Ultra-wideband (UWB) bandpass filters using hybrid microstrip/CPW structures

A novel class of ultra-wideband (UWB) bandpass filters are reportedly constructed using the hybrid microstrip and coplanar waveguide (CPW) structure. Two types of multiple-mode resonators (MMRs) on CPW are configured to allocate their first three resonant frequencies at about the lower end, center and higher end of the UWB band. Then, a microstrip/CPW back-to-back coupling structure with enhanced degree is modeled to allocate its coupling peak around the center of this UWB band, i.e., 6.85GHz. In final, two types of UWB bandpass filters with five poles are built up and realized with the passband covering the entire UWB band (3.1– 10.6GHz). Simulated frequency responses and group delays are well verified by experiments over a wide frequency range. In addition, the designed UWB filter is found to only occupy one full-wavelength.