planar circulator swith arbitrarily shaped ferrite resonators are analyzed in this paper. First, resonant frequencies and field distributions for the magnetized ferrite resonator are obtained using finite element method (FEM). Then the RF voltage distributions and other circuit parameters of the circulator which is formed by connecting three suitable transmission lines ot the ferrite resonator are derived from the green function . To remove the spurious solutions in analyzing the ferrite resonator, the results of eigenvalue analysis by node based FEM are comapred with the edge based fEM. The green function is expanded in terms of normalized eigenfunctions of th ecorresponding wave equation. Circulator parameters for circular disk resonator are clculated and compared with the analytical results. The experimental data for the designed circulator using hexagonal reosnator in the 850 MHz frequency range agree well iwth the simulated data.