研究目的
To develop a standard procedure for characterizing the electromagnetic properties of ferrites using a fully-loaded waveguide system.
研究成果
A standard procedure was developed to characterize the four major electromagnetic parameters of unknown ferrites with small errors (around 2% for dielectric constant and saturation magnetization). The method is efficient and accurate, simplifying the measuring and analyzing processes for ferrite-based microwave devices.
研究不足
The major error source is the slight nonuniformity of the bias, leading to weak distortion of the modal dispersions and slight deformation of the scattering spectrums. The method requires the ferrite to be driven to the magnetically saturated state and the probe window to be far beyond the band edge.
1：Experimental Design and Method Selection:
A fully-loaded waveguide system was developed to characterize ferrites. The Nicolson-Ross-Weir method was used for preliminary complex permittivity extraction in the absence of bias. Ferromagnetic resonant frequency was used to determine preliminary saturation magnetization in the presence of bias.
2：Sample Selection and Data Sources:
Four ferrite samples with distinctive electromagnetic characteristics were tested. Samples were prepared and enclosed in a standard X-band waveguide.
3：List of Experimental Equipment and Materials:
A standard X-band waveguide made by oxygen-free copper, dipole electromagnet (GMW Associates, model 3470) for DC magnetic bias, performance network analyzer (PNA, Agilent E8363B) for scattering parameters measurement.
4：Experimental Procedures and Operational Workflow:
The waveguide with the sample under test was connected to two well-calibrated X-band adapters. Scattering parameters were recorded for retrieval of ferrites' EM properties.
5：Data Analysis Methods:
Nonlinear regression based on the Nicolson-Ross-Weir model was applied to extract complex permittivity. A three-step fitting method was proposed for high precision retrieval of full electromagnetic information.
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