UWB bandpass filter: structure, performance and application to UWB pulse generation

This paper presented a novel full band (3.1-10.6 GHz) ultra-wideband (UWB) bandpass filter (BPF), including a brief review of the current progress on the development of the UWB filters. The filter structure, performance and it application to the UWB pulse generation and reshaping were described. The proposed BPF has a simple broadside-coupled microstrip-coplanar waveguide (CPW) structure, where the CPW was fabricated on the ground of the microstrip line. The measured results of a 3-section filter demonstrated the best UWB performance around the world: bandwidth from 3.0 GHz to 10.63 GHz (@-10 dB); insertion loss at central frequency about 0.32 dB and very flat over the whole band; group delay, which is important to an impulse radio UWB system, 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 better than 30 dB. Using the developed filter in pulse generation and reshaping experiments demonstrated that a step-like negative pulse with less than 5 ps falltime, generated from a pulse generator, was reshaped as a Gaussian doublet-like full UWB pulse which has its spectrum meets the FCC's mask.