Compact planar ultra-wideband (UWB) bandpass filter with notched band

This paper presents a compact planar microstrip ultra-wideband (UWB) bandpass filter (BPF) with notched band for the use in UWB wireless communication applications set by Federal Communications Commission (FCC). Three coupled lines and quarter-wave short-circuited shunt stubs are used to realize a bandpass filter with high selectivity. The narrow notched band was introduced to reject the undesired wireless local-area network (WLAN) radio signals by employing embedding open stubs. The bandwidth of the notched filter can be controlled by adjusting the width or length of the slot. The proposed component has been designed, simulated and fabricated for verification. Simulation results are confirmed via experiment, showing good wideband filtering performance with notched band. The measured insertion loss is less than 1.6 dB, the return loss is more than 15 dB, and the variation of group delay is less than 0.4 ns throughout the passband except for the notched band 5-6 GHz. The attenuation is more than 28 dB at the center frequency of notched band.