A novel DGS applied to design lowpass filter

摘要

A new compact defected ground structure (DGS) is proposed for the microstrip line. The compactness of the new pattern originates from the lengthened head of the pattern. Here this DGS is used to design an elliptic function lowpass filter1 (LPF). The fabricated filter is composed of the proposed pattern, two dumbbell DGSs at two sides of the proposed pattern and a broadened microstrip line on top. Combination of alternate stopbands in each structure creates a wide stopband; also using the sharp cutoff frequency characteristic of the proposed DGS cell and considering the coupling effect between slots provide elliptical function response of the filter. It has a 3dB cutoff frequency at 2.4 GHz and it is as small as 27 mm × 16 mm.