Transverse Electromagnetic Cell Research Articles

Electrooptic Probe Adapted for Bioelectromagnetic Experimental Investigations

In this paper, we present radio-frequency electro-magnetic field characterization of an electrooptic (EO) probe. This probe is able to simultaneously measure temperature and one component of the electric field (e-field) in a continuous wave (CW) or in a pulsed regime. For this purpose, linearity, selectivity, and sensitivity measurements are performed in air and in a cuvette filled with a water solution. The media are exposed to 1800-MHz CW electromagnetic wave through a transverse electromagnetic cell. Numerical characterization is also performed using finite-difference time-domain simulations. The EO probe presents a dynamic range exceeding 70 dB. Selectivity up to 25 dB is measured, demonstrating the ability of the EO probe to measure one unique component of the e-field. The EO probe sensitivity is equal to 0.77 and to 0.18 V · m-1Hz-½, in the air and in the water solution, respectively. This millimeter-sized EO probe is particularly suited for the measurement of ultrawide bandwidth and high-voltage e-fields up to a few megavolts per meter.

Microwave electromagnetic field regulates gene expression in T-lymphoblastoid leukemia CCRF-CEM cell line exposed to 900 MHz

Electric, magnetic, and electromagnetic fields are ubiquitous in our society, and concerns have been expressed regarding possible adverse effects of these exposures. Research on Extremely Low-Frequency (ELF) magnetic fields has been performed for more than two decades, and the methodology and quality of studies have improved over time. Studies have consistently shown increased risk for childhood leukemia associated with ELF magnetic fields. There are still inadequate data for other outcomes. More recently, focus has shifted toward Radio Frequencies (RF) exposures from mobile telephony. There are no persuasive data suggesting a health risk, but this research field is still immature with regard to the quantity and quality of available data. This technology is constantly changing and there is a need for continued research on this issue. To investigate whether exposure to high-frequency electromagnetic fields (EMF) could induce adverse health effects, we cultured acute T-lymphoblastoid leukemia cells (CCRF-CEM) in the presence of 900 MHz MW-EMF generated by a transverse electromagnetic (TEM) cell at short and long exposure times. We evaluated the effect of high-frequency EMF on gene expression and we identified functional pathways influenced by 900 MHz MW-EMF exposure.

Specific Absorption Rate Assessment Using Simultaneous Electric Field and Temperature Measurements

In this letter, the temperature measurement ability of an electrooptic probe as well as specific absorption rate (SAR) assessments via simultaneous in situ temperature and electric field characterization are reported. The measurements are carried out at 1800 MHz in a Petri dish filled with a water solution and placed in a transverse electromagnetic (TEM) cell. From the temperature sensitivity measurements, a standard deviation of 27 mK is obtained. The SAR values obtained both via temperature and electric field are also compared to finite-difference time-domain (FDTD) simulated numerical results. A difference of 5% is obtained between the two experimental SAR values. These measured SAR values are consistent with those obtained by the numerical simulations.

ELECTROMAGNETIC AND THERMAL ANALYSES OF IMPROVED GTEM CELLS FOR BIOELECTROMAGNETIC EXPERIMENTS

A GHz Transverse Electromagnetic (GTEM) cell is proposed to investigate the arising of biological efiects due to electromagnetic signals at the typical frequencies of mobile phone communications. The proposed GTEM cell, placed within a commercial incubator, has been ad hoc designed and fabricated to expose in vitro samples. The electromagnetic and the thermal analyses of the GTEM cell are reported. In particular, the inner electromagnetic fleld and the Speciflc Absorption Rate of the exposed sample (saline solution having 9g/l concentration) have been evaluated by a home- made computer code based on the transmission line matrix method. Furthermore, the thermal analysis of the exposure arrangement has been carried out by the flnite difierence time domain algorithm.

Higher-Order Transverse Electric and Transverse Magnetic Modes in Gigahertz Transverse Electromagnetic Cells

Higher-order transverse electric and transverse magnetic modes in gigahertz transverse electromagnetic cells are investigated using the mode-matching method. The gigahertz transverse electromagnetic cell is modeled as a right rectangular pyramid with a thin septum. Fields are expanded in eigenfunctions of spherical coordinates, and the orthogonality of sinusoidal functions is utilized to obtain simple modal equations. Computations are performed to check the accuracy and convergence of modal series solutions. The characteristics of modal series solutions are presented in terms of gigahertz transverse electromagnetic cell geometries.

Effect of Electromagnetic Pulses (EMP) on associative learning in mice and a preliminary study of mechanism

Purpose: To investigate the effects of electromagnetic pulses (EMP) on associative learning in mice and test a preliminary mechanism for these effects.Materials and methods: A tapered parallel plate gigahertz transverse electromagnetic (GTEM) cell with a flared rectangular coaxial transmission line was used to expose male BALB/c mice to EMP (peak-intensity 400 kV/m, rise-time 10 ns, pulse-width 350 ns, 0.5 Hz and total 200 pulses). Concurrent sham-exposed mice were used as a control. Associative learning, oxidative stress in the brain, serum chemistry and the protective action of tocopherol monoglucoside (TMG) in mice were measured, respectively.Results: (1) Twelve hour and 1 day post EMP exposure associative learning was reduced significantly compared with sham control (p < 0.05) but recovered at 2 d post EMP exposure. (2) Compared with the sham control, lipid peroxidation of brain tissue and chemiluminescence (CL) intensity increased significantly (p < 0.05), while the activity of the antioxidant enzymes Superoxide Dismutase [SOD], Glutathione [GSH], Glutathione Peroxidase [GSH-Px], Catalase [CAT]) decreased significantly (p < 0.05) at 3 h, 6 h, 12 h and 1 d post EMP exposure. All these parameters recovered at 2 d post EMP exposure. (3) No significant differences between the sham control group and EMP exposed group were observed in serum cholesterol and triglycerides. (4) Pretreatment of mice with TMG showed protective effects to EMP exposure.Conclusions: EMP exposure significantly decreased associative learning in mice and TMG acted as an effective protective agent from EMP exposure. This mechanism could involve an increase of oxidative stress in brain by EMP exposure.

Wireless Coexistence and EMC of Bluetooth and 802.11b Devices in Controlled Laboratory Settings

This paper presents experimental testing that has been performed on wireless communication devices as victims of electromagnetic interference (EMI). Wireless victims included universal serial bus (USB) network adapters and personal digital assistants (PDAs) equipped with IEEE 802.11b and Bluetooth technologies. The experimental data in this paper was gathered in an anechoic chamber and a gigahertz transverse electromagnetic (GTEM) cell to ensure reliable and repeatable results. This testing includes: Electromagnetic compatibility (EMC) testing performed in accordance with IEC 60601-1-2, an in-band sweep of EMC testing, and coexistence testing. The tests in this study show that a Bluetooth communication was able to coexist with other Bluetooth devices with no decrease in throughput and no communication breakdowns. However, testing revealed a significant decrease in throughput and increase in communication breakdowns when an 802.11b source is near an 802.11b victim. In a hospital setting decreased throughput and communication breakdowns can cause wireless medical devices to fail. It is therefore vital to have an understanding of the effect EMI can have on wireless communication devices.

Acute Effect of Exposure of Mollusk Single Neuron to 900-MHz Mobile Phone Radiation

The goal of the present work was to explore the influence of commercially available cell phone irradiation on the single neuron excitability and memory processes. A Transverse Electromagnetic Cell (TEM Cell) was used to expose single neurons of mollusk to the electromagnetic field.Finite-Difference Time-Domain (FDTD) method was used for modeling the TEM Cell and the electromagnetic field interactions with living nerve ganglion and neurons. Neuron electrophysiology was investigated using standard microelectrode technique.The specific absorption rate (SAR) deposited into the single neuron was calculated to be 0.63 W/kg with a temperature increment of 0.1°C. After acute exposure, average firing threshold of the action potentials was not changed. However, the average latent period was significantly decreased. This indicates that together with latent period the threshold and the time of habituation might be altered during exposure. However, these alterations are transient and only latent period remains on the changed level.

Unbalanced Currents in Integrated Circuits and Their Effect on TEM Cell Emissions

Transverse ElectroMagnetic (TEM) cell measurements are often used to evaluate the potential of ICs to cause radiated emissions in printed circuit boards. These measurements are a function of the unbalanced current on package power pins, for example, where more current enters one side of an IC than another, and the displacement current caused by capacitive coupling from the power grid mesh to the septum of the TEM cell. The relationship between unbalanced currents and TEM cell measurements is derived in this paper. A distributed model of the on-die power delivery network is developed to show that unbalanced currents may be caused by an asymmetric power pin arrangement, by an imbalance in package impedance, or by an imbalance in the impedance of the on-die power delivery network. To validate results, the magnitude and phase of high-frequency power-pin currents were measured on a test chip. Experiments showed that results could be used to guide modifications to the chip's connection to the printed circuit board power structure to minimize unbalanced currents and, thus, to minimize TEM cell measurements.

DC-DC Buck Converter EMI Reduction Using PCB Layout Modification

The paper treats the effect of layout on the electromagnetic interference (EMI) of buck converters. An optimized layout design for dc-dc synchronous buck converter is proposed for EMI reduction. Six different layout versions are analyzed with respect to loop area, loop inductance, radiating dipole moments, and far-field radiation. Optimizations are done with respect to field-effect transistor (FET), decoupling capacitor and via placement. Passive full-wave simulations are used to estimate and verify the loop inductance and far-field emissions. Those are compared with measurements. A gigahertz transverse electromagnetic (GTEM) cell is used to quantify the dipole moments in the printed circuit board (PCB) for estimating the far field and comparing to measurement.

Response of a Short-Dipole Probe to a Nonuniform $E$ -Field of a TEM Cell

A transverse electromagnetic cell is often used as a standard field generator since the E-field strength can be predicted using a simple formula. However, the E-field of the cell varies with respect to the location, and the estimated E-field strength is valid only at the center of the cell. Accordingly, the probe size should be sufficiently small compared with the field variation to ignore the nonuniformity of the field. Although the nonuniformity of the incident field can be improved by using a large cell, the usable upper frequency becomes low. In this paper, probe responses to the nonuniform E-field of a cell are investigated by a sequentially combined numerical method. The proposed method is validated by the comparison of the calculated results with the measured ones.

A Multistep Approach for Accurate Permittivity Measurements of Liquids Using a Transmission Line Method

High-precision permittivity measurements of liquids are essential for specifying the specific absorption rate (SAR) of radio-frequency power absorbed by the human tissue. At Van Swinden Laboratorium (VSL), a commercial unit is used for these measurements, which uses a combination of transmission and reflection methods. The permittivity of unknown liquids is derived from the measured different scattering parameters of a transverse electromagnetic cell when the cell is empty and when it is filled with liquid. The flat slab structure of the cell makes it convenient for liquid filling and cleaning. The method is an efficient complementary approach for permittivity measurements compared with more complex setups in other national metrology institutes, but for reaching a low uncertainty, some inherent disadvantages need to be overcome. In this paper, a multistep approach is proposed using a combination of curve fitting, nonlinear progressive technique, and improved transmission line models in order to improve the uncertainty of the permittivity measurements. This approach is applicable even without a priori knowledge of the liquid properties. Using this approach, the useful frequency range of the commercial unit is successfully extended from 200 MHz-3 GHz to at least 100 MHz-4 GHz, and the accuracy is significantly improved to the level where it becomes comparable to more primary methods. The results obtained with this new method agree very well with the reference data from the literature.

Calibration and uncertainties in personal exposure measurements of radiofrequency electromagnetic fields

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 influence of the body depends on the azimuth angle of arrival, it may lead to an over- or underestimation. Thus, the body correction factor is an average over the angles and should only be applied in activities involving movement through the full 360° range of random angles of arrival.

Performance test of personal RF monitor for area monitoring at magnetic confinement fusion facility

For safety management at a magnetic confinement fusion-test facility, protection from not only ionising radiation, but also non-ionising radiation such as the leakage of static magnetic and electromagnetic fields is an important issue. Accordingly, the use of a commercially available personal RF monitor for multipoint area monitoring is proposed. In this study, the performance of both fast- and slow-type personal RF monitors was investigated by using a transverse electromagnetic cell system. The range of target frequencies was between 10 and 300 MHz, corresponding to the ion cyclotron range of frequency in a fusion device. The personal RF monitor was found to have good linearity, frequency dependence and isotropic response. However, the time constant for the electric field sensor of the slow-type monitor was much longer than that for the fast-type monitor. Considering the time-varying field at the facility, it is found that the fast-type monitor is suitable for multipoint monitoring at magnetic confinement fusion test facilities.

Real-Time RF Exposure Setup Based on a Multiple Electrode Array (MEA) for Electrophysiological Recording of Neuronal Networks

Real-time investigations on the effects of mobile-phone exposure on neuronal activity are considered the highest priority in the health risk assessment of RF fields. Therefore, this paper describes a new real-time exposure setup for electrophysiology recordings, combining an open transverse electro-magnetic cell with a multiple electrode array. The system was numerically and experimentally characterized at a frequency of 1.8 GHz, representative of the uplink band of the GSM1800. Finite-difference time-domain simulations were performed, as well as measurements of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> scattering parameter and temperature increases for specific absorption rate (SAR) determination. The local mean SAR value near the solution-electrodes interface was evaluated from the temperature measurements and coincided with the simulated one. The same is true for <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> measurements that were consistent with numerical results; hence, confirming the accuracy of the modeling. Nevertheless, nonuniform SAR distributions were observed near the recording electrodes. Good system efficiency was determined from both numerical analysis and experimental data. Thermal behavior was evaluated and a small temperature increment of 0.3°C for a local experimental SAR of 3.2 W/kg was measured.

Using GTEM Cell to Measure RCS of Electrically Small Scatterers

A new method of using gigahertz transverse electromagnetic (GTEM) cells to measure backscattering cross section (BCS) of electrically small scatterers is put forward in this letter. Compared to the traditional method of measuring BCS, the cost of this new method is low, the measurement process is simple, and the required sites are small. The correctness and feasibility of this method are confirmed by experimental results. This letter provides a completely creative method of BCS measurement and expands a new application area for GTEM cell.

Evaluation of hematopoietic system effects after in vitro radiofrequency radiation exposure in rats

Purpose: This study was designed to investigate the effect of a 900-MHz continuous-wave (CW) radiofrequency radiation (RFR) exposure on the hematopoietic system in the rat.Materials and methods: Rat long bones (femur and tibia) were divided into two groups: Sham-exposed and radiofrequency (RF)-exposed. The mean Specific energy Absorption Rate (SAR) at 900-MHz averaged over the bone marrow (calculated by the finite-difference-time-domain ( fdtD) method) was 2 W/kg at 16.7 W root mean square (rms) forward power into a Transverse Electromagnetic (TEM) cell. The bones, placed in a Petri dish containing media, were kept in the TEM cell for 30 min duration of sham or RF exposure. After exposure, the bone marrow cells were extracted and the following end points were tested: (a) Proliferation rate of whole bone marrow cells, (b) maturation rate of erythrocytes, (c) proliferation rate of lymphocytes, and (d) DNA damage (strand breaks/alkali labile sites) of lymphocytes.Results: Our data did not indicate any significant change in the proliferation rate of bone marrow cells and lymphocytes, erythrocyte maturation rate and DNA damage of lymphocytes.Conclusion: Our findings revealed no effect on the hematopoietic system in rats for 900 MHz CW RF exposure at the 2 W/kg localised SAR limit value recommended by the International Commission for Non-Ionising Radiation Protection (ICNIRP) for public exposures.

Low intensity microwave radiation as modulator of the l-lactate dehydrogenase activity

In this study, we investigated experimentally the possibility of modulating protein activity by low intensity microwaves by measuring alternations of L: -Lactate Dehydrogenase enzyme (LDH) activity. The LDH enzyme solutions were irradiated by microwaves of the selected frequencies and powers using the Transverse Electro-Magnetic (TEM) cell. The kinetics of the irradiated LDH was measured by continuous monitoring of nicotine adenine dinucleotide, reduced (NADH) absorbance at 340 nm. A comparative analysis of changes in the activity of the irradiated LDH enzyme versus the non-radiated enzyme was performed for the selected frequencies and powers. It was found that LDH activity can be selectively increased only by irradiation at the particular frequencies of 500 MHz [electric field: 0.02 V/m (1.2 × 10⁻⁶ W/m²)-2.1 V/m (1.2 × 10⁻² W/m²)] and 900 MHz [electric field: 0.021-0.21 V/m (1.2 × 10⁻⁴ W/m²)]. Based on results obtained it was concluded that LDH enzyme activity can be modulated by specific frequencies of low power microwave radiation. This finding can serve to support the hypothesis that low intensity microwaves can induce non-thermal effects in bio-molecules.

A New Method of Interference Evaluation Between an Ultrawideband System and a Wireless LAN Using a Gigahertz Transverse Electromagnetic Cell

A new method of evaluating the interference to a wireless LAN with a built-in antenna using a gigahertz transverse electromagnetic (GTEM) cell is proposed. The GTEM cell can generate a wideband electromagnetic field from dc up to several gigahertz with a high spatial uniformity in the cell. This is advantageous for configuring a system for a victim receiver with a built-in antenna. Furthermore, the strength of the interfering electromagnetic field to be applied to the victim can be directly calculated from a given equivalent isotropically radiated power and propagation distance of the interfering signal in free space. It should also be noted that a GTEM has a conductive enclosed structure that is much smaller than typical anechoic rooms. As an example of use of the method, the evaluation of interference between an IEEE 802.11a wireless LAN and a direct-sequence spread-spectrum UWB was conducted. Investigations are further conducted on the effects of the UWB signal on the throughput of the victim wireless LAN system on the basis of bit error rate estimated with measurement results of the amplitude probability distribution of the UWB signal.

New Advances on Correlating TEM Cell and OATS Emission Measurements

This paper proposes an improvement for the standard algorithms used to correlate the radiated emission measurements performed in a gigahertz transverse electromagnetic (GTEM) cell to measurements performed at an open area test site (OATS). The improvement compared with standard correlation algorithms lies in the ability to use literally all data measured. This is achieved by using nonlinear regression models in order to estimate the amplitudes of a multipole model. Assuming equally phased dipole moments and using nine measurements, numerical simulations indicate significant superiority of this new algorithm in comparison to the standard approach. The results can be improved further by using additional measurements. The simulation results show strong evidence that the algorithm also provides precise results for the amplitudes, if not all components of the dipole moments are in phase. Experiments with a real-world test object further validate the method.