A compact filter with sharp-transition and wideband-rejection using the novel defected ground structure

A novel fork-shaped defected ground structure (DGS) is proposed. Compared to the conventional dumbbell-shaped DGS, the proposed DGS can change the shield current distribution in the ground plane more effectively which enhances the effective inductance of the resonance circuit, leading to deeper rejection and larger Q-factor. An equivalent circuit model has been given and a new parameter extraction method has been used. The circuit simulation results of the proposed model coincide with the EM simulation results well. Based on the fork-shaped DGS, a five-pole low-pass filter is developed which has better performance concerning the insertion loss, rejection level and passband to stopband transition knees. The simulations and measurements show excellent agreement.