Elevated Ferrite Film Circulator with Different Permittivities for Layers: An Analytical Expression for the Input Conductance Employing Perturbation Method

The main idea of this paper is to find an analytical formula for the input conductance of an elevated ferrite film circu-lator to match it systematically to the desired matching network. For solving the ferrite loaded dielectric resonator included in stripline elevated ferrite film circulator, the off diagonal components of the permeability tensor are taken as the perturbation. The electromagnetic fields computations are done for unperturbed structure. The dipolar resonant frequencies corresponding to harmonics of the resonant modes are then calculated using the perturbation integrals. The quality factor of the circulator is derived in terms of these dipolar resonant frequencies. Energy integrals are calculated to find the energy stored in the ferrite and dielectic layers. An analytical expression for the input conductance of the elevated ferrite film circulators is derived by using the quality factor and energy integrals. In this expression the ferrite and dielectric layers can have different permittivities. Some discussions about the effect of ferrite film thickness and permittivity mismatch on the bandwidth of the circulator are investigated by HFSS commercial software.

Experimental and FEM based investigation of the influence of the deposition temperature on the mechanical properties of SiC coatings

Scanning electron microscopy shows that the microstructure,in particular the overall grain size,of chemical vapor deposited silicon carbide coatings depends on the deposition temperature.Sofar,the influence of the microstructure on the mechanical properties of such coatings is not well described in literature.To investigate the influence of the deposition temperature on the mechanical properties of the coating,nanoindentation is used in this work.Since the measurement results of nanoindentation can be affected by the substrate material,the contribution of the substrate material is taken into account utilizing a finite element model.The model is then employed to generate information about elastic and plastic properties of the coating by inverse simulation.To evaluate the fracture toughness of the coating,the generated material model is used in a cohesive-zone based formulation of the fracture process during indentation at higher loads.The results of this model allow determining the fracture toughness of silicon carbide coatings deposited at different temperatures.