Novel Dual-Band In-Line Filters Using Coaxial Dual-Post Resonances

It is shown, that different resonances of close dual-post configurations can be utilized for dual-band filter designs. The resonances of close dual-post arrangements are no longer the resonances of the individual posts because of the strong coupling. The independent control of these dual-post resonances is one prerequisite for the design of the novel dual-band filters. The second one is the independent control of interface and inter-resonator couplings of the different resonances. Thus, possible measures that allow the individual adjustment of resonances and couplings for a dual-band filter design are introduced. The general feasibility of this novel approach is demonstrated by a dual-band filter design at 2.5GHz providing two 4-order filter characteristics.