研究目的
To accurately measure the complex permittivity of liquid crystals (LCs) for the design of materials and devices, using a double ridged waveguide cavity and the perturbation method.
研究成果
The proposed multi-mode double-ridged waveguide cavity method provides accurate and convenient broadband testing of low loss LC materials with minimal sample volume. The measured results for LC mixture MM closely match reference data, validating the method's effectiveness.
研究不足
The method requires very small sample volumes (about 0.02 ml) and assumes the sample is isotropic in the perturbation theory, necessitating orderly arrangement of LC in the tube.
1：Experimental Design and Method Selection:
The study uses a double-ridged waveguide cavity and the perturbation method for microwave characterizations of LCs. The multi-mode technique is introduced to achieve broadband testing with 6 modes (TE1,0,2n-1, n=1, 2, 3, 4, 5, 6) operating at 5-22 GHz.
2：Sample Selection and Data Sources:
Several LCs are measured, including a commercial mixture MM (Merck) and developed LC compositions M1~M
3：List of Experimental Equipment and Materials:
A double-ridged waveguide cavity, PTFE tubes for sample loading, and a vector network analyzer are used.
4：Experimental Procedures and Operational Workflow:
LCs are loaded into thin-walled PTFE tubes using capillary force, sealed with UV curing adhesives, and measured in different directions by rotating the cavity.
5：Data Analysis Methods:
The perturbation formula is used to extract the permittivity of LCs, with integrals solved numerically.
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