Harsh Electromagnetic Research Articles

Bayesian Decision Algorithm for Symbol Diversity in a Three-Channel Redundant System Under Harsh Electromagnetic Disturbances

Bayesian Decision Algorithm for Symbol Diversity in a Three-Channel Redundant System Under Harsh Electromagnetic Disturbances

Symbol Diversity as a Means to Make PAM-4 Modulation More Resilient in Harsh Electromagnetic Environments

In this article, symbol diversity is presented for the pulse amplitude modulation PAM-4 encoding scheme. This technique is implemented in order to incorporate electromagnetic resilience in a triple modular redundant communication channel that is subjected to electromagnetic disturbances in reverberant environments. An in-depth numerical study is carried out in light of new electromagnetic disturbance condition monitoring definitions that provide a better insight into the actual state of the system. An explanation of the different fault mechanisms based on the new definitions is provided for the proposed PAM-4 symbol diversity setup and is compared with an undiverse PAM-4 system with a two-out-of-three majority voter. The results show that the proposed symbol diversity technique is quite an effective measure for incorporating fault tolerance in the system design.

Mitigating False Negatives in Harsh Electromagnetic Environments by Combining Complementary Error Detection Codes

In our modern daily lives, more and more electronic systems are performing safety-critical tasks. For these systems, robust communication is crucial. Undetected corruptions of data (a.k.a. False Negatives) within these channels might lead to severe harm to humans or the environment. In order to detect corruptions, Error Detection Codes have since long been used. This letter assesses the resilience of a straightforward duplication mechanism against electromagnetic disturbances by simulating a harsh reverberating electromagnetic environment. The simulations reveal that simply duplicating the bits is not sufficient. By analysing the different fault mechanisms present in duplication, new Error Detection Codes are proposed. These new codes are derived from existing codes, with the explicit requirement to cover each other's vulnerabilities towards False Negatives. In this letter, the EMI-resilient codes are built based on a duplication methodology combined with a Hamming Double Error Detection Code. Due to the different coverage of failure mechanisms under the considered reverberating electromagnetic environment, the rate of False Negatives is significantly reduced.

Resilience of Error Correction Codes Against Harsh Electromagnetic Disturbances: Fault Elimination for Triplication-Based Error Correction Codes

Modern safety-critical systems rely heavily on robust communication channels. Even though these communication channels can be protected by error detection and correction codes, vulnerabilities caused by false negatives still exist. These false negatives can be caused by harsh electromagnetic disruptions and are detrimental to overall safety. This article considers the construction and structure of triplication-based error correction codes to find the most electromagnetic interference (EMI)-resilient code. Each code is tested and simulated in terms of the occurrence rate of false negatives under single-frequency disturbances. It is found that a code with inversion is significantly more robust to these disturbances. Furthermore, a systematic fault injection is also performed to search for vulnerabilities within the code itself. The systematic approach allows us to reverse engineer the expected vulnerabilities to real-world disturbances.

Resilience of Error Correction Codes Against Harsh Electromagnetic Disturbances: Fault Mechanisms

Modern electronic systems are performing more and more safety-critical tasks, whereby a robust communication is crucial. To protect those communication channels, error detection and correction codes (EDCCs) are widely used. The very construction of an EDCC has an impact on the resiliency against electromagnetic interference. Within this paper, the effectiveness of several EDCCs is assessed and compared. It is found that the effectiveness depends on the ratio between the channel's bit rate and the frequency of the incoming disturbance. Specific focus is being given to incorrect data perceived as correct: false negatives. Each of the considered EDCCs has an increased vulnerability for false negatives at bit rates that have a specific ratio to the disturbance frequency. The main cause behind this is the repetitive or alternating bit patterns within the codes themselves. Finally, foundations are laid to develop codes that are as robust as possible against harsh electromagnetic disturbances.

Design Considerations for Secure Wireless Sensor Communication Systems in Harsh Electromagnetic Environments of Nuclear Reactor Facilities

Wireless sensors can potentially play a significant role in safety, efficiency, and reliability of the instrumentation and control process in current and next generation nuclear power reactors. While conventional narrowband wireless sensors have shown a certain level of success in some nuclear power plants (NPPs), the radio frequency (RF) propagation challenges posed by the heavy metallic and cluttered environment of NPPs has prevented their widespread use in such operations. These challenges include RF wave propagation in harsh (reflective, absorptive, cluttered) environments, data security issues, and RF interference to and from other devices in the vicinity of a nuclear reactor core. In this paper, first we address how ultrawideband (UWB) RF technology can complement the narrowband (i.e., WiFi) solutions that have been used in some NPPs by providing an alternative solution in addressing the signal propagation issues in such electromagnetically harsh environments. Second, we discuss and present the UWB software simulation results on multipath harsh environments, and then address the data security issues. In the final sections of the paper, we present the experimental results of using UWB signaling in a representative harsh environment conducted at the Massachusetts Institute of Technology research reactor site. We plan to develop the UWB communications hardware based on the results of this paper and report on its performance in the field with emphasis on the security aspects of the system in a subsequent paper.

An Electromechanically Modulated Permanent Magnet Antenna for Wireless Communication in Harsh Electromagnetic Environments

High-frequency electromagnetic waves are greatly scattered and attenuated by soil, rocks, water, and the human body, which impede their propagation across these media. However, low-frequency magnetic waves propagate with low attenuations through these dispersive media as long as these media are nonmagnetic. Unlike static electric fields that can be produced by “free” positive/negative charges, static magnetic fields are divergence-free and thus can be produced only by particles with noninteger spins (i.e., electrons), or permanent magnets, or current loops. Fields produced by these dipoles decay steeply as a third-order function of distance. Hence, magnetic current loops require excessively large currents to produce detectable magnetic field at large distances. However, rare-earth magnets with surface magnetic flux densities of 0.3–0.6 T, provide sufficiently large fields at large distances, thus the fields produced by these magnets that can be modulated by mechanically modulating the magnets for portable wireless magnetic field communication. Here, we present the development of an electromechanically modulated permanent magnet antenna operating at a frequency of 22 Hz, producing a magnetic flux density of $0.6~\mu \text{T}$ amplitude at 1 m. This antenna requires a starting energy of 0.48 J and it is capable of data rate of 8 b/s. This magnet antenna can reliably transmit binary data over a distance of up to 70 cm through obstacles that would severely hamper electromagnetic wave propagation.