Microstrip Low Pass Filter Realized By EBGS Assisted T-Line

Abstract

The EBGSs provide passband and stopband performance. In this project the planar conventional structures and the defected ground structures have been described. In uniform conventional structures (circular, rectangular and triangular pattern) it is observed in the scattering parameter performance that the number and the depth of the ripple (-5 db) of the passband are high and the stopband is not much wider. Maximum 10 dB RL bandwidth is 7.4 GHz, the 20 dB rejection bandwidth is 4.8 GHz and the center frequency is 10GHz. The maximum value of isolation is found to be 54dB. Then, the structures with different filling factor (FF), different number of element and same area of different structures are investigated. Then, the results of non-uniform conventional are observed and the results are ripple free in passband. The 10 dB passband RL BW is found to be 6.88 GHz and the 20 dB rejection bandwidth is not found with maximum isolation of 13.26 dB. Next the uniform dumbbell shaped DGS is observed. The 20 dB rejection bandwidth is 4 GHz. The maximum value of isolation is found to be 62 dB. The 3dB cutoff frequency is shifted to 4GHz which provides more than 200% compactness from the conventional structure. Next the result of non-uniform dumbbell shaped DGS have been observed and 10 dB RL-BW is 4.4 GHz, 3 dB cut-off frequency is 4.2 GHz, 20 dB IL-BW is 17.5 GHz and maximum peak of IL is -55 dB have been found. Finally, the hybrid dumbbell shaped DGS is observed and we have found the best performance. The best performance of 10 dB RL-BW is 4.1 GHz, 3 dB cut-off frequency is 4.4 GHz, 20 dB IL-BW is more than 19 GHz and maximum peak of IL is -68 dB. So, we have found the best performance in the hybrid dumbbell shaped DGSs. The designs are more compact than the conventional designs and able to remove the unwanted spurious transmission in the band rejection region.

Finally, the insertion loss (IL) and return loss (RL) performances of the LPFs (non-uniform triangular dumbbell shaped DGSs and hybrid DGSs) have been compared. It is seen that they provide improved performance in terms of the ripple suppression in the passband and IL bandwidths. Thus we have realized microwave LPF by EBGS assisted T-Lines. At last the physical representation of designs and the validification of the results are provided as for the validification of the work.