575MHz and in the second band, the S21 is 0.31dB. The reflection coefficient (S11) in the first band is 20dB and in the second band, the S21 is 18.1dB. The DB-BPF can be implemented in landline M/W relay, fixed satellite communication, ultra-wideband (UWB), broadcast relay and others. The overall size of the DB-BPF is 15mm × 20mm

microstrip open stub, dual-band filter, SIR.