TEM Bandpass Filters Having Eighth-Wavelength Coupled Stubs

A simple technique is presented for design of TEM-mode bandpass filters that use eighth-wavelength coupled stubs in their realization. The filters, either of two dual forms, are identical in theoretical performance to conventional planar parallel-coupled filters often used in stripline fabrication; and to the interdigital filter, or the equivalent quarter-wavelength shorted stubs spaced at quarter-wavelength intervals along a transmission line. The design method uses existing tabulated element values and a novel Kuroda transformation which has been previously used in the design of directional filters.