Formulation of Transmission-Line Canonical Cross-Coupled Filters Based on Two Standard Building Blocks

This article presents a systematic approach for formulating transmission-line canonical cross-coupled filters. It will be shown that a filter schematic can be formulated from a coupling diagram having an arbitrary sign combination of the coupling coefficients by properly utilizing the two types (N-and P-types) of standard building blocks. Several practical filter schematics and their design formulas will be presented. Design instructions-how to use the design formulas in actual filter designs-will be provided as well. Design and implementation examples of two sixth-order filters will be discussed for demonstration.