Gigahertz Transverse Electromagnetic Cell Research Articles

Background levels and brain organoid impact of RF field exposure in a healthcare environment

Introduction: This study is an introduction to the empirical and impact evaluation of radiofrequency electromagnetic field (RF-EMF) radiation exposure in a healthcare environment, focusing on an indoor microenvironment. It explores the expression of various genes associated with cellular responses, cell proliferation, senescence, and apoptotic cell death. The assessment analyzes current personal mobile communications (2G-5G FR1), providing a clear understanding of RF-EMF exposure and compliance with regulatory limits.Methods: The signals from different wireless communication systems at Hospital Universitario de Canarias (HUC) in Tenerife, Canary Islands, Spain, were examined in 11 locations. Four measurement campaigns were performed with frequency-selective exposimeters (PEMs) and an EME Spy 200 MVG, and experimental electric field values were compared as a long-term exposition. The frequency with the highest contribution (2.174 V/m) observed (1840 MHz) in UMTS was selected for biological effects evaluation.Results: The study focuses on four locations with the highest exposure to communication systems (downlinks), analyzing the results to verify compliance with regulations that ensure the safety of patients, the general public, and healthcare workers. LTE B20 (DL), GSM+UMTS 900 (DL), GSM 1800 (DL), UMTS 2100 (DL), and LTE B7 (DL) exhibited relatively higher E/m values throughout the campaigns, and these values consistently remained below the ICNIRP reference levels, signifying a consistently low level of exposure. In addition, this work presents the biological effects on neural stem cells (NSCs) using 3D brain organoids (BOs) exposed to RF signals in a validated and commercial experimental setting: the Gigahertz Transverse Electromagnetic cell (GTEM). The GTEM allows for the creation of homogeneous field electromagnetic fields in a small, enclosed setting and guarantees exposure conditions in a wide range of frequencies. BOs are an in vitro 3D cell-culture technology that reproduces the cellular composition and structure of the developing brain. Analyzing the expression of several genes associated with cellular responses, cell proliferation, senescence, and apoptotic cell death, we found that exposure of BOs at 1840 MHz did not affect mRNA expression in brain genes related to apoptosis or senescence. However, a decrease in gene expression for cell proliferation and cell activity markers was observed during the differentiation stage of BOs.Discussion: The discussion emphasizes the coexistence and evolution of various heterogeneous networks and services throughout the four measurement campaigns. Across all measured results, the levels of the obtained E-field were consistently well below the exposure limits set by internationally accepted standards and guidelines. These obtained values have been established in order to consider their potential effects on cell proliferation and cell activity, especially in differentiating biological organisms. Consequently, the results obtained and the methodology presented could serve as a foundational framework for establishing the basis of RF-EMF assessment in future heterogeneous 5G developments, particularly in the millimeter wave (mmWave) frequency range, where the forecast is for massive high-node density networks.

Calibrating a Radio Frequency Electrooptic Sensor for Field-Relevant Temperature Conditions in a Laboratory Setting

Legacy high-powered electric field measurement devices, such as flush plate dipoles (D-dots) and waveguides, are the primary diagnostic tools used for free-field experimentation. Unfortunately, these metallic devices perturb the electric field of interest via scattering and require the use of coaxial cables (fluctuate with temperature). Electrooptic (EO) probes offer a potential solution as they minimally perturb the electric field, and fiber-optic cables can be designed to correct or prevent temperature fluctuations. However, to replace the legacy diagnostics, it is critical that the EO probes are calibrated in field-relevant conditions (outdoor temperatures between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.4~^{\circ} \text{C}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$49~^{\circ} \text{C}$ </tex-math></inline-formula> ). Characterization of a modern EO sensor is done by using an environmental chamber and a gigahertz transverse electromagnetic (GTEM) cell. The collected data in this article indicates that modern <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {LiNbO}_{{3}}$ </tex-math></inline-formula> EO sensors have linear changes across both various temperatures and electric fields. This article outlines the process of creating field-relevant conditions in laboratory settings. Because temperature effects are ubiquitous with most devices, the temperature response of the EO probe needed to be isolated from all other temperature effects. Using a novel way of applying the design of experiments (DoE) method, the temperature response of the EO probe can be isolated and a linear trend can be resolved. The data suggest that the EO probe under test can be used to measure RF fields as long as a small correction factor is applied to 0.52% per °C for every °C away from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$22.0~^{\circ} \text{C}$ </tex-math></inline-formula> in either direction.

Electric Field Sensor Approach to Determine Fidelity and Overmoding Region of GTEM Cell

Characterizing new electric field (E-field) sensors requires knowing the frequency limits of one’s radio-frequency (RF) chamber. A commonly used RF chamber is called a gigahertz transverse-electromagnetic (GTEM) cell that supports transverse-electromagnetic (TEM) fields through the gigahertz spectra. This manuscript proposes a new methodology for determining the range of usable frequencies within a GTEM cell having unknown characteristics (e.g., after moving a GTEM cell from one laboratory to another). Above a certain frequency, all frequencies become overmoded and yield unreliable measurements. We found that comparing international standards to measured data can provide insights into where overmoding occurs. The comparison to international standards was assisted by a derived free-space wave impedance formula in the frequency domain using both flush-plate dipole (D-dot) and magnetic field (B-dot) probes. Overall, this article proposes a new tool for determining the operating frequencies at which GTEM cells can reliably function in accordance with international standards before overmoding occurs.

Near-Field Shielding Analysis of Conformal Coating Materials for Integrated Circuits

This article analyzes a near-field shielding performance of conformal shielding materials for integrated-circuits (ICs) by experiments. Two test boards with loop-type and patch-type patterns are designed to generate magnetic-field and electric-field, respectively. These sources mimic typical electromagnetic radiations from actual ICs. For shielding analysis, single-layered conductive materials, multilayered conductive and magnetic materials, hybrid materials with a mixture of conductive and magnetic pastes are considered as conformal shielding materials, which are coated on the test boards for measurements. Magnetic-field and electric-field shielding effectiveness (SE) of the materials evaluate by measurements using loop-probe, strip-line, and gigahertz transverse electromagnetic cell at the frequency range from 300 kHz to 3 GHz. Near-field SEs measured by three methods correspond generally well with each other at the frequency range up to a few hundred MHz. At the higher frequency, the ambient EM environment can affect the accuracy of the near-field measurements by the loop-probe and strip-line. For validation, numerical simulation is fulfilled and compared with measured results. Theoretical interpretation based on the Schelkunoff's SE decomposition is also addressed.

Experiment Reproducibility and Electric Field Uniformity in GTEM

Giga-Hertz Transverse Electromagnetic (GTEM) cell is a simpler and cheaper alternative to the full-scale anechoic chamber. It is an equipment of choice in a lot of partial discharge (PD) research, especially for antenna validation. According to a good practice the cell must be validated, or also known as calibrated, for its usability. The calibration term means validating the uniformity of electrical field produced at the point of measurement. This paper introduced a verification technique to be used to validate the integrity of input and response signals. This step is essential so that the reproducibility of the experiment is warranted and also to support the calibration analysis result. It was found that the input and response signals were reproducible and consistent. The calibration analysis on the existing bespoke GTEM showed that electric field uniformity at the prescribed area of testing complied with an established practice. Therefore, the GTEM cell can be used to conduct related experiment.

Investigation of the plane wave coupling to a linearly loaded transmission line network

The article is concerned with a complex investigation of the influence of the plane wave coupling with a certain function of time, incident direction and polarization to a linearly loaded transmission line network comprised of three single-wire conductors with different lengths connected in the center. Line load is represented as 50 Ω resistors connected to all terminations of the transmission line network. The exemplary network was modeled on a computer and experimentally investigated in a gigahertz transverse electromagnetic GTEM cell, which allows creating an electromagnetic field of a certain direction. The coupled voltage at the terminals of the network was investigated in the frequency and time domains. To conduct an experiment in the frequency domain, both to create an electromagnetic field inside the GTEM camera and to measure the induced voltage at the terminations of the network, a vector network analyzer VNA was used. To conduct an experiment in the time domain for the sake of creating an electromagnetic field, a high-voltage voltage generator was used, whereas a strobing oscilloscope was used to measure the induced voltages. The simulation was performed in the LTspice software - a tool for calculating electrical and electronic circuits, and Matlab. It is also examined to show the compliance with the experimental results. On the basis of obtained results, the author was able to identify the main aspects that may be useful in modeling and predicting the electromagnetic processes occurring in linearly loaded conductors, power supply and / or data transmission systems.

On the design and fabrication of a large GTEM cell and its challenges

This paper presents the design of a large Gigahertz Transverse Electromagnetic (GTEM) cell for Electrical/Electronic Sub-Assembly (ESA) testing of a car or other information technology (IT) equipment as well as the challenges of its design and fabrication. The 7.5 meter long and 4 meter width and 4 meter height dimensions of this cell are large enough to test ESAs inside. The operating frequency band is from 30 MHz to 6 GHz based on CISPR standards. To increase the operating frequency of the GTEM and to improve the uniformity of the wave, hybrid absorbers are mounted at the end wall. These absorbers consist of ferrite tile and pyramid absorbers, which have large bandwidth and high performance. The dimensions of the GTEM cell are too large and therefore full wave simulation is difficult and time consuming. In this paper, we have introduced a two-step method to convert a pyramidal absorber into a one-layer flat absorber. This technique simplifies our GTEM cell full wave simulation. On the fabrication side, the effect of distortion of a long metal sheet on the performance of the room are numerically examined. Finally, the acceptable measurement results of the GTEM are reported.

Numerical Analysis and Measurement of Electric field Strength inside GTEM Cell at GSM Frequencies

A miniaturised gigahertz transverse electromagnetic (GTEM) cell is designed and fabricated to generate uniform electric (E-) field, essential for studying the radio frequency exposure effect on tissue equivalent liquids at global system for mobile (GSM) communication frequencies (914 MHz and 2.10 GHz). The simulation procedure is discussed and its results are compared with measurement data. The E-field strength inside the GTEM cell is scanned using a microstrip based E-field probe and complete uncertainty evaluation procedure is discussed. Theoretically, simulated and measured E-field strength is reported with expanded uncertainty.

Calibration Proposal for UHF Partial Discharge Measurements at Power Transformers

The continuous, non-intermitted service of electrical grids relies on the reliability of their assets, e.g., power transformers. Local insulation defects can result in serve failures such as breakdowns with severe subsequent costs. The prevention of such events is crucial. Hence, partial discharge (PD) activity at power transformers is evaluated directly in the factory before shipment. Additionally, PD activity can be monitored during service using the ultra-high frequency (UHF) method. In this contribution, a calibration procedure is proposed for the UHF method. The calibration process is required to ensure both, reproducibility and comparability of UHF measurements: Only a calibrated UHF measurement procedure can be introduced supplementary to IEC 60270 in acceptance tests of power transformers. The proposed calibration method considers two factors: The influence of the UHF-antenna’s sensitivity and the PD recorder characteristics including accessories such as cable damping, pre-amplifier, etc. The former is addressed by a characterization of UHF sensors using the standard antenna factor (AF) in a gigahertz transverse electromagnetic (GTEM) cell. The PD recorder’s influence is corrected by using a defined, invariable test signal as reference for all recording devices. A practical evaluation of the proposed calibration procedure is performed in a laboratory setup using different UHF recording devices and UHF sensors using artificial PD signals and real voltage-driven PD sources.

Field measurement and verification of the UHF calibration platform based on the GTEM cell

The measurable electric field of the partial discharge ultra-high-frequency (PD UHF) detection system calibrated by a gigahertz transverse electromagnetic cell (GTEM) has been used as a key indicator to evaluate the performance of the detection system and regarded as the electric power standard. In this study, the sweep frequency and pulse signal were injected to the GTEM cell, and then the waveform and amplitude of the calibrated field strength were calculated by using the transfer function and voltage response of the monopole antennas. In the case of sweep frequency, comparing the measured result of the Narda field strength metre and the calculated result of monopole antennas, the error was found to be <8%, which verifies the correctness of the calibration of the monopole antennas to the steady-state electric field in the GTEM. In the case of pulse injection, comparing the simulation result of computer simulation technology and the calculated result of monopole antennas, the error of the peak of the field strength was found to be 1.7%, which verifies the correctness of the calibration of the monopole antennas to the pulse electric field in the GTEM.

Design of Wideband GHz Electric Field Sensor Integrated with Optical Fiber Transmission Link for Electromagnetic Pulse Signal Measurement.

The detection of high frequency overvoltage and partial discharge is of great significance in evaluating the insulation condition of high-voltage power equipment. A wideband GHz electric field (E-field) sensor for electromagnetic pulse (EMP) signal measurement was proposed in this paper. An optical fiber transmission link was adopted in the design in order to implement high-voltage isolation and reduce electromagnetic interference during transmission. The designed sensor was mainly made up of a differential electric field (D-dot) antenna, transmitter, and receiver. The D-dot antenna was designed to detect high frequency E-field strength and generate a corresponding voltage signal, which was converted into an optical signal by the transmitter. The optical signal could be transmitted a large distance through an optical fiber without electromagnetic interference and changed back to a voltage signal again by a receiver. The design process of the sensor was introduced in detail, and experiments were performed using a gigahertz transverse electromagnetic (GTEM) cell and an EMP simulator to verify it. The results indicated that the designed sensor had a good performance besides an expectable delay due to the optional amplifier.

Near-Field Validation of Dipole-Moment Model Extracted From GTEM Cell Measurements and Application to a Real Application Processor

Source models for radiated emissions of test integrated circuits are extracted from measurements using a gigahertz transverse electromagnetic cell. The source model consists of magnitudes and relative phases of three dipole moments. The extracted source models are then validated by the measurements of a near-field scan. The measured near fields are quite similar with those calculated from extracted dipole moments when the target source size is small as compared to the observation distance. The effects and valid ranges of the proposed modeling method are quantitatively investigated in calculations and simulations. The proposed modeling and validation procedures are also applied to the radiated emissions of an application processor (AP) in a real operating mobile product. The extracted dipole models for the real AP show reasonable accuracy. The proposed source modeling approach should be helpful for investigating and resolving system-level radio frequency interference problems.

Taking Into Account GTEM Field Nonuniformities in Radiated Immunity Simulations Through a Simple Measurement

When performing immunity measurements through the 10 × 10 cm aperture that some gigahertz transverse electromagnetic (GTEM) cells feature, its field uniformity is generally unknown. Yet, this (non)uniformity causes an error on test results. Measuring the field uniformity by taking a grid of samples would be time-consuming. Even with such a measurement, it would be hard to predict the magnitude of this error in immunity measurement results. Therefore, another approach to the problem was taken: several imperfections of the GTEM cell were characterized simultaneously by measuring its input reflection coefficient. Then, the immunity of a device under test was simulated with the nominal GTEM field plus the first reflection. Entering this field model into the simulation corrected the major error in the 0.1-2.0 GHz range in some of our test cases, with no degradation in any case. Thanks to the speed of this method, it may be broadly applied, even only to quantify the effect of some of the GTEM's imperfections on a given immunity measurement.

Oxidative stress response in SH-SY5Y cells exposed to short-term 1800 MHz radiofrequency radiation

ABSTRACTThe exact mechanism that could explain the effects of radiofrequency (RF) radiation exposure at non-thermal level is still unknown. Increasing evidence suggests a possible involvement of reactive oxygen species (ROS) and development of oxidative stress. To test the proposed hypothesis, human neuroblastoma cells (SH-SY5Y) were exposed to 1800 MHz short-term RF exposure for 10, 30 and 60 minutes. Electric field strength within Gigahertz Transverse Electromagnetic cell (GTEM) was 30 V m−1 and specific absorption rate (SAR) was calculated to be 1.6 W kg−1. Cellular viability was measured by MTT assay and level of ROS was determined by fluorescent probe 2′,7′-dichlorofluorescin diacetate. Concentrations of malondialdehyde and protein carbonyls were used to assess lipid and protein oxidative damage and antioxidant activity was evaluated by measuring concentrations of total glutathione (GSH). After radiation exposure, viability of irradiated cells remained within normal physiological values. Significantly higher ROS level was observed for every radiation exposure time. After 60 min of exposure, the applied radiation caused significant lipid and protein damage. The highest GSH concentration was detected after 10 minute-exposure. The results of our study showed enhanced susceptibility of SH-SY5Y cells for development of oxidative stress even after short-term RF exposure.

A Novel Two-Cap Filter for Routing Noise Suppression Using Extended EBG Analysis

This paper proposes a novel two-cap wideband filter that suppresses the high-frequency noise in a power trace routing. By combining electromagnetic bandgap (EBG) theory and decoupling capacitors, the EBG propagation characteristics are studied and a systematic design procedure is proposed. Advanced Design System (ADS) and gigahertz transverse electromagnetic (GTEM) cell measurement are used to validate the accuracy of the proposed analysis and the validity of the design. It is found that the filter gives a 67% stopband with 20-dB suppression, using only two capacitors that are spaced one-twentieth of a wavelength apart.

Electromagnetic Susceptibility of Semiconductor Junction Igniter With Different Doping Density

The fabrication and radio frequency (RF) protection ability of semiconductor junction igniter (SJI) is presented. The SJI consists of two back-to-back PN junctions, with a predesigned size, which is designed to protect against the RF and electrostatic discharge events. The effect of doping density on electromagnetic susceptibility of SJI is studied by two kinds of SJI. In addition, SJI under different electromagnetic environments are tested, which are based on radiation and conductive coupling modes. For the radiated excitation, SJI with different doping density are tested by gigahertz transverse electromagnetic cell experiment ranging from 10 MHz to 1 GHz. The results show that the resonance frequency agrees with the resonance principle of antenna design. The best coupling frequency is 300 MHz and both types of SJI are not fired for the electric field strength of 500 V/m. For the excitation of directly injecting RF energy, both types of SJI are tested by RF sensitivity testing. Based on the Langlie method, the RF no-fired level is calculated. According to the results, we consider the SJI will become inert by increasing the doping density of n -type silicon. Furthermore, we conclude that there is little correlation between two kinds of coupling modes.

Study on the Disc Sensor Based on the Cavity Mold Theory

Ultra-high-frequency (UHF) sensor is the vital component of a partial discharge detection system and its coupling performance is affected by structural parameters. On the basis of the cavity model theory, this paper studied the influence of the disc electrode diameter, the thickness, the dielectric constant of the dielectric substrate, and the position of the coaxial connection on the performance of the disc-type UHF sensor with the application of the XFdtd software. The simplified finite-difference time-domain simulation model for the gigahertz transverse electromagnetic (GTEM) cell has been established, and the influence of the coaxial feed position on the performance of the disc-type UHF sensor is studied via the frequency domain effective heights in the simulation. The result shows that as the disc electrode diameter, the thickness, and the dielectric constant of the dielectric substrate increase, the working frequency band shifts toward the reducing direction. The position of the coaxial connection has an obvious effect on the resonant mode of sensor, too.

Near‐field shielding measurement of small shield cans in metallic mobile devices for RF interference analysis

A novel near-field shielding measurement method is presented for small shield cans used in modern mobile devices with metallic cases. To effectively capture electromagnetic leakage through the shield cans at the very near-field region, a stripline mounted on a test board is utilised similar to the integrated circuit stripline method. Using simulation and measurement, it is verified that the proposed method is more accurate and effective than the conventional gigahertz transverse electromagnetic (GTEM) cell measurement method for shielding evaluation of small shield cans used in metallic mobile devices from an radio-frequency interference point of view.

Experimental Characterization of the Response of an Electrical and Communication Raceway to IEMI

This paper reports the results of two experimental campaigns aimed at studying the high-frequency response of a raceway containing low voltage power, telephone, and Ethernet cables, to external electromagnetic field illumination. The raceway was tested against HPEM transients inside a gigahertz transverse electromagnetic (GTEM) cell and low-power fields inside a reverberation chamber (RC). The high-power electromagnetic (HPEM) tests revealed that the low-voltage power cables have the greatest coupling under a hyperband illumination, compared to telephone and Ethernet cables. The RC tests allowed the determination of statistical transfer functions from random incident field configurations into DM voltage in cable loads. The responses were found to be governed by the raceway under test at the lower frequencies (below 1 GHz). Between 0.2 and 1 GHz, the raceway gives about 10 dB higher coupling than a short patch cable. The difference is even greater at lower frequencies and for shielded cables. In the frequency band 1–3 GHz, little difference was observed between short patch cables and the full raceway, but both were still significantly higher than direct coupling to the measurement card. Beyond 3 GHz, the coupling is clearly dominated by the terminal equipment. The experiments performed in this paper provide a better understanding of the expected induced voltages and currents in commercial cable systems when exposed to intentional electromagnetic interference (IEMI)-like signals.

Far-Field Testing Method of Spurious Emission Produced by HF RFID

We present measurements of spurious emission produced by high-frequency radio frequency identification (HF RFID) using carrier frequency of 13.56 MHz. HF RFID tags produce unwanted emission due to rectification and more generally due to nonlinearity of analog front end. Depending on the conducting material of an HF RFID coil and surrounding dielectric material, the coil behaves as more or less good antenna on some harmonic frequencies. Exact characterization and analysis of unwanted emission is important from the security perspective as well as from the perspective of interference with other systems. Consequently we measured the harmonics produced in the integrated circuitry and characterized radiation properties of the antenna. Finally we present the measurements of the spurious emission performed in a Gigahertz Transverse Electromagnetic (GTEM) cell.