Band pass filter design using microstrip line loaded with open stepped impedance structure

In this paper a new design of periodic structure has been proposed. These periodic structures are stepped impedance open circuited stubs loaded on a 50 ohm microstrip line. On the ground plane of microstrip periodic rectangular slots are made. These slots are responsible for the enhancement of insertion loss characteristics and give wider stop band characteristic. The period of the structures loaded on the microstrip line and the period of the slots on the ground plane are having same dimensions. For the desired center frequency the unit cell of the periodic structure is designed and then loaded periodically on the microstrip line. The proposed structure is applied to design a narrow band pass filter for the center frequency 3 GHz. The design procedure is elaborated and analysis of periodically loaded microstrip line is also given in this article. The design procedure is simple and there is no fabrication problem due to strong coupling.