Reflection and Transmission Characteristics of Multilayer Thin-Film Screens of Electromagnetic Radiation in the Microwave Range

The results of substantiation of the improved technology for manufacturing of the frequency-selective electromagnetic shields are presented. The improvement of this technology was ensured by the following: 1) the inclusion of elements in the form of classical Archimedes spirals, formed from foil materials, into the volume of manufactured shields to ensure the frequency-selective properties of such shields; 2) fixing the specified elements in the volume of manufactured shields by thermal pressing. The indicated features determine the main advantage of the improved technology in comparison with its analogues — lower time costs required for its implementation. The substantiation of the improved technology was implemented in the following areas: 1) setting the parameters of Spiral elements, which correspond to the maximum values of energy losses of the electromagnetic radiation interacting with them in the microwave range; 2) determination of the order of arrangement of spiral elements in the volume of the screens, which corresponds to the lowest values of electromagnetic radiation transmission and reflection coefficients in the microwave range of these shields. The substantiation implemented in the first of the indicated directions was based on the results of the analysis of the content of scientific works devoted to mathematical modeling and the study of the electromagnetic radiation of the transmission characteristics of flat spiral antennas in the microwave range. The substantiation implemented in the second of the indicated directions was based on the manufacture of experimental samples of the shields, the volume of which includes spiral elements oriented in a certain way, and further obtaining and comparative analysis of electromagnetic radiation transmission and reflection characteristics in the microwave range of these shields. Shields manufactured in accordance with substantiated improved technology seem to be promising for use in order to protect electronic devices from the effects of electromagnetic interference.

Given the increasing human exposure to electromagnetic radiation of various frequen-cies, mostly in the microwave range, awareness of potential health problems caused by this radiation has begun to grow. New building materials are being developed and tested to prevent or limit the penetration of microwave radiation, especially those frequencies that are used in mobile telephony. In contrast with the majority of the available literature on the investigation of concrete (cement) materials, in this paper, clay composite materials with the addition of nanoparticles of antimony(III)–tin(IV) oxide, zinc ferrite, iron(III) oxide, and two crystal modifications of titanium dioxide (rutile and anatase) were prepared in order to examine their effect on the absorption of electro-magnetic radiation. Nanomaterials are characterized by different physical and chemical methods. Specific surface area (B.E.T.), thermal properties (TGA/DSC), phase composition (PXRD), morphology (SEM), and chemical and mineralogical composition (EDX, and ED–XRF,) were determined. Thermal conductivity of clay composites was tested, and these materials showed a positive effect on the thermal conductivity (λ) of the composite: a reduction of 10–33%. The reflection and transmission coefficients of microwave radiation in the frequency range used in mobile telephony (1.5–4.0 GHz) were determined. From these data, the absolute value of radiation absorption in the materials was calculated. The results showed that the addition of the tested nanomaterials in a mass fraction of 3 to 5 wt.% significantly increases the absorption (reduces the penetration) of microwave radiation. Two nanomaterials, Sb2O3·SnO2 and TiO2 (rutile), have proven to be particularly effective: the reduction in transmission is 30–50%. The results of the test were correlated with the crystal structures of the examined nanomaterials. The inclusion of titanium dioxide and antimony-doped tin oxide into the clay led to a significant enhancement in microwave electromagnetic radiation absorption, which can be attributed to their interaction with the dielectric and conductive phases present in clay-based building materials.

A method for creating the electromagnetic radiation shields, which consists in fixing fragments of aluminum foil on the surface of a needle-punched carbon-containing material has been proposed. In accordance to the proposed method the shield samples have been made. The fragments of the used aluminium foil were in the form of rectangles or half rings the overall dimensions of which didn't exceed 20 mm. Using an automated meter of transmission and reflection coefficients SNA 0.01–18, shielding characteristics in the frequency range 0.7–17 GHz of the shield samples made in accordance with the proposed method have been obtained. Using the measuring stand, the main components of which were a white noise generator, power amplifier, speaker, sound analyzer MANOM-2, in the frequency range 20–16000 Hz, the soundproofing properties of the shield samples made in accordance with the proposed method have been obtained. It was shown that the values of the electromagnetic radiation reflection coefficients in the frequency range of 0.7–17 GHz of the investigated shields vary from –0.5 to –19.0 dB, and the electromagnetic radiation transmission coefficient in the specified frequency range vary from –2.0 up to –18.0 dB. It was found that the of electromagnetic radiation reflection coefficient values in the frequency range 0.7–17 GHz and the electromagnet radiation transmission coefficient values in the frequency range 6–17 GHz of the shields made in accordance with the proposed method using fragments of aluminum foil in the form of half rings, by 1,0–6.0 dB below the same values of the shields made using fragments of aluminum foil in the form of rectangles. It was determined that the studied shields provide sound attenuation by 2–3 dB in the frequency range from 20–16000 Hz. In view of the obtained results, shields manufactured in accordance with the proposed method are recommended for use in order to protect information circulating in the premises from leakage through the acoustic channel and the channel of secondary electromagnetic radiation.

Recently, designers of electronic equipment have paid special attention to the issue of electromagnetic compatibility (EMC) of devices with their own components and assemblies. This is due to the high sensitivity of semiconductor microcircuits to electromagnetic interference. This interference can be caused either by natural phenomena, such as lightning strikes, or by technical processes, such as transients in circuits during fast periodic or random switching. Either way, interference implies a sudden change in voltage or current in a circuit, which is undesirable, whether it propagates along a cable or is transmitted as an electromagnetic wave. The purpose of this article is to review the works devoted to the development, creation, and investigation of modern polymeric nanocomposite materials used for shielding electromagnetic radiation and their effective application for solving problems of electromagnetic compatibility. Additionally, the approach to design EMI shielding complex media with predetermined parameters based on investigation of various properties of possible components is shown. In the review, all polymer composites are classified according to the type of filler. The issues of the interaction of a polymer with conductive fillers, the influence of the concentration of fillers and their location inside the matrix, and the structure of the nanocomposite on the mechanisms of electromagnetic interaction are considered. Particular attention is paid to a new generation of nanocomposite materials with widely adjustable electrical and magnetic properties. A wide class of modern filled polymeric materials with dielectric and magneto-dielectric losses is considered. These materials make it possible to create effective absorbers of electromagnetic waves that provide a low level of reflection coefficient in the microwave range. The model mechanisms for shielding electromagnetic radiation are considered in the paper. A detailed review of the electro-physical properties of polymer nanocomposites is provided. Multilayer electrodynamic media containing combinations of layers of filled polymer composite materials with nanoparticles of different compositions and manufactured using a single technology will make it possible to create electrodynamic media and coatings with the required electro-physical characteristics of absorption, transmission, and reflection. Within the framework of the two-layer coating model, the difference in the effects of the interaction of electromagnetic radiation with conductive layers located on a dielectric and metal substrate is demonstrated. It is shown that in order to achieve optimal (maximum) values of reflection and absorption of electromagnetic radiation in the appropriate frequency range, it is necessary to fit the appropriate layer thicknesses, specific conductivity, and permittivity. Such approach allows designers to create new shielding materials that can effectively vary the shielding, absorbing, and matching characteristics of coatings over a wide frequency band. In general, it can be said that the development of innovative polymer composite materials for shielding electronic devices from electromagnetic interference and excessive electromagnetic background is still an important task. Its solution will ensure the safe and uninterrupted operation of modern digital electronics and can be used for other applications.

The aim of the work, the results of which are presented in the framework of the article, was to study the of electromagnetic radiation interaction laws in the frequency range 0.7…17 GHz with two-layer structures, the surface layer of which was made using powdered titanium dioxide, and the inner layer was made using a powder material based on oxide ferric iron. The thickness of the layers of the studied structures varied from 0.3 to 1 cm. To achieve this goal, theobjectives associated with the development of a methodology for the manufacture of multilayer structures based on composite materials containing transition metal oxides, as well as with the measurement of such structures samples electromagnetic radiation reflection and transmission coefficients in the frequency range 0.7...17 GHz. These measurements were carried out using a panoramic meter of reflection and transmission coefficients SNA 0.01–17. Based on the obtained measurement results, it was shown that in the frequency range 0.7…2 GHz, the lowest values of electromagnetic radiation reflection coefficient, reaching –20 dB, are characterized by structures whose surface layer thickness is 1 cm, and in the range 2 ... 17 GHz – structures, thickness the surface layer of which is 0.5 or 1 cm (depending on the thickness of the inner layer). The values of electromagnetic radiation transmission coefficient in the frequency range of 0.7...17 GHz of such structures reach –23 dB. Based on the results of the study, it is proposed to use the considered structures in the process of creating shielded rooms or improving the latter (for example, in cases, when it's necessary to reduce the level of passive interference in rooms shielded with metal materials).

The method to produce electromagnetic radiation shields using a non-woven needle-punched fabric containing carbon additives and foamed polyethylene coated with aluminum foil is proposed. To increase the reflection and absorption coefficients, it is proposed to create a cellular structure containing fragments of both types of materials with length from 20 to 40 mm and width from 5 to 8 mm. The measurement of the shielding characteristics was carried out on the automated meter of the transmission and reflection coefficient SNA 0.01–18 in the frequency range 0.7…17.0 GHz. It is shown that the values of the reflection coefficients in the frequency range 0.7…17.0 GHz were –0.5…–4.5 dB and the values of the transmission coefficient of electromagnetic radiation were –4.0…–25.0 dB.

The article presents the technique for obtaining advanced layered radio-absorbing materials based on powdered charcoal. The technique includes the following technologies: incorporation of the electrolyte aqueous solution into the material particles pores; adhesive pressing. The developed technique is more manufacturable compared to the analogs. Materials obtained in accordance with this technique are characterized by the flexibility, as well as lower cost compared to other carbon-containing radio-absorbing materials. The experimental characteristics of electromagnetic radiation reflection and transmission coefficients in the frequency range 2.0 – 17.0 GHz of the materials obtained in accordance with the developed technique are described. The results of the comparative analysis of these characteristics are provided. Based on these results, it’s determined that the average values of electromagnetic radiation reflection coefficient in the specified frequency range of the materials based on powdered non-activated wood charcoal, powdered activated wood charcoal and powdered activated coconut charcoal are –4.5 dB, –8,5 dB and –9.0 dB (when these materials fixed on metal reflectors). The average values of their electromagnetic radiation transmission coefficient are –11.5 dB, –20.0 dB and –15.5 dB respectively. The investigated materials seem to be promising for use in order to protect electronic equipment from external electromagnetic interference.

Electromagnetic waves of the microwave range are an effective tool for solving problems of non-destructive testing and diagnostics as applied to dielectric, semiconductor, and composite materials, ferrite products. An algorithm is suggested for estimating the complex permittivity of non-magnetic materials by the frequency dependences of reflection and transmission coefficient magnitudes during the interaction of electromagnetic waves in the microwave range with a sample in the form of a plate located in the cross section of a closed rectangular waveguide. Statistical analysis methods are applied to evaluating the errors arising during the application of this algorithm due to imperfect matching of the waveguide measurement path with the receivers and generator of the scalar circuit analyzer. It is shown that the proposed algorithm using the results of measuring reflection and transmission coefficients in a wide frequency range can significantly reduce the influence of frequency-dependent measurement errors on the accuracy of complex permittivity estimation. An additional advantage of the algorithm is that its implementation does not require vector network analyzers, which are very expensive.

Plasma mediums have taken considerable interest in recent studies due to their tunable characteristics offering some advantages in radio communications, radio astronomy and military stealth applications. Special plasma mediums have been used as electromagnetic wave reflectors, absorbers and scatterers. Reflection, absorbtion and transmission of electromagnetic waves by a magnetized nonuniform plasma slab are analysed by different authors using different methods in literature. It is known that plasma parameters such as length, collision frequency and electron density distribution function considerably affect plasma response. Among those, especially the electron density distribution considerably affects the frequency selectivity of the plasma (Gurel & Oncu, 2009a, 2009b, 2009c). Conducting plane covered with plasma layer has been considered and analysed in literature for some specific density distribution functions such as exponential and hyperbolic distributions (Shi et al., 2001; Su et al., 2003 J. Zhang & Z. Liu, 2007). The effects of external magnetic field applied in different directions to the plasma are also important and considered in those studies. In order to analyze the characteristics of electromagnetic wave propagation in plasma, many theoretical methods have been developed. Gregoire et al. have used W.K.B approximate method to analyze the electromagnetic wave propagation in unmagnetized plasmas (Gregoire et al., 1992) and Cao et al. used the same method to find out the absorbtion characteristics of conductive targets coated with plasma (Cao et al., 2002). Hu et al. analyzed reflection, absorbtion, and transmission characteristics from nonuniform magnetized plasma slab by using scattering matrix method (SMM) (Hu et al., 1999). Zhang et al. and Yang et al. used the recursion formula for generalized reflection coefficient to find out electromagnetic wave reflection characteristics from nonuniform plasma (Yang et al., 2001; J. Zhang & Z. Liu, 2007). Liu et al. used the finite difference time domain method (FDTD) to analyze the electromagnetic reflection by conductive plane covered with magnetized inhomogeneous plasma (Liu et al., 2002). The aim of this study is to determine the effect of plasma covering on the reflection characteristics of conducting plane as the function of special electron density distributions and plasma parameters. Plasma covered conducting plane is taken to model general stealth application and normally incident electromagnetic wave propagation through the

The effect of plasma on the transmission properties of electromagnetic waves and its application have always been one of the key research directions of electromagnetic theory and technology and plasma physics. The enhancement effect of collisional plasma on electromagnetic waves is a classic subject of the interaction between electromagnetic waves and plasma. Based on the transmission characteristics of electromagnetic waves in medium, this paper takes plasma as a special medium, and carries out experimental, theoretical and simulation studies on the transmission characteristics of high power microwave (HPM) atmospheric plasma and a certain range of electromagnetic waves under certain experimental conditions. The study found that the plasma formed by the S-band HPM under a vacuum of 50 Pa has a great influence on the electromagnetic wave transmission characteristics of different frequencies, and the electromagnetic wave transmission signal enhancement effect occurs regularly within a certain frequency range. A series of transmission waveforms of continuous electromagnetic waves of different frequencies passing through the HPM plasma area were obtained, and the waveforms were normalized. At 32.4 GHz, the transmission coefficient of continuous electromagnetic waves passing through the plasma area with plasma is about twice as high as that through the area without plasma. A simulation model was established, and the transmission coefficient distribution curve in the range of 31.5−32.5 GHz was obtained. The electromagnetic wave passing through the plasma showed a transmission enhancement effect, and at some frequency points, there was a transmission enhancement of about 1.9 times. The research results provides important technical support for the application of plasma in stealth, emergency communications, and black barrier communications.

The paper presents new technique for fabrication of cost effective charcoal- and foil-containing materials, providing electromagnetic radiation energy attenuation. The materials, fabricated according to this technique, compared to the analogs, are characterized by the following three advantages: 1) wide-band property; 2) flexibility property; 3) decreased time expenses, which need for these materials fabrication. The regularities of change of the electromagnetic radiation reflection, transmission and absorption coefficients values of the materials, fabricated according to this technique, have been investigated. It was done depending on the frequency of electromagnetic radiation interacting with materials. According to the investigation results, it has been established, that the average value of electromagnetic radiation reflection coefficient of the materials, fabricated according to the proposed technique, is -10.0 dB in the frequency range 2.0-17.0 GHz, while the average values of electromagnetic radiation transmission and absorption coefficients are -25.0 dB and 0.8 respectively. Due to these facts such materials are prospective for use in order to protect the radio electronic control systems from electromagnetic interferences (in privacy, to ensure the electromagnetic compatibility of these units).

Effect of interconvertibility of electromagnetic and gravitational waves in strong external electromagnetic fields and the propagation of waves in the field of a charged “black hole”: PMM vol. 38, n≗ 6, 1974, pp. 1122–1129

The effect of continuous-wave (CW) and pulsed-wave (PW) radiofrequency radiation (RFR) in the microwave range on UV-induced DNA repair has been investigated in MRC-5 normal human diploid fibroblasts. RFR exposure at power densities of 1 (or 5) and 10 mW/cm2 gave a maximum specific absorption rate (SAR) (at 10 mW/cm2) of 0.39 +/- 0.15 W/kg for 350 MHz RFR, 4.5 +/- 3.0 W/kg for 850 MHz RFR, and 2.7 +/- 1.6 W/kg for 1.2 GHz RFR. RFR exposures for 1 to 3 h at 37 degrees C, in either continuous-wave or pulsed-wave modes, had no effect on the rate of repair replication label incorporated into preexisting UV-damaged DNA. RFR exposures (PW), with a constant medium temperature of 39 degrees C at 350 and 850 MHz during the repair period after UV damage, also had no effect. Assay for induction of repair synthesis by RFR exposure alone in non-UV irradiated cells was negative for the 350-, 850-, and 1200-MHz CW and PW RFR at 37 degrees C and the 350- and 850-MHz PW RFR at 39 degrees C. RFR does not induce DNA repair under these exposure conditions. In preliminary experiments--with the tissue culture medium maintained at 39 degrees C and RFR exposures (PW) at the frequencies of 350, 850, and 1200 MHz--no effect on incorporation of [3H]thymidine into DNA undergoing semiconservative synthesis was observed.

The experimentally established regularities of changes in electromagnetic radiation reflection, transmission and absorption characteristics in the frequency range of 2.0–17.0 GHz of materials are presented. These materials contained powdered activated birch charcoal impregnated with chlorides aqueous solutions (calcium chloride, magnesium chloride and sodium chloride). Using the established regularities, it was determined that materials based on powdered activated birch charcoal impregnated with calcium chloride aqueous solution are radioabsorbing if they interact with electromagnetic radiation in the frequency ranges of 3.5–4.5 and 5.5–17.0 GHz. In turn, materials based on powdered activated birch charcoal impregnated with magnesium and sodium chlorides aqueous solutions are radioabsorbing if they interact with electromagnetic radiation in the frequency ranges of 2.0–17.0 and 2.0–7.5 GHz (magnesium chloride solution), 10.0–17.0 GHz (sodium chloride solution). Electromagnetic radiation absorption coefficient values of the studied materials reach 0.95. These materials seem promising for the manufacture of partitions to shield sectors of premises where electronic devices sensitive to electromagnetic interference are located.

In this paper, the generation of the new modes in the problem of the transfer of the electromagnetic waves from a semi-bounded cylindrical waveguide with a metallic wall to a plasma column are investigated. An electromagnetic wave with the symmetric mode TM0j is send from a semi-bounded cylindrical dielectric waveguide to a plasma column. The plasma column is placed on the axis of another semi-bounded dielectric waveguide. Two mentioned waveguides are connected to each other in z=0. The incident wave is reflected and transmitted on the interface surface of two waveguides. The reflected and transmitted waves are considered as a series of the new modes and by using appropriate boundary conditions, the reflection and transmission coefficients of each new mode are calculated. The calculations are shown that the reflection and transmission coefficients of the reflected and transmitted waves are a function of the collision frequency of the plasma. Also, the phase different of the reflected and transmitted waves respect to the incident are shown because the reflection and transmission coefficients are obtained as a complex number. The graphs of the transmission and reflection coefficients and the graphs of the phase difference of the reflected and transmitted waves in terms of the collision frequency of the plasma are investigated.