Simulation Of Shielding Effectiveness Of Materials Using .

Stanislav Kovář, Jan Valouch,Hana Urbančoková, Milan Adámek, Václav MachWSEAS TRANSACTIONS on COMMUNICATIONSSimulation of Shielding Effectiveness of Materials using CST StudioSTANISLAV KOVÁŘ, JAN VALOUCH, HANA URBANČOKOVÁ, MILAN ADÁMEK andVÁCLAV MACHFaculty of Applied InformaticsTomas Bata University in ZlínNad Stráněmi 4511, 760 05 ZlínCZECH REPUBLICskovar@fai.utb.czAbstract: - Recently, the development of electronic and electric devices has caused an increase in the level ofelectromagnetic radiation; therefore, the demand for protection against this danger has increased. There aremany ways how to ensure the protection of device against electromagnetic interference; however, this paper isdevoted just one of the ways, the shielding. The paper is focused on calculation of shielding effectiveness ofmaterial used to protect facilities. The results of the experiment are made by using of CST simulation software.The findings presented in this study serve to find suitable shielding material.Key-Words: - Shielding effectiveness, CST Studio Suite, electromagnetic interference, electromagneticsusceptibility, attenuation, shielding material, electromagnetic simulationinterference is necessary to pay attention to allcomponents and shielding during the developmentof the facility. [2]Conversely, electromagnetic susceptibility isdefined as the ability of device or system to operatewithout a fault or with strictly defined permissibleinfluence in the electromagnetic environment. Theaim of electromagnetic susceptibility is to increasethe electromagnetic immunity of interferedequipment by technical means. EMS mainly studiesthe elimination of the consequences of interferencethan identifying its causes. [3]Electromagnetic interference can be limited inthree main areas, namely at the source of thedisturbance, at the receiver and in the transmissionroute. For the purpose of this work, it is necessary torestrict noise coming into the receiver because thereare many interference sources and it is not possibleto eliminate all of them. Depending on the methodof interference propagation, the means to reduceunwanted noise fall into two categories, namelydisturbance by conduction and radiation. In the caseof conducted interference, the device is equippedwith EMI filters, chokes, capacitors; it is alsopossible to change the transmission medium orarrangement of circuits. Radiated interference isreduced by selecting a suitable shielding. [4]Shielding can be defined as a structural means toreduce interfering electromagnetic fields within adefined area. In other words, it protects the devicesagainstunwantedexternalelectromagnetic1 IntroductionElectromagnetic interference has become theserious problem for all electronic and electricaldevices; that is why the demand for protection ofdevices against this danger has increased. This paperdescribes one of the ways how to ensure theelectromagnetic immunity of device against radiatedelectromagnetic emissions. This way is meant theusing of shielding material. Calculation of theshielding effectiveness of these materials wasperformed by using CST Studio Suite simulationsoftware, which is the suitable tool for thisexperimental attempt. The research is focused onobtaining information about the properties ofshielding materials.Electromagnetic interference and susceptibilityare two parts of the term called electromagneticcompatibility. This term means nothing more thanan electronic and electrical device or system is ableto resist to the impact of electromagneticinterference, and at the same time, this device orsystem can not affect other devices in itselectromagnetic environment. The definitionincludes two basic areas which characterize theterms electromagnetic interference and immunity.Electromagnetic interference is a processwherein the signal generated by the source ofinterference is transmitted via electromagneticconstraints to disturbed systems. EMI is concernedwith identifying causes of disturbance. [1] Toachieve adequate levels of electromagneticE-ISSN: 2224-2864131Volume 16, 2017

Stanislav Kovář, Jan Valouch,Hana Urbančoková, Milan Adámek, Václav MachWSEAS TRANSACTIONS on COMMUNICATIONSinterference and simultaneously it prevents leakageof electromagnetic disturbance from the device. [4]The mathematical relationship for this frequencyrange is the same as (1).2 Shielding EffectivenessThe equation (1) can be adjusted into a formwhich better corresponds to the physicalmechanisms of the shielding effect. [4] Thisadjustment is described in publications [6] and [7].(5)SE R A M [dB ]Individual characters indicate:R - attenuation by reflection;A - absorbent attenuation;M - attenuation caused by multiplied reflection.The significant parameter in this area is shieldingeffectiveness that describes how the materialeliminates the effects of electromagnetic radiationfrom the interference source. [4] According to [5],shielding effectiveness is defined as a ratio of thereceived signal from the transmitter withoutshielding to the received signal inside of shield. Inother words, it represents the insertion loss when theshielding material is placed between the transmittingand the receiving antenna. [5] According to [5],there is also defined the term known as shieldingenclosure. The shielding enclosure represents astructure protecting its interior against the effect ofan exterior electric or magnetic field, and at thesame time, it protects the environment of thestructure against the effect of an interior electric ormagnetic field. A high-performance shieldingenclosure is able to reduce the impact of electric andmagnetic field strengths by to seven orders ofmagnitude depending on current frequency. Theshielding structure is mostly created by the metalmaterial with continuous electrical contact betweenadjoining panels, including doors. [5] As can beseen, the definition is similarly the one defining theelectromagnetic compatibility mentioned in theintroduction of this paper.According to [6] and [7], this parameter can bedescribed by the following equation.SE 10 logP1[dB]P22.1 Attenuation by ReflectionThis type of attenuation indicates how much energyis reflected at the interface between the dielectricwith the impedance of Z0 and the metal barrier withthe impedance of ZM. The same situation occurs onthe output between the metal barrier and thedielectric. [4] According to [6] and [7], theattenuation can be written as follows.R 20 logR R1 R2 [dB ] This type of attenuation occurs by absorption ofenergy by the shielding material due to heat losses.[4] According to [6] and [7], the equations can bewritten as follows.(1)tA 20 log e δ [dB ]δ (2)(3)2.3 n the case, when the electromagnetic wave passesthrough the shielding material, then there aremultiple reflections on the interfaces betweenenvironments. If (t δ), the impact of multiplereflections is negligible; conversely, if (t δ) then(4)1.7GHz – 18GHzE-ISSN: 2224-2864(8)Individual characters indicate:t – material thickness;δ – intrusion depth;σ - conductivity;μ - permeability;ω – wave frequency.20MHz – 300MHzESE 20 log 1 [dB ]E2(7)2.2 Absorbent AttenuationThis equation is also shown in the publication[5], which describes mathematical shieldingrelationships depends on frequency. Thesemathematical relationships are following: 9kHz – 20MHzH1[dB]H2VSH 20 log 1 [dB ]V2(6)Individual characters indicate:Z0 – impedance of environment (dielectric);ZM – impedance of material.Individual characters indicate:P1 – power generated by interference source;P2 - power passing through the shielding material.SH 20 logZ0 ZM Z0 ZM[dB] 2Z M2Z 0132Volume 16, 2017

Stanislav Kovář, Jan Valouch,Hana Urbančoková, Milan Adámek, Václav MachWSEAS TRANSACTIONS on COMMUNICATIONSsingle complex task which can combine a circuit,cable, shielding, mechanical stress or thermalsimulation. [8]It leads to another advantage of this simulationsoftware the opportunity to combine circuit and 3Delements into one project. The electrical connectionsbetween single elements can be set and placed in a3D layout. The designer is able to watch multiplesimulation tasks at the same time such as drawingand behavior of designed object. [9]the attenuation is negative and shieldingeffectiveness decreases. According to theinformation given in publications [6] and [7], theattenuation may be described by the followingequation. [4] Z ZMM 20 log 1 0 Z0 ZM22t2t j e δ e δ [dB ](10) Individual characters indicate:Z0 – impedance of environment (dielectric);ZM – impedance of material;δ – intrusion depth.4 ExperimentThe software is suitable for this experimentbecause it includes a wide database of materials. Asrepresentatives of shielding materials, steel andaluminum were selected. These materials are readilyavailable and suitable for use with security devices.In addition, both materials are relatively cheap.The process of simulation began by modellingthe shielding material whose dimensions are 1x1mand thickness is 1mm. The receiver and transmitterare located facing each other on both sides of thematerial. The distance of transmitter and receiverfrom the material under test is 0.5m. The planewave serves the source of the electromagnetic fieldand the probe receives the intensity of fieldpenetrated through the shielding material. For anidea, Fig. 2 illustrates the process of testing whereTX antenna replaces the source of the field and theRX antenna substitutes the probe.Fig. 1. Attenuation by Multiplied Reflection. [7]3 CST Studio SuiteThe whole process of calculation of shieldingeffectiveness was performed using CST Studio Suitesimulation software. CST Studio Suite softwarerepresents a comprehensive simulation tool to dealmore tasks than just electromagnetic simulation. Itcan be used also to solve the issue such as circuitsimulation, shielding effectiveness, mechanicalstress or temperature of components. The simulationsoftware contains several simulation algorithmsbased on time, frequency or integral domainincluding: Finite Integration Technique (FIT) Transmission Line Matrix (TLM) method Finite Element Method (FEM) [8]Fig. 2. Testing of Shielding Effectiveness. [10]4.1Solver use is dependent upon required task;however, all these solvers can be used to solve oneproblem without having to create new objects. CSTStudio Suite allows to couple more tasks into aE-ISSN: 2224-2864Shielding materialsThe shielding material is one of the most famousways of the device to protect the device againstradiated electromagnetic interference. Shieldingmaterial can eliminate the level of disturbance and133Volume 16, 2017