Characterization of the lossy dielectric materials using contour mapping

Abstract

The imaginary part of the complex permittivity of a lossy dielectric material is large and couples with its real part. The resonant frequency of a cavity with the sample depends not only on the real part of the complex permittivity of the sample but also the imaginary part, resulting in serious ambiguity in determining the sample’s complex permittivity. This work proposes a contour mapping method to determine the complex permittivity. The full-wave simulation gives us the contours of the resonant frequency and the quality factor, which are functions of the relative dielectric constant and the loss tangent. By mapping the measured resonant frequency and the measured quality factor, one can uniquely determine the complex permittivity of the sample. Five liquids were examined, including three low-loss materials for benchmarking and two lossy materials. The measured complex permittivities of the three low-loss materials agree very well with the other methods. As for the lossy materials, the measured relative dielectric constant and the loss tangent of alcohol are 6.786 and 0.895, respectively. Besides, the measured dielectric constant of glycerin is 6.811, and its loss tangent is 0.562. The proposed contour mapping technique can be employed to measure the complex permittivity of liquids and solids from lossless to lossy materials.

Percolation Effect on the Complex Permittivities of Polymer Blends

“…The extrapolated data to 100% of the loaded volume are depicted in dashed lines. The dielectric constant and loss tangent of powder can be determined by the extrapolated method and the HFSS simulation curve [ 13 , 17 , 18 ].…”

“…The extrapolated data to 100% of the loaded volume are depicted in dashed lines. The dielectric constant and loss tangent of powder can be determined by the extrapolated method and the HFSS simulation curve [13,17,18]. If the loss tangent of the material is low (e.g., tan δ ≤ 0.1), the dielectric constant will monotonously depend on the resonant frequency, and the quality factor will depend on the loss tangent, as shown in Figure 3a,b.…”

Measuring the Complex Permittivities of Plastics in Irregular Shapes

“…We can establish the contour map spanned by the resonant frequency and the Q -factor using the HFSS simulation. The contour map can be used to uniquely determine the complex permittivity of a material [ 21 ]. The cross-sectional structure of the resonant cavity is shown in Figure 3 a, which includes an SMA port, a brass main cavity, a brass top cover, a Teflon top cover, and a Teflon holder.…”

“…In six plastic bulks, the experimental results are almost the same as the references. In other words, the enhanced electric field (E-field) method [ 19 , 20 ] of the resonant cavity and the contour mapping method [ 21 ] we proposed are very reliable.…”