In this paper

by means of treating the E.M. field problem of a double Y-junction circulator as a six-port net-work with symmetric nonreciprocal junction

the impedance matrix of the network is derived. On the basis of the principle of field matching at each port

three impedance eigenvalues of the symmetrical three-port dual Y-junction are obtained. By using the equation of eigenvalue

two circulating conditions are achieved. The normalized curves of the normal junction admittance

the field variables and the magnetic parameters are obtained with the circulating conditions satisfied. Finally

a new design approach for circulator is proposed with some normalized design examples of some classical circulator attac-hed. The forward and reverse frequency response characteristics are calculated.