Lattice Equivalent Circuits of Transmission-Line and Coupled-Line Sections

A lattice network with branches made up of open- and short-circuited transmission-line sections is proposed as an equivalent circuit for a wide range of so-called coupled-line filter sections. The proposed lattice equivalent circuits have proven to be an advantageous alternative to the equivalent circuits found in the technical literature (when available) as they are exact, useful in wide frequency bands, and take into account the different phase velocities of even and odd modes. Some examples of its application to elaborated Schiffman phase shifters are given, with the emphasis on the better insight into the coupled-line behavior provided by the lattice circuit.