Broadside Coupled UWB Filter with Dual Notched Band and Extended Upper Stopband

摘要

A broadside coupled planar ultra-wideband (UWB) filter with dual notched band and improved isolation is proposed. Application based notches at 5.6 and 8 GHz with extended stopband till 18 GHz is implemented. The UWB filter structure consists of microstrip lines on the top coupled in broadside manner to an open ended co-planar waveguide (CPW) in the ground plane. Dual narrow notches are generated by embedding two non equi-dimensional meander shaped defected ground structures (DGS) in the CPW under the patches. In order to extend the stopband, spur line structures are implemented into the input and output feeding lines. Approximate lumped equivalent circuit model of the proposed dual notch structure is developed. The proposed filter shows good passband and stopband performance with a flat and linear group delay in the passband. The structure is compact measuring 22.2 × 14.2 mm.