Dielectric properties of soils at UHF and microwave frequencies

Hoekstra, Pieter J.; Delaney, Allan J.

doi:10.1016/0148-9062(74)91148-6

Cited by 103 publications

(141 citation statements)

References 9 publications

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“…Many measurements of complex dielectric constant of soils as a function of moisture content have been carried out in recent years (Lundien, 1971;Newton, 1977;Wang and Schmugge, 1978;Hockstra and Delaney, 1974;Davis et. al., 1976).…”

Section: Introductionmentioning

confidence: 99%

The dielectric properties of soil‐water mixtures at microwave frequencies

Wang

1980

Radio Science

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Recent measurements of the dielectric constants of soil‐water mixtures have shown the existence of two frequency regions in which the dielectric behavior of these mixtures was quite different. At the frequencies of 1.4–5 GHz there was strong evidence that the variation of the dielectric constant ε with water content W depended on soil type. While the real part of ε, ε′, for sandy soils rose rapidly with the increase in W, ε′, for the high clay content soils rose only slowly with W. As a consequence, ε′ was generally higher for the sandy soils than for the high clay content soils at a given W. On the other hand, most of the measurements at frequencies < 1 GHz indicated the increase of ε with W to be independent of soil types. At a given W, ε′ (sandy soil) ≅ ε′ (high clay content soil) within the precision of the measurements. These observational features could be satisfactorily interpreted in terms of a simple dielectric relaxation model suggested by Schwarz (1962), with an appropriate choice of the mean relaxation frequency ƒm and the range of the activation energy β. It was found that smaller ƒm and larger β were required for the high clay content soils than for the sandy soils in order to be consistent with the measured data. These requirements on ƒm and β were strongly supported by the observed dependence of the soil surface area per unit weight on the soil types.

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Section: Introductionmentioning

confidence: 99%

The dielectric properties of soil‐water mixtures at microwave frequencies

Wang

1980

Radio Science

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“…4), or a frozen soil over thawed soil, wave energy continually transmits into the lower layer at a rate that can only be predicted by full wave modal theory. Theory and observations Hoeskstra andDelaney, 1974, Arcone et al, 2002, in review) have proved that when the upper thin layer has a slower speed than the sub-strata, modes will propagate at angles beyond the critical angle for both interfaces and the upper thin layer becomes a refractive waveguide, just like an optical fiber. This occurs when a wetter soil overlies a drier soil, or when an unfrozen soil sits on top of permafrost, or bedrock.…”

Section: Resultsmentioning

confidence: 99%

Numerical Simulation of the Wave-Guide Effect of the Near-Surface Thin Layer on Radar Wave Propagation

Liu

Arcone

2003

JEEG

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This paper assesses ground-penetrating radar (GPR) moveout survey performance in different near-surface geological stratigraphy and different antenna orientations using two-dimensional (2D) finite difference time domain (FDTD) numerical simulations of field data. We first treat the simple cases of radar pulses propagating along (a) the interface between two half-spaces (air/ice); and (b) an ice thinlayer wave-guide (air/ice/water) between two half-spaces. We then simulate four more complex cases combining two radiation polarizations (TM and TE), and two geological settings: a sandy/gravelly halfspace overlain by a silty/clayey layer, and a silty/clayey half-space overlain by a sandy/gravelly layer. Both cases are represented through different dielectric constants. The results show that, first, more EM energy is radiated as an air wave for the TM mode, and more EM energy will be sent into the ground when the TE mode is used, regardless of stratigraphic sequence. Second, where a gravelly sandy halfspace overlain by a silty/clayey layer, more EM energy will be trapped in the silty/clayey layer as the guided ground wave. Third, when the TE mode is used there is much less air radiation for the case of silt overlying gravel than that of silty/clayey half-space overlain by a gravel/sand layer. Fourth, for the stratigraphic sequence of a sandy/gravelly half-space overlain by a silty/clayey layer, the TE mode fundamentally contains only a ground wave, and the TM mode essentially contains only air wave energy. This implies that for this case a far more complete separation of the air wave and the ground wave can be reached. Fifth, dispersion of phase and group velocities of the guided ground wave will be well developed for the TE mode. These simulations imply that antenna polarization mode is an important factor when using moveout surveys to study subsurface electromagnetic properties.

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“…The frequency W will generally lie in the microwave range (18 Ghz in H 20), whereas the latter molecular excitations will be in the submillmeter or infrared regions of the spectrum (Bottcher, 1952;Hasted, 1974). In soils t, R is reduced to around 1 GH z due to the binding of the water molecules to the soil particles (Hoekstra and Delaney, 1974). …”

Section: Cmentioning

confidence: 99%

Survey of methods for soil moisture determination

Schmugge¹,

Jackson²,

Mckim³

1980

Water Resources Research

369

141

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With increased interest in soil moisture information for applice.tions in stch disciplines as hydrology, meteorology and agriculture, an overview is needed of both existing and proposed methods for soil moisture determination. This paper discusses the methods of in-situ soil moisture determination including gravimetric, nuclear, and electromagnetic techniques; remote sensing approaches that use the reflected solar, thermal infrared, and microwave portions of the electromagnetic spectrum; and soil physics models that track the behaviour of water in the soil in response to meteorological inputs (precipitation) and demands (evapotranspiration). The capacities of use approaches to satisfy various user needs for soil moisture information varies from application to application, but a conceptual scheme for merging these approaches into integrated systems to provide soil moisture information is proposed that has the potential for meeting various application requirements.

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Dielectric properties of soils at UHF and microwave frequencies

Cited by 103 publications

References 9 publications

The dielectric properties of soil‐water mixtures at microwave frequencies

The dielectric properties of soil‐water mixtures at microwave frequencies

Numerical Simulation of the Wave-Guide Effect of the Near-Surface Thin Layer on Radar Wave Propagation

Survey of methods for soil moisture determination

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