A new ultra-wideband (UWB) bandpass filter (BPF) is proposed, using coplanar waveguide (CPW) open-circuited and short-circuited resonators composite structure which is broadside-coupled to the top microstrip. The proposed filter has been simulated, optimized for UWB system, and the calculated results demonstrated the UWB properties from 3.0 GHz to 9.3 GHz (-3 dB bandwidth), which is fractional bandwidth of more than 100% at the center frequency 6.2 GHz. The Alter also exhibits a sharper slop response at the lower pass-band edge than the paper (Thomson and Hong, 2007), and deeper and wider stop-band rejection than the paper (Thomson and Hong) at the higher pass-band edge. Additionally, there are several finite-frequency transmission zeros closer to each side of the pass-band edges. Thus, a high selectivity is achieved using the microstrip/CPW broadside-coupled transition structure.