Precise design of interdigital filters, using even mode/odd mode parameters

This paper demonstrates that even-mode/odd-mode analysis, used for the design of parallel-coupled half-wavelength-resonator filters, can be used to design interdigital filters (quarter wavelength resonators, open circuited at one end, short circuited at the other). For an exact design, direct coupling to the input and output resonators must be used. However, with a resonable approximation, edge coupling can be utilized in place of direct coupling. Two design examples are given.