The Design of Multiport Combline Directional Couplers.

This work concerns a new design technique [1] where the phase and amplitude of a combline directional coupler with an arbitrary number of lines may be constrained to taking a desired form over a specified design bandwidth. Using this new method we have designed and constructed broadband microwave couplers with as many as five coupled outputs with specified phases, exhibiting low VSWR and a variety of coupling levels on the individual coupled lines. This paper deals in particular with a binomial five line coupler and the concept of `capacitive conjugate' design.