Design of Compact CPW Bandpass Filters with Wide Stopband

[[abstract]]Two compact bandpass filters composed of the lumped elements in various coplanar waveguide (CPW) forms have been presented in this study. The filters were designed to operate at the frequency of 2.45 GHz. The behaviors of these filters can be simulated by the equivalent lumped-element circuit models with each element realized by the corresponding CPW discontinuity. Simulation and measurements were found to be in good agreement. Most attractive of all, the improved-design filter has achieved about a 363% (9.04 GHz) stopband bandwidth under a 20 dB out-of-band rejection, and the measured passband's minimum insertion loss is around −1.24 dB with 10.84% 3-dB bandwidth