Harmonic-suppressed Elliptic-Function Low-pass Filter Using Defected Ground Structure

In this paper, a new microstrip elliptic-function low-pass filter(LPF) using a defected ground structure(DGS) is proposed. By integrating DGS units, the proposed filter provides attenuation- pole for the widc-stopband characteristic due to the resonance characteristic of DGS. The equivalent-circuit model and the 3-D model simulation for the DGS are used to determine the dimension parameters. Etching the designed DGS on the backside of an interdigital elliptic-function LPF, a new microstrip LPF with broad stopband is obtained after- impedance matching. The experimental results show the new filter can suppress the harmonic signal very well.