Swept frequency reflectometer design for in-situ permittivity measurements

1993 ◽  
Vol 42 (3) ◽  
pp. 730-734 ◽  
Author(s):  
R.G. Plumb ◽  
H. Ma
Keyword(s):  
Permittivity Measurements

Non-intrusive in-situ permittivity measurements dedicated to the development of a P and L band dielectric model of wood

2021 ◽  
Author(s):  
F. Demontoux ◽  
M. Gati ◽  
M. el Boudali ◽  
L. Villard ◽  
JP Wigneron ◽  
...  
Keyword(s):  
Dielectric Model ◽  
L Band ◽  
Permittivity Measurements

scholarly journals Dielectric characterization of vegetation at L band using an open-ended coaxial probe

2018 ◽  
Vol 7 (3) ◽  
pp. 195-208 ◽  
Author(s):  
Alex Mavrovic ◽  
Alexandre Roy ◽  
Alain Royer ◽  
Bilal Filali ◽  
François Boone ◽  
...  
Keyword(s):  
Black Spruce ◽  
Microwave Remote Sensing ◽  
Dielectric Characterization ◽  
Sensing Applications ◽  
Remote Sensing Applications ◽  
L Band ◽  
Permittivity Measurements ◽  
Coaxial Probe

Abstract. Decoupling the integrated microwave signal originating from soil and vegetation remains a challenge for all microwave remote sensing applications. To improve satellite and airborne microwave data products in forest environments, a precise and reliable estimation of the relative permittivity (ε=ε′-iε′′) of trees is required. We developed an open-ended coaxial probe suitable for in situ permittivity measurements of tree trunks at L-band frequencies (1–2 GHz). The probe is characterized by uncertainty ratios under 3.3 % for a broad range of relative permittivities (unitless), [2–40] for ε′ and [0.1–20] for ε′′. We quantified the complex number describing the permittivity of seven different tree species in both frozen and thawed states: black spruce, larch, red spruce, balsam fir, red pine, aspen and black cherry. Permittivity variability is substantial and can range up to 300 % for certain species. Our results show that the permittivity of wood is linked to the freeze–thaw state of vegetation and that even short winter thaw events can lead to an increase in vegetation permittivity. The open-ended coaxial probe proved to be precise enough to capture the diurnal cycle of water storage inside the trunk for the length of the growing season.

scholarly journals In situ measurement of low-frequency sea-ice dielectric properties and implications for tracking seasonal evolution of microstructure

2016 ◽  
Author(s):  
Megan O'Sadnick ◽  
Malcolm Ingham ◽  
Hajo Eicken ◽  
Erin Pettit
Keyword(s):  
Dielectric Permittivity ◽  
Sea Ice ◽  
Transport Properties ◽  
Pore Volume ◽  
Low Frequency ◽  
Complex Dielectric Permittivity ◽  
Microstructural Characteristics ◽  
Seasonal Evolution ◽  
Permittivity Measurements

Abstract. The seasonal evolution of sea-ice microstructure controls key ice properties, including those governing ocean-atmosphere heat and gas exchange, remote-sensing signatures and the role of the ice cover as a habitat. Non-destructive in situ monitoring of sea-ice microstructure is of value for sea-ice research and operations, but remains elusive to date. We examine the potential for the electric properties of sea ice, which is highly sensitive to the brine distribution within the ice, to serve as a proxy for microstructure and, hence, other ice transport properties. Throughout spring of 2013 and 2014, we measured complex dielectric permittivity in the range of 10 Hz to 95 kHz in landfast ice off the coast of Barrow, Alaska. Temperature and salinity measurements and ice samples provide data to characterize ice microstructure in relation to these permittivity measurements. The results reveal a significant correlation between complex dielectric permittivity, brine volume fraction, and microstructural characteristics including pore volume and connectivity, derived from x-ray microtomography of core samples. The influence of temperature and salinity variations, as well as the relationships between ice properties, microstructural characteristics, and dielectric behavior emerge from multivariate analysis of the combined data set. Our findings suggest some promise for low-frequency permittivity measurements to track seasonal evolution of a combination of mean pore volume, fractional connectivity, and pore surface area-to-volume ratio, which in turn may serve as proxies for key sea-ice transport properties.

scholarly journals Dielectric characterization of vegetation at L-band using an open-ended coaxial probe

2018 ◽  
Author(s):  
Alex Mavrovic ◽  
Alexandre Roy ◽  
Alain Royer ◽  
Filali Bilal ◽  
François Boone ◽  
...  
Keyword(s):  
Black Spruce ◽  
Microwave Remote Sensing ◽  
Dielectric Characterization ◽  
Sensing Applications ◽  
Remote Sensing Applications ◽  
L Band ◽  
Permittivity Measurements ◽  
Coaxial Probe

Abstract. Decoupling the integrated microwave signal originating from soil and vegetation remains a challenge for all microwave remote sensing applications. To improve satellite and airborne microwave data products in forest environments, a precise and reliable estimation of the relative permittivity (𝜺 = 𝜺’ – i 𝜺’’) of the trees is required. We developed an open-ended coaxial probe suitable for in situ permittivity measurements of tree trunks at L-band wavelengths (1–2 GHz). The probe is characterized by uncertainties under 3.3 % for a broad range of permittivities, [2–40] for 𝜺’ and [0.1–20] for 𝜺’’. We quantified the complex number describing the permittivity of seven different tree species in both frozen and thawed states: black spruce, larch, red spruce, balsam fir, red pine, aspen and black cherry. Variability in permittivity is substantial, and can range up to 300 % for some species. Our results show that the permittivity of wood is linked to the freeze/thaw state of the vegetation and that even short winter thaw events lead to an increase in vegetation permittivity. The open-ended coaxial probe proved to be precise enough to capture the diurnal cycle of water storage inside the trunk over the growing season.

scholarly journals Soil dielectric characterization at L-band microwave frequencies during freeze-thaw transitions

2020 ◽  
Author(s):  
Alex Mavrovic ◽  
Renato Pardo Lara ◽  
Aaron Berg ◽  
François Demontoux ◽  
Alain Royer ◽  
...  
Keyword(s):  
Current Model ◽  
Freezing And Thawing ◽  
Microwave Frequencies ◽  
Dielectric Characterization ◽  
Freeze Thaw ◽  
L Band ◽  
Satellite Microwave ◽  
Permittivity Measurements ◽  
Microwave Permittivity

Abstract. Soil microwave permittivity is a crucial parameter in passive microwave retrieval algorithms but remains a challenging variable to measure. To validate and improve satellite microwave data products, precise and reliable estimations of the relative permittivity (ɛr = ɛ / ɛ0 = ɛ’ - jɛ’’; unitless) of soils are required, particularly for frozen soils. In this study, permittivity measurements were acquired using two different instruments: the newly designed open-ended coaxial probe (OECP) and the conventional Stevens HydraProbe. Both instruments were used to characterize the permittivity of soil samples undergoing several freeze/thaw cycles in a laboratory environment. The measurements were compared to soil permittivity models. We show that the OECP is a suitable device for measuring frozen (ɛ’frozen = [3.5;6.0], ɛ’’frozen = [0.4;1.2]) and thawed (ɛ’thawed = [6.5;22.8], ɛ’’thawed = [1.4;5.7]) soil microwave permittivity. We also demonstrate that cheaper and widespread soil permittivity probes operating at lower frequencies (i.e. Stevens HydraProbe) can be used to estimate microwave permittivity given proper calibration relative to an L-band (1–2 GHz) probe. This study also highlighted the need to improve dielectric soil models, particularly during freeze/thaw transitions. There are still important discrepancies between in situ and modelled estimates and no current model accounts for the hysteresis effect shown between freezing and thawing processes which could have a significant impact on freeze/thaw detection from satellites.

scholarly journals Soil dielectric characterization during freeze–thaw transitions using L-band coaxial and soil moisture probes

2021 ◽  
Vol 25 (3) ◽  
pp. 1117-1131
Author(s):  
Alex Mavrovic ◽  
Renato Pardo Lara ◽  
Aaron Berg ◽  
François Demontoux ◽  
Alain Royer ◽  
...  
Keyword(s):  
Current Model ◽  
Freezing And Thawing ◽  
Dielectric Characterization ◽  
Freeze Thaw ◽  
Thawing Processes ◽  
L Band ◽  
Satellite Microwave ◽  
Permittivity Measurements ◽  
Microwave Permittivity

Abstract. Soil microwave permittivity is a crucial parameter in passive microwave retrieval algorithms but remains a challenging variable to measure. To validate and improve satellite microwave data products, precise and reliable estimations of the relative permittivity (εr=ε/ε0=ε′-jε′′; unitless) of soils are required, particularly for frozen soils. In this study, permittivity measurements were acquired using two different instruments: the newly designed open-ended coaxial probe (OECP) and the conventional Stevens HydraProbe. Both instruments were used to characterize the permittivity of soil samples undergoing several freeze–thaw cycles in a laboratory environment. The measurements were compared to soil permittivity models. The OECP measured frozen (εfrozen′=[3.5; 6.0], εfrozen′′=[0.46; 1.2]) and thawed (εthawed′=[6.5; 22.8], εthawed′′=[1.43; 5.7]) soil microwave permittivity. We also demonstrate that cheaper and widespread soil permittivity probes operating at lower frequencies (i.e., Stevens HydraProbe) can be used to estimate microwave permittivity given proper calibration relative to an L-band (1–2 GHz) probe. This study also highlighted the need to improve dielectric soil models, particularly during freeze–thaw transitions. There are still important discrepancies between in situ and modeled estimates and no current model accounts for the hysteresis effect shown between freezing and thawing processes, which could have a significant impact on freeze–thaw detection from satellites.

scholarly journals In situ field measurements of the temporal evolution of low-frequency sea-ice dielectric properties in relation to temperature, salinity, and microstructure

2016 ◽  
Vol 10 (6) ◽  
pp. 2923-2940 ◽  
Author(s):  
Megan O'Sadnick ◽  
Malcolm Ingham ◽  
Hajo Eicken ◽  
Erin Pettit
Keyword(s):  
Dielectric Permittivity ◽  
Sea Ice ◽  
Transport Properties ◽  
Pore Volume ◽  
Low Frequency ◽  
Complex Dielectric Permittivity ◽  
Microstructural Characteristics ◽  
Seasonal Evolution ◽  
Permittivity Measurements

Abstract. The seasonal evolution of sea-ice microstructure controls key ice properties, including those governing ocean–atmosphere heat and gas exchange, remote-sensing signatures, and the role of the ice cover as a habitat. Non-destructive in situ monitoring of sea-ice microstructure is of value for sea-ice research and operations but remains elusive to date. We examine the potential for the electric properties of sea ice, which is highly sensitive to the brine distribution within the ice, to serve as a proxy for microstructure and, hence, other ice transport properties. Throughout spring of 2013 and 2014, we measured complex dielectric permittivity in the range of 10 to 95 kHz in landfast ice off the coast of Barrow (Utqiaġvik), Alaska. Temperature and salinity measurements and ice samples provide data to characterize ice microstructure in relation to these permittivity measurements. The results reveal a significant correlation between complex dielectric permittivity, brine volume fraction, and microstructural characteristics including pore volume and connectivity, derived from X-ray microtomography of core samples. The influence of temperature and salinity variations as well as the relationships between ice properties, microstructural characteristics, and dielectric behavior emerge from multivariate analysis of the combined data set. Our findings suggest some promise for low-frequency permittivity measurements to track seasonal evolution of a combination of mean pore volume, fractional connectivity, and pore surface area-to-volume ratio, which in turn may serve as proxies for key sea-ice transport properties.

Efficiency of end effect probes for in-situ permittivity measurements in the 0.5–6GHz frequency range and their application for organic soil horizons study

2017 ◽  
Vol 254 ◽  
pp. 78-88 ◽  
Author(s):  
François Demontoux ◽  
Stephen Razafindratsima ◽  
Simone Bircher ◽  
Gilles Ruffié ◽  
Fabrice Bonnaudin ◽  
...  
Keyword(s):  
Organic Soil ◽  
Frequency Range ◽  
End Effect ◽  
Soil Horizons ◽  
Permittivity Measurements
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