A novel bandstop filter with wide stopband using signal interference technology

In this paper, we present a novel microstrip bandstop filter, where signal interference technology is applied for achieving the bandstop behavior. Two open loop resonators are introduced to instead the conventional transmission line with larger electrical length. Then, two transmission zeros can be obtained in the stopband. Meanwhile, several transmission poles are used to improve the flatness of the passband. In comparison with the traditional bandstop filters using signal interference technique, the proposed filter has wider stopband and flat passband. Finally, a filter sample is fabricated using the standard single layer printed circuit board technology, and measured results agrees well with the simulated ones.