Synthesis scheme of bandpass-to-all-stop switchable wideband filters based on coupled-lines

The paper presents a novel bandpass-to-all-stop switchable wideband filter composed of short-ended stubs and modified parallel-coupled-lines, as well as the corresponding synthesis/design scheme. By changing the end-states of the stubs, the bandpass or all-stop state can be realized and switched. To synthesize the two-filter-states simultaneously, firstly, the synthesis equations system for the bandpass state of the filter is derived based on Chebyshev characteristics. It can be found that, for the proposed structure, there will be a degree of freedom in filter synthesis. Accordingly, the equation used to estimate the insertion loss(IL) of the filter in all-stop state is added to the synthesis equations system, so that the two states of the switchable filter can be therefore theoretically synthesized. An example filter is then designed and confirmed in stripline line by simulation. A good agreement between the numerical experimental results and theoretical ones validates the proposed filter structure and corresponding design scheme.