Frequency Domain Analyses of TDR Waveforms for Soil Moisture Measurements

摘要: When time domain reflectometry (TDR) is applied to the field characterization of soil moisture, waveforms have typically been analyzed using traveltime along waveguide. The apparent dielectric constant traditionally determined by analysis a tangent-line method does not clear physical meaning and influenced several system material parameters. frequency analysis, however, can determine actual frequency-dependent permittivity be performed very short probe. This study presents numerical modeling approach for common unmatched TDR probes analyze signals in domain. also adopted examine how relaxation, electrical conductivity affect analysis. Simulation results indicated that, although effects bandwidth probe length could quantified calibrated, calibration equation moisture measurements was still affected relaxation conductivity, due differences texture density. density removed adding term equation. Correlating with water content at frequencies between 500 MHz 1 GHz, rather than constant, minimize influence texture.