Dual-mode microstrip bandstop filters

In this study, we proposed a novel bandstop filter using a square loop resonator. Dual-mode microstrip bandstop filters are designed and realized by employing two degenerate modes of a dual-mode microstrip square loop resonators. Microstrip loop resonators have been used extensively for bandpass filter applications. Dual-mode microstrip resonator is capacitively coupled to a straight microstrip line. Two types of the perturbation are used to excite the two degenerate modes of the dual-mode microstrip square loop resonator. The effect of these perturbation elements on filter characteristics is also investigated to realize the desired filter responses.