Planar ultra-wideband filter with triple notches and improved out-of-band performance

Planar Ultra-wideband (UWB) filter with controllable triple notches and simultaneously improved out-of-band performance is proposed. Initially an UWB filter is modeled based on back-to-back microstrip to co-planar waveguide (CPW) technology. Later, defected ground structures (DGS) are implemented to generate controllable notches and extended stopband. Complementary folded split ring resonators (CFSRR) implemented in the ground generate passband notches whereas cancelling of spurious stopband harmonics using dual attenuation poles of the double equilateral-U (DEU) DGS brings about extended stopband. An approximate lumped equivalent circuit model of the proposed filter structure is presented. Full wave and circuit simulations are in appreciable agreement with measured results.