Electromagnetic Interference Reduction Research Articles

High Q ultra-thin nona-band polarization insensitive homogeneous single layer metasurface for electronics and space industry with electromagnetic interference and antenna radar cross section reduction

In this article, a nona-band metasurface with unit cell dimensions of 0.038λo×0.038λo×0.019λo (20×20×1.0 mm3) is designed on a FR-4 substrate (Dielectric constant εr = 4.4 and loss tangent = 0.02) of 1.0 mm thickness with 35 µm copper (Conductivity = 5.8×107 S/m) cladding with unit cell periodicity is 20 mm. 10×10 metasurface array size is 200×200×1.0 mm3. In TE/TM mode, the absorbance is greater than 99 % at the intended frequency bands (i.e., 5.76, 8.6, 12.68, 14.38, 17.05, 17.94, 19.20, 20.88, 22.62, and 23.62 GHz), and its reflectivity is almost zero. Results indicated that the metasurface is found to extremely independent on the angles of polarization of the incident wave and the absorber is almost insensitive to the incident angle (0° – 90°) for TE/TM modes. The unit cell of metasurface is having negative permittivity, near zero permeability and negative refractive index at all intended bands which confirm exotic properties of the metasurface. The metasurface is having high quality-factor (Q = 72) at 5.76 GHz frequency therefore, this metasurface is also useful for dielectric sensing application in intended bands. The metasurfaces unparalleled properties make it suitable for EMI shielding, sensing applications in the C, X, and Ku-bands, the reduction of mono-static RCS, the improvement of isolation in MIMO antennas, and the reduction of unintended noise produced by copper components used in satellite and RADAR communication.

Investigation into active‐gate‐driving performance and potential closed‐loop controller implementations for silicon carbide MOSFET modules

Investigation into active‐gate‐driving performance and potential closed‐loop controller implementations for silicon carbide MOSFET modules

Investigation of microstructure evolution and electromagnetic shielding mechanism of absorbed MWCNTs-FeCo composites by one-step in situ deposition using high-speed laser cladding

Electromagnetic shielding materials can inhibit or reduce the harm of electromagnetic radiation and have become an important means to protect against electromagnetic pollution. In order to overcome the inconveniences of in situ or conformal manufacturing on the specific equipment, and the resulting assembly errors lead to the reduction of electromagnetic interference shielding effectiveness (EMI SE). As a new technology, high-speed laser cladding can directly design multi-walled carbon nanotubes (MWCNTs)-FeCo alloy composites as absorbents, and it is the first time to realize the rapid manufacturing of electromagnetic shielding materials by one-step in-situ deposition without adding auxiliary materials. According to the temperature field and stress field, it is found that the through-crack defects of electromagnetic shielding coating mainly resulted from the residual stress concentration of microcracks near the bottom fusion line. When the cladding strategy is 1600 W power deposition after preheating at 400 °C, a high-quality cladding layer can be obtained. When the addition of MWCNTs is 1.5 wt%, the material exhibits good electromagnetic shielding performance under the synergistic effect of dielectric loss, conductivity loss, and magnetic loss. And the average EMI SE is 23 dB in the range of 2-18GH. The research shows that high-speed laser cladding can simultaneously meet the requirements of flexible material design and efficient preparation, which realizes the integration of electromagnetic shielding material design and manufacturing.

Tunable asymmetric square split ring resonator based triple band metamaterial absorber for wireless communication system

This article presents a triple band square split ring with double circular split ring resonator incident angle-insensitive perfect metamaterial absorber. The MMA unit cell was manufactured using a FR4 substrate that had dimensions of 8 mm by 8 mm. With the flexibility of on-design adjusting of the highest absorption frequencies, the suggested MA displays peak absorption of 99.67 %, 99.85 %, and 99.97 % at 2.52 GHz, 6.99 GHz, and 9.28 GHz, correspondingly. The tuning metallic two circular split rings and square split ring resonator provide the possibility of frequency modification throughout three distinct frequency ranges: the first frequency range extends from 2.45 GHz to 2.53 GHz, the second frequency range extends from 6.91 GHz to 7 GHz, and the third frequency range extends from 8.85 GHz to 10.32 GHz. Furthermore, the suggested MA displays near-zero absorption at an oblique incidence angle of up to 45° for both the TE as well as TM modes. The unit cell demonstrates single negative properties, such as an effective medium ratio (EMR) of 14.88 and a quality factor (Q factor) that is more than 30 for both the TM mode as well as the TE mode. An equivalent circuit successfully demonstrated its performance capability, which indicated that it would create an MMA of good quality when using ADS software. A comparison between the measured results of the suggested MMA and the simulated one reveals that there is a significant amount of a similarity between both of them. Because of its easy design within small dimension, wide angular stability, strong absorption, good EMR, and flexibility to frequency tuning is suitable for a wide range of wireless communication system, especially satellite applications like electromagnetic interference reduction, radar systems, imaging, and stealth technology.

Toroidal Nanocrystalline Powder Core With Trapezoidal Cross Section

This paper introduces a toroidal nanocrystalline powder core with a trapezoidal cross section. The non-uniform magnetic flux distribution of toroidal cores with different cross sectional geometries is discussed, the inductance equations are derived, and the geometrical optimisation factor is given in order to retain the highest possible inductance value whilst minimising material usage. A 10-turn coil is wound on the core, with the measured inductance values showing a good match with both FEM and mathematical calculation. The near-field electromagnetic interference (EMI) radiation in close proximity to the inductor is investigated by both FEM and experimental validation, and the toroidal core with a trapezoidal cross section has shown reduced EMI. By adopting a trapezoidal cross section for the toroidal core, a 30 % reduction in material usage and lower EMI are achieved, albeit with a compromise of 14% in inductance.

The Performance of Hollow Pyramidal Microwave Absorber Using Different Slot Size

Microwave absorber is commonly used in defense, electromagnetic compatibility (EMC)/electromagnetic interference (EMI) reduction and anechoic chamber application. Conventional electromagnetic (EM) absorbers have some constraints in practical handling due to its heavy weight. In this paper, the research focuses on the development of high performance and lightweight microwave absorber. A lightweight and simple design configuration of different rectangular slot size array implemented on hollow pyramidal microwave absorber are carried out. There are two different designs of different slot size array calculated based on 3GHz, 6GHz and 9GHz frequency slot size. The two designs have an opposite slots size array arrangement namely different slot size 3GHz, 6GHz, 9GHz order design array and different slot size 9GHz, 6GHz, 3GHz order design array. The absorption is measured using the Naval Research Laboratory (NRL) arch free space method in the frequency range of 1GHz to 12GHz covering L, S, C and X band. In the measurement result, the maximum absorption performance is obtained by the different slot size 9GHz, 6GHz, 3GHz order design array which is up to -44.23dB at X-band. The measurement results for both designs array show good absorption performance which exhibit below than -20dB especially at high frequency band. The proposed designs have been identified as the new approach to increase absorption improvement over a broad frequency range application.

A survey of conductive and radiated EMI reduction techniques in power electronics converters across wide‐bandgap devices

AbstractNowadays, wide‐bandgap (WBG) devices, primarily made from silicon carbide (SiC) and gallium nitride (GaN), are widely applied in power generation, transmission, and conversion. Moreover, the application of WBG devices has had a transformative impact in the field of energy conversion. Compared with Si counterparts, SiC and GaN can remarkably improve the power conversion system efficiency and power density while generating higher electromagnetic interference (EMI) emissions. There are many studies on WBG devices and their behaviour in power systems. However, methods of mitigating EMI/electromagnetic compatibility (EMC) still lack scientific guidance. This article reviews the characteristics of WBG devices, and the significant EMI problems are discussed. Then, the EMI types, EMI causes, and methods of EMI reduction are summarized, and the advantages and disadvantages of these methods are presented as well. Based on the reviewed studies, future research, and the conclusions of this article on EMI/EMC are discussed to help relevant researchers deepen their understanding of the new challenges of EMI brought by the applications of WBG devices, which are useful in engineering.

Wireless Battery Chargers Operating at Multiple Switching Frequencies with Improved Performance

The operation of wireless battery chargers at multiple switching frequencies may lead to a noticeable suppression of conducted and radiated electromagnetic interference (EMI) at the cost of decreased efficiency (mainly at lower load resistances) and increased peak and root mean square values of currents of power components of the wireless battery charger. Moreover, the reduction in conducted EMI is only moderate (<8.3 dB). Therefore, a novel approach based on modified resonant circuits and a modified control technique to obtain better reduction in the conducted and radiated EMI without significantly compromising other performance characteristics of the wireless battery charger is proposed and validated by using simulations and experiments. It is shown in this paper that the wireless charger operating at multiple switching frequencies with the proposed approach for the performance improvement has a more effective implementation of the four-switching frequency spread-spectrum technique with better conducted and radiated EMI reduction at all load resistances, lower values of peak and RMS currents at all load resistances, and higher efficiency in constant current mode and in the beginning of constant voltage mode (at lower values of the load resistances) than that of the conventional wireless charger operating at multiple switching frequencies.

EMI shielding applications of PANI-Ferrite nanocomposite materials: A review

The issue of electromagnetic pollution, also known as electromagnetic interference (EMI), is brought on by the rapid development of electronic devices and wireless communication technology. The purpose of electromagnetic shielding interference is to shield the electronic device from interruptions and to prevent harm to the device. As a result, EMI shielding materials have been developed to address the pressing issue. In recent years, EMI shielding materials have changed from traditional single-function to multi-function designs to better accommodate diverse application contexts. Various strategies have been adopted to prevail over the limitations of metal-based EMI shielding materials. Ferrites and their composites have recently attracted the interest of researchers due to their biocompatibility, biodegradability, and variety of uses in various fields including EMI shielding. Ferrite nanocomposites are combined with Polyaniline (PANI) to form PANI-ferrite nanocomposites. In addition to having good qualities, polymer nanocomposites can be designed to display a combination of properties for multifunctional applications. When the particle size is decreased below 30 nm, the properties of ferrite particles, which are very relevant materials, perform better. Therefore, the size and distribution of the particles inside the polymer matrix play a major role in determining the superparamagnetic nature of ferrite particles and their polymer nanocomposites. In this work, we investigated ferrite-based materials for the reduction of EMI using reflection and absorption approaches. Also highlighted the popular techniques for the synthesis of ferrite composites and their EMI shielding efficiency.

A comparison statement on DCPWM based conducted EMI noise mitigation process in DC-DC converters for EV

Fast switching techniques at high frequencies are employed for quick charging and energy conversion in electric vehicle (EV) power converters. Electromagnetic interference (EMI) noise is produced due to the fast-switching process, which may result in malfunctioning and degraded EV performance. In this work, a digital chaotic pulse width modulation (DCPWM) technique-based EMI noise mitigation process has been applied to elementary positive output super lift Luo (EPOSLL), two-stage cascaded boost (TSCB), and ultra-lift Luo (ULL) converters, and a comparison study has been conducted with EMI reduction levels as per electromagnetic compatibility (EMC) standards. The duty cycle is varied from 0.5 to 0.67 to get the desired output voltage as an input of 10V to achieve the power ratings of 40 W to 80 W for various load conditions. A total of 4 dBV (3 V) to 15 dBV (10 V) of conducted EMI noise has been mitigated for the above-said converters. Simulation results based on power spectrum density and hardware results based on fast fourier transform (FFT) of output voltages are analyzed. According to the findings, the ULL converter is more acceptable for electromagnetic compatibility in EV applications than EPOSLL and TSCB DC-DC converters.

Electromagnetic interference modeling and elimination for a solar/hydrogen hybrid powered small-scale UAV

The trajectory related and Direct Current (DC) Electromagnetic Interference (EMI) of lithium battery, fuel cell and photovoltaic modules has a great influence on the small-scale Unmanned Aerial Vehicle (UAV) airborne magnetometer and is hard to be shielded, calibrated or filtered. Besides, the mechanisms underlying the DC EMI have been rarely investigated yet. To cope with this problem, this paper systematically studies the EMI models, and proposes an online 3-layer EMI reduction scheme. First, EMI coupled with UAV motion model and hybrid power system is established. Second, the mechanism EMI models of hybrid power system are established and verified based on the proposed concept “equivalent current”. Third, an online 3-layer EMI reduction scheme is proposed, including battery layer, trajectory planning layer and energy management layer. In the first main layer, EMI self-cancellation is realized by rotating battery inclinations and symmetrical circuits. In response to errors, the trajectory planning layer reduces the EMI intensity by optimizing an optimal trajectory, while the energy management layer prioritizes power allocation to power sources that can produce small and stable EMI. Simulation results of climb, level flight and descent illustrate the efficaciousness and applicability of the proposed online 3-layer EMI reduction scheme.

An Ultra-Thin, Triple-Band, Incident Angle-Insensitive Perfect Metamaterial Absorber.

We created an ultra-thin, triple-band incident angle-insensitive perfect metamaterial absorber (MMA) with a metallic patch and a continuous metal ground isolated by a central dielectric substrate. The top metallic patch, placed across the edges of the 0.58 mm thickness Rogers RO4003C (lossy) substrate, forms the bulk of the projected absorber's ultra-thin layer. Nonetheless, absorption is exceedingly strong, covering C-band, X-band and K-band and reaching levels of 97.8%, 99.9%, and 99.9%, respectively, under normal and even oblique (0° to 45°) incident conditions. In chosen ranges of frequency of 6.24, 10.608, and 18.624 GHz for both TM and TE mode, the displayed Q-factors were 62.4, 17.68, and 26.61, respectively. We correspondingly calculated the RAB (relative absorption bandwidth) to evaluate absorption performance. An equivalent circuit proved its performance capabilities, indicating that it would produce a high-quality MMA from ADS software. Furthermore, the absorber's performance has been verified in free space on a sample being tested using a different array of unit cells. Moreover, the proposed structures with HFSS simulators to display the MMA's absolute absorption at each absorption peak are somewhat inconsistent with the results of the CST simulator. Because of its superior performance, the ultra-thin absorber is suited for a wide range of applications, including satellite applications such as radar systems, stealth technology, imaging, and electromagnetic interference reduction.

Design and Assessment of a New Active CM Filtering Architecture for PWM Inverter-Fed Motor Drive Systems

The stepwise common-mode (CM) voltage at the output of inverters causes electromagnetic interference (EMI) and damage to motor bearings. This article proposed a new output active CM filter (ACF) to compensate for the steep rising/falling edges of CM voltage for EMI reduction and bearing protection. An input ACF is also necessary to attenuate the CM noise injected into the grid. Hence, a holistic assessment of input and output ACFs for inverter-fed motor drive systems has been demonstrated. The motor drive system satisfies the CM EMI standard with this new active CM filtering architecture. Ferrite materials and winding configurations of the CM transformer used in the output ACF have been investigated. Moreover, the relationship between the input and output ACFs has been discussed. This article aims to provide new perspectives and implementation guidelines for the ACFs in motor drive systems.

A Proof-of-Concept Study of Auxetic Composite Foams with Negative Poisson’s Ratio for Enhanced Strain-Stable Performance of Electromagnetic Shielding

Stretching of conductive polymer composite (CPC) foams always results in a severe reduction in electromagnetic interference shielding effectiveness (EMI SE) mainly due to the destruction of conductive networks and the decrement of sample thickness. Therefore, it is desirable to develop a novel strategy for preparing CPC foams with strain-stable EMI SE under moderate stretching. Herein, a strategy of constructing an auxetic structure to stabilize the EMI SE of CPC foams during stretching is proposed for the first time. Lightweight auxetic polyurethane/carbon nanotube (APU/CNT) composite foams were prepared by a solution dip-coating approach and triaxial volumetric compression. Compared with nonauxetic PU/CNT foam, the APU/CNT foam with similar filler loading and density of around 0.035 g/cm3 showed more stable SE values with the increase of tensile strain (especially within the first 20% strain, the SE/SE0 reduction of the APU/CNT foam is less than ∼5%), exhibiting enhanced strain-stable EMI-shielding behavior in the stretching process. The underlying reason is that the presence of auxetic structure with a negative Poisson’s ratio could not only slightly increase the thickness of the foam but also avoid the serious destruction of the conductive networks under stretching, which is beneficial to attenuate EM waves more stably. Moreover, the outstanding and more stable Joule-heating performance could also be observed in the stretched APU/CNT foam. This work reveals the potential of auxetic structures to solve the challenging problem of how to stabilize the EMI-shielding (or Joule-heating) performance of CPC foams during moderate stretching.

Effect of electric arc furnace slag and magnetite materials on EMI shielding properties of cementitious composites

To impart electromagnetic interference (EMI) shielding in cementitious composites, electrically conductive and electromagnetic absorbing additives are generally used. This research examined the effect of adding electric arc furnace slag (EAFS) or heavyweight aggregates (HWA), alone and in combination with carbon fibre (CF), on the EMI shielding properties of cementitious composites. Different percentages of both additives were added to a control mix to study the effect on mechanical properties, electrical conductivity and EMI shielding. Optimal shielding was produced for aggregate contents of 1.5 wt%, with values of 5.18 dB for the EAFS mixes and 3.25 dB for the HWA mixes, within the frequency range 30 MHz to 1.5 GHz. Hybrid mixes were fabricated using 0.7 wt% of 12 mm long CF and three different percentages of each aggregate. In combination with the CF, the optimal level of shielding was produced with EAFS and HWA contents of 1 wt%. These optimal shielding levels were 34.21 dB and 36.78 dB, respectively, within the 30 MHz to 1.5 GHz frequency range. A further increase in either type of aggregate produced a gradual reduction in EMI shielding effectiveness.

Analysis of Electromagnetic Interference Reduction from Printed Circuit Boards

Nowadays, electricity is the most important and necessary energy in human society and daily life, because electricity is convenient and safe to transfer between different locations. However, electromagnetic interference (EMI) always accompanies electricity and has brought a lot of problems. Especially in printed circuit boards (PCB), the EMI can break the circuit or cause a short circuit, which is dangerous in creating a PCB. To effectively reduce EMI from PCB, three different methods of reducing EMI from PCB were chosen to compare with each other. By comparing their price, practicability, effectiveness, data, and technology for reducing EMI from PCB, PCB designers can choose the methods that are suitable for their situation.

Preferential localization of conductive filler in ethylene‐co‐methyl acrylate/thermoplastic polyolefin polymer blends to reduce percolation threshold and enhanced electromagnetic radiation shielding over K band region

AbstractTo minimize radiation pollution at ultra‐low filler concentrations, there is a growing interest in microwave‐absorbing materials based on polymer blends composites. Herein, ethylene‐co‐methyl acrylate (EMA)/thermoplastic polyolefin (TPO) blend composites were prepared by employing solution mixing utilizing conductive Vulcan XC 72 carbon black (VCB) as nanofiller. The work focused on the reduction of electrical percolation and outstanding electromagnetic interference (EMI) shielding performance in low loading caused by the preferential distribution of carbon particles in one phase (ethylene‐co‐methyl acrylate copolymer) of the co‐continuous immiscible polymer blend. The fabricated conductive blend was further tested to ensure its superiority in physic‐mechanical and thermal stability. The morphology analysis reveals that the VCB particles are selectively localized in EMA phase of the blend which facilitates the formation of compact spatial conductive network throughout the matrix for electronic hopping. High electrical conductivity is achieved in the scale 10−2 S/cm for the prepared composites with 30 wt% of carbon black loading whereas a total EMI shielding effectiveness of −29 dB and thermal conductivity of ~0.75 W/m·K are achieved for this same filler content. This study reveals that the fabricated conductive polymer nanocomposites can be effectively utilized as promising EMI shields in the future generation of stretchable and wearable electronics.

A single-coil-based method for electromagnetic interference reduction in point-of-care low field MRI systems

One of the main challenges for point-of-care (POC) MRI systems is electromagnetic interference (EMI), since such systems are intended for use outside conventional Faraday-shielded rooms. Many methods have been proposed based on EMI detection via sensors external to the MRI system, followed by different types of signal processing to reduce artifacts in the image. Although these methods can be very effective, they do increase the complexity of the overall system, and introduce more potential failure points for systems designed for challenging environments. In this work we introduce a new method that does not require external sensors, but rather uses the “MR-silent” mode of an RF coil to detect the EMI, followed by simple subtraction from the signal from the “MR-active” mode. This method can be performed post-acquisition if there are two receive channels available, or as demonstrated here can operate with a single-channel receive detection system with the addition of a simple passive 180° power splitter/combiner into the receive chain. Proof-of-concept in vivo results show that a reduction in the standard deviation of the EMI up to ∼ 97 % is possible, with average values ∼ 90 %.

A Review of EMI Research in Modular Multilevel Converter for HVDC Applications

The modular multilevel converter (MMC) is one of the most critical implementation forms of high voltage direct current transmission. However, the electromagnetic interference (EMI) problems in MMC are unavoidable and complex due to the nonlinear switching behavior of a considerable number of submodules. In this article, the state of the art of EMI research in MMC is reviewed. The characteristics of MMC EMI sources are studied by analyzing the topology and modulation method of MMC and the dynamic turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> processes of the power electronic devices. The standard evaluation and the modeling methods of MMC EMI emission are reviewed by analyzing the EMI propagation paths. In addition, the EMI reduction methods of MMC at sources and along the propagation paths are summarized. Finally, the MMC EMI research is concluded and the future prospects are presented.

A Trigger Signals Modification Scheme for Common-Mode Conducted EMI Reduction of Modular Multilevel Converter

Modular multilevel converter (MMC), due to its features of modularization, high efficiency, and so on, has gradually become the mainstream multilevel converter. However, it can induce large electromagnetic interference (EMI) because of the high-level <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$dv/dt$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$di/dt$ </tex-math></inline-formula> during its commutation transient. Therefore, it is significant to analyze the characteristics of common-mode (CM) conducted EMI of MMC and propose a suppression scheme accordingly. In this article, considering the voltage to ground of submodule (SM) as a direct noise source, the relationship between CM current and equivalent noise source of one phase, as well as that between the equivalent noise source of one phase and switching action of each SM are deduced. Furthermore, a trigger signals modification (TSM) scheme is proposed, which can effectively suppress the CM conducted EMI on the dc side without obviously affecting the operating performance of MMC. In particular, this scheme manipulates the trigger signals already generated by the modulation and capacitor voltage balancing control, thus enabling good applicability. Finally, experimental results verify the validity of the analysis and the effectiveness of the proposed TSM scheme.