Study on Comb-Line Filters with Coupling Windows on the Grounding Conductor

This paper proposes a new type of multi-stratified comb-line filters of narrow pass band utilizing conductor-backed coplanar waveguides. It is shown through numerical simulations by means of FD-TD method that the filtering characteristics can be controlled effectively by introducing a grounding conductor with a window between the coupled two resonators. It is demonstrated that, by changing the dimensions of the window on the grounding conductor, we can change, without affecting the odd mode, the input susceptance of the even mode independently and that we can adjust the frequency of attenuation pole. An interesting feature of this filter is that an additional window on the grounding conductor makes another attenuation pole appear around the passband.