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(Database last updated on Mar 27, 2024)
| ID Number | 1559 | |
| Study Type | Engineering & Physics | |
| Model | RF Measurement Techniques (catch all). | |
| Details | AUTHORS' ABSTRACT: Aerts et al. 2013 (IEEE #5285): In this study, a novel methodology is proposed to create heat maps that accurately pinpoint the outdoor locations with elevated exposure to radiofrequency electromagnetic fields (RF-EMF) in an extensive urban region (or, hotspots), and that would allow local authorities and epidemiologists to efficiently assess the locations and spectral composition of these hotspots, while at the same time developing a global picture of the exposure in the area. Moreover, no prior knowledge about the presence of radiofrequency radiation sources (e.g., base station parameters) is required. After building a surrogate model from the available data using kriging, the proposed method makes use of an iterative sampling strategy that selects new measurement locations at spots which are deemed to contain the most valuable information-inside hotspots or in search of them-based on the prediction uncertainty of the model. The method was tested and validated in an urban subarea of Ghent, Belgium with a size of approximately 1km2. In total, 600 input and 50 validation measurements were performed using a broadband probe. Five hotspots were discovered and assessed, with maximum total electric-field strengths ranging from 1.3 to 3.1V/m, satisfying the reference levels issued by the International Commission on Non-Ionizing Radiation Protection for exposure of the general public to RF-EMF. Spectrum analyzer measurements in these hotspots revealed five radiofrequency signals with a relevant contribution to the exposure. The radiofrequency radiation emitted by 900MHz Global System for Mobile Communications (GSM) base stations was always dominant, with contributions ranging from 45% to 100%. Finally, validation of the subsequent surrogate models shows high prediction accuracy, with the final model featuring an average relative error of less than 2dB (factor 1.26 in electric-field strength), a correlation coefficient of 0.7, and a specificity of 0.96. AUTHORS' ABSTRACT: Plets et al. 2013 (IEEE #5291): Due to the increased use of indoor wireless networks and the concern about human exposure to radio-frequency sources, exposure awareness has increased during recent years. However, current-day network planners rarely take into account electric-field strengths when designing networks. Therefore, in this paper, a heuristic indoor network planner for exposure calculation and optimization of wireless networks is developed, jointly optimizing coverage and exposure, for homogeneous or heterogeneous networks. The implemented exposure models are validated by simulations and measurements. As a first novel optimization feature, networks are designed that do not exceed a user-defined electric-field strength value in the building. The infuence of the maximally allowed field strength, based on norms in different countries, and the assumed minimal separation between the access point and the human are investigated for a typical offce building. As a second feature, a novel heuristic exposure minimization algorithm is presented and applied to a wireless homogeneous WiFi and a heterogeneous WiFi-LTE femtocell network, using a new metric that is simple but accurate. Field strength reductions of a factor 3 to 6 compared to traditional network deployments are achieved and a more homogeneous distribution of the observed field values on the building floor is obtained. Also, the influence of the throughput requirement on the field strength distribution on the building floor is assessed. Moreover, it is shown that exposure minimization is more effective for high than for low throughput requirements and that high field values are more reduced than low field values. AUTHORS' ABSTRACT: Thielens et al. 2013 (IEEE #5352): For the first time, a personal distributed exposimeter (PDE) for radio frequency (RF) measurements is presented. This PDE is designed based on numerical simulations and is experimentally evaluated using textile antennas and wearable electronics. A prototype of the PDE is calibrated in an anechoic chamber. Compared to conventional exposimeters, which only measure in one position on the body, an excellent isotropy of 0.5 dB (a factor of 1.1) and a 95% confidence interval of 7 dB (a factor of 5) on power densities are measured. AUTHORS' ABSTRACT: Marin et al. 2013 (IEEE #5396): An improvement of the accuracy of dielectric measurements of the open-ended coaxial resonator method is described. The technique is based on an empirical technique for de-embedding the coupling network excited by electric probes. By this procedure, the influence of the coupling structure on the resonance can be precisely eliminated independently of the coupling conditions, which guarantees a high accuracy in the permittivity determination of materials by open-ended coaxial resonators. The technique is applicable to materials with a wide range of dielectric constants and losses. The results of dielectric measurements are compared with those obtained using other standard methods. AUTHORS' ABSTRACT: Lala, Cela and Kamo 2013 (IEEE #5399): This paper is motivated by the increased presence of the radio base stations, and the need to calculate the electromagnetic field near them. The debate on the effects of the electromagnetic field exposure, in line with the increased success and presence of the mobile telephony, has attracted the public interest and it has become a concern for the community. The standard procedures in place for estimation of the electromagnetic field require prior knowledge of the criteria for the field evaluation, be it near field, far field, presence of one or several base stations, the operating frequencies bands and their combinations. Aiming to have a practical method for the evaluation, the authors will try to do develop a theoretic model, on which base the authors will simulate the antenna of the base station and prepare the numeric method that will provide the baseline for the application. They will than compare the calculations for real situations for which all know the geometrical features, with the ones calculated based on a known theoretical method also knows as method of the moments MoM, simulated with NEC-2 (numerical electromagnetic code), and further more with the values measured in the field under the same conditions as the ones for the simulated environments. The results are interpreted in order to define the efficiency of the proposed method as well as to have an idea on the simplicity, accuracy and computing capacities. AUTHORS' ABSTRACT: Djuric et al. 2014 (IEEE #5402):The measurement procedure of the open area in situ electric field strength is presented, acquiring the real field data for testing of the Serbian electromagnetic field monitoring network (SEMONT) and its Internet portal. The SEMONT monitoring system introduces an advanced approach of wireless sensor network utilization for the continuous supervision of overall and cumulative level of electromagnetic field over the observed area. The aim of the SEMONT system is to become a useful tool for the national and municipal agencies for the environmental protection, regarding the electromagnetic pollution monitoring and the exposure assessment of the general population. Considering the public concern on the potentially harmful effects of the long-term exposure to electromagnetic radiation, as well as the public transparency principle that is incorporated into the Serbian law on non-ionizing radiation protection, the SEMONT monitoring system is designed for the long-term continuous monitoring, presenting real-time measurement results, and corresponding exposure assessment over the public Internet network. AUTHORS' ABSTRACT: Melia et al. 2013 (IEEE #5408): We present broadband reverberation chamber measurements of the absorption cross section (ACS) of the human body averaged over all directions of incidence and angles of polarization. This frequency-dependent parameter characterizes the interactions between the body and the enclosures of reverberant environments such as aircraft cabins, and is, therefore, important for the determination of the overall Q-factor and, hence, the field strength illuminating equipment inside such enclosures. It also correlates directly with the electromagnetic exposure of occupants of reverberant environments. The average ACS of nine subjects was measured at frequencies over the range 1-8.5 GHz. For a 75-kg male, the ACS varied between 0.18 and 0.45 square meters over this range. ACS also correlated with body surface area for the subjects tested. The results agree well with computational electromagnetic simulations, but are obtained much more rapidly. We have used the obtained values of ACS to estimate the effect of passengers on the Q-factor of a typical airliner cabin. AUTHORS' ABSTRACT: Beekhuizen et al. 2014 (IEEE #5428): The increase in mobile communication technology has led to concern about potential health effects of radio frequency electromagnetic fields (RF-EMFs) from mobile phone base stations. Different RF-EMF prediction models have been applied to assess population exposure to RF-EMF. Our study examines what input data are needed to accurately model RF-EMF, as detailed data are not always available for epidemiological studies. We used NISMap, a 3D radio wave propagation model, to test models with various levels of detail in building and antenna input data. The model outcomes were compared with outdoor measurements taken in Amsterdam, the Netherlands. Results showed good agreement between modelled and measured RF-EMF when 3D building data and basic antenna information (location, height, frequency and direction) were used: Spearman correlations were >0.6. Model performance was not sensitive to changes in building damping parameters. Antenna-specific information about down-tilt, type and output power did not significantly improve model performance compared with using average down-tilt and power values, or assuming one standard antenna type. We conclude that 3D radio wave propagation modelling is a feasible approach to predict outdoor RF-EMF levels for ranking exposure levels in epidemiological studies, when 3D building data and information on the antenna height, frequency, location and direction are available. AUTHORS' ABSTRACT: Thors et al. 2014 (IEEE #5455): In this paper, different methods for practical numerical radio frequency exposure compliance assessments of radio base station products were investigated. Both multi-band base station antennas and antennas designed for multiple input multiple output (MIMO) transmission schemes were considered. For the multi-band case, various standardized assessment methods were evaluated in terms of resulting compliance distance with respect to the reference levels and basic restrictions of the International Commission on Non-Ionizing Radiation Protection. Both single frequency and multiple frequency (cumulative) compliance distances were determined using numerical simulations for a mobile communication base station antenna transmitting in four frequency bands between 800 and 2600 MHz. The assessments were conducted in terms of root-mean-squared electromagnetic fields, whole-body averaged specific absorption rate (SAR) and peak 10 g averaged SAR. In general, assessments based on peak field strengths were found to be less computationally intensive, but lead to larger compliance distances than spatial averaging of electromagnetic fields used in combination with localized SAR assessments. For adult exposure, the results indicated that even shorter compliance distances were obtained by using assessments based on localized and whole-body SAR. Numerical simulations, using base station products employing MIMO transmission schemes, were performed as well and were in agreement with reference measurements. The applicability of various field combination methods for correlated exposure was investigated, and best estimate methods were proposed. Our results showed that field combining methods generally considered as conservative could be used to efficiently assess compliance boundary dimensions of single- and dual-polarized multicolumn base station antennas with only minor increases in compliance distances. AUTHORS' ABSTRACT: Beekhuizen et al. 2014 (IEEE #5457): The increase in mobile communication technology has led to concern about potential health effects of radio frequency electromagnetic fields (RF-EMFs) from mobile phone base stations. Different RF-EMF prediction models have been applied to assess population exposure to RF-EMF. Our study examines what input data are needed to accurately model RF-EMF, as detailed data are not always available for epidemiological studies. We used NISMap, a 3D radio wave propagation model, to test models with various levels of detail in building and antenna input data. The model outcomes were compared with outdoor measurements taken in Amsterdam, the Netherlands. Results showed good agreement between modelled and measured RF-EMF when 3D building data and basic antenna information (location, height, frequency and direction) were used: Spearman correlations were >0.6. Model performance was not sensitive to changes in building damping parameters. Antenna-specific information about down-tilt, type and output power did not significantly improve model performance compared with using average down-tilt and power values, or assuming one standard antenna type. We conclude that 3D radio wave propagation modelling is a feasible approach to predict outdoor RF-EMF levels for ranking exposure levels in epidemiological studies, when 3D building data and information on the antenna height, frequency, location and direction are available. AUTHORS' ABSTRACT: Thielens et al. 2014 (IEEE #5562): Two radio-frequency personal exposimeters (PEMs) worn on both hips are calibrated on a subject in an anechoic chamber. The PEMs' response and crosstalk are determined for realistically polarised incident electric fields using this calibration. The 50 % confidence interval of the PEMs' response is reduced (2.6 dB on average) when averaged over both PEMs. A significant crosstalk (up to a ratio of 1.2) is measured, indicating that PEM measurements can be obfuscated by crosstalk. Simultaneous measurements with two PEMs are carried out in Ghent, Belgium. The highest exposure is measured for Global System for Mobile Communication downlink (0.052 mW m2 on average), while the lowest exposure is found for Universal Mobile Telecommunications System uplink (0.061 ¼W m2 on average). The authors recommend the use of a combination of multiple PEMs and, considering the multivariate data, to provide the mean vector and the covariance matrix next to the commonly listed univariate summary statistics, in future PEM studies. Tesanovic et al. 2014 (IEEE #5707): The purpose of the LEXNET (Low EMF Exposure Networks) is to develop effective mechanisms to reduce 50% (at least) of the public exposure to EMF, without compromising the quality of service. Joe Wiart (France) is the coordinator of the project that involves 17 partners from 9 European countries. AUTHOR'S CONCLUSIONS: Roblin 2014 (IEEE #5716): The presented results confirm that the dispersion of measurements collected by exposimeters is large. It shows that resorting to a non polarimetric combined signal tends to improve the isotropy, but that taking account of the propagation channel is mandatory in order to correctly assess the field measurement reliability. Anyway, corrections schemes are required to overcome the body shadowing effect which is dominant. This aspect will be thoroughly studied in future works. To complete these first results, a comprehensive simulation campaign is on-going in the framework of the Lexnet project. Its objective is to take into account other significant parameters such as anthropometric characteristics (size, corpulence, or BMI), as it is expected that their impact on shadowing effects would be significant. AUTHORS' ABSTRACT: Zhao and Chen 2014 (IEEE #5733): An efficient algorithm is proposed to analyze the electromagnetic scattering problem from a high resolution head model with pixel data format. The algorithm is based on parallel technique and the conjugate gradient (CG) method combined with the fast Fourier transform(FFT).Using the parallel CG-FFT method, the proposed algorithm is very efficient and can solve very electrically large-scale problems which cannot be solved using the conventional CG-FFT method in a personal computer. The accuracy of the proposed algorithm is verified by comparing numerical results with analytical Mie-series solutions for dielectric spheres.Numerical experiments have demonstrated that the proposed method has good performance on parallel efficiency. AUTHORS' ABSTRACT: Sidi et al. 2014 (IEEE #5775): This paper focuses on the exposure to Radio Frequency (RF) Electromagnetic Fields (EMF) and on optimization methods to reduce it. Within the FP7 LEXNET project, an Exposure Index (EI) has been defined that aggregates the essential components that impact exposure to EMF. The EI includes, among other, downlink (DL) exposure induced by the base stations (BSs) and access points, the uplink (UL) exposure induced by the devices in communication, and the corresponding exposure time. Motivated by the EI definition, this paper develops stochastic approximation based self-optimizing algorithm that dynamically adapts the network to reduce the EI in a heterogeneous network with macro- and small cells. It is argued that the increase of the small cells coverage can, to a certain extent, reduce the EI, but above a certain limit, will deteriorate DL QoS. A load balancing algorithm is formulated that adapts the small cells coverage based on UL loads and a DL QoS indicator. The proof of convergence of the algorithm is provided and its performance in terms of EI reduction is illustrated through extensive numerical simulations. AUTHORS' ABSTRACT: Colombi et al. 2014 (IEEE #5778): In this study, an experimental method has been investigated for efficient assessments of whole-body specific absorption rates (SAR) from radio base station antennas. Using surface amplitude measurements of the electric field components together with an integral equation technique, a method is obtained which is not biased to specific antenna designs or phantom shapes. For realistic material parameters, it has been found that only the amplitude of the tangential field components over the phantom boundary is needed to accurately assess whole-body SAR, which makes the proposed method well suited for integration with commercially available SAR measurement systems. The method has been validated with simulations and measurements. Compared with a volumetric scan, and for the cases investigated, the measurement time was reduced with a factor larger than 3 while keeping the relative error smaller than 8%. AUTHORS' ABSTRACT: Beekhuizen et al. 2014 (IEEE #5789): Background With the increased availability of spatial data and computing power, spatial prediction approaches have become a standard tool for exposure assessment in environmental epidemiology. However, such models are largely dependent on accurate input data. Uncertainties in the input data can therefore have a large effect on model predictions, but are rarely quantified. Methods With Monte Carlo simulation we assessed the effect of input uncertainty on the prediction of radio-frequency electromagnetic fields (RF-EMF) from mobile phone base stations at 252 receptor sites in Amsterdam, The Netherlands. The impact on ranking and classification was determined by computing the Spearman correlations and weighted Cohenós Kappas (based on tertiles of the RF-EMF exposure distribution) between modelled values and RF-EMF measurements performed at the receptor sites. Results The uncertainty in modelled RF-EMF levels was large with a median coefficient of variation of 1.5. Uncertainty in receptor site height, building damping and building height contributed most to model output uncertainty. For exposure ranking and classification, the heights of buildings and receptor sites were the most important sources of uncertainty, followed by building damping, antenna- and site location. Uncertainty in antenna power, tilt, height and direction had a smaller impact on model performance. Conclusions We quantified the effect of input data uncertainty on the prediction accuracy of an RF-EMF environmental exposure model, thereby identifying the most important sources of uncertainty and estimating the total uncertainty stemming from potential errors in the input data. This approach can be used to optimize the model and better interpret model output. AUTHORS' ABSTRACT: de Miguel-Bilbao et al. 2015 (IEEE #5856): Personal exposure meters (PEMs) used for measuring exposure to electromagnetic fields (EMF) are typically used in epidemiological studies. As is well known, these measurement devices cause a perturbation of real EMF exposure levels due to the presence of the human body in the immediate proximity. This paper aims to model the alteration caused by the body shadow effect (BSE) in motion conditions and in indoor enclosures at the Wi-Fi frequency of 2.4 GHz. For this purpose, simulation techniques based on ray-tracing have been carried out, and their results have been verified experimentally. A good agreement exists between simulation and experimental results in terms of electric field (E-field) levels, and taking into account the cumulative distribution function (CDF) of the spatial distribution of amplitude. The KolmogorovSmirnov (KS) test provides a P-value greater than 0.05, in fact close to 1. It has been found that the influence of the presence of the human body can be characterized as an angle of shadow that depends on the dimensions of the indoor enclosure. The CDFs show that the E-field levels in indoor conditions follow a lognormal distribution in the absence of the human body and under the influence of BSE. In conclusion, the perturbation caused by BSE in PEMs readings cannot be compensated for by correction factors. Although the mean value is well adjusted, BSE causes changes in CDF that would require improvements in measurement protocols and in the design of measuring devices to subsequently avoid systematic errors. AUTHORS' ABSTRACT: Bamba et al. 2014 (IEEE #5860): A simple formula to determine the human average whole-body SAR (SARwb) under realistic propagation conditions is proposed in the GHz region, i.e. from 1.45 GHz to 5.8 GHz. The methodology is based on simulations of ellipsoidal human body models. Only the exposure (incident power densities) and the human mass are needed to apply the formula. Diffuse scattered illumination is addressed for the first time and the possible presence of a Line-of-Sight (LOS) component is addressed as well. As validation, the formula is applied to calculate the average whole-body SARwb in 3D heterogeneous phantoms, i.e. the virtual family (34 year-old male, 26 year-old female, 11 year-old girl, and 6 year-old boy) and the results are compared with numerical onesusing the Finite-Difference Time-Domain (FDTD) methodat 3 GHz. For the LOS exposure, the average relative error varies from 28% to 12% (resp. 1412%) for the vertical polarization (resp. horizontal polarization), depending on the heteregeneous phantom. Regarding the diffuse illumination, relative errors of 39.40%, 11.70%, 10.70%, and 10.60% are obtained for the 6 year-old boy, 11 year-old girl, 26 year-old female, and 34 year-old male, respectively. The proposed formula estimates well (especially for adults) the SARwb induced by diffuse illumination in realistic conditions. In general, the correctness of the formula improves when the human mass increases. Keeping the uncertainties of the FDTD simulations in mind, the proposed formula might be important for the dosimetry community to assess rapidly and accurately the human absorption of electromagnetic radiation caused by diffuse fields in the GHz region. Finally, we show the applicability of the proposed formula to personal dosimetry for epidemiological research. AUTHORS' ABSTRACT: Linhares et al. 2014 (IEEE #5868): A base station (BS) antenna operates in accordance with the established exposure limits if the values of electromagnetic fields (EMF) measured in points of maximum exposure are below these limits. In the case of BS in open areas, the maximum exposure to EMF probably occurs in the antennas boresight direction, from a few tens to a few hundred meters away. This is not a typical scenery for urban environments. However, in the line of sight (LOS) situation, the region of maximum exposure can still be analytically estimated with good results. This paper presents a methodology for the choice of measurement points in urban areas in order to assess compliance with the limits for exposure to EMF. AUTHORS' ABSTRACT: Prieto et al. 2014 (IEEE #5875): Misinterpretation of uncertainty in the measurement of the electromagnetic field (EMF) strength may lead to an underestimation of exposure risk or an overestimation of required measurements. The Guide to the Expression of Uncertainty in Measurement (GUM) has internationally been adopted as a de facto standard for uncertainty assessment. However, analyses under such an approach commonly assume unrealistic static models or neglect relevant prior information, resulting in non-robust uncertainties. This study proposes a principled and systematic framework for uncertainty analysis that fuses information from current measurements and prior knowledge. Such a framework dynamically adapts to data by exploiting a likelihood function based on kernel mixtures and incorporates flexible choices of prior information by applying importance sampling. The validity of the proposed techniques is assessed from measurements performed with a broadband radiation meter and an isotropic field probe. The developed framework significantly outperforms GUM approach, achieving a reduction of 28 % in measurement uncertainty. AUTHORS' ABSTRACT: Thielens et al. 2015 (IEEE #5884): This paper describes the design, calibration, and measurements with a personal, distributed exposimeter (PDE) for the on-body detection of radio frequency (RF) electromagnetic fields due to Wireless Fidelity (WiFi) networks. Numerical simulations show that using a combination of two RF nodes placed on the front and back of the body reduces the 50% prediction interval (PI50) on the incident free-space electric-field strength (Equation is included in full-text article.). Median reductions of 10 dB and 9.1 dB are obtained compared to the PI50 of a single antenna placed on the body using a weighted arithmetic and geometric average, respectively. Therefore, a simple PDE topology based on two nodes, which are deployed on opposite sides of the human torso, is applied for calibration and measurements. The PDE is constructed using flexible, dual-polarized textile antennas and wearable electronics, which communicate wirelessly with a Universal Serial Bus (USB) connected receiver and can be unobtrusively integrated into a garment. The calibration of the PDE in an anechoic chamber proves that the PI50 of the measured (Equation is included in full-text article.)is reduced to 3.2 dB. To demonstrate the real-life usability of the wireless device, a subject was equipped with the PDE during a walk in the city of Ghent, Belgium. Using a sample frequency of 2 Hz, an average incident power density of 59 nW m was registered in the WiFi frequency band during this walk. AUTHORS' ABSTRACT: Karada ,Yüceer and Abbasov 2015 (IEEE #5910): The present study analyses the electric field radiating from the GSM/UMTS base stations located in central Malatya, a densely populated urban area in Turkey. The authors have conducted both instant and continuous measurements of high-frequency electromagnetic fields throughout their research by using non-ionising radiation-monitoring networks. Over 15 000 instant and 13 000 000 continuous measurements were taken throughout the process. The authors have found that the normal electric field radiation can increase <25 % during daytime, depending on mobile communication traffic. The authors research work has also demonstrated the fact that the electric field intensity values can be modelled for each hour, day or week with the results obtained from continuous measurements. The authors have developed an estimation model based on these values, including mobile communication traffic (Erlang) values obtained from mobile phone base stations and the temperature and humidity values in the environment. The authors believe that their proposed artificial neural network model and multivariable least-squares regression analysis will help predict the electric field intensity in an environment in advance. AUTHORS' ABSTRACT: Lopez et al. 2015 (IEEE @5984): Purpose - Since first small personal exposimeters became available, some studies have characterized personal exposition to radio frequency electromagnetic fields. The effect of body and relative position of the exposimeter have been also analyzed but some questions are still unanswered. The paper aims to discuss these issues. Design/methodology/approach Using three personal exposimeters in four different subjects, the authors characterized and compared measurements in a controlled experiment. Findings The authors found statistically significance differences between exposimeters and subjects due to relative position (right and left) and a control position far from the body (center). It should indicate that body and relative position of the exposimeter affect directly to the measurement, conditioning final and average results. Research limitations/implications Measurements using personal exposimeters have to be reconsidered and controlled. AUTHORS' ABSTRACT: Varsier et al. 2015 (IEEE #6020): This paper presents a new metric to evaluate electromagnetic exposure induced by wireless cellular networks. This metric takes into account the exposure induced by base station antennas as well as exposure induced by wireless devices to evaluate average global exposure of the population in a specific geographical area. The paper first explains the concept and gives the formulation of the Exposure Index (EI). Then, the EI computation is illustrated through simple phone call scenarios (indoor office, in train) and a complete macro urban data long-term evolution scenario showing how, based on simulations, radio-planning predictions, realistic population statistics, user traffic data, and specific absorption rate calculations can be combined to assess the index. AUTHORS' ABSTRACT: Bolte, van der Zande and Kamer 2011 (IEEE #6026): In the past 5 years radiofrequency personal exposure meters have been used to characterize the exposure during daily activities. We found from calibration tests for the 12 frequency bands of the EME Spy 121 exposimeter in a Gigahertz Transverse Electromagnetic cell and an Open Area Test Site, that these measurements tend to underestimate the actual exposure. Therefore, a maximum frequency-dependent correction factor of 1.1-1.6 should be applied to the electric field. This correction factor consists of three multipliers correcting for calibration, elevation arrival angle, and influence of the body. The calibration correction factor should be determined per exposimeter, as the maximum range of response between exposimeters in a frequency band is 2.4 dB. Since the range of response for different elevation angles could reach 10.2 dB, a strict protocol for wearing the exposimeter during fieldwork should be followed to be able to compare and combine measurements made by different persons in the same microenvironments. Because the influenc |
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| Status | Completed With Publication | |
| Principal Investigator | ||
| Funding Agency | ????? | |
| Country | UNITED STATES | |
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| Comments | AUTHORS' ABSTRACT continued: AUTHORS' ABSTRACT: Huang and Wiart 2017 (IEEE 6839): This article presents a simplified method, based on surrogate modeling, to evaluate the day-to-day global population exposure to radio frequency (RF) electromagnetic fields (EMF) induced by a 4G network, from both uplink and downlink radio emissions in a typical urban city. The uncertainties of 4G-induced RF-EMF exposure of an entire population were characterized for the first time taking into account the variability linked to urban propagation environment, information and communication technology usage, EMF respectively from personal wireless devices and Evolved Node B (eNB), as well as uplink throughput. In addition, the study focuses on a sensitivity analysis in order to assess the influence of these parameters on RF-EMF exposure. Globally, results show that the 4G-induced RF-EMF exposure follows a Generalized Extreme Value distribution with an average value of 1.19×10 7 W/kg. Moreover, authors show that, contrary to what have been observed in the 3G-induced RF-EMF exposure, that is, the exposure is dominated by uplink radio emissions, results have highlighted the importance of received power density from eNB to the issue of 4G-induced RF-EMF exposure. In 4G, the uplink exposure from mobiles accounts for only 25% of global exposure, resulting from the high speed of uplink throughput. AUTHORS' ABSTRACT: Thors et al. 2017 (IEEE #6842): In this paper, a model for time-averaged realistic maximum power levels for the assessment of radio frequency (RF) electromagnetic field (EMF) exposure for the fifth generation (5G) radio base stations (RBS) employing massive MIMO is presented. The model is based on a statistical approach and developed to provide a realistic conservative RF exposure assessment for a significant proportion of all possible downlink exposure scenarios (95th percentile) in-line with requirements in a recently developed International Electrotechnical Commission standard for RF EMF exposure assessments of RBS. Factors, such as RBS utilization, time-division duplex, scheduling time, and spatial distribution of users within a cell are considered. The model is presented in terms of a closed-form equation. For an example scenario corresponding to an expected 5G RBS product, the largest realistic maximum power level was found to be less than 15% of the corresponding theoretical maximum. For far-field exposure scenarios, this corresponds to a reduction in RF EMF limit compliance distance with a factor of about 2.6. Results are given for antenna arrays of different sizes and for scenarios with beamforming in both azimuth and elevation. AUTHORS' ABSTRACT: Ying et al. 2017 (IEEE #6845): Fifth generation (5G) and beyond cellular systems are expected to support multiple uplink transmit antennas. Previous research demonstrates that designing waveforms satisfying near field user exposure constraints affects the farfield data rates achievable by portable devices using multiple transmit antennas. Therefore, user exposure constraints need to be taken into account in the uplink transmission covariance matrix design (e.g., precoder design) for 5G. Specific absorption rate (SAR) is a widely accepted user exposure measurement used in wireless communication regulations throughout the world. In this paper, we perform sum-rate analysis for a multi-user multiple-input multiple-output (MU-MIMO) system with SAR constraints enforced at each user. The maximum achievable sum rates for various channel state information at the transmitter (CSIT) scenarios are studied in this paper. The SAR-aware MIMO transmission methods are based on the modified waterfilling algorithm. Simulation results show our proposed methods outperform the conventional transmission strategy for the two user case. AUTHOR'S ABSTRACT: Zhao 2017 (IEEE #6853): An extrapolation method was proposed to increase the calculation efficiency and the accuracy of the incident power and specific absorption rate (SAR) in resonant exposure setups. The stable incident power and SAR were derived by observing the oscillating E-field envelope recorded during the finite-difference time-domain calculation. The extrapolation method was validated when applied to a waveguide loaded with two or four 35-mm-diameter Petri dishes at the H-field maximum for the resonant exposure at 1800 MHz. With the extrapolation, the computational time was reduced by 80% to derive the incident power with the error reduction of 93%, as compared to the calculation with the current mechanism until the accepted wave stability. For the SAR, the computational time was reduced by 77%. With the proper position and weighting of the E-field samples, the error of the averaged SAR in the cell monolayer was reduced from 4.62% to 1.31%. The proposed method applies to the scenario where the resonant frequency of the loaded setup drifts away from the driven frequency so that an oscillating E-field envelope is available. AUTHORS' ABSTRACT: Yu, Yang and Sim 2018 (IEEE #6905): The design of a novel practical 28 GHz beam steering phased array antenna for future fifth generation mobile device applications is presented in this communication. The proposed array antenna has 16 cavity-backed slot antenna elements that are implemented via the metallic back casing of the mobile device, in which two eight-element phased arrays are built on the left- and right-side edges of the mobile device. Each eight-element phased array can yield beam steering at broadside and gain of >15 dBi can be achieved at boresight. The measured 10 dB return loss bandwidth of the proposed cavity-backed slot antenna element was approximately 27.530 GHz. In addition, the impacts of users hand effects are also investigated. AUTHORS' ABSTRACT: Wen et al. 2017 (IEEE #6911): A new miniature circular high-impedance surface (HIS) is used to design a compact and low-profile multi-in multi-out (MIMO) antenna for wearable applications. The antenna is designed to operate from 2.4 to 2.49 GHz for wireless local area network application. By employing a pair of degenerated characteristic modes of a circular loop antenna, the MIMO antenna can achieve a good port-to-port isolation (>15 dB) without increasing its geometric size. A four-element HIS is chosen to match the antenna profile, and a 2 dBi antenna gain improvement is observed. The design was optimized considering the effect of packaging and then a prototype with the optimal parameters was fabricated and tested. Measurement results are in good agreement with simulation results. Furthermore, the loading effect due to lossy human tissue is also considered and the results show that the antenna has a robust performance against the human phantom and a low specific absorption rate can also be obtained. AUTHORS'ABSTRACT: Christ et al. 2022 (#9092): In this study, we investigate the absorption of the electric (E-) field induced in homogeneous biological tissue exposed to highly localized field sources, such as the charged tips of antennas, in proximity to the body, where E-field coupling dominates. These conditions are relevant for compliance testing of modern mobile phones, for which exposure is evaluated under conditions of a small separation between the radiator and the body. We derive an approximation that characterizes the decay of the induced E-field in the tissue as a function of distance. The absorption is quantified in terms of the local specific absorption rate (SAR) at the tissue surface as a function of the charge at the antenna tip. The approximation is based on the analytical evaluation of the E-fields of a charged disk under quasi-static conditions. We validate this approximation using full-wave simulations of dipoles. We demonstrate that the coupling mechanism of the E-field is dominated by the perpendicular field component, and that wave propagation need not be considered for the characterization of the exposure. The surface SAR decreases approximately with the 4th power of the distance and with the square of the ratio of the permittivities of the tissue and free-space. The approximation allows the induced maximum E-field to be predicted with an accuracy of better than 1.5 dB. The scientific and technical impact of the study can be summarized as: Capacitive coupling is dominant for electrically small antenna elements located close to the exposed tissue, whereas inductive coupling dominates at distances of a few millimeters or more The attenuation of the capacitively coupled E-fields in the tissue reaches the 4th power of the distance and is significantly higher than that of inductive coupling In the tissue, the amplitude of the perpendicular incident E-field is reduced by up to 60 dB in the extremely low frequency range because of the large contrast in dielectric properties of the tissue compared to free space For applications operating in the low MHz range, such as wireless chargers, exposure due to capacitive coupling is negligible due to the high dielectric contrast, and inductive coupling is dominant |