New bandstop filter using simple defected microstrip structure

A defected microstrip structure (DMS) has similar properties as a defected ground structure (DGS), but without any leakage through the ground plane. In this article, the stopband performance of a DMS is studied, and new single-band and dual-band bandstop filters with DMS are proposed. In order to verify the design, a single- and a dual-band bandstop filter are fabricated and the measured results are similar to the simulation. The new DMS bandstop filters have the advantages of better frequency selectivity, low loss and simple circuit topology, and simultaneously, have miniature circuit sizes.