In this paper a miniaturized dual wideband bandpass filter is designed by the modified extended composite right/left-handed transmission line (ECRLH-TL) under balanced conditions in each right/left-hand passbands. A novel equivalent circuit is proposed to provide the design and an implementation of ECRLH unit-cell by means of the complementary, split ring resonator (CSRR) on the ground plane. Since CSRR is utilized as an alternative to implementing one of the resonators of ECRLH unit-cell, the size and complexity of the structure can be consequently reduced. An example of a dual band pass filter with 3 dB frequency bands from 3.2 to 4.8 GHz and from 6 to 7 GHz is investigated. There is a good agreement among circuit, electromagnetic simulations and measured results in both passbands. The measured insertion loss is better than 0.5 and 1 dB in first and second bands central frequency, respectively. The group delay which is an important factor in wideband communications is about 0.62 ns and 0.71 ns, respectively, in the first and second band central frequencies. The final dimensions of the miniaturized filter are reduced to 8.88 mm X 8.18 mm.
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