Ultra-wideband (UWB) bandpass filter based on stub-loaded ring resonator

An ultra-wideband (UWB) bandpass filter with a notch-band and wide upper stopband is presented in this paper. The UWB filter is realized using a ring resonator which is loaded with two sets of stubs, i.e. one is loaded in the center and two little stubs at the symmetrical side locations. The loaded stubs are used to create transmission zeros in upper stopband thus high modes are suppressed greatly. Moreover, two identical meandered resonators are inserted within the stub-loaded ring resonator, creating a notch-band around 5.8 GHz. Finally, two UWB filters with and without notch-band are simulated, fabricated, and measured results provide an experimental validation of predicted performance of the filter.