Dual-band-stop filters with unsymmetrical T-shape DGS resonators

A kind of dual-band-stop filter with an unsymmetrical T-shape defected ground structure (DGS) is proposed. The filter has two band gap centers at 4.9 GHz and 7.35 GHz, respectively, where the two centre frequencies are just the second and third harmonics 2.45 GHz. The filters with high band-stop performance and wideband spurious suppression can be achieved by cascading miniaturized unsymmetrical T-shape DGS. The attenuation of three-cascaded T-shape DGS filter is 30.77 dB at 4.9 GHz and 17.96 dB at 7.35 GHz respectively. The above experimental results are in good agreement with the simulation results, especially for the third harmonic.