Porous materials are promising for use in the terahertz range, when they have valuable properties: low weight, chemical inertia, thermal stability, and relatively low cost. These materials are required for effective shielding of electromagnetic radiation, attenuators, filters. Electromagnetic characteristics in the frequency range of 0.15 – 0.5 THz are considered. Samples are porous composite materials filled with carbonyl iron, waste from semiconductor production, and carbon nanostructures. Foamed polyurethane and foam glass material is used as a dielectric binder. The combination of high electromagnetic efficiency and the "green" origin of the constituent composites opens the way for successful practical use.
The spectral sensitivity and morphological characteristics of a pyroelectric photosensor based on tetraaminodiphenyl thin films were investigated. It was found that the pyroelectric sensor sensitivity weakly depends on the radiation frequency in a wide spectral range from visible to millimeter waves and is 2...8 times higher than the sensitivity of known pyrodetectors and the Goley cell. The tetraaminodiphenyl surface morphopology has a significant roughness of up to few μm with a 1 μm film thickness. The role of the abnormal skin effect is discussed.
The mechanism of formation of a terahertz jet by a dielectric cuboid and a sphere surrounded by ideally conducting screens is considered. The maximum screen influence is observed when the screen is located near the alight cuboid base. The screen influence eases when the screen is shifting along the dielectric object. Power flux density localization area is almost completely shifted inside the object when the screen is situated in the center. The minimum influence is observed when screen placed in the shadow plane of the cuboid base. This effect caused by the screen influence on electric field component tangential to the side edges and thus on the power flux directed to the central axis of the object. The screen influence on the terahertz jet in spherical object has been compared. Value of the power flux density after passing the object is higher in a cuboid, but the focusing characteristics are better (appearing on shorter distances) in a sphere.
The spectral and amplitude-frequency characteristics of a new pyroelectric detector based on thin tetraaminodiphenyl polycyclic polymer films with a thickness of <1 μm were studied in the electromagnetic radiation ranges of 0.4 to 10 and 300 to 3000 μm and at local wavelengths of 81 and 100 μm, respectively. It is shown that the volt–watt sensitivity of such a detector in the entire range is practically nonselective and is 2 to 10 times higher than the sensitivity of other pyroelectric detectors and the Golay cell. The bandwidth of the proposed pyrodetector was 330 to 500 Hz. The results showed good prospects of these sensors for fast ultrawideband spectroscopy, covering visible, infrared, terahertz, and millimeter wave ranges.
Quite extensive test sites are needed to provide remote sensing methods of the Earth with reliable information on the electrical characteristics of the surface layer and on their daily-seasonal changes. Observation is constantly made on them for the main indicators that determine the results of sensing. The paper discusses a set of tools using radiophysical and optical methods for long-term studies of the properties of the environment at the test station "Kaybasovo".
The concentration and temperature dependences of the imaginary part of the permittivity of water with conducting impurities are determined on the basis of mathematical modeling and experimental studies. It is shown that the values of permittivity imaginary part of water samples of thermokarst lakes calculated using the Stogrin formulas and measured are different. Experimental data on the permittivity of water bodies of the test area at the operating frequency of an aerospace vehicle in the temperature range is needed for interpretation of remote sensing results of the Earth.
The possibility of monitoring of thermokarst lake water volume of arctic and subarctic regions by remote sensing radiophysical methods is considered. The purpose of monitoring is to control global changes in the Earth's climate. Samples of natural water from water sources of the Tomsk region and the Yamalo-Nenets autonomous region (test site is the village of Khanomyi) are studied. The measurements were carried out by a microwave instrument based on an irregular microstrip resonator and by a conductometer made according to the original scheme.
The results of development the automated system of two-dimensional diagnostics of defects of crystalline materials are presented. Used technology imaging. The structural scheme of the system is given, its main blocks are indicated, the approbation process is described, the software of the system is described.
The results of measurements of the complex permittivity at the range of 100 MHz - 40 GHz and the conductivity of the water out of the reservoirs of Tomsk and Kemerovo regions and the Altai Territory are presented in the article. The method of the open-end-coaxial was applied. The conductivity was measured with LCR-meter at a frequency of 100 kHz. All the measurements were performed at temperatures of 10°C and 23°C. The samples are varied significantly in the values of conductivity, which is related to the geographical sampling place. Differences in permittivity values are greater at the low temperature and low frequencies and at the same time they are also significant at the high temperature and at high frequencies. The results of this study in order to improve the reliability of the analysis of the pollution degree and water salt content of natural water reservoirs should be taken into account the measurement made at wide frequency range.
The present work is devoted to the measurement of the dielectric properties of mosses and lichens in the frequency range from 500 MHz to 18 GHz. Subjects of this research were three species of march vegetation – moss (Dicranum polysetum Michx), groundcedar (Diphasiastrum complanatum (L.) Holub) and lichen (Cladonia stellaris). Samples of vegetation were collected in Tomsk region, Western Siberia, Russia. Complex dielectric permittivity was measured in coaxial section by Agilent Technologies vector network analyzer E8363B. Green samples was measured for some moisture contents from 100% to 3–5 % during a natural drying. The measurements were performed at room temperature, which remained within 21 ÷ 23 ° C.
The frequency dependence of the dielectric constant for the three species of marsh vegetation differ markedly. Different parts of the complex permittivity dependency on moisture were fitted by line for all frequency points. Two break point were observed corresponding to the transition of water in the vegetation in various phase states. The complex permittivity spectra of water in the vegetation allow determining the most likely corresponding dielectric model of water in the vegetation by the method of hypothesis testing. It is the Debye’s model. Parameters of Debye’s model were obtained by numerical methods for all of three states of water. This enables to calculate the dielectric constant of water at any frequency range from 500 MHz to 18 GHz and to find the parameters of the dielectric model of the vegetation.
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