External Electromagnetic Interference Research Articles

An integrated high precision absolute angular displacement sensor

Abstract This paper proposed a high precision absolute angular displacement time grating sensor, and was assembled into an integrated encoder. This absolute angle sensor contains two incremental sensors, namely, N1 measurement period fine measurement component and N2 measurement period coarse measurement component, N1 and N2 are mutually prime, and N1 > N2. The induction electrodes of the fine measurement component adopt differential design to minimize the effects of external electromagnetic interference and common mode interference between different sensing units so as to achieve high precision displacement measurement, the phase difference between two incremental sensor is used for absolute positioning. The reflecting ring design simplifies the structure of the encoder and facilitates sensor integration. The induction output signals of different components are cross connected through leads to the reflecting ring far away from the measurement component to the first harmonic error during the measurement period. The reading heads adopt a round, uniformly distributed design scheme, and the average effect of the whole circumference closed ring sampling scheme is beneficial for improving measurement accuracy and eliminating harmonic errors. A sensor prototype with a diameter of 83mm was manufactured and assembled into an integrated encoder. Experimental results show that the sensor achieve a precision of 12" over a full 360° measurement range and a resolution of 0.5", and it can realize absolute positioning.

Environmental Interference Suppression by Hybrid Segmentation Algorithm for Open-Area Electromagnetic Capability Testing

Compared with electromagnetic compatibility (EMC) testing in anechoic rooms, open-area EMC testing takes advantage of in situ and engine running status measurement but suffers from non-negligible external electromagnetic interference. This paper proposes a novel environmental interference suppression method (named the EMC environmental interference suppression algorithm (E2ISA)) that separates signals from backgrounds via image segmentation and recognizes the near–far site signal via a group of time-varying features based on the difference in the near-site EM radiative characteristic. We find that the proposed E2ISA method, which combines the deep learning segmentation network with the classical recognition methods, is able to suppress environmental interference signals accurately. The experiment results show that the accuracy of E2ISA reaches up to 95% in the face of VHF (Very High Frequency) EMC testing tasks.

Dynamic stabilisation of magnetic fields measured inside a magnetically shielded room using an external coil system *

Magnetoencephalography (MEG) system based on optically pumped magnetometers (OPMs) requires a magnetically shielded room (MSR) to establish a stable near-zero field environment. Affected by external environmental electromagnetic interference, the magnetic noise in the MSR will become very severe. In order to overcome this problem, this paper proposes a method for dynamic stabilisation of magnetic fields measured inside a MSR using an external coil system. Firstly, the field form of the external compensation coil was analysed by taking the AC characteristics of the material into consideration. Then, the linear characteristic of the control system is studied and a high performance magnetic noise suppression controller is designed based on the environment noise characteristics. Finally, simulation and experimental are carried out through a self-developed 1250 mm × 1250 mm × 2100 mm MSR, which indicates that the proposed method can effectively suppress dynamic magnetic fluctuation and noise.

Design and Implementation of a Specialised Millimetre-Wave Exposure System for Investigating the Radiation Effects of 5G and Future Technologies.

As the fifth-generation (5G) network is introduced in the millimetre-wave (mmWave) spectrum, and the widespread deployment of 5G standalone (SA) is approaching, it becomes essential to establish scientifically grounded exposure limits in the mmWave frequency band. To achieve this, conducting experiments at specific frequencies is crucial for obtaining reliable evidence of potential biological impacts. However, there is a literature gap where experimental research either does not utilise the mmWave high band (e.g., the 26 Gigahertz (GHz) band) or most studies mainly rely on computational approaches. Moreover, some experimental studies do not establish reproducible test environment and exposure systems. Addressing these gaps is vital for a comprehensive exploration of the biological implications associated with mmWave exposure. This study was designed to develop and implement a mmWave exposure system operating at 26 GHz. The step-by-step design and development of the system are explained. This specialised system was designed and implemented within an anechoic chamber to minimise external electromagnetic (EM) interference, creating a controlled and reproducible environment for experiments involving high-frequency EM fields. The exposure system features a 1 cm radiation spot size, enabling highly localised exposure for various biological studies. This configuration facilitates numerous dosimetry studies related to mmWave frequencies.

Electromagnetic interference compensation method of TMR current sensor

TMR current sensor has excellent characteristics such as high sensitivity, good temperature characteristics, and wide dynamic range, which can meet the new needs of smart grid development. However, the measured value of the output of the TMR current sensor changes with the change in the spatial magnetic field strength. External electromagnetic interference will bring large errors and DC bias to the measurement of the sensor, resulting in a narrowing of the measurement current range. Therefore, an electromagnetic interference compensation method for TMR current sensor is proposed. Two TMR chips are used to measure the synthetic magnetic field signal and the interference magnetic field signal, respectively. Then the output signals of the two TMR chips are compensated and reduced by the signal conditioning unit. The final output analog signal is the magnetic field intensity signal generated by the current of the line to be tested without interference. Finally, the effectiveness of the proposed method is verified by field tests.

A visual faulty feeder detection method for power distribution network based on spatial image generation and deep learning

AbstractIn the case of a single‐phase grounding fault in the distribution network, the transient zero‐sequence current (TZSC) tends to be non‐linear and non‐stationary. The faulty line selection is relatively difficult. The distributed power access further brings many difficulties to faulty line selection. This work proposes a novel method of faulty line selection using spatial image generation and deep learning. At first, the optimal smooth denoising model can be used to smooth the zero‐sequence current for each line, reducing the external environment electromagnetic interference. Then, the treated zero‐sequence current is mapped into the colorful floral hoop image by using symmetrized Hilbert transform pattern (SHTP). The SHTP transforms the one‐dimensional time domain signal into the two‐dimensional space domain image, enhancing invisible information and obtaining more abundant feature information. Finally, the deep features of the SHTP floral hoop image are extracted by means of deep learning method. In order to improve the faulty line selection universality, a mixed sample library containing three different topologies is established, including the 10 kV radial distribution network, IEEE‐13 node model, IEEE‐34 node model and StarSim platform. The comparisons show that the proposed method has a more noticeable visualization effect on fault features, higher classification precision rate, and better anti‐noise performance.

Research on a portable shielding-free ultra-low field magnetic resonance imaging system

The portable light-weight magnetic resonance imaging system can be deployed in special occasions such as Intensive Care Unit (ICU) and ambulances, making it possible to implement bedside monitoring imaging systems, mobile stroke units and magnetic resonance platforms in remote areas. Compared with medium and high field imaging systems, ultra-low-field magnetic resonance imaging equipment utilizes light-weight permanent magnets, which are compact and easy to move. However, the image quality is highly susceptible to external electromagnetic interference without a shielded room and there are still many key technical problems in hardware design to be solved. In this paper, the system hardware design and environmental electromagnetic interference elimination algorithm were studied. Consequently, some research results were obtained and a prototype of portable shielding-free 50 mT magnetic resonance imaging system was built. The light-weight magnet and its uniformity, coil system and noise elimination algorithm and human brain imaging were verified. Finally, high-quality images of the healthy human brain were obtained. The results of this study would provide reference for the development and application of ultra-low-field magnetic resonance imaging technology.

Shielding Effectiveness of Unmanned Aerial Vehicle Electronics with Graphene-Based Absorber

Within this study, we explored the augmented security measures for the electronics of unmanned aerial vehicles (UAVs) within an RF environment. UAVs are commonly utilised across various sectors, and their use as auxiliary platforms for cellular networks, as parallel networks working in tandem with ground-based base stations, holds considerable promise. In this context, ensuring the uninterrupted operation of UAVs is a paramount objective. However, the considerable external electromagnetic interference emitted by existing base stations may jeopardise the functionality of UAV electronics. This could potentially lead to an unintended flight path and a sudden cessation of communication with the operator. To mitigate the detrimental impact of the RF field, we advocate covering the UAV casing with reduced graphene oxide (RGO). The efficacy of RGO’s shielding effectiveness (SE) was investigated over a frequency spectrum from 100 MHz to 10 GHz. Our scrutiny of this property was centred around the measurement of scattering matrix coefficients of the unadulterated material—without additives of any kind. Our findings show that this material is a favourable candidate for UAV absorbers due to its low reflection coefficient coupled with its high absorption capacity. The studied absorber ensures an SE value of 25 dB and 30 dB for a 3 mm layer at frequencies of 3.6 GHz (pertaining to the 5G system) and 5.8 GHz (pertaining to LTE), respectively.

Design and Optimization of Multi-Stage TMR Sensors for Power Equipment AC/DC Leakage Current Detection

Tunnel magnetoresistance (TMR) can measure weak magnetic fields and has significant advantages for use in alternating current/direct current (AC/DC ) leakage current sensors for power equipment; however, TMR current sensors are easily perturbed by external magnetic fields, and their measurement accuracy and measurement stability are limited in complex engineering application environments. To enhance the TMR sensor measurement performance, this paper proposes a new multi-stage TMR weak AC/DC sensor structure with high measurement sensitivity and anti-magnetic interference capability. The front-end magnetic measurement characteristics and interference immunity of the multi-stage TMR sensor are found to be closely related to the multi-stage ring size design via finite element simulation. The optimal size of the multipole magnetic ring is determined using an improved non-dominated ranking genetic algorithm (ACGWO-BP-NSGA-II) to derive the optimal sensor structure. Experimental results demonstrate that the newly designed multi-stage TMR current sensor has a measurement range of 60 mA, a fitting nonlinearity error of less than 1%, a measurement bandwidth of 0–80 kHz, a minimum AC measurement value of 85 μA and a minimum DC measurement value of 50 μA, as well as a strong external electromagnetic interference. The TMR sensor can effectively enhance measurement precision and stability in the presence of intense external electromagnetic interference.

An investigation on electromagnetic shielding effectiveness of metallic enclosure depending on aperture position

Electromagnetic compatibility (EMC) become one of the most important topics during electric vehicle design due to incorporating high voltage systems into conventional vehicle electronic architecture. Electromagnetic shielding enclosure is a conductive barrier utilized for protecting electronic circuits against external electromagnetic interference (EMI). Shielding effectiveness (SE) is a measure of shielding performance for the enclosures. Aperture of the enclosures attenuate SE by permitting EMI leakage to affect the electronic circuits. In this study, the effect of aperture position on SE is investigated while the dimensions of the enclosure remain fixed. It is obtained that SE varies depending on the aperture positions and it gets better while aperture is closer to the corners of the front panel. Then, the effects of different observation points, the dimensions of enclosure and aperture on SE are analysed while keeping the aperture position at the corner. It is obtained that SE gets better when the observation point is located far away from the aperture. Enlarging the enclosure dimensions makes SE better while increasing aperture dimensions attenuates SE. Finally, it is concluded that it is crucial to consider aperture position, observation point, the dimensions of enclosure and aperture to obtain better SE.

Predictive Modeling of Quasi-Static Electromagnetic Interference Effects on Electro-Optic Modulators

Electro-optic modulators (EOMs) are an interface between electrical and optical components, making them susceptible to external electromagnetic interference (EMI). In this article, we investigate the effects of low-frequency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\sim }$</tex-math></inline-formula> 15 MHz) EMI on lithium niobate (LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) EOMs. A predictive model for low-frequency EMI injection into a commercially available EOM is developed and validated experimentally. Specifically, analytical expressions for eye height and Q-factor are derived that predict the changes in the receiver end eye diagram, when the EOM modulation process is interrupted by the RF injection. The eye diagram gradually closes down as the RF injection power increases, owing to the signal degradation in the receiver end. A simple expression for calculating the maximum peak RF injected voltage that the EOM can tolerate prior to the system experiencing significant bit error rate is also presented. This model can be utilized to assess the survivability of EOMs under EMI.

Biomathematical analysis on impedance measurement during COVID-19 pandemic

The coating impedance size can reflect the aging degree of the coating to a certain extent; therefore, the measurement of the coating impedance size can monitor the aging degree of the coating in real time. Since the coating is traditionally considered as an insulating medium, its impedance value before aging is as high as 10^8 Ω or more, it is difficult to achieve accurate impedance measurement, and the current generated by loading by voltammetry at low voltage is very weak and easily affected by external electromagnetic interference noise, and the measurement accuracy is low. In this paper, by pluralizing the high impedance, establishing the mathematical model of differential amplification circuit, and then using sinusoidal fitting in which processing, so that the obtained signal is more accurate during COVID-19 pandemic.

Перспективные слоистые гибкие радиопоглощающие материалы на основе порошкообразного угля

The article presents the technique for obtaining advanced layered radio-absorbing materials based on powdered charcoal. The technique includes the following technologies: incorporation of the electrolyte aqueous solution into the material particles pores; adhesive pressing. The developed technique is more manufacturable compared to the analogs. Materials obtained in accordance with this technique are characterized by the flexibility, as well as lower cost compared to other carbon-containing radio-absorbing materials. The experimental characteristics of electromagnetic radiation reflection and transmission coefficients in the frequency range 2.0 – 17.0 GHz of the materials obtained in accordance with the developed technique are described. The results of the comparative analysis of these characteristics are provided. Based on these results, it’s determined that the average values of electromagnetic radiation reflection coefficient in the specified frequency range of the materials based on powdered non-activated wood charcoal, powdered activated wood charcoal and powdered activated coconut charcoal are –4.5 dB, –8,5 dB and –9.0 dB (when these materials fixed on metal reflectors). The average values of their electromagnetic radiation transmission coefficient are –11.5 dB, –20.0 dB and –15.5 dB respectively. The investigated materials seem to be promising for use in order to protect electronic equipment from external electromagnetic interference.

Compact Fiber-Optic Current Sensor With a Polarization Splitter and a 22.5$^\circ$ Faraday Rotator

In this letter, a novel implementation of a polarimetric fiber-optic current sensor scheme based on polarizing beam splitter and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$22.5^{\circ }$</tex-math></inline-formula> Faraday rotator will be presented. The developed sensor employs a compact and pigtailed component realized by joining a polarizing beam splitter and a Faraday rotator, it does not require any external adjustment to work and shows very high immunity to external electromagnetic and mechanical interference. The experimental results prove good sensitivity of the sensor allowing for the measurement of small value of current down to 100 mA.

FARKLI AÇIKLIK ŞEKİLLERİNE SAHİP EKRANLAMA KUTULARI İÇİN GRAFEN PLAKA KAPLAMANIN EKRANLAMA ETKİNLİĞİNE ETKİSİNİN ANALİZİ

Electromagnetic compatibility (EMC) has become much more important especially over the last decade due to incorporating advanced driver assistance and electric propulsion systems into conventional vehicle architecture. Electromagnetic shielding is a conductive barrier used for protecting electronic circuits against external electromagnetic interference (EMI). Shielding effectiveness (SE) is a measure of shielding performance against an interfering electromagnetic source. Design limitations inside electric vehicles (EV) forces to investigate on increasing SE without changing the shielding enclosure dimensions. Graphene is widely used in many studies due to its good conductivity and strong structure. In this study, a numerical model for a shielding enclosure in which inner surfaces are coated with graphene sheets, is designed. The effect of different aperture shapes on SE is analyzed according to coating different inner surfaces of the enclosure with graphene sheets.

Anti-Electromagnetic Interference Design of Rail Transit Vehicles Based on the Magnetic Induction and Magnetoelectric Characteristics of Ferroelectric Ceramics

The various properties of ferroelectric ceramics bring extremely rich colors to life. Its various properties such as dielectric properties, electromagnetic properties, and anti-magnetic interference properties have been successively studied in various fields, except for stone carvings, outdoor environmental sculptures, ornamental ceramics, etc. Because of its superior performance, it can also be used in aircraft manufacturing, anti-interference materials for train tracks, and can even realize unmanned driving, workshop networks and other environments, which can meet the normal operation of electronic equipment in the car under the state of preventing external electromagnetic interference. This requires the superior electromagnetic properties of ferroelectric ceramics. Dielectric properties, dielectric relaxation, and ferromagnetic effects all need to be optimized. This article first introduces the performance test methods of ferroelectric ceramics, and describes the dielectric relaxation through Debye equation He phenomenon, test dielectric loss and dipole interaction, magnetic coupling effect and multiferrocity, and carry out electromagnetic coexistence, based on MATLAB/Simulink rail vehicle dynamics model, composed of sensors, control center and bogie, forming a coupling The functioning anti-roll structure makes the magnetic potential energy evenly distributed in the track span, forming a single suspended electromagnet modular transportation train dynamic model, which can carry the load force of the air and the gravity of the module itself. The traditional solid-phase method is used to dope at the A site. As the doped sample gradually increases, the peak value of the derivative peak changes, causing the original diamagnetic sample to carry a certain degree of ferromagnetism, and the doping amount and ferromagnetism are positively correlated. Then, experiments were performed on the composite ferroelectric ceramic materials doped with ion pairs, and the tests were carried out at different temperatures and different doping amounts. The conclusions about the coupling of dielectric constant, dielectric loss, magnetic properties and magneto electric properties were obtained and obtained the anti-magnetic interference ability. The application in the anti-magnetic interference of rail trains has a certain guiding effect. The results show that when the doping amount reaches m = 0.02, the dielectric loss is reduced by 22.58 times. The impedance change rate of the ferroelectric ceramic material with no doped Al3 +-Li + ion pair under 9 kOe is 3.95%, while at m = 0.015 Al3+ With -Li + doping, the impedance change rate of ferroelectric ceramics is 14.45%, which is 3.17 times the original.

Research on Navigation Path Extraction and Obstacle Avoidance Strategy for Pusher Robot in Dairy Farm

Existing push robots mainly use magnetic induction technology. These devices are susceptible to external electromagnetic interference and have a low degree of intelligence. To make up for the insufficiency of the existing material pushing robots, and at the same time solve the problems of labor-intensive, labor-intensive, and inability to push material in time at night, etc., in this study, an autonomous navigation pusher robot based on 3D lidar is designed, and an obstacle avoidance strategy based on the improved artificial potential field method is proposed. Firstly, the 3D point cloud data of the barn is collected by the self-designed pushing robot, the point cloud data of the area of interest is extracted using a direct-pass filtering algorithm, and the 3D point cloud of the barn is segmented using a height threshold. Secondly, the Least-Squares Method (LSM) and Random Sample Consensus (RANSAC) were used to extract fence lines, and then the boundary contour features were extracted by projection onto the ground. Finally, a target influence factor is added to the repulsive potential field function to determine the principle of optimal selection of the parameters of the improved artificial potential field method and the repulsive direction, and to clarify the optimal obstacle avoidance strategy for the pusher robot. It can verify the obstacle avoidance effect of the improved algorithm. The experimental results showed that under three different environments: no noise, Gaussian noise, and artificial noise, the fence lines were extracted using RANSAC. Taking the change in the slope as an indicator, the obtained results were about −0.058, 0.058, and −0.061, respectively. The slope obtained by the RANSAC method has less variation compared to the no-noise group. Compared with LSM, the extraction results did not change significantly, indicating that RANSAC has a certain resistance to various noises, but RANSAC performs better in extraction effect and real-time performance. The simulation and actual test results show that the improved artificial potential field method can select reasonable parameters and repulsive force directions. The optimized path increases the shortest distance of the obstacle point cloud from the navigation path from 0.18 to 0.41 m, where the average time is 0.059 s, and the standard deviation is 0.007 s. This shows that the optimization method can optimize the path in real time to avoid obstacles, basically meet the requirements of security and real-time performance, and effectively avoid the local minimum problem. This research will provide corresponding technical references for pusher robots to overcome the problems existing in the process of autonomous navigation and pushing operation in complex open scenarios.

Ultra-Broadband Strong Electromagnetic Interference Shielding with Ferromagnetic Graphene Quartz Fabric.

Flexible electromagnetic interference (EMI) shielding materials with ultrahigh shielding effectiveness (SE) are highly desirable for high-speed electronic devices to attenuate radiated emissions. For hindering interference of their internal or external EMI fields, however, a metallic enclosure suffers from relatively low SE, band-limited anti-EMI responses, poor corrosion resistance, and non-adaptability to the complex geometry of a given circuit. Here, a broadband, strong EMI shielding response fabric is demonstrated based on a highly structured ferromagnetic graphene quartz fiber (FGQF) via a modulation-doped chemical vapor deposition (CVD) growth process. The precise control of the graphitic N-doping configuration endows graphene coatings on specifically designable quartz fabric weave with both high conductivity (3906 Scm-1 ) and high magnetic responsiveness (a saturation magnetization of ≈0.14 emug-1 under 300 K), thus attaining synergistic effect of EMI shielding and electromagnetic wave (EMW) absorption for broadband anti-EMI technology. The large-scale durable FGQF exhibits extraordinary EMI SE of ≈107dB over a broadband frequency (1-18GHz), by configuring ≈20nm-thick graphene coatings on a millimeter-thick quartz fabric. This work enables the potential for development of an industrial-scale, flexible, lightweight, durable, and ultra-broadband strong shielding material in advanced applications of flexible anti-electronic reconnaissance, antiradiation, and stealthy technologies.

Analysis of the Impact of Substation Switching Operations on 5G Base Station Antenna Feeder Ports

With the rapid development of the construction and application of 5G communication networks in the power grid, more and more 5G base stations need to be built in substations. 5G base stations have antennas placed outside in a complex electromagnetic environment, and they also become sensitive ports that induce external electromagnetic interference while sending and receiving signals. Especially the Electrical Fast Transient/Burst generated during the switch operation in the substation through the cable connecting the antenna and the base station equipment, at the antenna feeder port, generates electromagnetic disturbance that poses a potential threat to the operation of the equipment. This paper proposes an analysis method of an electromagnetic disturbance at the antenna feeder port of a 5G base station under the condition of switching operation of a substation. A 500kV substation is used to calculate the impact size, and the minimum distance between the antenna of the 5G base station and the switch operation device is determined. When the distance between the cable and the ground is two meters, the cable disturbance voltage reaches the maximum.

Superheterodyne Microwave System for the Detection of Bioparticles With Coplanar Electrodes on a Microfluidic Platform

The combination of microwave and microfluidic technologies has the potential to enable wireless monitoring and interaction with bioparticles, facilitating in this way the exploration of a still largely uncharted territory at the intersection of biology, communication engineering and microscale physics. Opportunely, the scientific and technical requirements of microfluidics and microwave techniques converge to the need of system miniaturization to achieve the required sensitivity levels. This work, therefore, presents the design and optimization of a measurement system for the detection of bioparticles over the frequency range $0.01$ to $10$ $\mathrm{GHz}$, with different coplanar electrodes configurations on a microfluidic platform. The design of the measurement signal-chain setup is optimized for a novel real-time superheterodyne microwave detection system. In particular, signal integrity is achieved by means of a microwave-shielded chamber, which is protected from external electromagnetic interference that may potentially impact the coplanar electrodes mounted on the microfluidic device. Additionally, analytical expressions and experimental validation of the system-level performance are provided and discussed for the different designs of the coplanar electrodes. This technique is applied to measure the electrical field perturbation produced by $10$ $\mathrm{\mu m}$ polystyrene beads with a concentration of $10^5$ $\mathrm{beads/mL}$, and flowing at a rate of $10$ $\mathrm{\mu L/m}$. The achieved SNR is in the order of $40$ $\mathrm{dB}$ for the three coplanar electrodes considered.