Microstrip based UWB filter with controllable multiple notches and extended upper stopband

Microstrip based ultra-wideband (UWB) bandpass filter (BPF) with controllable triple notches and simultaneously extended upper stopband is proposed. Initially an UWB filter based on back-to-back microstrip to co-planar waveguide (CPW) technology is constructed. Band notch property is integrated into the UWB filter by implementing complementary split ring resonators (CSRR) based defected ground structures (DGS) in the ground of this filter. Double equilateral-U (DEU) DGS etched under the input and output feeding lines suppress the spurious stopband harmonics and extend the stopband. An approximate lumped equivalent circuit model of the proposed structure is presented. Full wave and circuit simulations are in good agreement with measured results.