研究目的
To improve the measurement method of materials in the coaxial line, particularly for high dielectric permittivity materials, by implementing a full-wave analysis for easily adaptable geometries.
研究成果
The mode-matching based mathematical model of a partially filled circular waveguide shows excellent agreement with FEM calculations, extending the frequency range for reliable permittivity determination without the need for samples of different geometries. It performs well for cylindrical and square cross-section rods within certain frequency limits.
研究不足
The method's accuracy may be affected by VNA errors, parasitic parameters of the real system, and errors in sample geometry. Additionally, the model's validity for rectangular cross-section rods is limited to frequencies up to two times higher than the resonance frequency.
1:Experimental Design and Method Selection:
The study employs a full-wave analysis for a coaxial line with a 'short-circuited' discontinuity, treating the sample region as a partially filled circular waveguide. The mode-matching technique is used to solve the direct problem, relating the complex reflection coefficient to the dielectric permittivity of the sample.
2:Sample Selection and Data Sources:
The method is tested on BaTiO3 doped with 0.4% Nb and 0.1% Mn, with sample dimensions Rs = 0.34 mm and d = 0.26 mm, and coaxial line dimensions R2 = 3.5 mm and R1 = 1.52 mm.
3:4% Nb and 1% Mn, with sample dimensions Rs = 34 mm and d = 26 mm, and coaxial line dimensions R2 = 5 mm and R1 = 52 mm.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Coaxial lines, vector network analyzers (VNAs), and samples of BaTiO3 doped with Nb and Mn.
4:Experimental Procedures and Operational Workflow:
The reflection coefficient Γ is calculated for various numbers of modes to ensure accuracy. The inverse problem is solved iteratively to obtain complex dielectric permittivity from experimental scattering matrix values.
5:Data Analysis Methods:
The results are verified using finite element modeling (FEM) with Ansoft HFSS software, comparing S parameters between FEM and the multimode model.
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