Study of the dielectric properties of water in the frequency range 75–120 GHz

Abstract

We study experimentally the frequency dependences of the refractive index n and the absorption coefficient k of distilled, sea, and river water. The measurements were performed using a quasioptical device with a backward-wave oscillator as the radiation source and OAP-7 optical-acoustic receivers at a water temperature of 27 • C in the cell. The quantities n and k were determined from the measured transmission and reflection coefficients of the cell with water by means of joint numerical solution of the equations for these quantities. For distilled water in the frequency range f = 75-120 GHz, we obtained n = 6.142 − 3.926On the whole, these data are in good agreement with the measurement results obtained by other authors at several frequencies of the indicated range and coincide with the calculation data based on the models by Meissner and Wentz and by Liebe et al. within the limits of the rms determination errors 0.05 and 0.02 for the parameters n and k, respectively. The values of n and k for different seawater samples and river water containing insoluble admixtures coincide with the values of these quantities for distilled water within the limits of the experimental measurement errors 3-5% and 1-2%, respectively. The dependences n(f ) and k(f ) obtained experimentally for seawater are compared with those calculated on the basis of the developed models.Measurements of the transmission spectrum of a cell with double distilled water were performed for low power density of radiation (less than µW/cm 2 ) to reproduce the effect of water resonant transparency reported many times in the literature. Our measurements did not reveal any resonant features in the spectral behavior of the refractive index n and the absorption coefficient k of water and gave the same result as for a power density exceeding the threshold of appearance of this effect.

Spectral measurements of dielectric characteristics of petroleum and petroleum oils in the millimeter wave range

“…The complex dielectric permittivity of water can be calculated using empirical models developed for both fresh water [3,4] and sea water [4][5][6] in a wide electromagnetic spectral range (up to frequencies f ≤ 30 THz). Recent spectral dielectric measurements for distilled and sea water [7] performed in the short-wavelength part of the millimeter-wave range confirmed good calculation accuracy of these models. The situation for dielectric properties of petroleum and petroleum products, which are very diverse, is not as definite.…”

“…Measurements were performed in a quasioptical device with an OV-71 backward-wave oscillator (BWO) generating the radiation and OAP-7 optical-acoustical receivers [7]. The BWO calibration with respect to the wavelength was performed by the Fabry-Perot interferometer with reflectors in the form of wire gratings with a period much smaller than λ.…”

“…Since petroleum and petroleum products can contain a certain amount of water and the absorption index of water has a rather significant negative variation in the range 75-120 GHz (see, e.g., Fig. 3 in [7]), we may assume that the negative frequency variation of the dependence k(f ) for petroleum and SM-4.5 oil is related to the presence of water in these petroleum products. The conducted experiments show that this is not related to water, at least for petroleum, because the frequency variation of the dependence k(f ) remains negative after the petroleum dehydration (see Sec.…”

High-Q Reflection Notch Method for Mm Wave Measurements of Large Dielectric Losses Using a Stack Resonator: Analysis and Simulations

“…A weakly resonant cell as needed for the effects to appear is [18,19]. Assuming a uniform plane wave of linear polarization propagating along the z-axis and incident on the stack from the left side, we can easily obtain (by utilizing, e.g., a transmission matrix method [20]) an exact solution for the field distribution in the stack and for the complex scattering matrix coefficients S 11 and S 21 (here, S 12 = S 21 and, due to the stack symmetry, S 22 = S 11 ).…”

“…Here we consider the model case of a water solution as a test liquid of permittivity (ω) evaluated as complex permittivity of pure water w (ω) [18,19] with additional conductivity σ add . In this case, we assume, as an approximation, (ω) = w (ω) + iσ add /ω 0 so as the effective total conductivity is evaluated as σ(ω) = ω 0 Im (ω) (Figure 8 appears to be remarkably similar to the one computed for the model liquid considered earlier).…”