Compact Single-layer CPW Ultra-wide Band BPF with a notch band

This paper presents a compact ultra-wide band (UWB) band-pass filter (BPF) with a notch band based on single coplanar waveguide (CPW) and defected ground structure (DGS), which can effectively restrain the electromagnetic interference between systems and be integrated easily, to ensure immunity and miniaturization of the system. The proposed filter realizes UWB property using a couple of inter-digital coupled-lines and micro-strip line, whose ground layer is located at both sides of the micro-strip inter-digital structure. A couple of spiral rings are respectively embedded on the two ground layer, which gets the adjustable notch band, thereby gaining the dual band. Experiment results demonstrated that the bandwidth of filter designed is from 2.2 to 11.8 GHz (-3 dB bandwidth), fractional bandwidth of 137% at the central frequency 7 GHz and the notch band can be changed optionally from 5.01 to 10.26 GHz.