Band-Notched UWB BPF Design Using Parasitic Coupled Line

A compact microstrip ultrawideband (UWB) bandpass filter (BPF) with a narrow notched band in the UWB passband is presented. The narrow notched band was introduced by using a new technique that involves embedding a parasitic coupled line to the UWB BPF in order to reject any undesired existing radio signal that may interfere with the determined UWB passband. The notched band can be easily generated and set at any desired frequency by varying the structural parameters of parasitic coupled line. The design is successfully realized in theory and verified by electromagnetic (EM) simulation and the experiment. This filter can be integrated in UWB radio systems and efficiently enhance the interference immunity from undesired signals such as wireless local area network (WLAN).