Wide stopband band-notched UWB BPF and its application to determination of material dielectric constant

An ultra-wideband (UWB) bandpass filter (BPF) with notched band and wide stopband has been designed, fabricated, and discussed in this work. The proposed UWB BPF is constructed on the basis of microstrip/slotline transitions, which can be used as the feeding structure to provide strong coupling for wideband BPF. The fabricated BPF has good in-band performance with a notched band centered at 8.0 GHz with 8.5% 10-dB fractional bandwidth and the wide stopband with 20-dB attenuation extends to 40 GHz. In addition, a transmission zero, i.e., the notched band can be used for determination of dielectric properties. The effective permittivity of some common materials namely FR-4 or glasses are computed with better than 10% relative error.