ANALYSIS OF FERRITE CIRCULATORS BY 2-D FINITE-ELEMENT AND RECURSIVE GREENS-FUNCTION TECHNIQUES

Ferrite circulator operation is analyzed here by two techniques, The f irst employs a two-dimensional (2-D) finite-element (FE) technique, us ing a publicly available FE package. We show how to adapt this code to the solution of the magnetostatic equations and solve for the distrib ution of internal magnetic field inside a round ferrite puck of finite thickness, and use it to verify existing approximations for the demag netizing fields. Additionally, the 2-D FE method has also been used to calculate the RF fields and scattering parameters in circulators havi ng noncircular shapes, as well as nonuniform material properties and b ias conditions, We have also investigated the field solutions for roun d circulators, calculated using a recursive Green's function (RGF) tec hnique. This technique allows for radially varying properties in the m aterial or bias fields, and thus accommodates the nonuniform demagneti zing field distribution in finite pucks, A comparison of the results o f this technique with experiment is made. We show how the impedance-ma tching structures attached to the circulator affect the field distribu tions inside, and present plots of the field distributions as a functi on of frequency, which provide insight into circulator operation.