The growth in the application of electronic devices across a broad spectrum of military, industrial, commercial and consumer sectors has created a new form of pollution known as noise or radio frequency interference (RFI) or electromagnetic radiation or electromagnetic interference (EMI) that can cause interference or malfunctioning of equipment. Therefore, there is a greater need for the effective shielding of components from its adverse effects. This review surveys the shielding materials like metals, conducting plastics and conducting polymers for the control of electromagnetic radiations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

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EMI shielding: Methods and materials—A review

Electromagnetic interference (EMI) shielding characteristics of natural rubber and ethylene vinyl acetate filled with conductive carbon black (Vulcan XC-72) and short carbon fibre (SCF) have been studied. The measurements of shielding effectiveness (SE) were carried out in two different frequency ranges 100–2000 MHz and 8–12 GHz (X-band range). The return loss and loss due to absorption were also measured as a function of frequency in the X-band range and microwave region. It is observed that the SE of the composites is frequency dependent, especially at higher frequency range, and it increases with the increasing frequency. The SE also increases with the increase in filler loading. The SCF filled composites show higher SE compared to that of conductive carbon black. The correlation between SE and conductivity of the various composites is also discussed. The results indicate that the composites having higher fibre loading (≥20 phr) can be used for the purpose of EMI shielding, as well as for some microwave applications.

Electromagnetic interference shielding effectiveness of carbon black and carbon fibre filled EVA and NR based composites

IEEE Antennas and Wireless Propagation Letters

https://iopscience.iop.org/article/10.1016/S1468-6996(02)00053-0/pdf

Electromagnetic shielding behaviour of conducting polyaniline composites

Effect of short carbon fibers and MWCNTs on microwave absorbing properties of polyester composites containing nickel-coated carbon fibers

In this paper designs of both planar ultra-wide band (UWB) antenna and UWB antenna with two rejected bands are given. The antenna consists of a rectangular patch etched on FR4-substrate with 50 Ω feed line. The rectangular patch has one round cut at each corner with one slot in the ground plane. The simulated bandwidth with return loss (RL) ⩾ 10 dB is 3.42–11.7 GHz. The rejected bands are the WLAN and X-bands, achieved by inserting slots in the patch and the feed. The simulated results of the proposed antenna indicate higher gain at the passbands while a sharp drop at the rejected bands is seen. The radiation pattern is of dipole shape in the E-plane and almost omnidirectional in the H-plane. The high frequency structure simulator (HFSS) is used to design and simulate the antennas behavior over the different frequency ranges. Measurements confirm the antenna characteristic as predicted in the simulation with a slight shift in frequencies.

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Multislot microstrip antenna for ultra-wide band applications

This paper deals with the measurements of the equivalent impedance, insertion loss (IL), and return loss (RL) of a conductive composite material called “Magnex DC”, performed at microwave frequencies. It is found that the equivalent impedance of this composite material decreases as the frequency increases in the X-band (8–12.4 GHZ) and the IL of a 1.4 mm thick specimen is greater than 9 dB over the whole band. The utilization of this material in electromagnetic shielding is considered. Furthermore, results of the measurements performed on a tapered specimen are also reported.

Measurements of the Magnex DC characteristics at microwave frequencies

This paper presents the acoustical problems associated with a huge mosque that has been built recently in Amman, Jordan. These problems include very high reverberation time values inside the mosque, reaching more than 15 s at midfrequencies, and more than 22 s for all frequencies below 500 Hz. In addition, the articulation index was very low and the ambient noise level was very high. These conditions produced an unacceptable acoustic environment for this place, and their reduction was essential. To remedy these problems, most of the interior surfaces of the mosque were treated using appropriate types of materials. Final measurements indicate that the reverberation time in the midfrequencies is around 1 s. Furthermore, the use of an electroacoustic system provides an almost uniform sound level inside the mosque. The articulation index measurements show good to excellent response.

Acoustics of King Abdullah Mosque

A microwave bench operating in the frequency range 8–12 GHz (X-band) was used to investigate some of the electrical characteristics of the talc filled polypropylene composite. The impedance, return loss, and insertion loss are measured as a function of frequency in the X-band range. It was found that electromagnetic waves interact with the material via the impurities, inclusions and voids existing in the bulk composite. The impedance, return loss and insertion loss show relatively low frequency dependence. Also, the return loss and the impedance exhibit a resonance behaviour at 11.91 GHz. The results suggest that this composite material could be used in some microwave applications.

Microwave properties of the talc filled polypropylene

Some properties of nickel-coated carbon fibre-polypropylene composite are considered at microwave frequencies in the range 8 to 12 GHz. The paper presents the measured values of the insertion and return losses and the equivalent input impedance in the above frequency band. Measurements were performed on composite material for different nickel-coated fibre concentrations of 0, 5, 10, 16 and 28 wt%. The filler effects shows a transition region and identifies the dependency of the electrical properties on these concentrations. Furthermore, shielding effectiveness is calculated for the given concentrations and it is found that its value could reach more than 30 dB over the whole frequency band for a specimen of 2.6 mm thickness and with 28 wt% concentration.

M.K. Abdelazeez

Papers

Multislot microstrip antenna for ultra-wide band applications

Measurements of the Magnex DC characteristics at microwave frequencies

Acoustics of King Abdullah Mosque

Microwave properties of the talc filled polypropylene

Some properties of nickel-coated carbon fibre-polypropylene composite at microwave frequencies