Showing papers in "IEEE Transactions on Electromagnetic Compatibility in 2017"

A Resonant Reactive Shielding for Planar Wireless Power Transfer System in Smartphone Application

Abstract: Demand and interest in wireless power transfer (WPT) have been rapidly increasing lately. However, WPT systems have problems with electromagnetic field (EMF) leakage, which has stimulated interest in methods to suppress EMF leakage levels. In this paper, we propose a compact resonant reactive shielding coil topology for reducing EMF in a near-field WPT mobile device application. The proposed shielding coil employs a closed loop and matching capacitors, and is demonstrated to dramatically reduce the leakage magnetic field from a WPT system. For validation, the proposed shielding was implemented with other shielding topologies and the EMFs were measured and compared. The analytical, simulation, and measurement results were all strongly correlated.

5G Over-the-Air Measurement Challenges: Overview

Abstract: Over-the-air (OTA) measurements are the standardized methods to evaluate radio performance in wireless systems EMC issues such as interference and receiver desensitization are important factors In this paper, OTA measurement challenges in the upcoming fiftth generation (5G) wireless systems are overviewed Several key technologies that could be widely used in the 5G OTA measurements are discussed, including near-field to far-field transformation, anechoic chamber absorbers, and sampling antennas The most important devices under test (DUT) for 5G OTA are chip sets, user equipment, and active array systems The OTA test challenges for certification, research and development, and mass production for these DUTs are introduced

Atom-Based RF Electric Field Metrology: From Self-Calibrated Measurements to Subwavelength and Near-Field Imaging

Abstract: We discuss a fundamentally new method for electric (E) field strength (V/m) metrology applicable to the near-field. This new approach is significantly different from currently used field measurement techniques in that it is based on the interaction of radio-frequency (RF) E-fields with Rydberg atoms (alkali atoms placed in a glass vapor cell that are excited optically to Rydberg states). The applied RF E-field alters the state of the atoms. The Rydberg atoms act like an RF-to-optical transducer, converting an RF E-field strength to an optical-frequency response. In this new approach, we employ the phenomena of electromagnetically induced transparency (EIT) and Autler-Townes splitting. The RF transition in the four-level atomic system causes a split of the EIT transmission spectrum of a probe laser into two peaks. This splitting is easily measured and is directly proportional to the applied RF E-field amplitude. The significant dipole response of Rydberg atoms enables this technique to make self-calibrating measurements over a large frequency band including 500 MHz to 500 GHz (and possibly up to 1 THz and down to 10s of megahertz). In this paper, we report on our results in the development of this metrology approach, including the first fiber-coupled vapor-cell for E-field measurements. We also discuss key applications, including self-calibrated measurements, millimeter-wave and sub-THz measurements, field mapping, and sub-wavelength and near-field imaging. We show results for mapping the fields inside vapor cells, for measuring the E-field distribution along the surface of a circuit board, and for measuring the near-field at the aperture in a cavity. We also discuss the uncertainties of this measurement technique.

Near-Field Reduction in a Wireless Power Transfer System Using LCC Compensation

Abstract: This paper deals with wireless power transfer technology applied to charge the battery of a short-distance electric vehicle. Different compensation topologies (series-series and LCC compensations) are examined and compared in terms of magnetic field emission and system efficiency. The investigation is carried out by simulations and measurements taking into account the variation of the coupling factor due to possible lateral misalignment of the parallel coils, and of the load conditions that depend on the level of the battery charge.

Design of PIFA With Metamaterials for Body-SAR Reduction in Wearable Applications

Abstract: This letter proposes a planar inverted-F antenna (PIFA) with an artificial magnetic conductor (AMC) structure for body specific absorption rate (SAR) reduction in a wideband-code-division-multiple-access band. As wireless devices such as wearable phones and smart watches become more common, health risks originating from electromagnetic waves generated by devices worn on the body have become an important issue. AMC structures are a type of metamaterial that can act as a perfect magnetic conductor and control the radiation pattern of an antenna. Thus, an antenna with an AMC structure is capable of preventing hazardous electromagnetic fields being emitted in the direction of the body. The S-parameters, radiation patterns, total radiated power values, and SAR values of such a designed structure are presented. The results demonstrate a 43.3% reduction in the SAR value at the center frequency. Thus, the human body can be protected from electromagnetic waves using metamaterials.

A Low-Profile Broadband Bandpass Frequency Selective Surface With Two Rapid Band Edges for 5G Near-Field Applications

Abstract: A low-profile broadband bandpass frequency selective surface (FSS) with two rapid band edges is proposed in this paper for 5G near-field applications. The overall structure consists of three metallic layers, separated by two thin substrates with a thickness of 0.07λ. In addition, some centro-symmetric miniaturized slots are introduced in the middle metallic layer to further improve its stability and reduce its physical dimensions. A corresponding equivalent circuit model (ECM) is also proposed to better analyze the principles of the proposed FSS. Finally, an FSS prototype working at the center frequency of 27.5 GHz with a relative -3 dB bandwidth of 20.5% is fabricated and measured. More than 25 dB shielding effectiveness can be obtained out of the passband for a bandwidth of 1.46 GHz in this experiment. Both 3-D full-wave simulations and ECM results are in good agreement with the experimental results, having a maximum deviation of only 2.257% in the transmission zeros and poles. These results demonstrate that the proposed FSS is a good candidate for 5G near-field EMI shielding.

An Alternative Method for Locating Faults in Transmission Line Networks Based on Time Reversal

Abstract: We present an alternative method based on the time-reversal process to locate faults in transmission line networks. The proposed procedure considers different media for the forward and the backward propagation phases. Specifically, the transverse branch representing the fault is removed from the circuit in the backward propagation since its location represents the solution of the process and, therefore, is not known in advance. The advantage of the proposed method is twofold. First, the proposed backward model requires only one simulation for the time-reversed backward propagation phase, thus reducing significantly the computational burden. Second, we demonstrate that this modified backward propagation medium satisfies a property such that the fault location can be identified by computing, in the frequency domain, the argument of the voltage along the line. The theory is first formulated for the case of a lossless homogeneous single-phase transmission line; then, its applicability is extended to lossy inhomogeneous transmission line networks. A single-phase inhomogeneous transmission line and an inhomogeneous Y-shape network are specifically considered to support this claim. We show that the proposed procedure can provide high fault location accuracy (i.e., in the range of $\pm 1$ m), using only one observation point. Furthermore, we propose a criterion to link the bandwidth of the sampling system to the desired fault location accuracy.

Evaluation of Power System Lightning Performance, Part I: Model and Numerical Solution Using the PSCAD-EMTDC Platform

Abstract: The paper addresses the important issue of evaluating the overvoltages produced on a power system by a lightning event. First, the theoretical formulation of the problem in the time domain is presented. Then its numerical solution together with its implementation is described. Finally, a PSCAD-EMTDC interface and platform is developed, which allows us to model a realistic network, automatically distinguish between direct and indirect strokes and account for power network precontingency conditions. The obtained results are compared with a frequency-domain solution for a simple case in order to validate the finite-difference time-domain method adopted to solve the coupling equations and the interface with PSCAD. The comparison with the well-known LIOV code for a more complex case is used as a general validation of the overall tool. In a companion paper, the developed platform will be used to evaluate the lightning performance of a portion of the Italian MV distribution network.

Physics-Based Dipole Moment Source Reconstruction for RFI on a Practical Cellphone

Abstract: A physics-based dipole moment source reconstruction is proposed to estimate the near-field coupling between a liquid crystal display panel to a cellphone's cellular antenna. Based on the understanding of the current distribution on the source, a magnetic dipole moment source is reconstructed to replace the real radiation source that is located at the edge of the flexible printed circuit board. To characterize the coupling from the equivalent dipole moment source to the victim antenna, the noise transfer coefficient is proposed. The noise transfer coefficient can be calculated from the near-field scanning and the direct coupling measurements using a wideband source. The proposed physics-based dipole moment source reconstruction and noise transfer coefficient are successfully validated through the measured near-field coupling in a practical cellphone.

Metamaterial Structure Integrated With a Dielectric Absorber for Wideband Reduction of Antennas Radar Cross Section

Abstract: This paper presents the design, synthesis, and testing of a novel wide band electromagnetic hybrid absorber (HA) for the radar cross section (RCS) reduction of antennas. The proposed HA is based on the design of a metamaterial structure coated with the synthesized dielectric absorber material. The dielectric filler based composite absorber is fabricated by optimizing weight percentage of graphite and glass microballoon powders mixed into an epoxy medium. The proposed HA shows minimum –10 dB reflection loss (RL) in the 6–12 GHz frequency region having maximum absorption of 99.56% (–20 dB RL) at 9.26 GHz. The proposed HA is ultimately loaded onto a wide band antenna in order to reduce the in-band RCS of the antenna. The simulated and the experimental results show remarkable RCS reduction of the antenna over the full operating frequency range. It is also observed that the antenna characteristics, e.g., the gain and the radiation pattern remain almost preserved after loading the antenna with HA. The significant RCS reduction capability of the proposed HA shows that it has the potential applications for RF stealth technology.

Electrical-Thermal Co-Simulation for Analysis of High-Power RF/Microwave Components

Abstract: An electrical-thermal co-simulation based on the finite element method is presented for analysis of high-power RF/microwave circuits. The co-simulation integrates a full-wave electromagnetic analysis and a transient thermal analysis through an iterative scheme, and is devised for the design and analysis of RF/microwave circuits operated at high frequencies and high power levels. To enhance the efficiency in solving large-scale problems, a domain decomposition scheme called the finite element tearing and interconnecting and an adaptive time-stepping scheme based on the algorithm of proportional-integral-derivative control are incorporated into the co-simulation. Temperature stability analysis is performed with the proposed co-simulation for a matching network in high-power RF amplifiers and for a substrate integrated waveguide filter.

A Method for Finding Frequency-Modulated and Amplitude-Modulated Electromagnetic Emanations in Computer Systems

Abstract: This paper presents an algorithm for finding carriers of frequency-modulated (FM) and amplitude-modulated (AM) electromagnetic (EM) emanations from computer systems. Computer systems create EM emanations across the RF spectrum making it difficult, error-prone, and time consuming to find the relatively few emanations that expose sensitive information. One of the most common and simplest mechanisms for information leakage occurs when an amplitude or a frequency of an existing strong signal (e.g., a processor or memory clock) is amplitude or frequency modulated by a system activity. If the system activity can be linked to sensitive information, this results in information leakage. We present an algorithm for automatically finding these AM and FM signals, demonstrate the algorithm's performance on several different types of processors and systems (desktop, laptop, and smartphone), and compare the results to an exhaustive manual search. We also verify that all signals identified by the algorithm can be traced to plausible unintentional modulation mechanisms to illustrate that these signals can potentially cause information leakage. This algorithm can be an important tool for system designers to quickly identify circuits that are leaking sensitive information.

Source Reconstruction for IC Radiated Emissions Based on Magnitude-Only Near-Field Scanning

Abstract: Near-field scanning with phase measurement is always a challenge in practical experiments because of its complexity and lack of accuracy. Therefore, utilizing the magnitude-only information to achieve phase-retrieval and emissions source reconstruction is preferred. This paper proposes a fast and accurate algorithm that can model the emissions from ICs by generating a set of equivalent dipole elements. The process of this algorithm only requires the information of the field magnitudes on two near-field scanning planes of different heights. Unlike other conventional source reconstruction techniques (such as genetic algorithm, gradient optimization), the proposed approach iteratively performs the back-and-forth transformations among the fields and equivalent dipole elements. By optimizing the locations of the equivalent dipole array and the initial values of these dipole elements, the iteration process is capable of quickly converging to the correct electromagnetic field values, including both magnitude and phase. The fields recovered from the calculated equivalent dipole sources have been validated by comparing to the fields emitted from a practical IC source.

Self-Capacitance of Single-Layer Inductors With Separation Between Conductor Turns

Abstract: This letter presents the technique for estimating the self-capacitance of single-layer air-core solenoid inductors with separation between the insulated turns. In single-layer air-core inductors, the self-capacitance is due to the conductor turn-to-turn capacitances. The analytical framework to determine the turn-to-turn capacitances of single-layer air-core inductors with uniformly and nonuniformly separated conductor turns is established. The influence of the wire insulation coating is taken into consideration. A representative design example of a single-layer air-core inductor is presented and its self-capacitance and self-resonant frequency are predicted. The presented analytical approach was tested by experimental measurements on the designed inductor. The derived analytical expressions are useful for designing air-core inductors for high frequency (HF) and very HF applications such as electromagnetic interference/electromagnetic compatibility filters and radio and TV transmitters.

A Comparison Between Different Reception Diversity Schemes of a 4G-LTE Base Station in Reverberation Chamber: A Deployment in a Live Cellular Network

Abstract: The uplink performance of a real fourth-generation long-term-evolution (LTE) frequency-division multiplexing base station was observed by adopting a reverberation chamber as propagating environment. In the downlink direction, the reception of the LTE signal is limited to mobile station receivers. On the other hand, different reception schemes could be implemented by the base station in the uplink direction. Interference rejection and coordinated multipoint reception criteria are based on spatial diversity and are analyzed in a rich multipath environment. These options could be susceptible to impairments due to the presence of Gaussian noise, also including the more realistic case of a discontinuous noise source. The testing session was carried out under a collaboration program between TIM S.p.A., Nokia, and Universita Politecnica delle Marche, and it ended up by introducing envisioned reception solutions of the base station in a live customer's cellular network.

Using the ADI-FDTD Method to Simulate Graphene-Based FSS at Terahertz Frequency

Abstract: The alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method is modified to simulate a graphene-based frequency selective surface. By using the auxiliary differential equation and Pade fitting method, both the interband and intraband conductivity of the graphene are incorporated into the ADI-FDTD method. The ADI-FDTD method has excellent computational accuracy and its computational efficiency is considerably improved from that of the conventional FDTD method. By using the proposed ADI-FDTD method, a graphene-based frequency selective surface is simulated and analyzed at terahertz frequency. The numerical results show that the graphene can achieve a tunable frequency selective surface through controlling its chemical potential, and the interband conductivity of the graphene has important effect on the performance of the frequency selective surface.

Near-Field Shielding Performances of EMI Noise Suppression Absorbers

Abstract: This paper describes a systematic study on the near-field behavior of an electromagnetic interference (EMI) noise suppression absorber materials considering two different types of commercial absorbers and different types of excitation source: at first, elementary electric dipole and elementary magnetic loop, and then using real dimensions of a coaxial cable for designing a dipole and loop. Virtual versions of the material are created and simulated with the purpose of understanding the mechanisms of high values of power loss when the absorber is in the near field of the source The focus of this study is the evaluation of the electromagnetic power balance in near field for each absorbing material and considered source to understand their near-field shielding properties. Full-wave simulations and measurement are performed and compared to verify the performance of the EMI noise suppression absorber materials in the near field.

Kron–Branin Modeling of Y-Y-Tree Interconnects for the PCB Signal Integrity Analysis

Abstract: The signal distribution interconnect network modeling plays an important role during the digital/mixed printed circuit board (PCB) design. With the increase of the design complexity, the PCB interconnect modeling becomes a challenging task. This paper proposes an innovative circuit theory of the PCB electrical interconnects modeling based on the tensorial analysis of network (TAN). The model under study, fundamentally built with the Kron–Branin formalism, is applied to the asymmetrical 1:3 Y-Y-tree interconnects. This Kron–Branin method enables to establish quickly the tree interconnects equivalent model for the signal integrity (SI) analysis. An asymmetrical microstrip circuit was designed and fabricated to validate the developed TAN concept. The modeled, simulated, and measured S-parameters are in good agreement in the broad frequency band 0.1 MHz to 8 GHz. The electrical power budget distributed through the Y-Y-tree prototype in dc and in the considered entire frequency band was analyzed. Furthermore, the Kron–Branin model was also validated in the time domain with 1-Gb/s-rate 8-bits serial data and eye diagram analyses. This innovative formalism presents a considerably high computation speed and is beneficial for the SI analyses thanks to its adaptability to the complex system.

Evaluation of Power System Lightning Performance—Part II: Application to an Overhead Distribution Network

Abstract: The paper aims at defining a methodology to evaluate the lightning performance of a system of overhead distribution lines. As is well known, the evaluation of the lightning performance relies generally on a Monte Carlo approach that generates many different lightning events and calculates the corresponding overvoltages. To perform such calculation, the power system computer aided design (PSCAD) module developed in the companion paper is adopted. However, as any call to PSCAD implies a nonnegligible computational effort, here an efficient approach is presented in order to limit the number of simulations as much as possible. The obtained results are compared with the ones provided by other available techniques both on simple structures in order to highlight the main features of the method and on a typical Italian distribution network segment. The comparative analysis shows good agreement between the methods and the effectiveness of the proposed technique in terms of computational effort reduction.

Transient Heterogeneous Electromagnetic Simulation With DGTD and Behavioral Macromodel

Abstract: A novel hybrid field-circuit simulation method is proposed for transient heterogeneous electromagnetic simulations. It adopts the discontinuous Galerkin time domain (DGTD) method and behavioral macromodel trained by artificial neural network to analyze the electromagnetic structure and circuit network, respectively. Due to the feature of DGTD method and behavioral macromodel, the proposed method can handle not only electromagnetic structures with complex geometries and materials but also manage circuits with unknown internal details. It provides a new approach that has the trainable accuracy to meet today's IP projection requestions. It is also the first time for DGTD algorithm to work with the behavior model. Numerical examples have been benchmarked to demonstrate the capability of the proposed method.

A Novel Unified Model for Copper and MLGNR Interconnects Using Voltage- and Current-Mode Signaling Schemes

Abstract: A novel unified model, for conventional copper and futuristic multilayer graphene nanoribbon (MLGNR) interconnects, based on a finite-difference time-domain (FDTD) technique has been proposed in this paper. The performance of quasi-transverse electromagnetic model of interconnects has been exhaustively analyzed for both voltage-mode signaling (VMS) and current-mode signaling (CMS) schemes. The effect of variations in edge roughness and dopant dependent Fermi energy in MLGNR interconnects has been examined. The crosstalk and coupling effects in interconnects have been investigated by incorporating capacitive and inductive interconnect parasitic elements. From the results carried out for 32-nm technology node, it has been observed that for similar dimensions and operating conditions, MLGNR interconnects show a significant performance improvement over the copper interconnects. The results also show that the CMS scheme outperforms VMS scheme at global wire lengths and is very suitable for state-of-the-art chip applications. The proposed model results are in close propinquity with the SPICE results. Furthermore, the FDTD-based model is computationally efficient compared to SPICE.

Modeling and Analysis of Conducted and Radiated Emissions Due to Common Mode Current of a Buck Converter

Abstract: This paper presents the study of conducted and radiated emissions due to common-mode (CM) currents flowing through the power cables of a DC–DC converter system. In order to predict the conducted electromagnetic interferences (EMI) emissions, a model of power converter system is presented. The finite-difference time-domain method (FDTD) is used for predicting the magnetic near field radiated by the power supply cable of a buck converter and that due to CM current flowing through the cable. The CM current resulting from the model is compared with the experimental ones and implemented in the FDTD algorithm as current source of disturbance. The comparison with experimental results shows the validity of the FDTD model over a wide frequency range. The goal of this study is to predict the level of conducted and radiated EMI emissions. Therefore, proposing and investigating a simple and effective filtering solution that allows to reduce the emissions located in the switching noise zone, the results show that the conducted and radiated emission levels can be reduced by as much as 30 dB when using this technique.

Transient Analysis of Dispersive Power-Ground Plate Pairs With Arbitrarily Shaped Antipads by the DGTD Method With Wave Port Excitation

Abstract: A discontinuous Galerkin time-domain (DGTD) method analyzing signal/power integrity on multilayered power-ground parallel plate pairs is proposed. The excitation is realized by introducing wave ports on the antipads where electric/magnetic current sources are represented in terms of the eigenmodes of the antipads. Since closed-forms solutions do not exist for the eigenmodes of the arbitrarily shaped antipads, they have to be calculated using numerical schemes. Spatial orthogonality of the eigenmodes permits determination of each mode's temporal expansion coefficient by integrating the product of the electric field and the mode over the wave port. The temporal mode coefficients are then Fourier transformed to accurately calculate the S-parameters corresponding to different modes. Additionally, to generalize the DGTD to manipulate dispersive media, the auxiliary differential equation method is employed. This is done by introducing a time-dependent polarization volume current as an auxiliary unknown and the constitutive relation between this current and the electric field as an auxiliary equation. Consequently, computationally expensive temporal convolution is avoided. Various numerical examples, which demonstrate the applicability, robustness, and accuracy of the proposed method, are presented.

Maximum Radiated Emissions Evaluation for the Heatsink/IC Structure Using the Measured Near Electrical Field

Abstract: Creating an equivalent field source is an efficient method for predicting radiated emissions from IC structures. In this paper, the maximum radiated emissions for a heat-sink/IC structure is predicted by creating an equivalent source from the measured electrical field (E-field) in the gap between the heatsink and IC. The E-field is detected by an E-field probe made of an open coaxial cable coated with absorbing material. A numerical model is built in the computer simulation technology microwave studio to obtain the maximum radiated field, where the measured E-field is used as a source to excite the heat-sink model. The evaluated maximum radiated field is in good agreement with the measured value; the error is within 7 dB up to 40 GHz for the source with phase, and 7 dB up to 10 GHz for the phaseless measurement.

Investigation of Unintentional Video Emanations From a VGA Connector in the Desktop Computers

Abstract: This paper focuses on the compromising video emanations from a desktop computer with a liquid-crystal display (LCD). Near-field tests are performed in a common unshielded office environment to investigate the video information leakage, and the tests show that the video graphics adapter (VGA) connector is a leaking source. To illustrate the mechanism of the video leakage, a wire antenna model is developed according to the physical dimensions of the connector. The radiated fields of the connector are calculated in the time domain from this model, the results are verified by the tests. Combining the expressions of the radiated fields and the transfer function of the test probe, the function relationship between the original red/green/blue signal and the intercepted signal is established. Finally, a readable text is reconstructed from the intercepted signal when a Chinese document is displayed on the LCD.

Uncertainty Quantification of Crosstalk Using Stochastic Reduced Order Models

Abstract: This paper introduces a novel statistical method, referred to as the stochastic reduced order model (SROM) method, to predict the variability of cable crosstalk subject to a range of parametric uncertainties. The SROM method is a new member of the family of stochastic approaches to quantify propagated uncertainty in the presence of multiple uncertainty sources. It is nonintrusive, accurate, efficient, and stable, thus could be a promising alternative to some well-established methods, such as the Stochastic Galerkin and stochastic collocation (SC) methods. In this paper, the SROM method is successfully applied to obtain the statistics of cable crosstalk subject to single and multiple uncertainty sources. The statistics of uncertain cable parameters is first accurately approximated by SROM, i.e., pairs of very few samples with known probabilities, such that the uncertain input space is well represented. Then, a deterministic solver is used to produce the samples of cable crosstalk with the corresponding probabilities, and finally the uncertainty propagated to the crosstalk is quantified with good accuracy. Compared to the conventional Monte–Carlo simulation, the statistics of crosstalk obtained by the SROM method converge much faster by orders of magnitude. Also, the computational cost of the SROM method is shown to be small and can be tuned flexibly depending on the accuracy requirement. The SC method based on tensor product sampling strategy is also implemented to validate the efficacy of the SROM method.

Design of a Patterned Soft Magnetic Structure to Reduce Magnetic Flux Leakage of Magnetic Induction Wireless Power Transfer Systems

Abstract: A soft-magnetic-metal-based shield structure was designed to reduce magnetic flux leakage in magnetic-induction wireless power transfer systems. Soft magnetic metals have the advantages of high permeability and low magnetic loss, but have the disadvantage of high power loss owing to eddy current that is induced on the surface as a result of low-insulating characteristics. In order to solve this problem, a patterned soft magnetic metal was used to cut the route of the induced current. This decreases the power loss and reduces the leakage of magnetic field. A soft-magnetic-metal-based structure that has various patterns was designed to find the optimal structure for reducing the leaking magnetic field. By applying this structure to Wireless Power Consortium commercial A10 coil, the inductance, transfer efficiency, and magnetic flux leakage of the coil according to the material and the structure of the soft-magnetic-metal-based structure were observed. Fabrication and measurement tests were performed to verify the proposed structure, and it was found that the test results corresponded to the simulation results. It was confirmed that the proposed structure had a 84% thinner thickness compared with that of a conventional ferrite shield, an equivalent transfer efficiency of 74.5%, and a reduction in magnetic flux leakage of 20.9%.

Investigation of the Effects of Receptors on the Lightning Strike Protection of Wind Turbine Blades

Abstract: Receptor plays an essential role in determining the efficiency of lightning strike protection (LSP) on wind turbine blades. To investigate the effects of receptors with different shapes and sizes on the LSP, we apply five different receptor configurations to the blade of a high-fidelity wind turbine model. The static electric field strength on the blade surfaces due to a lightning stepped leader is predicted through the development of a numerical model with finite element analysis. The interception efficiency is evaluated by comparing the predicted maximum electric field strength in the vicinity of the receptors. In addition, the locations of the predicted lightning strike attachment points match well with those obtained by experimental measurements, which validate the current numerical approach.

Life-Time Dosimetric Assessment for Mice and Rats Exposed in Reverberation Chambers for the Two-Year NTP Cancer Bioassay Study on Cell Phone Radiation

Abstract: In this paper, we present the detailed life-time dosimetry analysis for rodents exposed in the reverberation exposure system designed for the two-year cancer bioassay study conducted by the National Toxicology Program of the National Institute of Environmental Health Sciences. The study required the well-controlled and characterized exposure of individually housed, unrestrained mice at 1900 MHz and rats at 900 MHz, frequencies chosen to give best uniformity exposure of organs and tissues. The wbSAR, the peak spatial SAR, and the organ specific SAR as well as the uncertainty and variation due to the exposure environment, differences in the growth rates, and animal posture were assessed. Compared to the wbSAR, the average exposure of the high-water-content tissues (blood, heart, lung) were higher by $\sim$ 4 dB, while the low-loss tissues (bone and fat) were less by $\sim$ 9 dB. The maximum uncertainty over the exposure period for the SAR was estimated to be $ 49% ( k = 2) for the rodents whereas the relative uncertainty between the exposure groups was $ 14% ( k = 1). The instantaneous variation (averaged over 1 min) was $ 13% ( k = 1), which is small compared to other long term exposure research projects. These detailed dosimetric results empowers comparison with other studies and provides a reference for studies of long-term biological effects of exposure

Evaluation of Different Approximations for Correlation Coefficients in Stochastic FDTD to Estimate SAR Variance in a Human Head Model

Abstract: In this paper, the stochastic finite-difference time domain (S-FDTD) method is employed to calculate the standard deviation of specific absorption rate (SAR) in a two-dimensional (2-D) slice of human head. S-FDTD calculates both the mean and standard deviation of SAR caused by variability or uncertainty in the electrical properties of the human head tissues. The accuracy of the S-FDTD result is controlled by the approximations for correlation coefficients between the electrical properties of the tissues and the fields propagating in them. Hence, different approximations for correlation coefficients are tested in order to evaluate their effect on the standard deviation of SAR. The 1-D Monte Carlo correlation coefficient (MC-CC) approximation reported in our previous work is successfully extended to 2-D and also tested for the head model. Then, all the results are compared with that of full-fledged Monte Carlo method (considered as gold standard in statistical simulations). In order to accelerate the simulations, the proposed algorithm is run on graphics processing unit by exploiting OpenACC application program interface. Using different correlation coefficients shows that the extended 2-D MC-CC S-FDTD results are very close to that of Monte Carlo and yield more accurate results than other approximations in SAR calculations.