Compact Ultra-Wideband BPF with broad Stopband Using Improved Short-Circuited Coplanar Waveguide Multiple-Mode Resonator

A novel structure of miniaturized ultra-wideband (UWB) bandpass filter (BPF) with wide stopband has been proposed. By introducing defected ground structure (DGS), a short circuited coplanar waveguide (CPW) multiple-mode resonator (MMR) is constituted by a pair of improved complementary split-ring. Stepped impedance microstrip line is employed on the top plane to achieve broadband coupling and high selectivity. This configuration can obtain an UWB response between 3.1 and 11.3 GHz and a wide stopband region up to 24.2 GHz with perfect rejection characteristic of below 19.5dB. In addition, the effective overall size is less than 13mmx8mm. Design, simulation and measurement of filter prototypes are presented.