Application of 2D defected ground structures in microstrip lines

In this paper, two-dimensional (2D) defected ground structures (DGSs) are proposed in microstrip lines. The dumbbell structure is added as a unit-cell in a systematic manner in both horizontal and vertical directions to construct the 2D DGSs. The proposed scheme efficiently utilizes the ground area to achieve very low stop band frequencies. The EM simulation with experimental validation has been carried out to study the transmission behavior of proposed structures. The variation of center frequency have been achieved from 10.4 GHz down to 4.4 GHz with more than 25 dB rejection in the stop band when the number of cells increases from 1 to 5 cells. We have also exhaustively studied the effect of DGSs in horizontal and vertical directions in microstrip lines. Further the proposed DGSs have been modeled as a parallel LC circuit connected in series to the main microstrip line. In order to validate model, the extracted circuit values with ADS circuit simulator has been used to compare the transmission behavior with EM simulation results obtained by IE3D. The comparison of experimental results show an excellent matching with EM simulation and equivalent circuit model.