A prototype for the design of planar waveguide filters, also containing transmission zeros, with close correspondence to the physical structure

This paper presents a circuit prototype suitable for modeling of planar waveguide filters, where cavities are coupled to each other either by in-line or side elements. In addition, the cross couplings between cavities can be easily included in the model to produce transmission zeros. The parameters of the new prototype are explicitly derived from those of a standard in-line filter, which is assumed as reference. The correspondence between circuit prototypes and physical structures is one-to-one and of immediate interpretation. Some practical examples show the usefulness and accuracy of the proposed prototypes.