A design of the novel coupled-line bandpass filter using defected ground structure with wide stopband performance

• Published in: IEEE transactions on microwave theory and techniques Vol. 50; no. 9; pp. 2037 - 2043
• Main Authors: Park, Jun-Seok, Yun, Jun-Sik, Ahn, Dal
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-09-2002; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Attenuation; Band pass filters; Bandpass filters; Coupling circuits; Design engineering; Equivalence; Equivalent circuits; Filtering theory; Frequency; Grounds; Inverters; Joining; Microstrip filters; Microwaves; Resonance; Resonator filters; Shape
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2002.802313

In this paper, a novel three-pole coupled-line bandpass filter with a microstrip configuration is presented. Presented bandpass filters use defected ground structure (DGS) sections to simultaneously realize a resonator and an inverter. The proposed coupled-line bandpass filter provides compact size with low insertion-loss characteristic. Furthermore, a DGS shape for a microstrip line is newly proposed. The proposed DGS unit structure has a resonance characteristic in some frequency band. The proposed coupled-line filter can provide attenuation poles for wide stopband characteristic due to resonance characteristic of DGS. The equivalent circuit for the proposed DGS unit section is described. The equivalent-circuit parameters for DGS are extracted by using a three-dimensional finite-element-method calculation and simple circuit analysis method. A design method for the proposed coupled-line filter is derived based on coupled-line filter theory and the equivalent circuit of the DGS. The experimental results show excellent agreements with theoretical simulation results.