Design of Bandstop filters using defected ground structures

In this thesis, modified design of band stop filters using defected ground structures have been proposed. The new proposed structures have conventional dumbbell DGS integrated with U-slot and the conventional spiral DGS integrated with U-slot both designed using microstrip lines. These structures provide high Q-factor with low insertion loss (below 1dB) in the pass band. By adding the U-slot to the conventional structures, the overall capacitance and inductance are increased which results in low resonance frequency of 1.4GHz with a notch depth of -39.13dB for dumbbell-slot when compared to 2.6 GHz with a notch depth of -32.21dB for conventional dumbbell DGS. The resonance frequency is 1.2GHz with a notch depth of -35.4 dB for spiral-slot when compared to 1.4GHz and a notch depth of -14.6dB for conventional spiral DGS. Sharp transition is achieved from pass band to stop band for the new proposed DGS while the DGS sizes remained the same. The proposed designs were fabricated for a dielectric substrate with a dielectric constant, er of 10