The Synthesis of N-Port Circulators

It is shown that there is a certain wide class of three-port network that can be transformed into a circulator by the addition of reactive elements. For such synthesis from a symmetrical three-port junction it is necessary and sufficient for it to be loss-free and for the moduli of the two transmission coefficients to be different. This approach may be used in the design of broad-band circulators. For junctions approximating to an n-port circulator with n>3, it is shown that when the n reflection coefficients are matched by reactive networks in each arm, n particular transmission coefficients also vanish.