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When a personal exposure meter (PEM) is worn by a human subject, the electric-field strength measured at the PEM is affected by a body shadowing effect. In our study, a hybrid model is proposed for modeling the body shadowing effect for when the PEM is used in an outdoor environment. The hybrid model contains responses to direct and diffused waves, the factors related to the transmission path and cross-polarization discrimination, respectively. To derive the hybrid model, responses for the direct and diffused waves are measured using a human phantom in an anechoic chamber and a reverberation chamber, respectively. Responses are measured at multiple locations in an outdoor environment and compared to the responses of the hybrid model. The hybrid model response has quartiles that deviate by an average of only 2.2 dB (1.29) from the same quartiles of the outdoor responses. Such quartile deviations are significantly smaller than those of the previous model with a body shadowing effect. Bioelectromagnetics. 2017;9999:1–22. © 2017 Wiley Periodicals, Inc.

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

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

In this paper, a simulation-based system-level conducted susceptibility (CS) testing method for a wireless power transfer (WPT) system is proposed. The proposed method employs 3-dimensional electromagnetic (3D EM) models as well as equivalent circuit models to replace the measurement-based CS testing method based on the International Electrotechnical Commission 61000-4-6 standard. The conducted-noise source and equipment under test (EUT) are modeled in a circuit simulator. The conduction path, bulk current injection probe, and calibration jig are modeled using the 3D field simulator. A simple WPT system is designed and fabricated as the EUT for the CS test. The proposed method is successfully verified by comparing the voltage waveforms with measurement-based CS testing method. Additionally, as an application of the proposed method, a simulation-based evaluation of the conducted-noise filters is conducted. By using the proposed method, it is expected that the time and cost expense of setting up the test setup, as well as the testing procedure for the conventional measurement-based CS testing, will be drastically reduced. In addition, the proposed method can be used to estimate the conducted immunity of a system in the early stage of the design cycle prior to production.

This paper presents a rigorous analysis of electromagnetic (EM) field penetration into multiple slits on a metal plate loaded with a ferrite sheet having frequency-dependent complex permeability. The Fourier transform is used to represent the EM fields in the spectral domain, and the mode-matching technique is enforced to obtain a solution in rapidly converging series form, leading to numerically efficient results. Electric and magnetic shielding characteristics in near-field region are investigated over wideband frequency range in terms of the presence or absence of a ferrite sheet with frequency-dependent magnetic permeability. It is observed that the shielding characteristics of electric and magnetic fields are different from each other at the low-frequency range in the near-field region. The number of slits and the ferrite sheet have significant influence on the magnetic shielding performance. In addition, the effect of nonperiodic multiple slits on the shielding effectiveness is examined. The proposed method is verified by comparing the results with those of a commercial EM solver, and good agreement is achieved using the feature selective validation.

In this letter, experimental results are shown for an E-field probe using variable chip resistor values to improve performance. The E-field probe consists of three small orthogonal dipoles with a diode and a lossy transmission line. Since the transmission line does not receive transmitted signals directly or indirectly, a high impedance value of the transmission line is required. To achieve such a high impedance value, chip resistors are inserted in the transmission line. In this letter, variable resistors are used in the transmission line to improve probe performance of such areas as sensitivity and isotropy. Finally, probes with identical and variable resistance values are fabricated, performance levels are measured, and characteristics are compared.

In this paper, a simulation-based conducted susceptibility (CS) testing method for wireless power transfer (WPT) systems is presented. The presented method is meant to replace the measurement-based CS testing specified in IEC 61000-4-6 standard with circuit and 3-dimensional field simulators. The conduction noise sources, propagation path, and equipment under test are modeled by the equivalent circuit models in a circuit simulator. The calibration jig dedicated to inject the standard testing noise is modeled in a 3-dimensional field solver. A wireless power transfer (WPT) system is designed to apply the presented CS testing method. The voltage and timing noise on the transferred signals and the output DC levels at the receiver are employed as criteria in the presented simulation-based CS testing method. With the presented method, time expense for the conventional measurement-based CS testing is dramatically reduced, and the testing reliability is improved without human errors that can occur in the conventional measurement-based CS testing methodology.

This paper presents a radiated emission measurement using an antenna diversity method in a reverberation chamber. Based on a method in the IEC 61000-4-21, a receiving antenna is rotated in three directions during the measurement.

This paper presents an immunity test method using a correction factor to improve an uniformity of an E-field strength in a reverberation chamber. Based on a method in the IEC 61000-4-21, input powers are varied according to stirrer steps to create a uniform field.

This paper presents an estimation method to obtain shielding effectiveness (SE) of a shielding box. The estimation method can be applied even when an aperture on the surface of the shielding box is unknown.

This paper proposes a reverberation chamber structure consisting of new reflectors and mode stirrers for electromagnetic compatibility and wireless terminal measurements. The key design considerations for them are determined through a reasonable approach to analyze the eigenmode for a reverberation chamber and the standard deviation of its working volume based on 3D simulation. The final designs are expected to improve the standard deviation performance of the initial structure of the reverberation chamber and provide a better mode stirring environment. The results measured in the fabricated chamber demonstrate that these predictions are clearly realized. The results satisfy the main requirements of this paper, which are defined in consideration of the specifications of commercial reverberation chamber products. Therefore, the reverberation chamber of this paper is expected to be useful for performance measurement and evaluation of commercial wireless terminals. To verify this logical approach to obtain a good design and its results, the results measured in the actual fabricated reverberation chamber are described along with analytical and computational results.

This paper explores the effect of an air-gap between a ferrite plate and metal strips on magnetic shielding in the presence of a periodic line current source based on an analytical solution. The Fourier transform is used to represent the magnetic vector potentials in the spectral domain, and the mode-matching technique is enforced to obtain a modal solution in rapidly converging series form, leading to numerically efficient results. Magnetic shielding effectiveness is investigated in terms of the air-gap thickness between the ferrite plate and metal strips, the metal strip width, and the position of a periodic line current source.

This paper proposes a novel shield structure to enhance the shielding performance of the conventional ferrite plate by inserting a periodic metal strip. An analytical solution is also presented for effective and adequate analysis of quasi-static magnetic field penetration into the proposed shield structure instead of numerical analyses. The effect of the metal strips on the shielding property of the ferrite plate is investigated in terms of the geometrical parameters, such as the period of the metal strip and the source position, with respect to the metal strips. In addition, the influence of the partially filled metal strips along the thickness of the ferrite plate on the shielding performance is investigated. The proposed method is verified by a commercial finite-element solver with good agreement.

This paper presents an analytical solution for low-frequency magnetic shielding analysis of a multiply-slotted metal plate coated with a ferrite sheet in the presence of a periodic line current source. The Fourier transform is used to represent the magnetic vector potentials in the spectral domain and the mode matching technique is enforced to obtain a modal solution in rapidly converging series form, leading to numerically efficient results. Shielding effectiveness is investigated in terms of the geometrical configuration of multiple slots, ferrite sheet, and periodic line current source. The proposed solution is verified by a commercial finite element solver with good agreement.

This paper proposes an autonomous coil alignment system (ACAS) for electric vehicles (EVs) with dynamic wireless charging (DWC) to mitigate the reduction in received power caused by lateral misalignment between the source and load coils. The key component of the ACAS is a novel sensor coil design, which can detect the load coil's left or right position relative to the source coil by observing the change in voltage phase. This allows the lateral misalignment to be estimated through the wireless power transfer (WPT) system alone, which is a novel tracking method for vehicular applications. Once misalignment is detected, the vehicle's lateral position is self-adjusted by an autonomous steering function. The feasibility of the overall operation of the ACAS was verified through simulation and experiments. In addition, an analysis based on experimental results was conducted, demonstrating that 26% more energy can be transferred during DWC with the ACAS, just by keeping the vehicle's load coil aligned with the source coil.

When a personal exposure meter (PEM) is worn by a human subject, the electric-field strength measured at the PEM is affected by a body shadowing effect. In our study, a hybrid model is proposed for modeling the body shadowing effect for when the PEM is used in an outdoor environment. The hybrid model contains responses to direct and diffused waves, the factors related to the transmission path and cross-polarization discrimination, respectively. To derive the hybrid model, responses for the direct and diffused waves are measured using a human phantom in an anechoic chamber and a reverberation chamber, respectively. Responses are measured at multiple locations in an outdoor environment and compared to the responses of the hybrid model. The hybrid model response has quartiles that deviate by an average of only 2.2 dB (1.29) from the same quartiles of the outdoor responses. Such quartile deviations are significantly smaller than those of the previous model with a body shadowing effect. Bioelectromagnetics. 38:626-647, 2017. © 2017 Wiley Periodicals, Inc.

This paper presents development of a multi-band dosimeter to detect exposure to a radio frequency electric field (RF-EF) and an extremely low-frequency magnetic field (ELF-MF). For the RF-EF detection, an infinitesimal dipole antenna is designed to achieve the dosimeter operation of a wide bandwidth. A signal amplifier is integrated into the antenna, so the dosimeter has a high sensitivity level. When a human subject wears the dosimeter, the human body of the subject attenuates the signal received through the antenna. The signal attenuation caused by the human body is investigated by measurement. For the ELF-MF detection, a signal processing module including induction coils is designed. When an ELF-MF induces a signal at the induction coil, the processing module processes the induced signal using a fast Fourier transform (FFT) technique. The processing module is equipped with signal channels for RF-EFs to process the signal received through the dipole antenna; hence, the exposure detection is possible at the multi-band of RF and ELF. The developed technologies can be effectively applied to realize the multifunctional dosimeter that provides useful data for exposure assessment.

Modern mobile devices require electromagnetic shielding structures with light weight, physical flexibility, and even optical transparency. Wire-mesh screens have been considered as the best alternative electromagnetic shields satisfied these requirements. So far, considerable research has been conducted with respect to the electromagnetic properties of wire-meshes or perforated screens. In [1], the far-field shielding behavior of mesh-screens with square shape and small size in comparison to the wavelength was investigated by employing an equivalent sheet-impedance concept. Recently, the near-field shielding performance of the perforated screen in the presence of a high impedance dipole source was studied [2].

To supply a power distribution network with stable power in a high-speed mixed mode system, simultaneous switching noise caused at the multilayer PCB and package structures needs to be sufficiently suppressed. The uni-planar compact electromagnetic bandgap (UC-EBG) structure is well known as a promising solution to suppress the power noise and isolate noise-sensitive analog/RF circuits from a noisy digital circuit. However, a typical UC-EBG structure has several severe problems, such as a limitation in the stop band’s lower cutoff frequency and signal quality degradation. To make up for the defects of a conventional EBG structure, a partially located EBG structure with decoupling capacitors is proposed in this paper as a means of both suppressing the power noise propagation and minimizing the effects of the perforated reference plane on the signal quality. The proposed structure is validated and investigated through simulation and measurement in both frequency and time domains. Keywords: Electromagnetic bandgap (EBG), signal integrity (SI), power integrity (PI), simultaneous switching noise (SSN), decoupling capacitor (DeCap).

This paper proposes two types of electromagnetic bandgap (EBG) structures aimed for SAR reduction on a mobile phone antenna. The EBG structures, one which uses vias while the other does not can reduce the surface wave and prevent the undesired radiation from the antenna. Thus, these structures can reduce the electromagnetic fields toward the human head direction and reduction the SAR value. Tests demonstrate the reduction of SAR values and therefore, the human body can be protected from hazard electromagnetic fields by using the proposed EBG structures, regardless of whether vias are used or not.

In this paper, active frequency selective surfaces (FSS) having a squared aperture with a metal plate loading are described. Active FSS elements using switched PIN diodes are discussed with an equivalent circuit model. A unit cell consists of a square aperture element with metal island loading and one PIN diode placed at the upper gap, considering the vertical polarization. The electromagnetic properties of the active FSS structure are changed by applying dc bias to the substrate, and they can be estimated by the equivalent circuit model of the FSS structure and PIN diode. This active FSS design enables transmission to be switched on or off at 2.3GHz, providing high transmission when the diodes are in an off state and high isolation when the diodes are on. The equivalent circuit model in the structure is investigated by analyzing transmission and reflection spectra. Measurements on active FSS are compared with numerical calculations. The experimentally observed frequency responses are also scrutinized.

To build a stable power distribution network for high-speed digital systems, simultaneous switching noise (SSN) should be sufficiently suppressed in multi-layer PCBs. In this paper, novel uni-planar compact electromagnetic bandgap (UC-EBG) structures with triangular-type unit cells designed on power/ground planes are proposed for the ultra-broadband suppression of SSN. The effect of the structural parameters on the EBG bandgap changing their parameter values is investigated. The SSN suppression performance of the proposed structure is validated both numerically and experimentally. A -30 dB suppression bandwidth for SSN is achieved, starting at 830 MHz and extending to 15 GHz and beyond, thereby covering almost the entire noise band.

Wireless power transfer (WPT) systems have been increasingly employed in modern electric vehicles and electronic devices [1]. Leakage magnetic fields from the WPT systems are an important design issue for mitigating electromagnetic field (EMF) hazard to human body [2]. In many cases of electric vehicles and electronic devices, inductive coils of the WPT systems are typically placed near metallic plates such as vehicles bodies or batteries of mobile devices. The metal plate is helpful for shielding efficiency, but it deteriorates the magnetic coupling between the coils due to eddy current cancellation. To enhance the magnetic coupling, a ferrite plate or sheet is typically employed and located between the coil and the metal plate. A metal strip structure instead of the solid plate is also considered to reduce the eddy current on the metal surface.

An autonomous coil alignment system (ACAS) using fuzzy steering control is proposed for vehicles with dynamic wireless charging. The misalignment between the power receiver coil and power transmitter coil is determined based on the voltage difference between two coils installed on the front-left/front-right of the power receiver coil and is corrected through autonomous steering using fuzzy control. The fuzzy control is chosen over other control methods for implementation in ACAS due to the nonlinear characteristic between voltage difference and lateral misalignment distance, as well as the imprecise and constantly varying voltage readings from sensors. The operational validity and feasibility of the ACAS are verified through simulation, where the vehicle equipped with ACAS is able to align with the power transmitter in the road majority of the time during operation, which also implies achieving better wireless power delivery.

This paper shows a development of the E-field probe in the personal exposure measurement meter. This instrument is a detector that measures the human body proximity E-field. The probe composes of three orthogonal dipoles with diode and resistive transmission line with chip resistors. The bandwidth of the E-field probe is from 800 MHz to 2.5 GHz, mobile communication bands. The proposed probe is fabricated and the characteristics such as linearity and is the radiation pattern for isotropy deviation are presented in this paper.

In this letter, a microstrip slot antenna using a wiggly line for suppressed harmonics is proposed. To eliminate unwanted radiation at harmonic frequencies, a wiggly-line band-stop filter structure applying the Bragg conditions is used. The size of the proposed slot antenna is 60

To build a stable power distribution network for high-speed digital systems, simultaneous switching noise (SSN) in multilayer PCBs and packages needs to be sufficiently suppressed. In this article, a novel triangular-type uniplanar compact electromagnetic band-gap with different bridges designed for power/ground planes is proposed for the ultra-broadband suppression of SSN. The SSN suppression performance of the proposed structure is validated both numerically and experimentally. A −30 dB suppression bandwidth for SSN is achieved starting at 800 MHz and extending to 15 GHz and beyond, that is, almost the entire noise band. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1356–1358, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24322

To build a stable power distribution network for high-speed digital systems, simultaneous switching noise (SSN) should be sufficiently suppressed in multi-layer PCBs and packages. In this paper, a novel hybrid uni-planar compact electromagnetic bandgap (UC-EBG) with two triangular-type unit cells designed on power/ground planes is proposed for the ultra-broadband suppression of SSN. The SSN suppression performance of the proposed structure is validated both numerically and experimentally. A ―35 dB suppression bandwidth for SSN is achieved, starting at 800 MHz and extending to 15 GHz and beyond, thereby covering almost the entire noise band.

This paper shows a parameter study of isotropic deviation in the electric-fields probe for the personal exposure measurement meter. To detect the exposed E-fields near the human body, a 3-axis E-fields probe is used in the personal exposure measurement meter. The designed probe is consists of three orthogonal dipole antennas with a diode and a lossy transmission line. The proposed probe bandwidth is 10 MHz to 6 GHz. To accurate measurement of the E-fields, the isotropic radiation pattern of the probe is required. To analyze the isotropic deviation of the E-fields probe with the readout device, a parameter study about dipole height, transmission length and resistor value is performed.

From the results of recent research, the coplanar electromagnetic band-gap (C-EBG) structure is regarded as a promising solution to cope with the problem of SSN over the GHz frequency range. However, if the C-EBG is adopted for the power/ground planes, problems of signal integrity may result from the high-speed signals passing over the EBG patterns because of the discontinuities of the etched reference plane. In order both to effectively minimize the effects of a discontinuous reference plane and to sufficiently suppress the propagation of noise, P/G plane structure with C-EBG pattern is proposed in this study. The proposed structure is validated and investigated through simulation and measurement.

A novel broadband microwave absorber based on a lossy Electromagnetic Bandgap (EBG) structure is presented, and the absorption performance is examined. The proposed absorber includes a lossy EBG surface with the specific sheet resistance, which replaces the conventional resistive sheet of Salisbury screen. The measured result for the absorber showing a broadband reflectivity response with about 76% fractional bandwidth below −10 dB is presented, and a new structure with more enhanced absorption characteristic and other computational results to confirm the functioning of the absorber are presented. The measured and simulated results for the proposed absorber are in good agreement.

To build a stable power distribution network (PDN) in high-speed digital systems, the simultaneous switching noise (SSN) should be sufficiently suppressed. In view of the results of recent research, the uni-planar compact electromagnetic bandgap (UC-EBG) structure is regarded as a promising solution to cope with the SSN problems until the GHz frequency ranges. However, if UC-EBG is adopted for the power/ground plane in the multilayer PCB/package structures, problems of signal integrity may result from the high speed signals passing over the EBG patterns because of the discontinuities of the etched reference plane. In this paper, the partial placement of EBG unit cells only near the sources of noise and/or the noise sensitive components is proposed as a means of both suppressing the noise propagation and minimizing the effects of a discontinuous reference plane. The SSN suppression performance of the proposed structure is validated and investigated both numerically and experimentally.

In this paper, we propose a small antenna based on composite right/left-handed (CRLH) transmission lines. Interdigital capacitors are used to enhance series capacitances and it is built in a single layer, so that it lowers a resonant frequency while keeping a physical same size. It is observed that the resonant frequencies are 3.028 GHz and 2.724 GHz, corresponding to n=-1 and -2 modes, respectively. Therefore, the proposed structure enables the antenna size more compact and simplifies a fabrication.

In this paper, specific absorption rate (SAR) reduction at the PIFA type for a mobile phone using various types of EBG structure are tested. Two EBG structures, that is a via or a via-less, are designed. The EBG structures can reduce the surface wave and prevent the undesired radiation from the ground plane. Thus, the EBG structure which is designed for mobile terminal enables to comply with the exposure guideline. From the simulation and measured results demonstrated the reduction of the radiation pattern towards the direction of human head and the SAR value.

The design method and analysis of novel broadband electromagnetic (EM) wave absorbers is presented in this paper. The proposed absorber is a planar structure based on lossy Electromagnetic Bandgap (EBG) surface with the specific sheet resistance, which replaces conventional resistive layer of Salisbury screen. The absorber performance can be easily controlled by simply modifying the EBG surface. The analysis for the reflectivity response due to the phase variation of the reflection and transmission recognizes electrical characteristics of the proposed absorber. A broadband reflectivity response with about 96% fractional bandwidth below -10 dB is presented. The computational results are presented to verify the functioning of the proposed absorber.

In this paper, active frequency selective surfaces (FSS) with squared aperture with loading are described. Active FSS elements using switched PIN diodes are discussed. The unit cell consists of a square aperture element with a metal island loading and one PIN diode placed at the upper gap considering the vertical polarization. The electromagnetic properties of the active FSS structure are changed by applying a dc bias to the substrate, and estimated by the equivalent circuit model of FSS structure and PIN diode. This active FSS design enables transmission to be switched on or off at 2.3 GHz, providing high transmission when the diodes are in off state and high isolation when the diodes are on. Equivalent circuit in the structure is investigated by analyzing transmission and reflection spectra. Measurements on active FSS are compared with numerical calculation based on the scattering matrix formalism. The origin of experimentally observed frequency responses will be scrutinized.

In this paper, the SAR measurement values are compared with a conventional mobile handset and with EBG structures. In order to protect a human head from the exposure of electromagnetic field and to comply with the exposure guideline, the designed EBG components are inserted in a commercial US-PCS handset. The total width and length of the EBG structures are 31 mm and 8 mm, respectively. The measured results in this paper demonstrated the movement of a hot spot, the reduction of total radiated power toward the head direction and the reduction of the SAR in the human head.

In this paper, the ultra-wide band spiral shaped small antenna for the implantable micro systems is proposed. Among these implantable systems, the capsule endoscope system operates inside the human body. The human body tissues which have effects on the antenna propagation characteristics are considered. To transmit the diagnostic real-time image data of high resolution at high speed, the system with larger bandwidth is needed. Thus, the bandwidth enhancement of the antenna is needed. To encase the system in the capsule module and to obtain ultra-wide band characteristics, the small sized spiral antenna is designed. The proposed antenna has the bandwidth of 400-510 MHz for VSWR

In this paper, the small-sized spiral dipole antenna for UHF RFID transponder is proposed. For the expected application of the UHF RFID systems, such as a supply chain integration, industrial automation, track and trace, and so on, the small and efficient printed antenna is required. To reduce the antenna size and to minimize the efficiency lowering due to small size, the proposed antenna is designed to have the spiral structure rather than the meander structure. In this structure, the current cancellation on the antenna is much less than in the meander structures, and the total current induces an identical magnetic dipole, which makes the omni-directional radiation pattern. The proposed antenna is designed for UHF RFID systems of Korea, to have the operating frequency bandwidth of 908 MHz-913 MHz for VSWR < 2. The antenna has the physical size of 15.5 mm by 14.8 mm, which is about lambda over 16 in electrical length. This antenna is fabricated on the PET dielectric, to be utilized as an antenna of the transponder for the application of the UHF RFID systems.

In this paper, a helical antenna for a capsule endoscope is designed. To encase the system in a small capsule module and to obtain omni-directional radiation pattern for detecting the transmitted signal independent of the transmitter positions, and to obtain wide bandwidth, a small sized normal mode helical antenna whose end is connected to the ground is designed. The diameter and the height of the helix are 8 mm and 5.6 mm, respectively. Measured results show that the antenna has 32 MHz bandwidth for VSWR

Experimental tests of specific absorption rate (SAR) reduction on a mobile phone have been performed. To protect a human head from exposure to electromagnetic fields and comply with exposure guidelines, the electromagnetic bandgap (EBG) structures are inserted in a commercial personal communication services (PCS) mobile phone. The measured results demonstrate the movement of a hot spot and the reduction of SAR in the human head.