In this paper, a folded stepped impedance resonator (SIR), modified by adding an inner quasi-lumped SIR stub, is used as a basis block for a new implementation of dual-band bandpass filters. The main advantage of the proposed filter is to make it possible to independently control the electrical features of the first and second bands. The behavior of the first band basically depends on the geometry of the outer folded SIR. The second band, however, is strongly influenced by the presence of the

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... ner stub. Additional design flexibility is achieved by allowing the inner stub to be located at an arbitrary position along the high impedance line section of the main SIR. The position of the tapped input and output lines can be Corresponding author: M. D. C. Velázquez-Ahumada (velazquez@us.es).