A Free-Space Measurement Method for the Low-Loss Dielectric Characterization Without Prior Need for Sample Thickness...

Area of Science:

• Electromagnetics
• Materials Science
• Metamaterials

Background:

• Accurate characterization of dielectric material properties is essential for advanced electronic and photonic applications.
• Existing methods for measuring complex permittivity often require precise knowledge of sample thickness, limiting their applicability.
• Millimeter-wave frequencies present unique challenges for material characterization due to wavelength and interaction complexities.

Purpose of the Study:

• To develop and validate a free-space measurement method for determining the complex permittivity of low-loss dielectric materials at millimeter-wave frequencies.
• To eliminate the need for *a priori* knowledge of sample thickness in dielectric material characterization.
• To provide a comprehensive uncertainty analysis for the extracted complex permittivity values.

Main Methods:

• Utilizes maximal and minimal envelopes of transmission scattering parameters to determine the real part of permittivity (${\epsilon }_r^{\text{'}}$).
• Estimates sample thickness based on the determined real permittivity and frequencies of scattering parameter peaks.
• Calculates the imaginary part of permittivity (${\epsilon }_r^{″}$) using the derived thickness and scattering data.

Main Results:

• Successfully characterized four different low-loss dielectric materials (polystyrene, polytetrafluoroethylene, polymethylpentene) in the 220-325 GHz range.
• Demonstrated the method's effectiveness at various incident angles (0°, 10°, 20°, 30°).
• Provided an explicit uncertainty analysis and reported the uncertainties associated with the extracted complex permittivity.

Conclusions:

• The presented free-space measurement method offers a robust and accurate approach for characterizing low-loss dielectric materials at millimeter-wave frequencies.
• The technique's independence from sample thickness simplifies experimental procedures and expands its practical utility.
• The detailed uncertainty analysis enhances the reliability and credibility of the obtained material property data.