An ultrawideband bandpass filter using broadside-coupled microstrip-coplanar waveguide structure

This paper presented an ultra-wideband (UWB) bandpass filter using broadside-coupled microstrip-coplanar waveguide structure. The filter consists of a microstrip line coupled to a coplanar waveguide (CPW) that was fabricated on the ground of the microstrip line. The proposed filter has been simulated, fabricated and measured for UWB system. The measured results demonstrated the UWB properties from 3.0 GHz to 10.63 GHz (-10 dB bandwidth) and the potential to be wider. A threesection filter shown insertion loss at central frequency is about 0.32 dB and very flat over the whole band. The group delay, which is important to an impulse radio UWB system, is about 0.42 ns over the most central band and less than 0.95 ns over the whole band. The filter also exhibited a good performance outside the band, both at low frequency end (to meet FCC limit) and high frequency end higher than 18 GHz with insertion loss larger than 30 dB.