Anti-electromagnetic Interference Research Articles

All-optical photoacoustic detection of SF6 decomposition component SO2 based on fiber-coupled UV-LED

An all-optical photoacoustic sensor for measuring the concentration of SF6 decomposition derivative SO2 was designed, whose detection limit was in the order of ppb-level. An UV-fiber and a single-mode fiber were utilized to transmit excitation light and probe light, respectively. The technical scheme of all-optical gas sensing has realized the competitive advantages of long-distance detection and anti-electromagnetic interference. As an UV-LED was the excitation light, the challenge of designing all-optical SO2 sensor was to effectively couple UV-LED with large divergence angle into an UV- fiber. Theoretical calculation and experiment have proved that the lens assembly as an effective strategy to realize the efficient coupling and beam collimation, which can achieve high excitation power and low solid photoacoustic background interference. The lens assembly with high focusing property was the key to improve the signal-to-noise ratio (SNR) by 5.2 times. To detect photoacoustic pressure with high sensitivity, a fiber optic cantilever acoustic sensor based on F-P interference was designed. Based on the demodulation algorithm of white light interference, dynamic cavity length of F-P was demodulated with high-resolution. Allan-Werle analysis result indicate that the detection limit of SO2 gas was 48 ppb with an averaging time of 100 s

Functional near-infrared spectroscopy in non-invasive neuromodulation.

Non-invasive cerebral neuromodulation technologies are essential for the reorganization of cerebral neural networks, which have been widely applied in the field of central neurological diseases, such as stroke, Parkinson's disease, and mental disorders. Although significant advances have been made in neuromodulation technologies, the identification of optimal neurostimulation parameters including the cortical target, duration, and inhibition or excitation pattern is still limited due to the lack of guidance for neural circuits. Moreover, the neural mechanism underlying neuromodulation for improved behavioral performance remains poorly understood. Recently, advancements in neuroimaging have provided insight into neuromodulation techniques. Functional near-infrared spectroscopy, as a novel non-invasive optical brain imaging method, can detect brain activity by measuring cerebral hemodynamics with the advantages of portability, high motion tolerance, and anti-electromagnetic interference. Coupling functional near-infrared spectroscopy with neuromodulation technologies offers an opportunity to monitor the cortical response, provide real-time feedback, and establish a closed-loop strategy integrating evaluation, feedback, and intervention for neurostimulation, which provides a theoretical basis for development of individualized precise neurorehabilitation. We aimed to summarize the advantages of functional near-infrared spectroscopy and provide an overview of the current research on functional near-infrared spectroscopy in transcranial magnetic stimulation, transcranial electrical stimulation, neurofeedback, and brain-computer interfaces. Furthermore, the future perspectives and directions for the application of functional near-infrared spectroscopy in neuromodulation are summarized. In conclusion, functional near-infrared spectroscopy combined with neuromodulation may promote the optimization of central neural reorganization to achieve better functional recovery from central nervous system diseases.

UAV-assisted FSO communication system with amplify-and-forward protocol under AOA fluctuations: A performance analysis

Free space optical (FSO) communication has recently aroused great interest in academia due to its unique features, such as large transmission band, high data rates, and strong anti-electromagnetic interference. With the aim of evaluating the performance of an FSO communication system and extending the line-of-sight transmission distance, we propose an unmanned aerial vehicle (UAV)-assisted dual-hop FSO communication system equipped with amplify-and-forward protocol at the relay node. Specifically, we consider impairments of atmospheric absorption, pointing errors, atmospheric turbulence, and link interruptions due to angle-of-arrival fluctuations in the relay system. The Gamma-Gamma and Malaga distributions are used to model the influence of atmospheric turbulence on the source-to-UAV and UAV-to-destination links, respectively. We derive closed-form expressions of the probability density function (PDF) and cumulative distribution function (CDF) for the proposed communication system, in terms of the Meijer-G function. Based on the precise PDF and CDF, analytical expressions for the outage probability, average bit error rate, and ergodic capacity are proposed with the aid of the extended generalized bivariate Fox's H function. Finally, we show that there is a match between the analytical results and numerical results, and we analyze the influence of the system and channel parameters on the performance.

Fiber optic room temperature ethanol sensor based on ZnSnO3/TiO2 with UV radiation sensitization

A fiber optic ethanol gas sensor with ZnSnO3 hollow cube/nano-TiO2 composite coating based on ultraviolet (UV) radiation sensitization was proposed, which can realize high sensitivity, high selectivity, and fast ethanol gas sensing at room temperature. The probe adopted a simple single-mode fiber (SMF)-multi-mode fiber-SMF structure. The ZnSnO3/TiO2 gas-sensitive film was coated on the sensing area by dip-coating method. Experiment results show that the probe sensitized by UV radiation has a linear sensitivity of 3.85 pm/ppm for ethanol gas at 0–250 ppm, which is about 6.6 times more sensitive than the probe without UV radiation (0.582 pm/ppm). In addition, the probe with UV radiation has good time measurement stability, a fast response time (response time is about 20 s, recovery time is about 60 s), and excellent ethanol gas selectivity. This study proves that UV radiation is an effective method to increase the sensitivity of gas sensing. This is also the first application of ZnSnO3/TiO2 composite material in fiber optic sensors. Combined with the advantages of fiber optic sensing, it shows anti-electromagnetic interference, micro size, high sensitivity, high selectivity, fast response, and remote sensing.

Oscillator design for high efficiency DC-DC of micro direct methanol fuel cell

This paper develops a novel oscillator with wide output frequency range, continuous frequency adoption, anti-electromagnetic interference (EMI), and high precision in order to achieve the high energy conversion efficiency of DC-DC for micro direct methanol fuel cell (μDMFC). The oscillator employs the state of art including frequency jitter, slope compensation, and digital trimming to perform the load mode control and detection module, thus linearly adjusting the operating frequency and modulation according to the load. Based on the 0.18 μm microelectronics process, the transient output of the presented oscillator during continuously turning on exports a stable voltage square wave. The jitter frequency ranges only about −1.66% to +4.3% of the base frequency. Moreover, the oscillator can adjust the typical output frequency linearly from 100 kHz to 1 MHz continuously based on the light or heavy load state. The oscillator yields stable performance under EMI with the jittering rate ranges from −31.82% to 36.2%. The quantitative results validates the wide frequency range, continuous frequency adoption, anti-EMI, and high precision of the oscillator. The oscillator solves the low energy conversion efficiency of the μDMFC DC-DC. The oscillator will achieve high energy conversion efficiency and stable output voltage of μDMFC for practical application.

Superhydrophobic Flexible Strain Sensors Constructed Using Nanomaterials: Their Fabrications and Sustainable Applications.

Superhydrophobic flexible strain sensors, which combine superhydrophobic coatings with highly sensitive flexible sensors, significantly enhance sensor performance and expand applications in human motion monitoring. Superhydrophobic coatings provide water repellency, surface self-cleaning, anti-corrosion, and anti-fouling properties for the sensors. Additionally, they enhance equipment durability. At present, many studies on superhydrophobic flexible sensors are still in the early research stage; the wear resistance and stability of sensors are far from reaching the level of industrial application. This paper discusses fundamental theories such as the wetting mechanism, tunneling effect, and percolation theory of superhydrophobic flexible sensors. Additionally, it reviews commonly used construction materials and principles of these sensors. This paper discusses the common preparation methods for superhydrophobic flexible sensors and summarizes the advantages and disadvantages of each method to identify the most suitable approach. Additionally, this paper summarizes the wide-ranging applications of the superhydrophobic flexible sensor in medical health, human motion monitoring, anti-electromagnetic interference, and de-icing/anti-icing, offering insights into these fields.

Optical Fiber Sensor with Novel Structure and Its Applications in Oil and Gas Exploration

Compared to electronic sensors, Optical Fiber Sensors (OFSs) have received increasing attention due to their advantages, such as small size, light weight, anti-electromagnetic interference, easy reuse, and remote sensing. This paper proposes a novel all-fiber mode interferometer. This interferometer excites higher-order cladding modes through mode mismatch between standard single-mode fibers and thin cores. There is interference between higher-order cladding mode and core layer mode, resulting in interference fringes used as sensing signals. Sensitivity testing is conducted on the designed OFS to demonstrate whether it meets the application requirements for petroleum exploration. Transmission-type Thin-Core Fiber Modal Interferometers (TCFMIs) with different lengths of Thin-Core Fibers (TCFs) (20 mm, 40 mm, and 60 mm) are produced in the experiment. Among them, TCFMIs at 60 mm TCF length can obtain ideal sensing signals. The TCFMI (with a length of 20 mm TCF) is encapsulated in a self-made aluminum groove in rosin to test its Refractive Index (RI). The results show that as the RI increases, the central wavelength shifts towards the long wavelength direction. Its sensitivity reaches 146 nm/R.I.U. When the temperature is increased, the central wavelength shifts towards the long wavelength direction, resulting in lower temperature sensitivity. In the sensitivity test, the phase change obtained by designing OFSs is proportional to the vibration acceleration. It is fixed on the vibration table to keep the acceleration of the vibration table constant and adjust the vibration frequency of the vibration table. The results show that the vibration spectral line of the sensor is relatively flat within 100 Hz, and resonance occurs within the range of 200 Hz to 350 Hz. Through phase demodulation, sensors loaded with different oscillator masses increase linearly in the low-frequency range. When the vibration frequency approaches the resonance frequency of the sensor, the phase sensitivity of the sensor increases nonlinearly.

Transmissive fluorescent temperature sensor based on Er3+/Yb3+/Mo6+ tri-doped tellurite fiber for real-time thermal monitoring of motors using the FIR technique.

In this paper, we fabricate a transmissive fluorescent temperature sensor (TFTS) that based on Er3+/Yb3+/Mo6+ tri-doped tellurite fiber, which has the advantages of compactness and simplicity, corrosion resistance, high stability and anti-electromagnetic interference. The doping of Mo6+ ions will enhance the up-conversion (UC) fluorescence emission efficiency of Er3+ ions, thus improving the signal-to-noise ratio of TFTS. Using the fluorescence intensity ratio (FIR) technique, the real-time thermal monitoring performance of TFTS is evaluated experimentally. Apart from good stability, its maximum relative sensitivity is 0.01068 K-1 at 274 K in the measured temperature range. In addition, it is successfully used to monitor the temperature variation of the stator core and stator winding of the motor in actual operation. The results show that the maximum error between the FIR-demodulated temperature and the reference temperature is less than 1.2 K, which fully confirms the effectiveness of the TFTS for temperature monitoring. Finally, the FIR-based TFTS in this work is expected to provide a new solution for accurate and real-time thermal monitoring of motors and the like.

Enhanced Semi-active piezoelectric vibration control method with shunt circuit by energy dissipations switching

Piezoelectric vibration control holds the advantages of lightweight and anti-electromagnetic interference, and has broad application prospects in fields such as aerospace and mechanical engineering. A semi-active control method based on a piezoelectric smart cantilever beam with a passive shunt circuit is proposed for vibration control. The contribution is that the proposed semi-active control method is used to achieve energy dissipations switching by changing the piezoelectric electrical boundary conditions. The open-circuit state of piezoelectric materials corresponds to higher stiffness and dissipation of elastic potential energy, while the short-circuit state is accompanied by lower stiffness and dissipation of electrical energy. Firstly, the stiffness difference of different electrical boundary conditions of the piezoelectric materials is derived and its effect on the vibration characteristics is analyzed. Then, the proposed passive shunt circuit for the vibration control principle is analyzed, and the modeling of the piezoelectric smart cantilever beam with the passive shunt circuit is developed. Finally, a prototype is manufactured and the measurement system is constructed. The correctness and the feasibility of the semi-active vibration control method are verified by experiments, and the logarithmic damping coefficient is 0.8919. The superiority of the proposed shunt circuit is demonstrated experimentally with the comparison groups including depolarized comparison group and the common shunt circuits.

Electro-optical hybrid full-adder based on surface plasmon polaritons

Optical computing has advantages such as high speed and anti-electromagnetic interference, and the adder is the key component that composes optical computing units. This paper proposes an electro-optic hybrid full-adder based on surface plasmon polaritons, which combines the advantages of flexible circuit control, storability, high speed and electromagnetic interference immunity in optical computing. By using surface plasmon polariton technology, the limitation of optical diffraction is overcome, and the size of the full-adder is limited to 26.7 µm2, which improves the integration of more logical computing units on a single chip. By utilizing the MOS structure, the addition operation function of optical logic is controlled, thus reducing the junction capacitance area and improving the operation speed. The feasibility of the design scheme was verified through FDTD simulation experiments, and the correctness of the logic was achieved when the transmission rate exceeded 200 Gbit. This research provides a theoretical and practical reference for the electro-optical hybrid full addition operation of surface plasmon polaritons.

Characterization of Fiber-Optic Vector Magnetic Field Sensors Based on the Magneto-Strictive Effect.

Fiber-optic magnetic field sensors have garnered considerable attention in the field of marine monitoring due to their compact size, robust anti-electromagnetic interference capabilities, corrosion resistance, high sensitivity, ease of multiplexing and integration, and potential for large-scale sensing networks. To enable the detection of marine magnetic field vector information, we propose an optical fiber vector magnetic field sensor that integrates three single-axis sensors in an orthogonal configuration. Theoretical analysis and experimental verification are conducted to investigate its magnetic field and temperature sensing characteristics, and a sensitivity matrix is established to address the cross-sensitivity between the magnetic field and temperature; experimental tests were conducted to assess the vector response of the three-dimensional (3D) vector sensor across the three orthogonal axes; the obtained experimental results illustrate the commendable magnetic field vector response exhibited by the sensor in the orthogonal axes, enabling precise demodulation of vector magnetic field information. This sensor presents several advantages, including cost-effectiveness, easy integration, and reliability vectorially. Consequently, it holds immense potential for critical applications in marine magnetic field network detection.

A Compact Fabry–Pérot Acoustic Sensor Based on Silicon Optical Waveguide Bragg Gratings

No membranous optical sensors have excellent development prospects in aerospace and other industrial fields due to their small size and anti-electromagnetic interference. Here, we proposed a novel Fabry–Pérot (FP) cavity acoustic sensor based on silicon optical waveguide Bragg gratings. The FP cavity consists of two Bragg gratings written on the silicon-based optical waveguide and a miniature air groove. When the sound signal acts on the miniature air groove, the sound pressure changes the density of air molecules near the waveguide grating’s evanescent field, causing variation in the air’s refractive index. This results in a shift in the reflection spectrum of the FP cavity to detect the sound signal. The effects of the grating period, grating pitch quantity, and groove depth of the FP cavity on acoustic sensing were studied. The modelling predicts that the sensing sensitivity could be 0.4 nm/Pa. Theoretically, the compact self-designed acoustic sensor can withstand temperatures above 800 °C. Therefore, it has significant potential applications in precision measurement in high-temperature and high-pressure environments.

Sagnac Magnetic Field Sensor Based on Sinusoidal Modulation and Empirical Mode Decomposition

A direct current (DC) Sagnac magnetic field sensor is a kind of fiber sensor based on alternate current magnetic field (ACMF) demodulation and empirical mode decomposition (EMD) to detect the magnetic field by measuring the phase variety caused by direct current magnetic field (DCMF). Commonly, Sagnac DCMF sensors can improve the magnetic detection sensitivity by using high Verdet constant (HVC) medium, which is expensive to prepare, or optical resonant cavity. However, the polarization diffraction in cavity restricts the performance of these devices. Meanwhile, none of them can suppress the electrical noise of the system such as 1/f noise. In this paper, we use ACMF modulation to couple the phase containing the DCMF information into the amplitude of the fundamental frequency component of the interference signal. Then we demodulate the signal by EMD to extract the fundamental frequency component. The designed sensor demonstrates a sensitivity of 4.651 mV/μT with an accuracy of 1.649 nT in the magnetic field range of 0-40 mT. It has the advantages of high stability, anti-electromagnetic interference and miniaturization.

Graphene/Polyaniline Film Optical Fiber Ammonia Gas Sensor With Excellent Sensing Performance

The possibility to improve the detection index of the optical ammonia gas sensors on the basis of the graphene/polyaniline (graphene/PANI) coated Mach–Zehnder interferometric optical fiber structure with etched thinned core fiber(e-TCF) is investigated. Based on the analysis of the output wavelength, a significant increase in sensitivity and stability of the ammonia sensors is achieved by using TCF. Experimental results show that its sensitivity is -27.8 pm/ppm, the response time is 32 s, dip wavelength error is lower than ±0.02 nm, and the dip intensity error is lower than ±0.002 dB in the stability test. This research illustrates that the proposed sensor has numerous advantages, including small size, strong anti-electromagnetic interference, and excellent repeatability characteristics. Furthermore, it can be applied in biomedical detection applications as it can improve the detection resolution of ammonia concentration at room temperature.

Acoustic microfiber sensor for gas pipeline leakage detection

Gas pipeline leakage can have significant environmental and industrial consequences, making it crucial to safely and efficiently detect such leaks. This study introduces a novel microfiber sensor based on the Mach-Zehnder structure, designed specifically for detecting small gas pipeline leaks. Initially, simulations were conducted to analyze the electric field distribution of the microfiber and the changes in sound pressure caused by pipeline leakage. Subsequently, the sensor was developed by encasing the microfiber in a double layer of polydimethylsiloxane (PDMS) and utilizing a nut with a hole as an external fixation device. To ensure accurate measurement of low-frequency acoustic pressure changes, the sensor's installation structure was integrated into the pipeline branch pipe. Experimental results demonstrate sensor's capability to detect acoustic signals generated by small leakage apertures measuring 0.1 mm in diameter. The received voltage signal exhibited a strong linear relationship with the size of the leakage aperture within the range of 0.1-6 mm, with a correlation coefficient exceeding 0.97. In addition, the sensor has reliable electrical safety and anti-electromagnetic interference capability.

Development of an FPGA-Based Robotic Anti-Electromagnetic Interference Unsorted Bin-Picking System

In response to the problem of robots needing to perform bin-picking in many industries, a small robot system was developed with a workpiece-position-detection system based on Field-Programmable Gate Array (FPGA) technology. The system integrated object detection and feature matching techniques, bolstered by optimization methods, to enhance its functionality on the FPGA platform. Furthermore, a two-wire control bus was designed specifically for reliable operation in environments characterized by strong interference, drawing inspiration from the Controller Area Network (CAN) bus. The experimental results demonstrated that the system’s performance was comparable to that of the point-cloud-algorithm-based bin-picking system, while also exhibiting greater stability. Notably, the cost of the controller was significantly reduced, and the embedded hardware and software design ensured stability and adaptability for deployment in demanding settings, such as small-scale heavy industry factories.

Nanoengineering Natural Leather for Dynamic Thermal Management and Electromagnetic Interference Shielding.

Unpredictable and extreme weather conditions, along with increasing electromagnetic pollution, have resulted in a significant threat to human health and productivity, causing irreversible damage to society's well-being and economy. However, existing personal temperature management and electromagnetic protection materials lack adaptability to dynamic environmental changes. To address this, a unique asymmetric bilayer leather/a-MWCNTs/CA fabric isdeveloped by vacuum-infiltrating interconnected a-MWCNTs networks into natural leather's microfiber backbone and spraying porous acetic acid (CA) on the reverse side. Such fabric achieves simultaneous passive radiation cooling, heating, and anti-electromagnetic interference functions without external energy input. The fabric's cooling layer has high solar reflectance (92.0%) and high infrared emissivity (90.2%), providing an average subambient radiation cooling effect of 10 °C, while the heating layer has high solar absorption (98.0%), enabling excellent passive radiative heating and effective compensation for warming via Joule heating. Additionally, the fabric's 3D conductive a-MWCNTs network provides electromagnetic interference shielding effectiveness of 35.0dB mainly through electromagnetic wave absorption. This multimode electromagnetic shielding fabric can switch between cooling and heating modes to adapt to dynamic cooling and heating scenarios, providing a new avenue for sustainable temperature management and electromagnetic protection applications.

Wearable Optical Fiber Sensors for Biomechanical Measurement in Medical Rehabilitation: A Review

With the increasing demand for rehabilitation of the elderly population and patients with limb injuries, it is imperative to develop new wearable health monitoring system and assistive rehabilitation equipment. Optical fiber sensing has the advantages of light-weight, anti-electromagnetic interference, higher strain and elastic limit, safety and dependableness. It has been significantly utilized in engineering prospecting, building structure monitoring, and medical and health fields. At present, the application of optical fiber sensing in medical rehabilitation has been developed rapidly, however, the discussion and summary of its key theories and technologies are insufficient. This review details different types of optical fiber sensing mechanisms and devices, as well as the measurement of physical parameters using optical fiber sensors and application examples in the field of medical rehabilitation. This review systematically analyzes the advance of the sensitivity, flexibility, accuracy, and wearability of the optical fiber sensing in the monitoring of human body sign information. This review also discusses the challenges of making a new generation of optical fiber sensors that fit human joints, muscles, and rehabilitation equipment. Finally, this review provides a research direction for the realization of flexible, comfortable, safe, stable monitoring of human biomechanical parameters and real-time precise control of rehabilitation equipment in the future.

Cuttlefish‐Inspired Self‐Adaptive Liquid Metal Network Enabling Electromagnetic Interference Shielding and Thermal Management

AbstractWith the refinement and miniaturization of integrated electronic devices, the requirements for stable operating temperature and antielectromagnetic interference are increasingly high. However, most of the current materials necessitate to develop the intelligent self‐adaptive regulation in response to external field stimuli to gratify the stipulations of different operating environments. Herein, cuttlefish‐inspired smart liquid metal based‐liquid crystal elastomer (LGN‐LCE) dual‐functional material enabling self‐adaptive electromagnetic wave interference shielding and thermal management is presented. Liquid crystal elastomer matrix endows the LGN‐LCE dynamic self‐morphing properties under thermal activation, which leads to the liquid metal network with tunable thermal/electrical conduction. The thermal conductivity of LGN‐LCE can be increased to 10.3 W m−1 K−1 with the rise of surrounding temperature, while the electrical conductivity of LGN‐LCE can be enhanced to 4.3 × 105 S m−1. Such promoted electrical conductivity helps strengthen electromagnetic interference (EMI) shielding performance of LGN‐LCE, and the minimum EMI shielding effectiveness of LGN‐LCE can be improved from 48 to 62 dB within the X‐band. This work may not only pave a new way to rationally design a self‐adaptive EMI shielding and thermal management systems, but also show good prospects for practical applications, including thermal management materials, EMI materials, flexible electronic materials, smart materials, artificial intelligence systems, biomedical, and aerospace applications.

Structure shape measurement method based on an optical fiber shape sensor

In industry and architecture, real-time and complete measurement of structures has become a research frontier since it is directly related to the safety of life and property. Optical fibers have the potential to monitor constructions due to advantages such as small size, anti-electromagnetic interference, etc. However, existing research on optical fiber sensors pays attention to the sensing fiber itself and ignores the layout of the optical fibers. As a result, currently available fiber sensors are only suitable for monitoring one-dimensional rigid structures such as surgical robots and puncture needles. They may face challenges when measuring the freeform surfaces encountered in industrial and architectural scenarios. In this paper, a cross-orthogonal measurement method based on optical fiber shape sensors is proposed to meet the shape measurement requirements of freeform surfaces. The cross-orthogonal network allows global measurement and performs surface reconstructions more easily as compared to single-fiber arrays. It also divides the sensing fiber into several segments that are reconstructed separately (with different initial frames), avoiding the cumulative error at the end of the sensing fiber. Results of verification experiments using four-core fibers indicate that the presented method can improve measurement accuracy.