Severe Electromagnetic Interference Research Articles

Influence of electronic apex locators and a gutta-percha heating device on implanted cardiac devices: an invivo study.

To evaluate the potential for electromagnetic interference (EMI) of electronic apex locators (EALs) and a gutta-percha heating device (HD) in patients with implantable cardiac pacemakers (ICPs) or cardioverter-defibrillators (ICDs). Two types of EALs (Romiapex A-15 and Novapex) and a HD (Touch'n Heat) were tested in patients followed in an outpatient clinic for cardiac arrhythmias. The heart rhythm was monitored on a computer screen during all experimental phases. After baseline data collection, the patient held each appliance (turned on) for 30s, simulating their clinical use. If background noise was detected on the cardiac monitor, the sensitivity of the ICP/ICD was lowered by the cardiologist to evaluate the intensity of the detected EMI. Twelve patients were evaluated (5 female and 7 male), and in nine instances, background noise in their cardiac devices related to the use of the endodontic devices was detected (6 patients). After lowering the sensitivity of the cardiac implants, three patients had more severe EMI in six instances, including pauses in ICP function. The presence of a symptomatic or asymptomatic pause was related to the patient's underlying heart rhythm. The HD device produced background noise more often compared to EALs. These were associated with more severe types of EMI. The EALs and gutta-percha HD were capable of causing background noise detection or pauses in cardiac implants invivo. The use of electronic dental devices nearby patients with cardiac implants should be carefully considered in clinical practice.

Investigation on electromagnetic environment of radio-over-fiber-based broadband wireless access scheme in aircraft cabin

Broadband wireless access services inside aircraft cabin are highly desired, but they may bring severe electromagnetic interference (EMI) threats to the avionic system and the flight safety. A radio-over-fiber (ROF)-based distributed scheme is proposed to provide onboard wireless access services. Due to the low emission power of the ROF-based distributed antennas and the electromagnetic radiation-free fiber links, the proposed scheme can effectively reduce the EMI threats from the in-flight wireless access. To evaluate the electromagnetic environment of the ROF-based distributed access scheme, the coupling electric field inside the cabin is calculated by using EMPIRE-XCcel (electromagnetic simulation software). Taking the aircraft-Advanced Regional Jet for the twenty-first century (ARJ21) for example, the results show that inside the cabin, a reduction of 4–8 dB in the coupling electric field strength is achieved using the ROF-based access scheme, compared with that in conventional centralized system. Meanwhile, a higher energy efficiency is ensured as well. Likewise, lower coupling electric field strength can also be provided for other large-size aircrafts of Airbus and Boeing, by using the ROF-based distributed scheme.

Compatibility of electroanatomical mapping systems with a concurrent percutaneous axial flow ventricular assist device.

Hemodynamic instability hinders activation and entrainment mapping during ventricular tachycardia ablation. The Impella 2.5 microaxial flow device (MFD; Abiomed Inc., Danvers, MA, USA) is used to prevent hemodynamic instability during electrophysiologic study. However, electromagnetic interference (EMI) generated by this device can preclude accurate electroanatomic mapping. Impella was placed in the left ventricle of 7 canines for circulatory support. Electroanatomic mapping during sinus rhythm, ventricular pacing, and ventricular fibrillation (VF) was performed using magnet- (CARTO3, Biosense Webster Inc., Diamond Bar, CA, USA) and impedance- (EnSite Velocity System/EnSite NavX, St. Jude Medical Inc., St. Paul, MN, USA) based systems. Distance from device to points with severe EMI precluding acquisition was compared to points with mild/no EMI. Two methods were used to reduce EMI: (1) titration of MFD performance, and (2) impedance-only mapping combined with manual annotation of activation. Severe EMI did not occur during impedance-based mapping. Severe EMI was observed using CARTO3 at 9.4% of all points attempted at maximum performance level (P8) of device. Severe EMI occurred at points closer to device (40.1 ± 16.8 mm) versus (55.5 ± 20.0 mm) for mild/no EMI, P < 0.0001. Severe EMI using CARTO3 was resolved by either (1) reduction of performance from P8 to P6 or (2) impedance-only mapping with manual annotation. Concurrent use of MFD caused EMI to prevent acquisition of points with magnet-based mapping. Predictors for EMI were distance from device and performance level. Temporary reductions to P6 or impedance-only mapping are 2 methods to resolve EMI.

Optical study of a diffuse bipolar nanosecond pulsed dielectric barrier discharge with different dielectric thicknesses in air

In this paper, a bipolar nanosecond high-voltage pulse power supply with about 20 ns rising time is employed to generate a diffuse dielectric barrier discharge using dielectric plates of different thicknesses. Dielectric thickness, which is regarded as an important discharge parameter, can improve diffuse discharge characteristics. Both the images of the diffuse dielectric barrier discharge and the optical emission spectra with different dielectric thicknesses are recorded successfully under severe electromagnetic interference. The effects of the discharge gap distance, pulse peak voltage, and pulse repetition rate on the emission intensity of N2 (C3Πu → B3Πg) of nanosecond pulsed dielectric barrier discharge with different dielectric thicknesses were investigated. It was found that increasing dielectric thickness is not conducive to acquiring a larger area of diffuse discharge. Also, the intensity of discharge decays and the discharge volume constricts in a horizontal direction with increasing dielectric thickness. The experimental result also shows that the emission intensity of N2 (C3Πu → B3Πg) decreases with the increase of the dielectric thickness and the discharge gap distance, but rises with both increasing both pulse peak voltage and pulse repetition rate.

A homogeneous dielectric barrier discharge plasma excited by a bipolar nanosecond pulse in nitrogen and air

In this paper, a nanosecond bipolar pulse voltage with 20 ns rise time is employed to generate a low gas temperature homogeneous dielectric barrier discharge plasma both in nitrogen and air at atmospheric pressure. Images of the discharge, waveforms of pulse voltage and discharge current, and the optical emission spectra emitted from the discharge are recorded successfully under severe electromagnetic interference. The effects of pulse peak voltage, pulse repetition rate and the gap distance between electrodes on gas temperature and the emission intensities of NO (A 2Σ → X 2Π), OH (A 2Σ → X 2Π) and N2 are discussed. It is found that the emission intensities of NO (A 2Σ → X 2Π), OH (A 2Σ → X 2Π) and N2 rise with increasing both pulse peak voltage and pulse repetition rate but decrease with gap distance between the electrodes when it is above 2.5 mm. The effect of concentrations of O2 on the emission intensities of NO (A 2Σ → X 2Π), OH (A 2Σ → X 2Π) and N2 is also investigated, and it is found that the emission intensities of both NO (A 2Σ → X 2Π) and OH (A 2Σ → X 2Π) reach maximum values when the O2 concentration is 0.3%.

Experimental research of diffuse bi-directional pulsed dielectric barrier discharge plasma

A bi-directional nanosecond pulsed power supply is employed to generate diffuse dielectric barrier discharge in N2 using needle-plate electrode configuration at atmospheric pressure. Both discharge images and optical emission spectra of diffuse bi-directional nanosecond high-voltage pulsed dielectric barrier discharge are successfully recorded under severe electromagnetic interference. The diffuse performance of the discharge at different electrode gap distances is observed. The effects of pulse peak voltage, pulse repetition rate, electrode gap distance, He addition, and O2 addition on the optical emission spectra are investigated. The main physicochemical processes involved are discussed.

Method for acquiring pressure measurements in presence of plasma-induced interference for supersonic flow control applications

The operation of pulsed-plasma actuators for flow control is often associated with the presence of charged species in the flow and severe electromagnetic interference with external circuitry. These effects can lead to time-resolved transducer pressure measurements that are contaminated with electromagnetic interference effects or even transducer damage due to the interaction with charged species. A new technique is developed that enables high-bandwidth pressure measurements to be made in the presence of such rapidly switched plasma actuators. The technique is applied for the specific configuration of a pulsed-plasma jet actuator (spark jet) that is used to control the unsteadiness of a shock wave/boundary layer interaction generated by a compression ramp in a Mach 3 flow. The critical component of the technique involves using a pulsed-ground electrode to drain the charged species from the plasma jet before they reach the pressure transducer. The pulsed-ground electrode was shown to drain charged species into the pulsed ground prior to interacting with the transducer, which made it possible to make measurements without damaging the transducer. The resulting signals were still contaminated by electromagnetic interference spikes and so a data-processing technique was used to remove the artifacts and recover a largely uncontaminated power spectrum. The signal processing scheme used interpolation schemes previously developed for laser Doppler velocimetry applications. The data-processing procedure is demonstrated with a benchmark case in which the electromagnetic interference was isolated from the pulsed-plasma jet actuation effect. It is shown that the data-processing procedure removed the contamination from the electromagnetic interference at all frequencies but for the pulsing frequency and its higher harmonics.

Optical study of diffuse bi-directional nanosecond pulsed dielectric barrier discharge in nitrogen

In this study, a bi-directional high voltage pulse with 20 ns rising time is employed to generate diffuse glow-like dielectric barrier discharge plasma with very low gas temperature in N 2 using needle-plate electrode configuration at atmospheric pressure. Both the diffuse nanosecond pulsed dielectric barrier discharge images and the optical emission spectra of the discharge are recorded successfully under severe electromagnetic interference. The effects of pulse peak voltage, pulse repetition rate, and the concentrations of Ar and O 2 on the emission intensities of NO (A 2Σ → X 2Π), OH (A 2Σ → X 2Π, 0-0), N 2 (C 3Π u → B 3Π g, 0-0, 337.1 nm), and N 2 + (B 2Σ u + → X 2Σ g +, 0-0, 391.4 nm) are investigated. The effects of the concentrations of Ar and O 2 on the discharge diffuse performance are also studied. It is found that the emission intensities of NO (A 2Σ → X 2Π), OH (A 2Σ → X 2Π, 0-0), N 2 (C 3Π u → B 3Π g, 0-0, 337.1 nm), and N 2 + (B 2Σ u + → X 2Σ g +, 0-0, 391.4 nm) rise with increasing pulse peak voltage, pulse repetition rate, and the concentration of Ar, but decrease with increasing the concentration of O 2. The main physicochemical processes involved are also discussed.

An investigation of flying capacitor converter for circuit integration

AbstractOutput power density of power converters has been increased. In power converters with lower harmonic distortion and lower electromagnetic interference (EMI) which are required in many applications, bulky harmonic and EMI filters are usually connected. The volume of the harmonic filters can be reduced by increasing the switching frequency. However, higher switching frequency will cause larger switching loss and severe EMI. As another approach, there is possibility of intrinsic elimination of harmonics and EMI by introducing multilevel converters. However, as the number of levels increases, the number of circuit components will exceed the practical limit of the implementation. Thus, from a practical viewpoint, the main circuit and related circuits should be integrated. However, it has not been clarified which multilevel topology is suitable for circuit integration. In addition, the effectiveness in reducing total device loss considering chip size has not been evaluated. In this paper, the advantage of a flying capacitor multilevel topology for circuit integration is clarified by theoretical and experimental investigations. Also, the total device loss and chip size of the flying capacitor converter are estimated. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

A diffusive air plasma in bi-directional nanosecond pulsed dielectric barrier discharge

In this study, a diffuse dielectric barrier discharge in air is generated by a bi-directional nanosecond pulsed power supply using a needle–plate electrode configuration at atmospheric pressure. Time-resolved spectra of N2(C 3Πu → B 3Πg, 0–0, 337.1 nm) for both positive and negative pulse discharges are recorded under severe electromagnetic interference. It is found that the lagged time of the photocurrent pulse compared with the voltage pulse in the negative pulse discharge is about 50 times longer than that in the positive pulse discharge at 16 kV pulse peak voltage and becomes shorter with an increase in pulse peak voltage. In addition, the gas temperature of the air plasma is determined to be approximately 395 K by measuring the optical emission spectra of the first negative band of , 0–0, 391.4 nm).

EMI Reduction by Spread-Spectrum Clocking in Digitally-Controlled DC-DC Converters

SUMMARY This paper proposes spread-spectrum clock modulationalgorithms for EMI reduction in digitally-controlled DC-DC converters.In switching regulators using PWM, switching noise and harmonic noiseconcentrated in a narrow spectrum around the switching frequency cancause severe EMI. Spread-spectrum clock modulation can be used to min-imize EMI. In conventional switching regulators using analog control it isvery difficult to realize complex spread-spectrum clocking, however thispaper shows that it is relatively easy to implement spread-spectrum EMI-reduction using digital control. The proposed algorithm was verified usinga power converter simulator (SCAT). key words: PWM control, spread-spectrum clock modulation, EMI,digitally-controlled DC-DC converter 1. Introduction Most portable electronic devices have low-voltage high-current power supplies using high-efficiency switching reg-ulators. However, the considerable switching noise (andEMI) that switching regulators produce is a big demerit.EMI-related regulations are becoming more severe [1]. Reg-ulations prescribe limits on the generation of Electromag-netic Interference (EMI) and also noise-tolerance or Elec-tromagnetic Susceptibility (EMS) requirements; the combi-nation of both EMI and EMS is called EMC (Electromag-netic Compatibility). In many countries it is illegal to sellelectrical and electronic devices that do not comply with lo-cal EMC standards (in many cases devices must be type-approved, or tested and certified as complying). In mostconventional switching regulators, shielding and filteringare used to reduce EMI. While shielding and filtering areeffective ways of reducing noise, penalties associated withthis approach include the cost of transformers and coils andthe size/weight of shielding.We considered, as an alternative to extensive shield-ing and filtering, how to reduce EMI by switching regu-lator control-module design changes. After examining thepossible application of digital control systems with spread-spectrum technology [2]–[5] to analog-controlled switching

Measurement and Modeling of the Magnetic Near Field Radiated by a Buck Chopper

Static converters are used with increasingly high switching frequencies. Consequently, they impose increasingly severe electromagnetic interference(EMI) constraints in their environment. In order to study and to quantify the radiated perturbations, we have used a test bench for measuring the magnetic field radiated in the near zone. In this paper, we present measurements of the magnetic field radiated by the switching cell of a Buck chopper in the near field at high and low frequencies. By comparing the mappings of the magnetic field over the switching cell with the ones of a circular loop, we have deduced that the switching cell can be effectively modeled by a loop. The loop's geometric characteristics and its equivalent current flowing in have been determined from near magnetic field data. The model has been validated at high and low frequencies.

Investigation of spatially resolved spectra of OH and N 2+ in N 2 and H 2O mixture wire-plate positive pulsed streamer discharge

Optical emission spectroscopy has been applied to study the spatially resolved measurements of the emission intensities of OH (A 2Σ → X 2Π, 0–0) and N 2 + (B 2Σ u + → X 2Σ g +, 0–0, 391.4 nm) produced by a high-voltage positive pulsed streamer discharge consisting of a gas mixture of N 2 and H 2O in a wire-plate reactor under severe electromagnetic interference at atmospheric pressure. The effects of pulse peak voltage, pulse repetition rate, and the added O 2 flow rate on the spatial distributions of the emission intensity of OH (A 2Σ → X 2Π, 0–0) and N 2 + (B 2Σ u + → X 2Σ g +, 0–0, 391.4 nm) in the lengthwise direction (direction from wire to plate) are investigated. It has been found that the emission intensities of OH (A 2Σ → X 2Π, 0–0) and N 2 + (B 2Σ u + → X 2Σ g +, 0–0, 391.4 nm) rise with an increase in both pulse peak voltage and pulse repetition rate and decrease with an increase in oxygen flows added in an N 2 and H 2O gas mixture. The emission intensity of OH (A 2Σ → X 2Π, 0–0) decreases with increasing the distance from the wire electrode. The emission intensity of N 2 + (B 2Σ u + → X 2Σ g +, 0–0, 391.4 nm) is nearly constant at 0–4 mm from wire electrode, and sharply increases near the ground electrode. The vibrational temperature of N 2 (C) increases with increasing O 2 flows and keeps almost constant in the lengthwise direction under the present experimental conditions. The main physicochemical processes involved are also discussed in this paper.

Diagnosis of OH radical by optical emission spectroscopy in a wire-plate bi-directional pulsed corona discharge

The emission spectrum of the molecule OH (A 2Σ→X 2Π, 0–0) during a high-voltage, bi-directional pulsed corona discharge consisting of a gas mixture of N 2 and H 2O in a wire-plate reactor has been successfully recorded under severe electromagnetic interference at atmospheric pressure. The relative vibrational populations and the vibrational temperature of N 2 (C, v′) have also been determined. Due to the difficulty of determining the exact overlapping spectral line shape function of the OH (A 2Σ→X 2Π, 0–0) and the Δ v=+1 vibrational transition band of N 2 (C 3Π u→B 3Π g), a practicable Gaussian form is used for calculating the emission intensity of OH (A 2Σ→X 2Π, 0-0) and the Δ v=+1 vibrational transition band of N 2 (C 3Π u→B 3Π g). The emission intensity of OH (A 2Σ→X 2Π, 0–0) has been evaluated with a satisfactory accuracy by subtracting the emission intensity of the Δ v=+1 vibrational transition band of N 2 (C 3Π u→B 3Π g) from the overlapping spectra. The relative population of OH (A 2Σ) has been obtained by the emission intensity of OH (A 2Σ→X 2Π, 0–0) and Einstein's transition probability. The influences of peak voltage, pulse repetition rate and O 2 flow rate on the relative population of OH (A 2Σ) radicals have also been investigated. We found that the relative population of OH (A 2Σ) rises with an increase in both the peak applied voltage and the pulse repetition rate. When oxygen is added to an N 2 and H 2O gas mixture, the relative population of OH (A 2Σ) radicals decreases exponentially with an increase in added oxygen. The main physicochemical processes involved are also discussed in this paper.

Optical study of OH radical in a wire-plate pulsed corona discharge

In this study, the emission spectra of OH (A 2Σ → X 2Π, 0–0) emitted from the high-voltage pulsed corona discharge (HVPCD) of N 2 and H 2O mixture gas and humid air in a wire-plate reactor were successfully recorded against a severe electromagnetic interference coming from HVPCD at one atmosphere. The relative vibrational populations and the vibrational temperature of N 2 (C, v′) were determined. The emission spectra of the Δ v = + 1 (1–0, 2–1, 3–2, 4–3) vibration transition band of N 2 (C 3Π u → B 3Π g) is simulated through gauss distribution. The emission intensity of OH (A 2Σ → X 2Π, 0–0) has been exactly gotten by subtracting the emission intensity of the Δ v = + 1 vibration transition band of N 2 (C 3Π u → B 3Π g) from the overlapping spectra. The relative population of OH (A 2Σ) has been obtained by the emission intensity of OH (A 2Σ → X 2Π, 0–0) and Einstein's transition probability. The influences of pulsed peak voltage and pulse repetition rate on the relative population of OH (A 2Σ) radicals in N 2 and H 2O mixture gas and humid air are investigated separately. It is found that the relative population of OH (A 2Σ) rises linearly with increasing the applied peak voltage and the pulse repetition rate. When the oxygen is added in N 2 and H 2O mixture gas, the relative population of OH (A 2Σ) radicals decreases exponentially with increasing the added oxygen. The main involved physicochemical processes have also been discussed.

The Study of Active Atoms in High-Voltage Pulsed Coronal Discharge by Optical Diagnostics

In this study, the emission spectra of active atoms O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3s4S0 742.3 nm, 744.2 nm, 746.8 nm) produced by the positive high-voltage pulsed corona discharge (HVPCD) of N2 and H2O mixture in a needle-plate reactor have successfully been recorded against a severe electromagnetic interference coming from the HVPCD at one atmosphere. The effects of the peak voltage, the repetition rate of pulsed discharge and the flow rate of oxygen on the production of those active atoms are investigated. It is found that when the peak voltage and the repetition rate of the pulsed discharge are increased, the emission intensities of those active atoms rise correspondingly. And the emission intensities of O (3p5P → 3s5S20 777.4 nm), Hα (3P → 2S 656.3 nm) and N (3p4P → 3s4S0 742.3 nm, 744.2 nm, 746.8 nm) increase with the flow rate of oxygen (from 0 to 25 ml/min) and achieve a maximum value at a flow rate of 25 ml/min. When the flow rate of oxygen is increased further, the emission intensities of those atoms visibly decrease correspondingly. The main physicochemical processes of interaction involved between electrons, neutrals and ions are also discussed.

Modal Analysis for a Bounded-Wave EMP Simulator—Part II: Radiation Leakage and Mode Suppression

Radiation leakage from a high-power bounded-wave electromagnetic pulse simulator can cause severe electromagnetic interference (EMI) with surrounding equipment. In Part I, we analyzed the electromagnetic mode structure inside a simulator. In Part II, we examine the relative contribution of these modes to radiation leakage. We have calculated the temporal cross correlation between the electromagnetic modes inside the simulator and the temporal waveform of the forward-radiated far field. The TM1 and TM2 modes show strong cross correlation over a range of switching times. For the TEM mode, on the other hand, this holds true only for larger values of the switching time. Hence, for a given mode amplitude, higher order TM modes tend to produce more leakage than the TEM mode. However, since TEM is far stronger than TM throughout the simulator, it may still contribute more in absolute terms. Increasing the angle between simulator plates excites more higher order modes and increases their strength, thereby enhancing leakage. Pulse compression with respect to time increases the relative strength of higher order modes. Placing a spatial mode filter inside the simulator significantly reduces TM/sub 1/ without modifying the desired TEM mode. However, TM/sub 2/ remains largely unchanged. The reduction in TM/sub 1/ depends sensitively upon the parameters of the filter. These observations illustrate a new method of understanding and improving simulator design from the point of view of EMI.

Study on density distribution of high-energy electrons in pulsed corona discharge

In this study, the radial profile of the overall emission intensity of the second positive system (C 3 Π u→B 3 Π g) emitted from the positive pulse corona discharge of N 2 and air in a line-cylinder reactor was successfully recorded against a severe electromagnetic pulse interference coming from the corona discharge at room temperature and 1 atm. The relation between the density distributions of the high-energy electron (whose energy is higher than 11.03 eV and enough to excite N 2 to its C 3 Π u state from the ground state) and the emission profiles is studied with the aid of a reaction radiation rate analysis method. By the relation, it is found that the radial distribution of the high-energy electron decreases nonlinearly with the radial distance from the reactor axis and increases directly with the discharge voltage for any sampling apertures. These experimental results would be helpful to establish the molecule reaction dynamics model of pulsed corona discharge deSO 2/deNO x and optimize the power supply and reactor.

Density distribution of high energy electrons in pulsed corona discharge of NO+N 2 mixture

Emission spectroscopy of the high-voltage pulsed positive corona discharge in a line-cylinder reactor is used to investigate the high-energy electron density distribution in the discharge gap. The relative overall emission intensity spatial distribution profile of the A 2Σ +→X 2Π transition of NO is successfully recorded against a severe electromagnetic pulse interference coming from the corona discharge at one atmosphere. The spectroscopic investigation shows that the high-energy electron density in the discharge has a nonlinearly decline in the radial distribution. When varying the discharge voltage, the absolute emission intensity of NO is different but the radial distribution profile is similar. If an oxygen flow was introduced into the discharge reactor, the emission intensity of NO decreases tremendously and, therefore, the high-energy electron density decreases reasonably.

A simple and effective method to alleviate the rectifier reverse-recovery problem in continuous-current-mode boost converters

Rectifier reverse-recovery problems cause a significant efficiency reduction as well as severe electromagnetic interference (EMI) in continuous-current-mode (CCM) boost converters. To alleviate these problems, this paper presents a simple and effective solution that involves shifting the original rectifier current to a new branch, which consists of a rectifier and a coupled winding of the boost inductor. When the active switch turns on, the current through the original boost rectifier is zero and the current decrease rate di/dt in the new branch is controlled by the leakage inductor. Based on the operation analysis, design issues to guarantee complete current shift are also addressed. Applying the proposed concept to a 500 W CCM DC/DC boost converter and a 500 W CCM power factor correction (PFC) boost converter with universal-line input generates a 2% efficiency improvement. The same concept can be easily extended to other basic DC/DC and CCM PFC converters.