In this paper, a microstrip transmission line combined with a new U-headed dumb-bell defected ground structure (DGS) is investigated.The proposed DGS of two U-shape slots connected by a thin transverse slot is placed in the ground plane of a microstrip line.A finite cutoff frequency and attenuation pole is observed and thus, the equivalent circuit of the DGS unit can be represented PURE BORAX by a parallel LC resonant circuit in series with the transmission line.A two-cell DGS microstrip line yields a better lowpass filtering characteristics.The simulation is carried out by the MoM based IE3D software and in the experimental measurements a vector network analyzer is used.
The effects of the transverse slot width and the distance between arms of the U-slot on the filter response curve are studied.This DGS is utilized for different microstrip circuit applications.The DGS is placed in the ground of a capacitive loaded microstrip line and a very low cutoff frequency is obtained.The DGS is adopted under the coupled lines of a parallel line coupler and an improvement in coupling coefficient is noticed.The proposed DGS is also incorporated in the ground plane under the feed lines and Christmas Village the coupled lines of a bandpass filter to improve separately the stopband and passband performances.