TDR Phase Velocity Analysis for Measuring Apparent Dielectric Spectrum of Soil

Lin, Chih‐Ping; Ngui, Yin Jeh

doi:10.1190/igc2017-252

Cited by 1 publication

(2 citation statements)

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“…Time-domain reflectometry (TDR) has been a robust tool for measuring soil dielectric properties, ranging from apparent dielectric constant (Ka) measurement to both apparent and complex dielectric spectroscopies. TDR has since provided accurate complex dielectric permittivity (CDP) estimation in soil sciences [1,2,3,4] throughout the MHz to GHz frequency bands. Originally, implementation of TDR in soil water content relied upon the empirical correlation between volumetric water content and Ka [5].…”

Section: Introductionmentioning

confidence: 99%

“…PVA measures the ADP spectrum by explicitly solving for the phase angle difference in the frequency domain after applying a fast Fourier Transform (FFT) to the time domain signals. PVA is shown to be capable of accurately determining the ADP of various liquids and soils without any prior knowledge of system input function or leading transmission line setup [4,10]. Although PVA is a model-free and inversion-free algorithm, both real and imaginary parts of CDP are yet to be decoupled in order to identify dielectric polarization behavior and energy dissipation characteristics due to electrical conductivity and dielectric loss.…”

Section: Introductionmentioning

confidence: 99%

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Dielectric Spectroscopy Using Dual Reflection Analysis of TDR Signals

Ngui¹,

Lin²,

Wu³

2019

Sensors

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Time-domain reflectometry (TDR) has been a powerful tool for measuring soil dielectric properties. Initiating from apparent dielectric constant ( K a ) measurement up until apparent and complex dielectric spectroscopies, the embedded information in the TDR signal can be extracted to inspire our understanding of the underlying dielectric behaviors. Multiple full waveform inversion techniques have been developed to extract complex dielectric permittivity (CDP) spectrum, but most of them involved prior knowledge of input function and tedious calibration. This rendered the field dielectric spectroscopy challenging and expensive to conduct. Dual reflection analysis (DRA) is proposed in this study to measure CDP spectrum from 10 MHz to 1 GHz. DRA is a simple, robust, model-free, and source-function free algorithm which requires minimal calibration effort. The theoretical framework of DRA is established and the necessary signal processing procedures are elaborated in this study. Eight materials with different dielectric characteristics are selected to evaluate DRA’s performance, by using both simulated and experimental signals. DRA is capable of measuring non-dispersive materials very well, whereas dispersive materials require the assistance of a long-time-window (LTW) extraction method to further extend the effective bandwidth. The DRA approach is suitable for field applications that can only record a limited amount of data points and in-situ dielectric spectroscopy.

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