Abstract: This paper presents a method to use the equivalent-circuit model and 3-D model simulation for the DGS to extract the dimension parameters. Combining an inter-digital elliptic-function low-pass filter with the DGS structure, a novel filter is proposed. A compensated feed-line structure on the side of the inter-digital elliptic-function low-pass filter is designed, and a couple of suitable DGSs are etched under compensated lines. Furthermore, full-wave simulation and optimization of the proposed filter are obtained with HFSS to get better impedance match. The design gives performances of a flat passband, a wide stopband and a compact structure. Agreement between experimental results and measurements shows validity of the DGS filter, which has good harmonic-suppressed characterizes.

Key words: elliptic-function filter, distributed element, defected ground structure (DGS), harmonic suppress, low-pass filter