Multi-band Rejection DGS with Improved Slow-wave Effect

New techniques to suppress multiple frequency bands with a single defected ground structure(DGS) unit are developed. The proposed stacked spiral DGS, in which the spiral-shaped defects with different size are aligned in the transverse direction to the guiding direction of the coplanar waveguide (CPW), provides multiple resonance frequencies. Also, a composite spiral-rectangular DGS is proposed to provide two resonance frequencies with the same characteristic of the cascaded spiral-and dumbbell-shaped DGS units. The slow-wave effects for the proposed DGSs are greater than that of conventional spiral-or dumbbell-shaped DGS. The proposed DGSs are successfully designed and fabricated and the measured results are in a very good agreement with the simulated results.