Notched UWB filter using exponential tapered impedance line stub loaded microstrip resonator

In this study, two ultra-wideband (UWB) filters having the fractional bandwidth >120% are designed, analysed and fabricated. The first filter is designed with three quarter-wavelength short-circuited stubs and second by using exponential tapered impedance line stub loaded microstrip resonator. The first filter consists of five transmission poles within the passband. The second filter with tapered inductive loading on quarter-wavelength high impedance line exhibits a sharp notch stopband around 5.5 GHz, to suppress the interference from IEEE 302.11a WLAN band signals with an attenuation level >30 dB. A good agreement between the measured and predicted results is achieved, which validate the authors' filter designs.