TY - JOUR

T1 - Multisection transmission line scatter function theory for measurements of soil dielectric properties

AU - Shuai, Xiufu

AU - Green, Timothy R.

AU - Ray, Chittaranjan

AU - Syrmos, Vassilis L.

PY - 2014

Y1 - 2014

N2 - Vector network analyzers measure both reflection (S and transmission (S functions, but Shas not been used to estimate soil dielectric permittivity independently. The objectives of this study were to (i) derive the mathematical model for Sof a multisection transmission line and (ii) test this model and demonstrate the method. The mathematical model for Sintegrates multiple transmissions across a section as a feedback subsystem. Two experiments were conducted using oven-dried sand and air to examine the Smodel. In the first experiment, a waveguide was filled with one section of sand to form a three-section transmission line; in the second experiment, two sections of sand formed a five-section transmission line. The S11 and Sfunctions were measured with a vector network analyzer, and the complex dielectric permittivity values were calculated. Results of Debye model fitting and sensitivity analysis demonstrated that the complex dielectric permittivity of low-loss sand estimated from the measured Swere less variable and followed the Debye model more closely than those from the measured S11 in the frequency range from 45.0 MHz to 3.0 GHz. Therefore, the complex dielectric permittivity of low-loss materials may be estimated more precisely using measurements of Swith the derived feedback model than with the widely used method based on S11. These general behaviors are also expected for more lossy media within a limited frequency range, but the present theory and testing methods should be used to evaluate permittivity measurements under field conditions in moist heterogeneous soils.

AB - Vector network analyzers measure both reflection (S and transmission (S functions, but Shas not been used to estimate soil dielectric permittivity independently. The objectives of this study were to (i) derive the mathematical model for Sof a multisection transmission line and (ii) test this model and demonstrate the method. The mathematical model for Sintegrates multiple transmissions across a section as a feedback subsystem. Two experiments were conducted using oven-dried sand and air to examine the Smodel. In the first experiment, a waveguide was filled with one section of sand to form a three-section transmission line; in the second experiment, two sections of sand formed a five-section transmission line. The S11 and Sfunctions were measured with a vector network analyzer, and the complex dielectric permittivity values were calculated. Results of Debye model fitting and sensitivity analysis demonstrated that the complex dielectric permittivity of low-loss sand estimated from the measured Swere less variable and followed the Debye model more closely than those from the measured S11 in the frequency range from 45.0 MHz to 3.0 GHz. Therefore, the complex dielectric permittivity of low-loss materials may be estimated more precisely using measurements of Swith the derived feedback model than with the widely used method based on S11. These general behaviors are also expected for more lossy media within a limited frequency range, but the present theory and testing methods should be used to evaluate permittivity measurements under field conditions in moist heterogeneous soils.

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U2 - 10.2136/sssaj2013.11.0505

DO - 10.2136/sssaj2013.11.0505

M3 - Article

AN - SCOPUS:84906252437

SN - 0361-5995

VL - 78

SP - 1139

EP - 1145

JO - Soil Science Society of America Journal

JF - Soil Science Society of America Journal

IS - 4

ER -