In this paper, a novel ultra-wideband (UWB: 3.1 ~ 10.6 GHz) bandpass filter on coplanar waveguide (CPW) is presented, designed and implemented. At first, an openended nonuniform or multiple-mode resonator with three distinctive sections is constructed and investigated toward generating the first three resonant modes occurring around the lower-end, center, and higher-end of the UWB band. Then, a CPW interdigital capacitor element with enlarged ground-to-ground distance is characterized to excite two additional resonant poles below and above the UWB’s center. As a result, a five-pole UWB bandpass filter with only one full-wavelength is constituted. Its performance is studied on the basis of a simple cascaded transmission-line network, whose parameters are extracted from our selfcalibrated method of moments. After the optimized results are confirmed by full-wave simulation over the filter layout, a UWB filter sample is fabricated to demonstrate the actual UWB passband behavior with the 2.8–10.2 GHz bandwidth, where the insertion loss is less than 1.5 dB and variation in group delay is less than 0.33 ns.