Internal Electromagnetic Interference Research Articles

A Scalable Formal Framework for the Verification and Vulnerability Analysis of Redundancy-Based Error-Resilient Null Convention Logic Asynchronous Circuits

The increasing demand for high-speed, energy-efficient, and miniaturized electronics has led to significant challenges and compromises in the domain of conventional clock-based digital designs, most notably reduced circuit reliability, particularly in mission-critical hardware. At scaled technology nodes, devices are vulnerable to transient or soft errors, such as Single Event Upset (SEU) and Single Event Latch-up (SEL). External radiation, internal electromagnetic interference (EMI), or noise are the primary sources of these errors, which can compromise the circuit functionality. In response to these challenges, the Quasi-Delay-Insensitive (QDI) Null Convention Logic (NCL) asynchronous design paradigm has emerged as a promising alternative, offering advantages such as ultra-low power performance, reduced noise and EMI, and resilience to process, voltage, and temperature variations. Moreover, its unique architecture and insensitivity to timing variations offers a degree of resistance against transient errors; however, it is not entirely resilient. Several resiliency schemes are available to detect and mitigate soft errors in QDI circuits, with approaches based on redundancy proving to be the most effective in ensuring complete resilience across all major QDI implementation paradigms, including NCL, Pre-charge/Weak-charge Half Buffers (PCHB/WCHB), and Sleep Convention Logic (SCL). This research focuses on one such redundancy-based resiliency scheme for QDI NCL circuits, known as the dual-modular redundancy-based NCL (DMR-NCL) architecture, and addresses the absence of formal methods for the verification and analysis of such circuits. A novel methodology has been proposed for formally verifying the correctness of DMR-NCL circuits synthesized from their synchronous counterparts, covering both safety (functional correctness) and liveness (the absence of deadlock). In addition, this research introduces a formal framework for the vulnerability analysis of DMR-NCL circuits against SEU/SEL. To demonstrate the framework’s efficacy and scalability, a prototype computer-aided support tool has been developed, which verifies and analyzes multiple DMR-NCL benchmark circuits of varying sizes and complexities.

Electromagnetic Disturbed Mechanism of Electronic Current Transformer Acquisition Card under High Frequency Electromagnetic Interference

The electronic current transformer (ECT) acquisition card is widely used in smart grids with many advantages. However, with the continuous improvement of the power grid and localized intelligent electronic devices, the electromagnetic environment under the operating conditions of gas insulated switchgear (GIS) substations is becoming more complicated. The reliability and safety of the ECT acquisition card will be endangered due to the complicated electromagnetic environment. In order to solve these problems, this paper investigates the electromagnetic disturbed mechanism of the ECT acquisition card. The effects of different grounding methods on the electromagnetic interference of the ECT acquisition card were studied. A platform based on IEC 61000-4-4 was built, and the electromagnetic interference (EMI) of the ECT acquisition card with different grounding methods was measured. The results show that the lower grounding impedance of the ECT acquisition system increased the internal EMI. Further, the high frequency electrical fast transient/burst coupling mechanism was analyzed. The parasitic parameters of the acquisition card were extracted based on the critical circuit by using the finite element method. Then, the high-frequency EMI coupling model of the ECT acquisition card was established.

Low-drift and compact readout electronics for practical SQUID magnetocardiography working in unshielded environment

To promote the adaptability of the practical Magnetocardiography (MCG) system working in unshielded environment, the SQUID readout electronics is required to improve its stability and the Electromagnetic Compatibility (EMC). It should be low-drift to the variation of cryogenic liquid level in long-time running, avoid Electromagnetic Interference (EMI) internally from the control circuit, be electrical isolated from host computer, and finally be compact to be embedded in the cryostat to implement external EMI shielding and filtering. Accordingly, we presented a low-drift and compact readout circuit design. It applies the differential amplifier in the Flux-Locked Loop (FLL) to reject the voltage drift, and avoids the internal EMI by using control circuit without Micro-Controller Unit (MCU). It simplifies the integration of multi-channel FLLs and the isolated accessing from host computer by using the Inter-Integrated Circuit (IIC) bus with fiber optic interface. In the experimental results, our MCU-free FLLs successfully suppressed the voltage drift, and exhibited the high consistency in reading of 9-channel gradiometers with noise level of about 6.5μΦ0 /√Hz. Finally, we set up a 9-channel MCG system using our multi-channel SQUID readout electronics, and demonstrated the high quality 9-channel measurements of adult MCG signals in the unshielded environment.

ELECTROMAGNETIC COMPATIBILITY OF RES ON RAILWAY

This work reviews the main related problems of electromagnetic compatibility (EMC) of the locomotive radio system GSM-R in modern railway transport. The typical internal electromagnetic interference (EMI), caused by the high density of the equipment layout in the rolling stock, and external electromagnetic interference generated by public cellular mobile communication networks and other radio systems are considered. The results of experiments to determine the parameters of public cellular mobile communication networks along the selected railway section show a rather high level of signals that are EMI for GSM-R and affecting on EMC.

Shaping SiC MOSFET Voltage and Current Transitions by Intelligent Control for Reduced EMI Generation

In power converters, the fast switching of the power conversion components results in rapid changes in voltage and current, which results in oscillations and high-level electromagnetic interference (EMI), so the power components become a source of internal electromagnetic interference. Taking SiC Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) as an example, an intelligent control method to suppressing interference sources is proposed in this paper. The combination of open-loop and closed-loop methods can simultaneously reduce the electromagnetic interference generated by voltage and current. Firstly, this paper analyzes how to select a reference signal. The relationship between the time domain and the frequency domain of the noise signal is analyzed. The convolution of the trapezoidal signal and the Gaussian signal is selected as the reference signal, which is named S-shaped signal in this paper. The S-shaped signal has continuous infinitely conductive characteristics, so its spectrum has a large attenuation in the high frequency region. Secondly, a new topology is proposed. Based on the closed-loop gate control, a current control signal is added, which can simultaneously shape the output voltage and control the output current slope. Both the simulation results and the experimental results show that the output voltage can follow the reference signal, S-shaped signal, and the slope and overshoot of output current can be changed. Compared with classical gate driver method, the spectrum of output voltage and output current obtained by the method proposed in this paper has a large attenuation, in other words, the electromagnetic interference is significantly reduced.

Differential-Mode EMI Reduction in a Multiphase DCM Flyback Converter

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Switched converters are a source of electromagnetic interference (EMI) due to the hard switching and abrupt edges in the current and voltage waveforms. Multiphase converters can reduce the EMI at the source, minimizing the conducted EMI generation, without changing dramatically the normal operation of the circuit. Input filter can be greatly reduced, radiated EMI is lower, and internal EMI problems are minimized. This paper is focused on exploring multiphase converters as a topological technique to reduce conducted differential-mode EMI generation at the source, considering some nonidealities of the multiphase converter. </para>

Multiple targets characterization of electromagnetic vulnerability

We use statistical selection methodology to characterize multiple targets in electromagnetic fields, which result from ground, weather, and sea clutter or internal electromagnetic interference due to the antenna subsystems. This electromagnetic interference occurs at the same frequencies as the target returns yet a specific statistical distribution in amplitude emerges over time. Holland and St. John [Statistical electromagnetics, Technical Report AFRL-DE-PS-TR-1998-1025, Air Force Research Laboratory, Direct Energy Directorate, Air Force Material Command, Kirtland Air Force Base, 1988] concluded that the observed EM field power fluxes and cable powers follow either a chi-square distribution or a log-normal distribution, which implies either distribution in all measurements due to internal electromagnetic interference (EMI) problems. That is such an EM field can be characterized by either an exponential distribution or a log-normal distribution. These cases exist also in a far field as a result of what the aircraft returns, while the distribution exists due to multiple reflecting surfaces instead of internal EM fields from radar subsystems previously mentioned. Clutter also produces these same distributions in the far field. For the exponential distribution case, we propose subset selection procedure to identify EM fields whose reference parameters are those of candidate targets rather than the interfering EM sources. We discuss the properties of our proposed procedure by numerical examples and give simulation examples to illustrate the procedure.

Reduction in conducted EMI noises of a switching power supply after thermal management design

Owing to the increasing power density of a switching power supply (SPS), the placement of the components for thermal management and electromagnetic interference (EMI) characteristics is more difficult to design at a given form factor. When thermal management is a critical issue for the SPS, then methods for improving EMI noises seem not to be simultaneously successful at this design stage. As a result, the conducted EMI noises will deteriorate due to the placement of components for thermal management. Furthermore, the performance of the designed EMI filter will deteriorate due to severe internal electromagnetic interference, and thus lead to failure in the EMI conducted measurement. To improve this condition, the locations of EMI noise sources, modes of conducted EMI noise, their coupling paths and the characteristics of the electromagnetic field are investigated in detail. Various shielding schemes are proposed to reduce the EMI inside the SPS. Through this, the interference between the EMI sources, coupling paths and receivers can be significantly reduced so that the conducted EMI measurement of the SPS can meet the requirements. Finally, the effectiveness of the shielding schemes will be demonstrated by some experimental results and some EMI reduction methods will be suggested.