Permittivity measurements of lossy liquids in the range 26 110 GHz

Abstract

We describe a free air transmission method for the determination of the permittivity of lossy liquids in the frequency range 26-110 GHz and the temperature range −5 to 70 • C. For pure water the method gives permittivity values with a dispersion of less than 3% about the true value. We give new permittivity data for an aqueous NaCl solution and for synthetic sea water in the temperature range −2 to 30 • C. The permittivity data obtained with this technique have been incorporated in a number of numerical weather prediction models and have resulted in more accurate ocean surface emissivity functions for use with microwave and millimetre wave imaging and sounding instruments.

A comparison of ocean emissivity models using the Advanced Microwave Sounding Unit, the Special Sensor Microwave Imager, the TRMM Microwave Imager, and airborne radiometer observations

“…The ABmm measuring system, described by Ellison et al [1997] and Lamkaouchi et al [2003], was used to determine the permittivity of synthetic seawater with a salinity of 35/1000 in ∼2 GHz steps from 30 to 105 GHz and at temperatures of −2°, 5°, 10°, 15°, 20°, 25°, and 30°C. It is shown by Lamkaouchi et al [2003] that this system is capable of producing permittivity data for aqueous solutions with a dispersion of ∼3% about the true value. The numerical data is given in Tables 1 and 2.…”

“…In order to compare the measured values in the frequency range 30–105 GHz with extrapolated values of a permittivity model valid in the frequency range 3–20 GHz, we also measured the permittivity of synthetic seawater over this frequency range and over the temperature range −2 to 30°C in 1°C steps. This was done using the Hewlett‐Packard measuring system described by Ellison et al [1997] and Lamkaouchi et al [2003]. The appropriate permittivity model is that of Debye: The corresponding parameters for each temperature are given in Table 3.…”

0.15 – 3.72 THz absorption of aqueous salts and saline solutions

“…Recent advances in terahertz sources and detection methods have stimulated experimental researchers to employ absorption spectroscopy to directly probe the collective dynamics in both biomolecules [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and inorganic materials ranging from water [14][15][16][17][18][19][20][21] to explosives. [22][23][24][25] Unlike near infrared spectroscopy, which measures the local vibrations of individual bonds, or visible/ultraviolet spectroscopy, which monitors electronic transitions, terahertz resonances are sensitive to the global distributions of charge, mass, and force in a molecule or molecular assembly.…”

Performance and non-destructive evaluation methods of airborne radome and stealth structures

“…The MM-WI technique can also be employed to extract the ε data of lossy liquids in the range 26-110 GHz. Such data can be incorporated in a number of numerical weather prediction models and microwave and MM-WI instruments (Lamkaouchi 2003). To obtain a high-resolution image of large area samples in a short duration of time is very much required for a good imaging system.…”