High Performance Wide Stopband Lowpass Filter Using Complementary Split Ring Resonators as Defected Ground Plane

A novel design of a wide stopband, microstrip technology based low pass filter using defected ground plane is reported in this paper. The filter structure has varied dimensions of periodic complementary square split ring resonator (CSSRR) in the ground plane. The periodic arrangement of non-uniformly spaced CSSRR units in the defected ground structure (DGS) provides sharp cutoff frequency and wide stopband behavior. The optimized design has stop bandwidth (2 to 8 GHz) around four times the cutoff frequency. Improvement in stop bandwidth of CSSRR based design is compared with that of the square-split-ring-resonator (SSRR) and non-uniformly Dumbbell shaped DGS resonator based design. An improved Slow-wave factor is found as compared to Dumbbell shaped DGS.