Analysis of ferrite circulators by 2-D finite-element and recursive Green's function techniques

Abstract

Ferrite circulator operation is analyzed here by two techniques. The first employs a two-dimensional (2-D) finiteelement (FE) technique, using a publicly available FE package. We show how to adapt this code to the solution of the magnetostatic equations and solve for the distribution of internal magnetic field inside a round ferrite puck of finite thickness, and use it to verify existing approximations for the demagnetizing fields. Additionally, the 2-D FE method has also been used to calculate the RF fields and scattering parameters in circulators having noncircular shapes, as well as nonuniform material properties and bias conditions. We have also investigated the field solutions for round circulators, calculated using a recursive Green's function (RGF) technique. This technique allows for radially varying properties in the material or bias fields, and thus accommodates the nonuniform demagnetizing field distribution in finite pucks. A comparison of the results of this technique with experiment is made. We show how the impedance-matching structures attached to the circulator affect the field distributions inside, and present plots of the field distributions as a function of frequency, which provide insight into circulator operation.

Ferrite devices and materials

“…These idealizations have now been removed. Nonideal boundary conditions and inhomogeneous magnetization in the ferrite disk in junction circulators have been modeled using annular structures and recursive Green's functions in two and three dimensions [37], [38]. Using the two-dimensional (2-D) approach [37], the frequency response of a circulator with quarter-wave matching transformers has been computed including the demagnetizing effects.…”

“…Nonideal boundary conditions and inhomogeneous magnetization in the ferrite disk in junction circulators have been modeled using annular structures and recursive Green's functions in two and three dimensions [37], [38]. Using the two-dimensional (2-D) approach [37], the frequency response of a circulator with quarter-wave matching transformers has been computed including the demagnetizing effects. The three-dimensional (3-D) analysis [38] enables horizontal inhomogeneities in the layer structure, and RF fringing fields above the microstrip surface to be taken into account in addition to the 2-D variations described above.…”

Analysis, Simulation and Measurements of CBS Antennas Loaded With Non-Uniformly Biased Ferrite Material

“…where parameter H 1 is described in [46] as the 'corner' magnetic field where the magnetization reaches 0.707 of its saturation value. Since such a value is usually not known unless the magnetization curve is already available, H 1 is treated as an adjustable parameter in this study.…”

Nanowire and Nanocable Intrinsic Quantum Capacitances and Junction Capacitances: Results for Metal and Semiconducting Oxides

“…Equation 53enables the use of a single permittivity, which was the basis of developing a tractable kernel or electrostatic Green's function approach. Without this assumption, a much more complicated field matching approach must be utilized, involving continuity conditions at cylindrical interfaces implying Bessel function type solutions [66][67][68][69][70][71]. It should be noted that a more accurate form of C NC can be found by using the equality in (50) and taking the derivative of both sides of that equation with respect to V bias , solving for dW/dV bias , and inserting that into the capacitive expression of (46).…”