Shielding Effectiveness Measurements Research Articles

The Influence of Various Commonly Used Building Materials on the Shielding Effectiveness, Reflection and Absorption of the Electromagnetic Wave

People spend two-thirds of their time in buildings. Building materials are, therefore, natural shielding for us. Many studies describe the shielding effect of non-building materials. This study evaluates the shielding effectiveness (SE) of electromagnetic fields for various building materials over a frequency range of 1 GHz to 9 GHz. Measurements of SE, reflection (R), and calculated absorption (A) were conducted to determine the shielding properties of mineral wool (MW), hardened polystyrene (PT), extruded polystyrene (PE), polyurethane board (PUR), brick wall (BW), brick wall filled with mineral wool (BW-MW), and concrete wall. The results demonstrate that MW, PT, PE, and PUR exhibit low SE and R, indicating minimal shielding capabilities, with absorption values that do not significantly deviate from the level of measurement uncertainty. Conversely, BW, BW-MW, and concrete wall materials exhibit high SE, with notably increased absorption at higher frequencies, highlighting their potential for effective EMI shielding. Particularly, the concrete wall presents the highest absorption values, making it a superior choice for shielding applications. Reflection trends revealed a plateau for BW in the 6 GHz to 9 GHz range, indicating a frequency-dependent behavior of shielding mechanisms. This study underscores the importance of balancing reflective and absorptive properties in shielding materials and suggests that composite materials may offer enhanced performance. The findings of this research provide guidance for the selection and design of shielding materials in environments with a frequency spectrum of electromagnetic frequencies from 1 GHz to 9 GHz.

Highly Visible–NIR Transparent Metamaterial‐Window for Broadband Microwave Absorption and Shielding

AbstractOptically transparent metamaterial absorbers have unexceptionally encountered a great challenge in further improving optical transparency ranging from visible (Vis) to near‐infrared (NIR) and environmental applicability, due to the limitations of constituent materials and multilayer structures. To overcome this limitation, a highly Vis‐NIR transparent metamaterial‐window with outstanding microwave broadband absorption and practical durability is proposed in this paper, which adopts a typical sandwich structure consisting of a cross‐ and cross‐ring‐shaped resonator and a reflective backplane, separated by a quartz glass. Experimental results indicate that the proposed metamaterial‐window achieves >80% absorptivity, covering a wide frequency range of 6.6–13.8 GHz with a relative bandwidth of 70.59%, while the measured shielding effectiveness is >16.94 dB, at 4.0–16.0 GHz. In addition, the corresponding physical mechanism is revealed by exploiting a classical multiple reflections interference model. More significantly, both the patterned resonator and backplane layers are formed by microscale gold meshes with high Vis‐NIR transmittance and environmental resistance, thereby enabling excellent salt spray corrosion resistance and high‐temperature stability, as well as an average optical transmittance of ≈87.35% at 400–1 800 nm. These advantages endow the design a promising candidate for addressing anti‐electromagnetic interference and electromagnetic shielding both in military and civilian.

Software-Defined Radio Applied to a Shielding Effectiveness Measurement

Software-Defined Radio Applied to a Shielding Effectiveness Measurement

Shielding Effectiveness Measurement Method for Planar Nanomaterial Samples Based on CNT Materials up to 18 GHz

The study and measurement of the shielding effectiveness (SE) of planar materials is required to predict the suitability of a certain material to form an enclosed electromagnetic shield. One of the most widely used standards for measuring the SE of planar materials is ASMT D4935-18. It is based on a coaxial sample holder (CSH) that operates up to 1.5 GHz. Due to this standard’s frequency limitations, new variants with higher frequency limits have been developed by decreasing the size of the CSH conductors and the samples. However, this method and its high-frequency variants require two types of samples with very specific geometries and sizes. This method is unsuitable for certain types of nanomaterials due to their complex mechanization at such undersized scales. This contribution proposes an alternative SE measurement method based on an absorber box that mitigates the problems presented by the ASTM D4935-18 standard. The SE of rigid nanomaterial samples based on several concentrations of multi-walled carbon nanotubes (MWCNT) and two different fiber reinforcements have been obtained.

Statistical Analysis for Shielding Effectiveness Measurement of Materials Using Reverberation Chambers

Statistical analysis for material shielding effectiveness (SE) measurement in a nested reverberation chamber (RC) and a contiguous RC is given in this article. By using Mellin transform and the associated statistical methods, the corresponding analytical expressions of the SE are derived, respectively, for the sample material under test with good and poor electromagnetic shielding performance. Moreover, the probability density function, the expected value, and the standard deviation of SE in different scenarios using nested and contiguous RCs are obtained analytically. Monte Carlo simulation and measurements in nested and contiguous RCs are performed to verify the analytical expressions.

EMI Shielding Effectiveness Study for Innovative Carbon Nanotube Materials in the 5G Frequency Region

It is crucial to extend the electromagnetic compatibility (EMC) studies to the new frequency regions where modern telecommunication systems operate, specifically those related to the fifth-generation (5G) technology standard for broadband cellular networks. Electric autonomous vehicles (EAVs) are systems that feature 5G technology on board and for which it is essential to ensure the proper management of EMC to prevent malfunctions. Given the considerable development of the EAV-related sector, new materials and solutions for EMI shielding with properties that reduce interference in the frequency regions of 5G technology are being investigated. Today, meatal-based solutions are the most common EMI shielding materials used to mitigate EMC problems. Nevertheless, with the appearance of EAVs, it is needed the design of novel materials that provide a significant balance in terms of shielding effectiveness (SE) and mechanical properties. Thereby, carbon nanotubes (CNTs) are an attractive alternative to conventional EMI shielding materials due to their characteristics. The lightweight condition, flexibility, cost-effectiveness, easy processing, and resistance to corrosion made this new type of material perfect to be used in the field of EAVs. This contribution focuses on describing and characterizing three nanocomposite materials manufactured by loading a polymer matrix with 5%, 7%, and 10% CNT concentrations, respectively. The SE measurement is carried out with a coaxial sample holder based on the standard ASTM D4935-18. This measurement setup makes it possible to determine the performance of the three materials under test up to 18 GHz, covering part of the operation frequencies of 5G systems.

Shielding Effectiveness of a PC Case Using Three-Axis Electro-optic Sensors

This paper presents a measurement method for the shielding effectiveness (SE) of a personal computer (PC) case using three-axis electrooptic sensors and a vector network analyzer (VNA). The SE is obtained by taking the difference between the logarithmic values of the ratios of transmitted power to the input power for conditions with and without the PC case. The SE measurements versus the incident angle and polarization of incident electromagnetic fields are performed in a fully anechoic chamber (FAC) in the frequency range of 1 GHz to 4 GHz. A computer simulation is conducted to compare the experimental and numerical results. Additionally, we measured the SE of the PC case in a reverberation chamber (RC). The SE values of the PC case for the three axes in the case of FAC and RC are within 4 dB. The results show that this SE measurement technique, using electro-optic sensors and a VNA, is useful for both FAC and RC.

Designer Fe3O4@Ag Core–Shell Porous Nanospheres for Enhanced Electromagnetic Interference Shielding of Polymer Nanocomposites

Electromagnetic (EM) pollution is a pressing concern owing to the increasing usage of electronic gadgets. To this end, lightweight and flexible shields are in huge demand to comply with modern electronics, Herein, designer core–shell porous nanospheres (PNSs) are synthesized, and along with multiwalled carbon nanotubes (MWCNTs), their composites are developed in ethylene‐vinyl acetate (EVA) with excellent EM interference (EMI) shielding ability. The Fe3O4 PNSs synthesized through controlled solvothermal synthesis are systematically evaluated to elucidate the formation of PNSs to attain porous core–shell morphology. The as‐prepared Fe3O4 PNSs are coated with Ag by electroless deposition. The developed polymer nanocomposite is flexible and lightweight that effectively attenuates the incoming EM radiation with measured shielding effectiveness (SE) up to 29 dB. This work presents novel insights into the evolution of designer PNSs and presents lightweight polymer composites containing the designer PNSs with excellent radiation shielding activity.

Return Loss Removal in Shielding Effectiveness Measurement Using IEEE 299.1

In this article, a method for removing the return loss effect during shielding effectiveness (SE) measurements for a shielding enclosure is proposed. According to the IEEE 299.1 standard, a receiving antenna is located inside the enclosure to be measured, and this antenna measures the signal loss after passing through the enclosure. The receiving antenna experiences the return loss at its input, and this return loss increases the SE because the occurrence of the return loss is equivalent to the increasing loss when passing through the enclosure. The IEEE 299.1 standard provides a method for removing the return loss effect. The return-loss removal is only effective, however, when the receiving antenna has an input impedance that does not significantly change, remaining almost constant at the adjacent frequencies. The proposed method generalizes the return-loss removal, and thus the return loss effect can be removed irrespective of the input impedance condition of the receiving antenna. As the return loss is removed for any type of the receiving antenna, the SE can be accurately measured to prevent an overestimation of the SE.

On the Improvement of Shielding Effectiveness Measurements of Materials and Gaskets in Reverberation Chambers

In this article, we will show how to improve the standard procedure in the Annex G of IEC 61000-4-21 on the shielding effectiveness (SE) of materials and gaskets through measurements performed in reverberation chambers. We thoroughly analyze and discuss measurement models (MMs), which are already present in the literature including the standardized model. Moreover, we further derive one of these MMs in a different way and introduce a different application, which is suitable to measure high SE values. We apply such MMs and compare results. By the analysis, discussion, and comparisons of measurement results, we clearly provide a robust improvement to the standard measurement procedure.

Shielding Effectiveness Measurement of an UAV Simplified Demonstrator Through Low-Level Swept Field (LLSF) Test

The increasing number of electronic devices on board and the use of novel composite materials in the aerospace industry create a harsh electromagnetic environment that must be studied. In this article, a UAV demonstrator (DEMO-E3) with different test cases is evaluated through the low-level swept field test following a nested resonant chambers approach, which is framed under the high intensity radio frequency measurements. The aim is to analyze the difference in terms of the shielding effectiveness of the enclosure considering the different materials and apertures of each test sample. Some of the test cases had been previously measured independently, according to the IEC 61000-4-21 standard, while in this study, they are incorporated into the demonstrator and former results are used as a comparison.

Degradation of Dynamic Range for Shielding Effectiveness Measurements Due to Long-Term Use of a Dual Vibrating Intrinsic Reverberation Chamber

This article presents the degradation effects of long-term use of a dual vibrating intrinsic reverberation chamber (dual VIRC) for shielding effectiveness (SE) measurements. At the beginning with a new fresh dual VIRC setup it is possible to achieve a very high dynamic range (DR) but the DR degrades due to long-term use of the dual VIRC. The effect of 10 years use of the dual VIRC on the DR is shown as function of usage time. Also, the effect on the DR of a new dual VIRC with better conductive cloth has been presented.

Enhanced Electromagnetic Absorption of Cement Composites by Controlling the Effective Cross-sectional Area of MXene Flakes with Diffuse Reflection Based on Carbon Fibers

• Re-vitalizing MXene’s superior SE performance in the cement composites by adding CF. • The cement composites’ SE reached 41.35 dB with MXene (0.5 wt%) and CF (2.5 wt%) • SE limit of MXene in cement comes from low concentrations and random orientations. • Diffuse reflections of CF compensate the reduced cross-sectional area of MXene. We studied the potential application of MXene flakes for electromagnetic interference (EMI) shielding in cement matrices. Despite their superior electrical and shielding properties, MXene flakes cannot be used in cement for building construction owing to the poor effective cross-sectional area, which is induced by low concentrations and random orientations of small MXene flakes. This reduced the MXene effect on EMI shielding, which could be compensated by co-inserting carbon fibers for diffuse reflections, recovering the reduced effective cross-sectional area of MXene flakes for incident EM waves. Even with a small amount (0.5 wt%) of MXene with 2.5 wt% of carbon fibers, the shielding effectiveness (SE) of cement composites was enhanced to 41.35 dB at 1.0 GHz at a thickness of 3 mm, which is 800 % enhanced compare with the cement composite only with MXene (3.0 wt%). Scanning electron microscopy and permittivity measurements were performed after SE measurements to further analyze the multi-interface structure in detail. This synergetic EMI SE enhancement behavior caused by adding layered materials can be an efficient way to improve the SE of constructing materials with applicable fluidity to form building construction.

Shielding Effectiveness Measurements of Drywall Panel Coated with Biochar Layers

Shielding against electromagnetic interference (EMI) is a critical issue in civil applications generally solved with metal screens. In recent years, the properties of many composite materials filled with carbon nanotubes or graphene or materials with a carbon-based coating have been analysed with the aim of using them for electromagnetic shielding applications. Among other carbon materials, biochar, derived from biomass and characterized by high carbon content, emerges as a sustainable, renewable, environmentally friendly, and inexpensive material. In this paper, commercial biochar thermally treated at 750 °C is used to coat with several layers common building components such as drywall panel. Shielding effectiveness is measured in the frequency band 1–18 GHz for normal incidence and skew angles 10, 20 and 30 deg in a full anechoic chamber with double ridged, vertically and horizontally polarized broadband horn antennas. The results show that the proposed biochar-coated drywall panels provide a good shielding effectiveness compared to similar solutions, with the advantage of a less expensive and easier to realize building material.

Consistent Shielding Effectiveness Measurements for Small Enclosures in Reverberation and Semianechoic Chambers

In this paper, a correction method is proposed for removing the antenna effects when measuring the shielding effectiveness (SE) using the IEEE 299.1 standard. For a small shielding enclosure with a maximum dimension of less than 2 m, the IEEE 299.1 standard provides reverberation chamber (RC) and semi-anechoic chamber (SAC) based methods for SE measurements. However, these two methods are inconsistent each other. Even for the same enclosure, the measured SE has a different value depending on which measurement method is used. Such an inconsistency results in an incompatibility between the two approaches, and thus the IEEE 299.1 standard uses the maximum dimension of an enclosure to determine which method should be applied for measuring the SE. The inconsistency is caused by the measurement antennas used inside and outside of an enclosure. Procedures to remove the antenna effects are also proposed herein. After the removal of the antenna effects, consistency is established between the SEs measured at the RC and SAC. The SE is measured for three enclosures having an SE of 30 to 100 dB at 1 GHz, and the antenna effects are removed from the measured SE to investigate the consistency. The consistency is investigated at up to 16 GHz for a 100-dB enclosure. Removal of the antenna effects and the resulting consistency make it possible to measure the SE using either the RC or SAC method irrespective of the maximum dimension of the enclosure to be measured. In addition, an overestimation is prevented in the SE measurement, improving the measurement accuracy.

Method for Optimization of a Shielding Effectiveness Measurement System Using Shielding Concrete Blocks for IEMI

The recent digitization of many technologies has made information communication facilities vulnerable to intentional electromagnetic interference (IEMI) and electromagnetic pulses (EMPs). Concrete with shielding capability is being studied to protect entire information facilities or security facilities from these threats. Although the conventional standards ASTM D 4935 and MIL-STD-188-125-1 provide guidelines with regard to the assessment of the shielding effectiveness (SE) of materials, these standards are not applicable to concrete owing to the thickness of concrete, particularly when reinforced with rebar, the composition of building materials, time, and cost. To solve this problem, this paper proposes a method for measuring the SE of concrete used for building construction. The proposed measuring method is based on the MIL-STD-188-125-1 standard. Small concrete blocks are used as specimens for testing the suggested SE measurement method, which is designed to operate in the frequency range of 600 MHz to 1.5 GHz. The accuracy of the proposed method is optimized by varying parameters such as the size of the concrete blocks, incidence angle of electromagnetic waves, fixture materials, and the use of absorbers. The results of the proposed method are compared with those of the ASTM D 4935 standard. The SE of concrete blocks, concrete walls, and concrete buildings is also tested using the proposed method and MIL-STD-188-125-1. Similar results were obtained with all of these methods. Therefore, the proposed method to measure the SE of concrete blocks might be suitable to ascertain that buildings constructed with the same concrete could be expected to have the same SE.

Measuring shielding effectiveness of electromagnetic field for degradation shielding paint

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Shielding Effectiveness Measurement With Wide Dynamic Range for a Small Enclosure in a Nested Reverberation Chamber

For a small shielding enclosure, its shielding effectiveness (SE) is measured using the frequency-domain method that is defined in the IEEE 299.1 standard. The frequency-domain method, however, has a reduced dynamic range so that a high level of SE is measured inaccurately. Such dynamic range reduction in SE measurement is caused by cable coupling of transmitting signal during measurement. This article proposes a time-domain method that measures even a high level of SE accurately. Unlike the frequency-domain method, the proposed method does not experience dynamic range reduction. Instead of a continuous wave signal, a pulse signal is transmitted in a nested reverberation chamber for SE measurement. After the pulse transmission, a receiving signal is measured and sampled for the SE calculation. The receiving signal is sampled only after the transmitting pulse signal dissipates completely in the nested reverberation chamber. As a result, the cable coupling and dynamic range reduction do not occur in proposed time-domain method. The proposed time-domain method extends a dynamic range over 30 dB in comparison with the frequency-domain method. The proposed method can measure a high level of SE over 120 dB accurately without being affected by the cable coupling.

Preparation and evaluation of polyester-cotton/wire blended conductive woven fabrics for electromagnetic shielding

For the pursuit of conductive textiles with high electromagnetic shielding performance, specified yarns are processed with a special spinning feeding device with twist counts of 40 T, 50 T, 60 T, 70 T, 80 T, and 90 T, for Next, the optimal yarns from each group are made into SS/Pc-70 and Cu/Pc-80 conductive woven fabrics with a plain weave structure design. In addition, the surface resistivity, electromagnetic shielding effectiveness measurement and air permeability of the two conductive woven fabrics were tested and analyzed. Regarding the electromagnetic shielding performance test, the effects of the complete shielding network, the lamination layers of fabric, and lamination angle on the electromagnetic shielding performance are discussed. The test results indicate that Cu/Pc-80 woven fabrics has the lowest surface resistivity, which means it has the best electrical conductivity; Moreover, different types of metal wires provide the conductive fabrics with different levels of surface resistance. The variations in the lamination angles help attain a complete conductive network that significantly enhances the EMSE, and Cu/Pc-80 have a greater average shielding value comparatively and thus greater EMSE. For both types of conductive woven fabrics, one-layered conductive woven fabrics exhibit the maximal air permeability. As the air permeability of conductive woven fabrics is correlated with the thickness of fabrics, the greater the number of lamination layers, the lower the air permeability of the conductive fabrics.

A novel miniaturized dual-layer frequency selective surface

A novel dual-layer frequency selective surface (FSS) with extended cross-dipole structure is reported in this paper. The elementary form of the FSS is designed at high frequency which is then made to operate at low frequency by increasing the arm length without increasing the footprint of the FSS. The extended arm runs on both the sides of the printed circuit board (PCB) where the connection is accomplished using plated through-hole (PTH) vias. The miniaturized FSS unit cell provides band-stop response at 1.6 GHz within a small footprint of 0.026λo × 0.026λo (5 mm × 5 mm) where λo is the free-space wavelength. The proposed unit cell has rotational symmetry and hence provides good polarization stability. The angular stability is investigated and stable shielding effectiveness performance is witnessed. The proposed FSS offers angular stability up to 60 degrees. The prototype FSS screen is fabricated and the measurement results are presented. The measured shielding effectiveness is greater than 26 dB for both TE and TM mode of operation. The proposed FSS is suitable for antenna gain enhancement and radome applications in L-band.