A novel UWB bandpass filter using highpass and lowpass filters

A Novel microstrip ultra-wideband (UWB) bandpass filter (BPF) is presented, which is realized by cascading a three pole highpass filter and a five pole lowpass filter. The highpass filter consists of an improved dumbbell shaped defected ground structure (DGS) and two grounded stubs, while the lowpass filter is realized by an improved dumbbell shaped DGS, a conventional dumbbell shaped DGS and a broadened microsrip line. Cascading these two filters, a UWB BPF is constructed and fabricated by the standard printed circuit board (PCB) process. The measured results show that the proposed UWB BPF has a passband from 3.17 to 10.65 GHz with a group delay variation of less than 0.18 ns, and the insertion loss is less than 0.9 dB over the passband.