Exact Synthesis of Inline Fully Canonical Dual-Band Filters Using Dual Extracted-Pole Sections

This letter provides a new mapping function which allows us to carry out the dual extracted-pole synthesis in inline fully canonical dual-band filters for the first time. To do this, it is a necessary condition that the reflection coefficient phase takes exactly the same value at the position of the two prescribed transmission zeros (TZs), one belonging to one band and the other to the second band, involved at simultaneous extraction. This is achieved by applying an antisymmetric or odd symmetry mapping function. Two different filters, one with asymmetric and the other with symmetric prescribed TZs at each of the passbands have been synthesized which validates the proposed approach.