Dielectric Permittivity Measurement Using Open-Ended Coaxial Probe-Modeling and Simulation Based on the Simple...

Area of Science:

• Electromagnetics
• Materials Science
• Measurement Science

Background:

• Dielectric permittivity measurement is vital for characterizing materials.
• Open-ended coaxial probes are common tools for such measurements.
• Accurate modeling is needed to interpret probe measurements, especially with varying ionic conductivity.

Purpose of the Study:

• To validate a simple capacitive-load model for dielectric permittivity measurement using open-ended coaxial probes.
• To assess the model's reliability through electromagnetic simulations and physical experiments.
• To investigate the impact of ionic conductivity on model validity using saline solutions.

Main Methods:

• Electromagnetic modeling and simulations using FEKO (frequency domain) and CST (time domain).
• Physical experiments with an open-ended coaxial probe and saline solutions of varying NaCl concentrations.
• Postprocessing calculations using a simple capacitive-load model for both simulated and measured data.

Main Results:

• The capacitive-load model showed relative errors within 10% compared to reference permittivity values.
• Average relative errors were below 1% for physiological saline, indicating high accuracy for biological materials.
• Model accuracy decreased slightly with higher concentrations and lower frequencies but remained within probe's declared accuracy.

Conclusions:

• The simple capacitive-load model is validated for dielectric permittivity measurement using open-ended coaxial probes.
• The model is reliable across a range of NaCl concentrations and microwave frequencies (0.5-18 GHz).
• This validated model is suitable for analyzing biological materials with varying ionic conductivity.