Design of compact stop-band extended microstrip low-pass filters by employing mutual-coupled square-shaped defected ground structures

Abstract

A new technique to reduce the size, improve the rejection in the stop-band of a low-pass filter using modified defected ground structure (DGS) is proposed. An equivalent circuit model is used to study the DGS characteristics. The parameters are extracted by using a simple circuit analysis method. Several comparisons between the EM-simulations and the circuit simulations of the new structure are demonstrated to show the validity of the proposed equivalent circuit model. We demonstrated that the filter can provide a sharp transition domain and a wide rejection in stop-band. To further verify the new technique, a filter employing the new deformed DGS is fabricated and measured. The agreement between the simulation and the measured results confirms the effectiveness of the proposed concept. © 2008 Wiley Periodicals, Inc.