Electromagnetic Waves Part 14 pdf

EMI Shielding using Composite Materials with Plasma Layers 445 titanium (Ti), and of composites with the outer layer formed by a titanium monoxide (TiO). For composites with outer titanium layer (Ti and 3TiO samples) in the measuring frequency range, we observe very little differences in frequency spectrums of measured parameters and in the Cole-Cole diagrams independently from a number of layers Ti-TiO. In the diagram form of the imaginary component of the complex capacitance as a function of frequency, we do not observe a relaxation pick. At the same time, the diagram form of this characteristic suggests the presence of a relaxation pick at frequencies higher than the measuring range. Quite a different situation for composites with the outer layer formed by a titanium monoxide (1TiO and 2TiO samples) appears. In this case we can observe the strong dependence of dielectric composite properties upon a number of formed Ti-TiO layers. Frequency diagram forms of the imaginary component of the complex capacitance shows, in the examined measuring frequency range, the presence of a relaxation pick and a possibility of a presence of the second relaxation phenomenon at higher frequencies. The value and frequency of a relaxation pick presence are strictly depended on a number of Ti-TiO layers forming a composite. Increasing a number of layers results in reducing of a relaxation pick value and in displacement in the lower frequencies direction. It is confirmed by Cole-Cole diagrams of the complex capacitance, in which there is a clear presence of a displacement of the semicircle centre to the right for 1TiO sample. The capability of composite materials to shield electromagnetic fields is coherently associated with their dielectric properties in a wide frequency band. The method of impedance spectroscopy allows one to connect the measured frequency characteristics with the physical structure of tested material and the alternations in the structure. The method has been used by the authors to determine the connection between surface structure of a fabric being a substrate and dielectric properties of obtained composite fabric –carbon (Jaroszewski et al., 2010) and to evaluate the correlation between dielectric response of the system and surface resistance of the carbon layer (Pospieszna et al., 2010, Pospieszna & Jaroszewski, 2010). The possibilities to design desired electric properties of composite materials are also used to improve the shielding properties of the materials. Thus, the connection of the impedance spectroscopy method with those properties. 6. Summary It should be noted that the performed studies and collected experience in the field of modern technologies of shielding have already solved a lot of actual problems but there is still a challenge for further work to improve the efficiency of shielding and to develop new designs of electromagnetic shields. They can also be used in the shielding of power engineering systems, where a compatibility with environment in a wide sense of this meaning is the main problem (i.e. not only in the aspect of emission and electromagnetic disturbances). In the light of the latest experiences it seems that the future in the area of EM field shielding is connected with the application of modern technologies to fabricate thin- film composite coatings, including nano-composites. The materials are capable to fulfil all conditions of effective shielding from EM fields and to eliminate all undesired occurrences associated with operation of the shielded systems. The results of our investigations, presented above, point out the possibility of industrial fabrication of the composite shielding materials with the coefficient of shielding efficiency exceeding 50 dB. Good mechanical properties and high resistance to environmental effects are additional advantages of such materials. Electromagnetic Waves 446 7. Acknowledgment This publication was prepared with the key project – POIG no. 01.03.01-00-006/08 co- financed from the founds of European Regional Development Found within the framework of the Operational Programme Innovative Economy. 8. References Bula K., Koprowska J., Janukiewicz J. (2006). Application of Cathode Sputtering for Obtaining Ultra-thin Metallic Coatings on Textile Products , Fibres & Textiles in EE, Vol. 14, No. 5 (59) (2006) pp.75 – 79 Holloway C. L., Sarto M. S., Johansson M., (2005). Analyzing Carbon-Fiber Composite Materials with Equivalent-Layer Models , IEEE Trans. on Electromagnetic Compatibility, 47, n.4, 833-844, Huang Yi, Ning Li, Yanfeng Ma, Feng Du, Feifei Li , Xiaobo He ,Xiao Lin, Hongjun Gao, Yongsheng Chen, (2007). The influence of single-walled carbon nanotube structure on the electromagnetic interference shielding efficiency of its epoxy composites , Carbon 45 1614– 1621 Hong Y.K., Lee C.Y., Jeong C.K., Sim J.H., Kim K., J oo J ., Kim M.S., Lee J.Y., Jeong S.H., Byun S.W., (2001). Electromagnetic interference shielding characteristics of fabric complexes coated with conductive polypyrrole and thermally evaporated Ag , Current Applied Physics 1 439–442 Jaroszewski M., Ziaja J. (2010). Zinck-unvowen fabric composite obtained by magnetron sputtering , Proceedings of Twelfth International Conference on Plasma Surface Engineering; September 13 - 17, 2010, PSE 2010, Garmisch-Partenkirchen, Germany, PSE 2010 Jaroszewski M., Pospieszna J., Ziaja J. (2010). 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Eklund, (2006) Electromagnetic Interference (EMI) Shielding of Single-Walled Carbon Nanotube Epoxy Composites , Nano Letters, 2006,, Vol. 6, No 5, 1141-1145 Nitsch K. (1999). Application of impedance spectroscopy in the study of electronic materials, Wroclaw University of Technology Press, in Polish, ISBN 83-7085-417-6 EMI Shielding using Composite Materials with Plasma Layers 447 Pospieszna J., Jaroszewski M., Bretuj W. (2010). Tchórzewski M. Influence of surface and volume electrical resistivity on dielectric properties of carbon-polypropylene fabric composite obtained by plasma deposition , Electrotech. Rev. 2010, R. 86, nr 5, pp. 275-278 Pospieszna J., Jaroszewski M., Szafran G. (2010). Influence of substratum on dielectric properties of plasma carbon films , presented at X Symposium on High-Voltage Engineering IW2010, 7-9 Jun 2010, Poznań-Będlewo Pospieszna J., Material advances in electromagnetic field shielding technology. (2006) Electrotechnical Review, n. 1, 2006, 205-207, Sarto F., Sarto M.S., Larciprete M.C., Sibilia C. (2003). Transparent films for electromagnetic shielding of plastics , Rev. Adv. Mater. Sci., (2003), n.5, 329-336 Sarto F., Sarto M. S., Larciprete M.C., Sibilia C., (2004). Electromagnetics of nanolayered transparent metals , Conference materials URSI EMTS 2004, 683-684 Sarto M. S., Li Voti R., Sarto F., Larciprete M. C. (2005). Nanolayered Lightweight Flexible Shields with Multidirectional Optical Transparency , IEEE Trans. on EMC, vol. 47, No 3, (2005) pp.602- 611 Schulz R. B., Plantz V. C., Brusch D. R., Shielding Theory and Practice ;(1998). IEEE Transactions On Electromagnetic Compatibility, VOL. 30, NO. 3, AUGUST 1988, 187-201 Tzong-Lin Wu, Wern-Shiarng Jou, S. G. Dai, Wood-Hi Cheng,(2006). Effective Electromagnetic Shielding of Plastic Packaging in Low-Cost Optical Transceiver Modules , Journal of Lightwave Technology, VOL. 21, NO. 6, JUNE 2003, 1536-1542 Wang Li-Li, Tay Beng-Kang, See Kye-Yak, Sun Zhuo, Tan Lin-Kin, Lua Darren (2009). Electromagnetic interference shielding effectiveness of carbon-based materials prepared by screen printing . Carbon 47, s. 1905-1910 Wei Q. F., Xu W. Z., Ye H., Huang F. L. (2006). Surface Functionalization of Polymer Fibres by Sputtering Coating , J. Industrial Textiles , Vol. 35 No. 4 (2006) pp.287-294 Wojkiewicz J. L., Hoang N. N., Redon N., Miane J. L., (2005). Intrinsically Conducting Nanocomposites: High Performance Electomagnetic Shielding Materials , VIth Int. Symp. on Electromagnetic Compatibility and Electromagnetic Ecology, St Petersburg, Russia ; pp. 58-61 Ziaja J., Ozimek M., Janukiewicz J. (2010). Application of thin films prepared by impulse magnetron sputtering for shielding of electromagnetic fields, Electrotech. Rev. 2010, R. 86, nr 5, pp. 222-224 Ziaja J., Ozimek M., Koprowska J. (2009). Metallic and oxide Zn and Ti layers on textile as shields for electromagnetic fields, EMC Europe 2009 Workshop, Athens, Greece, 11-12 June 2009, pp. 30-33 Ziaja J., Koprowska J., Janukiewicz J. (2008). The use of plasma metallization in the manufacture of textile screens for protection against electromagnetic fields , Fibres & Textiles in Eastern Europe. 2008, vol. 16, nr 5, pp. 64-66 Ziaja J., Koprowska J., Janukiewicz J., (2008a). Using of plasma metallization for fabrication of fabric screens against electromagnetic field , FIBRES & TEXTILES in Eastern Europe 5, s. 70-72 Ziaja J., Koprowska J., Żyłka P. (2008b). Influence of nonwoven structures on surface resistivity of plasma titanium films . Proceedings of 6th International Conference ELMECO-6 : Electromagnetic Waves 448 electromagnetic devices and processes in environment protection joint with 9th Seminar "Applications of Superconductors" AoS-9, Nałęczów, Poland, June 24-27, 2008. s. 95-96 Ziaja J. ZnO thin film deposition with pulsed magnetron sputtering. (2007). Electrotechnical Review. 2007, R. 83, nr 11, s. 235-239 21 Reduction of Reflection from Conducting Surfaces using Plasma Shielding Çiğdem Seçkin Gürel and Emrah Öncü 1 Department of Electrical and Electronics Engineering, Hacettepe University, 2 Communication Systems Group, TUBITAK Space Technologies Research Institute, Turkey 1. Introduction 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 Electromagnetic Waves 450 plasma medium is assumed. Special distribution functions are chosen as linearly varying electron density distribution having positive or negative slopes and purely sinusoidal distribution which have shown to provide wideband frequency selectivity characteristics in plasma shielding applications in recent studies (Gurel & Oncu, 2009a, 2009b, 2009c). It is shown that linearly varying profile with positive and negative slopes can provide adjustable reflection or absorbtion performances in different frequency bands due to proper selection of operational parameters. Sinusoidally-varying electron distribution with adjustable phase shift is also important to provide tunable plasma response. The positions of maximums and minimums of the electron number density along the slab can be changed by adjusting the phase of the sinusoid as well as the other plasma parameters. Thus plasma layer can be tuned to behave as a good reflector or as a good absorber. In this study, plasma is taken as cold, weakly ionized, steady state, collisional, nonuniform while background magnetic field is assumed to be uniform and parallel to the magnetized slab. 2. Physical model and basic theory There are several theoretical methods as mentioned in the previous section for the analysis of electromagnetic wave propagation through the plasma which will be summarized in this part. 2.1 Generalized reflection coefficient formula Firstly two successive subslabs of plasma layer are considered as shown in Fig. 1. Fig. 1. Two successive plasma subslabs. The incident and reflected field equations for the th m subslab can be written as           ,exp ii m Emz em jkmz Z (1)           ,exp rr m Emz em jkmzZ (2) where i E is the incident field and r E is the reflected field. Then, incident and reflected field equations for the (m+1) th subslab can be similarly given as m+1 m Zm Zm+1 z Reduction of Reflection from Conducting Surfaces using Plasma Shielding 451           1 1, 1 exp 1 ii m Em z em jkm z Z      (3)           1 1, 1 exp 1 rr m Em z em jkm zZ      (4) Then total electric field in the th m subslab is                   ,exp exp yi mr m Emz em jkmzZ em jkmzZ  (5) and for  1 th m  subslab                   11 1, 1 exp 1 1 exp 1 yi mr m Em z em jkm zZ em jkm zZ        (6) After getting the electric field equations, magnetic field equations are obtained as follows          1 ,exp exp xi mr m m Hmz em jkmzZ em jkmzZ           (7)          1 1 1 1 1, 1 exp 1 1exp 1 xi m m rm Hm z em jkm zZ em jkm zZ               (8) where m  and 1m   are the intrinsic impedances of th m and  1 th m  subslabs respectively. The intrinsic impedance for the m th subslab is 0 m m r m or       (9) To match the boundary conditions at m zZ  , following two equations can be written   ,(1,) yy Emz Em z (10)   ,(1,) xx Hmz Hm z (11) Then (5) and (6) are inserted into equation (10), and it is obtained that                   11 exp exp 1 . .exp 1 1 exp 1 imrmi mr m em jkmzZ em jkmzZ em jk m z Z e m jk m z Z       (12) Since m zZ at the boundary, equation (12) can be arranged as below                 11 exp 1 1 exp 2 1 1 ir mi mr emem jkmd em jkmd em           (13) where 1m d  is the thickness of the  1 th m  subslab. By using the following equalities, Electromagnetic Waves 452     1 exp 1 m jk m d A    (14)     1 exp 2 1 m jk m d B    (15) Equation (13) becomes         11 ir i r em em Aem Bem        (16) By inserting equations (7) and (8) into (11), it is obtained that                 1 11 1 11 exp exp 1 . 1 exp 1 1 exp 1 imrmi m m mr m m em jkmz Z em jkmz Z em jk m z Z e m jk m z Z              (17) Then by replacing m zZ  in (17) it is obtained that         1 1 11. 11 1exp 1 exp 1 mr ir i m m jk m d e m em em em m jk m d                             (18) By relating the intrinsic impedance to permittivity and arranging the equation (18),         1 1 1exp 2 1 1 () exp 1 1 im r ir m r r em jkm d m em em jkm d m em                        (19) Now, the final equation is obtained as       () 1 1 ir i r em em A em Bem C     (20) where   1 r r m C m     (21) Then equations (16) and (20) are combined and expressed in matrix form as       11 1 1 11 1 2 rr ii em B C C em A em B C C em                  (22)   11 1 11 2 m BC C SA BC C         (23) For 1mn     1 1 1 r r n i i en en S en en              (25) Reduction of Reflection from Conducting Surfaces using Plasma Shielding 453 where n is the last boundary of the plasma slab which is located before conductive target. For 2mn     2 21 21 rr n ii en en S en en             (25) When we continue to write the field equations iteratively until m=0 which means the boundary between free space and the first subslab of plasma, we have     0123 1 0 0 rr n ii een SSSS S een         (26) This can be written in the following compact form,     1 0 0 0 n rr m ii m een S een                 (27) Letting 1 0 n m m S        = 12 34 MM M MM     (28) Then by inserting equation (28) into equation (27)     12 34 0 0 rr ii MM een MM een           (29) Hence       12 0 rri eMenMen (30)       34 0 iri eMenMen (31) By dividing the both sides of the equations by  ne i , the following two equations are obtained       12 0 rr ii een MM en en  (32)       34 0 ir ii een MM en en  (33) Then by dividing these two equations side by side, we get (J. Zhang & Z. Liu, 2007)       12 34 0 0 r i eMnM eMnM    (34) [...]... Oncology Department Trabzon 2Denizli Goverment Hospital, Medical Oncology Department Denizli, Turkey 1 Introduction Electromagnetic waves are produced by the motion of electrically charged particles These waves are also called electromagnetic radiation because they radiate from the electrically charged particles They travel through empty space as well as through air and other substances Electromagnetic waves. .. frequencies are referred to as electromagnetic fields and those at very high frequencies are called electromagnetic radiations (1,2) 2 Classification of electromagnetic waves According to their frequency and energy, electromagnetic waves can be classified as either ionizing radiations or non-ionizing radiations (NIR) Ionizing radiations are extremely high frequency electromagnetic waves (X-rays and gamma... associated with changes in distribution of ions (6) 476 Electromagnetic Waves According to some authors, there is connection with electromagnetic fields and disappearance of bees known as colony collapse disorder in Europe and the US, and that it could also interfere with bird migration (7,8) Fig 1 The Electromagnetic waves spectrum Adopted from Electromagnetic cellular interactions Cifra M, Fields JZ,... negative effects A discussion about the adverse effects of electromagnetic waves on the biological life has been ongoing since the discovery of electricity in the 19th century (6) Electromagnetic waves generated by many natural and human-made sources can travel for long distances and play a very important role in daily life In particular, the electromagnetic fields in the Radiofrequency (RF) zone are... Resulting from the technological innovations, the use of electromagnetic fields gradually increases and thus people are exposed to electromagnetic waves at levels much higher than those present in the nature (1,2,5) Along with the widespread use of technological products in daily life, the biological effects of electromagnetic waves started to be discussed Particularly, the dramatically increasing number of... from 2-, 6- and 24-hour exposure of mononuclear cells isolated from the peripheral blood to 450, 900 and 1784 MHz electromagnetic waves Data obtained showed that electromagnetic waves didn’t have any effect on cell viability, rates of apoptosis and proliferation index 478 Electromagnetic Waves Author Year Studied subject Frequencies Results Goodman et al 1983 RNA transciption Pulsed EMF increased activity... evidence of hazardous effects on human health incurred by low-frequency radiofrequency waves Studies at the cellular level, which uses Electromagnetic Waves and Human Health 477 relatively higher frequencies, demonstrate undesirable effects (10-11) Some studies revealed that different dimensions of electromagnetic waves have not shown any DNA damage on different cell lines For example, in a comprehensive... plasma, International Journal of Infrared and Millimeter Waves, Vol 28, 7178, 2007 Zhang, S.; Hu, X., W.; Jiang, H.; Liu, M., H.; He, Y (2006), Propagation of an Electromagnetic Wave in an Atmospheric Pressure Plasma: Numerical Solutions Phys Plasmas, Vol 13., No 1, pp 13502-13509 Part 7 Biological Effects and Medical Imaging 22 Electromagnetic Waves and Human Health 1The Feyyaz Özdemir1 and Aysegül... (1970) The Propagation of Electromagnetic Waves in Plasmas Pergamon Press, New York Gregoire, D., J.; Santoru, J.; Schumacher, R., W (1992) Electromagnetic- wave propagation in Unmagnetized Plasmas AD250710, 1992 Gurel, C., S; Oncu, E., (2009) Frequency Selective Characteristics of a Plasma Layer with Sinusoidally Varying Electron Density Profile, Int J Infrared Millimeter Waves, Vol 30, pp.589-597,... C., S; Oncu, E., (2009) Interaction of electromagnetic wave and plasma slab with partially linear and sinusoidal electron density profile, Electromagn Research Lett PIERL, Vol 12, pp.171-181, 2009 Gurel, C., S; Oncu, E., (2009) Characteristics of electromagnetic wave propagation through a magnetised plasma slab with linearly varying electron density, Progress In Electromagnetics Research B, Vol 21, 385-398, . 1986). SMM analysis gives the partial reflection and transmission Electromagnetic Waves 456 coefficients in the subslabs. This makes it easy to analyze the partial absorbed power in each. plasma titanium films . Proceedings of 6th International Conference ELMECO-6 : Electromagnetic Waves 448 electromagnetic devices and processes in environment protection joint with 9th Seminar. 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