Design Equations for Symmetric Microstrip DC Blocks

The design formulas are presented for achieving either a rippled or a maximally flat response of the dc blocks built with symmetrical coupled microstrip lines. The selection of characteristic impedances of the odd and even modes is facilitated by the use of a universal diagram containing the equicontours of the standing wave ratio and of the band-width. The deformation of the frequency response due to a difference in wavelengths of the odd and even modes is analyzed and the design procedure is adjusted accordingly.