The passband characteristics of proposed DGS filter matches that of the ideal quasi-ellipticmodel concerned. The two transmission zeros near the band edges have almost the same frequencies as those ofthe model. In the lower stopband, the overall attenuation is better than 60 dB whilst the attenuation in the upper stopband has similar level as the model. Moreover, the upper stopband characteristic of this filter is also examined up to 10 GHz, as shown in Fig. 6. A wide upper stopband with 20 dB attenuation is observed. This also demonstrates an intrinsic harmonic-free (up to 6 times of center frequency) characteristics of the proposed DGS filter.
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