Lower Specific Absorption Rate Values Research Articles

تقييم أداء هوائي المايكروسترب لتقليل إمتصاص الموجات الكهرومغناطيسية في األنسجة البشرية في نطاقات 5جي

The absorption of electromagnetic waves emitted by wireless devices in human tissues is quantified by the Specific Absorption Rate (SAR) measured for 1g or 10g of body tissues. The primary objective of this research is to identify an effective shield material that can minimize the impact and potential harm of electromagnetic waves on human tissues. The study involves the design of a single radiator Microstrip antenna operating at 28 GHz and the modelling of human tissue layers. SAR calculations for 1g of body tissues are performed based on the distance between the antenna and the head model. To evaluate the influence of antenna position on the head model, SAR calculations are conducted using two different approaches. In the first approach, the head model is positioned on the patch radiator side, while in the second approach, it is placed on the ground plane side. The aim is to determine which configuration yields lower SAR values. Furthermore, SAR calculations are reanalysed by incorporating shielding materials onto the Microstrip antenna. Three different absorbed materials are used as shields, and their impact on SAR reduction and radiation parameters of the Microstrip antenna are evaluated. The objective is to identify the shield material that achieves the highest SAR reduction while minimally affecting the radiation parameters of the antenna.

A dual‐band dual‐polarized omnidirectional patch antenna for on‐body application

AbstractAiming at the 3.5 GHz world interoperability for microwave access band and 5.8 GHz industrial scientific medical band, a dual‐band antenna operating in omnidirectional mode is proposed. The antenna uses a single‐layer dielectric substrate made of FR‐4, which is cheap and easy to process. It uses circular patches and metal branches to generate orthogonal electric fields to achieve circular polarization. At the same time, the upper patch is symmetrically slotted in a T shape, so that the patch produces two resonance frequencies. The measured impedance bandwidth of the antenna in circular polarization on‐body mode and linear polarization on‐body mode is 110 MHz (3.41–3.52 GHz) and 460 MHz (5.42–5.88 GHz), respectively. In addition, the antenna shows good performance under bending conditions and close to human tissue. At the same time, the low specific absorption rate value proves that the antenna is safe to wear on the human body.

Numerical Modeling and Computer Simulation of a Meander Line Antenna for Alzheimer's Disease Treatment, a Feasibility Study.

Alzheimer's disease (AD) is a brain disorder that eventually causes memory loss and the ability to perform simple cognitive functions; research efforts within pharmaceuticals and other medical treatments have minimal impact on the disease. Our preliminary biological studies showed that Repeated Electromagnetic Field Stimulation (REFMS) applying an EM frequency of 64 MHz and a specific absorption rate (SAR) of 0.4 - 0.9 W/kg decrease the level of amyloid-β peptides (Aβ), which is the most likely etiology of AD. This study emphasizes uniform E/H field and SAR distribution with adequate penetration depth penetration through multiple human head layers driven with low input power for safety treatments. In this work, we performed numerical modeling and computer simulations of a portable Meander Line antenna (MLA) to achieve the required EMF parameters to treat AD. The MLA device features a low cost, small size, wide bandwidth, and the ability to integrate into a portable system. This study utilized a High-Frequency Simulation System (HFSS) in the design of the MLA with the desired characteristics suited for AD treatment in humans. The team designed a 24-turn antenna with a 60 cm length and 25 cm width and achieved the required resonant frequency of 64 MHz. Here we used two numerical human head phantoms to test the antenna, the MIDA and spherical head phantom with six and seven tissue layers, respectively. The antenna was fed from a 50-Watt input source to obtain the SAR of 0.6 W/kg requirement in the center of the simulated brain tissue layer. We found that the E/H field and SAR distribution produced was not homogeneous; there were areas of high SAR values close to the antenna transmitter, also areas of low SAR value far away from the antenna. This paper details the antenna parameters, the scattering parameters response, the efficiency response, and the E and H field distribution; we presented the computer simulation results and discussed future work for a practical model.

A triple-band spiral-shaped antenna for high data rate fully passive implantable devices

A spiral-shape, multi-band and compact antenna for healthcare and high-speed biomedical devices is presented. It operates simultaneously at 2.4/5.8 GHz of the industrial scientific medical (ISM) band and 4.8 GHz as the first-band harmonic. Therefore, it is suitable for fully-passive in-body systems. The compact size of the designed antenna is 9.2 × 9.2 × 0.5 mm3 and shorting pins are not used to reduce the dimensions. The results have been checked by full wave software in both three-layer and one-layer phantoms with different body tissues. The presented antenna has been embedded in two implantable systems and integrated with other components to evaluate real working scenarios. In addition, for safety study and numerical analysis of radiation absorption per unit mass of human tissue, the antenna specific absorption rate (SAR) has been analyzed. The designed antenna has been implanted in a muscle liquid phantom and parameters were evaluated experimentally. The proposed antenna exhibits multi-band characteristics, has a via-less and simple configuration, a compact size, low SAR, and suitable gain value making it a proper and applicable choice for implantable passive devices.

A fully flexible, high gain saw-tooth-shaped boundary fractal wearable patch antenna for WBAN applications

AbstractA flexible and high gain saw-tooth-shaped boundary fractal wearable antenna is anticipated for WBAN applications. A square shape is converted to the saw-tooth-shaped boundary by sequentially rotating the square at an angle of 45° and overlaid on one another and repeated the same for three iterations. The geometry is built on a flexible jeans substrate, and the total size of the anticipated antenna is 0.583λ × 0.583λ × 0.02λ at 2.4 GHz. A prototype has been made to test its suitability for wearable applications' gain, bandwidth, and efficiency. The results revealed that the proposed antenna provides an impedance bandwidth of 4.2% and a peak gain of 5.76 dBi at the 2.45 GHz ISM band. The anticipated antenna is wrapped around foam cylinders of radii 70 and 50 mm to test the stability and deformability of its performance. The full ground plane isolates the antenna from the human body contributing to the lower SAR values. The simulated maximum achieved specific absorption rate (SAR) of 0.3025 and 1.16 W/kg for 10 and 1 g of average tissue for the input power of 100 mW, respectively, found within the standards as per FCC. The peak gain, compact size, and SAR permanence made the anticipated antenna a worthy candidate for wearable on/off body applications.

Substrate integrated waveguide‐based simultaneous transmit and receive antenna for full‐duplex wearable devices

In this paper, a low-size and compact substrate integrated waveguide (SIW)-based simultaneous transmit and receive antenna is developed for full-duplex wearable telemetry applications. The antenna operates at 4.9 GHz (Wireless Local Area Network [WLAN]) and 5.8 GHz (Industrial, Scientific and Medical [ISM]) bands with acceptable gains. Keeping a proper gap between the two ports achieves an isolation of better than 29.8 dB. This antenna is kept compact (0.20 λg2, where λg is the wavelength at 4.9 GHz) by additional arc-shaped slot in each radiator, which adds additional capacitance. The suggested antenna is simulated inside a 52 × 63 × 17 mm3 dummy wearable telemetry device and is worn on the subject's chest. Thanks to SIW technology, it has unidirectional radiation patterns, allowing a minimum beam towards the human body, and thus, offers lower specific absorption rate (SAR) at both frequency bands. The unique advantage is its capacity to receive and transmit the telemetry signals simultaneously. Its low profile, flexibility in the resonant bands, simultaneous transmission and reception, and lower SAR values make this antenna suitable for full-duplex wearable telemetry devices.

A Compact Flexible Circularly Polarized Implantable Antenna for燘iotelemetry Applications

With the help of in-body antennas, the wireless communication among the implantable medical devices (IMDs) and exterior monitoring equipment, the telemetry system has brought us many benefits. Thus, a very thin-profile circularly polarized (CP) in-body antenna, functioning in ISM band at 2.45 GHz, is proposed. A tapered coplanar waveguide (CPW) method is used to excite the antenna. The radiator contains a pentagonal shape with five horizontal slits inside to obtain a circular polarization behavior. A bendable Roger Duroid RT5880 material (εr = 2.2, tanδ = 0.0009) with a typical 0.25 mm-thickness is used as a substrate. The proposed antenna has a total volume of 21 × 13 × 0.25 mm3. The antenna covers up a bandwidth of 2.38 to 2.53 GHz (150 MHz) in vacuum, while in skin tissue it covers 1.56 to 2.72 GHz (1.16 GHz) and in the muscle tissue covers 2.16 to 3.17 GHz (1.01 GHz). GHz). The flexion analysis in the x and y axes was also performed in simulation as the proposed antenna works with a wider bandwidth in the skin and muscle tissue. The simulation and the curved antenna measurements turned out to be in good agreement. The impedance bandwidth of −10 dB and the axis ratio bandwidth of 3 dB (AR) are measured on the skin and imitative gel of the pig at 27.78% and 35.5%, 13.5% and 4.9%, respectively, at a frequency of 2.45 GHz. The simulations revealed that the specific absorption rate (SAR) in the skin is 0.634 and 0.914 W/kg in muscle on 1g-tissue. The recommended SAR values are below the limits set by the federal communications commission (FCC). Finally, the proposed low-profile implantable antenna has achieved very compact size, flexibility, lower SAR values, high gain, higher impedance and axis ratio bandwidths in the skin and muscle tissues of the human body. This antenna is smaller in size and a good applicant for application in medical implants.

A Bandwidth-Enhanced Sub-GHz Wristwatch Antenna Using an Optimized Feed Structure

In this letter, the design and modeling of a bandwidth-enhanced 915 MHz wristwatch antenna is presented. This letter extends previous work by the authors, with a key focus on significantly improving the impedance bandwidth of the antenna. The antenna proposed here achieves a measured 107% bandwidth improvement compared to the previously reported work. This is achieved by optimizing the feed structure to excite two closely located resonant modes that can be independently tuned to maximize the impedance bandwidth. Conceptual equivalent circuit models for the previous and proposed antennas are derived to explain the bandwidth enhancement. In addition, an equivalent transmission line model is, then, presented in order to accurately explain and analyze the impedance characteristics of the antenna. On-body measurements of the prototype antenna show a –10 dB impedance bandwidth of 62 MHz, a peak realized gain of –4.6 dBi, and a simulated radiation efficiency of 17.8% at 915 MHz. This antenna exhibits a low specific absorption rate value of 0.02 W/kg with 11 dBm input power. The previous performance makes the antenna a suitable candidate for 915 MHz wristwatch-based wireless applications.

Confining Iron Oxide Nanocubes inside Submicrometric Cavities as a Key Strategy To Preserve Magnetic Heat Losses in an Intracellular Environment.

The design of magnetic nanostructures whose magnetic heating efficiency remains unaffected at the tumor site is a fundamental requirement to further advance magnetic hyperthermia in the clinic. This work demonstrates that the confinement of magnetic nanoparticles (NPs) into a sub-micrometer cavity is a key strategy to enable a certain degree of nanoparticle motion and minimize aggregation effects, consequently preserving the magnetic heat loss of iron oxide nanocubes (IONCs) under different conditions, including intracellular environments. We fabricated magnetic layer-by-layer (LbL) self-assembled polyelectrolyte sub-micrometer capsules using three different approaches, and we studied their heating efficiency as obtained in aqueous dispersions and after internalization by tumor cells. First, IONCs were added to the hollow cavities of LbL submicrocapsules, allowing the IONCs to move to a certain extent in the capsule cavities. Second, IONCs were coencapsulated into solid calcium carbonate cores coated with LbL polymer shells. Third, IONCs were incorporated within the polymer layers of the LbL capsule walls. In aqueous solution, higher specific absorption rate (SAR) values were related to those of free IONCs, while lower SAR values were recorded for capsule/core assemblies. However, after uptake by cancer cell lines (SKOV-3 cells), the SAR values of the free IONCs were significantly lower than those observed for capsule/core assemblies, especially after prolonged incubation periods (24 and 48 h). These results show that IONCs packed into submicrocavities preserve the magnetic losses, as the SAR values remained almost invariable. Conversely, free IONCs without the protective capsule shell agglomerated and their magnetic losses were strongly reduced. Indeed, IONC-loaded capsules and free IONCs reside inside endosomal and lysosomal compartments after cellular uptake and show strongly reduced magnetic losses due to the immobilization and aggregation in centrosymmetrical structures in the intracellular vesicles. The confinement of IONCs into sub-micrometer cavities is a key strategy to provide a sustained and predictable heating dose inside biological matrices.

A miniaturized implantable planar inverted‐F antenna for biotelemetry applications at 2.45 GHz industrial, scientific, and medical band

AbstractThis letter proposes an implantable planar inverted‐F antenna for biotelemetry applications, which operates at 2.4 GHz‐2.48 GHz industrial, scientific, and medical band. The antenna is miniaturized by loading a shorting metal surface between the radiating patch and the ground. Moreover, biocompatible substrate‐superstrate layers are used to achieve low specific absorption rate (SAR). We study the performance of antennas at different implant depths. The simulated and measured results show the proposed antenna has higher realized gain of −4.5 dB at 2.45 GHz. The impedance bandwidth (−10 dB) of 180 MHz (2.34 GHz‐2.52 GHz) can be obtained. Moreover, this antenna has a lower SAR value of 113.5 W/kg for a 1‐g standard, which satisfies the regulations in the IEEE standard.

기생 소자를 이용한 3중 대역 모노폴 안테나 SAR 저감 설계

In this study, a triple-band antenna that can be used in WLAN(Wireless Local Area Network) at 2.4 GHz, 5.8 GHz, and 5G at 3.5 GHz is fabricated. The proposed antenna uses a parasitic element to show the triple band, and the reflector is used at a distance of λ/4 from the antenna to reduce the Specific Absorption Rate(SAR). Its dimensions are 100×75×1.6 mm3 and each parameter value is optimized for better performance and a lower SAR value. As a result, we obtained a bandwidth of 540 MHz(2.02～2.56 GHz), 390 MHz(3.39～3.78 GHz), and 1,210 MHz(5.56～6.77 GHz) based on the reflection loss factor of −10 dB. In addition, the SAR values of the antenna with reflector are observed to reduce below the SAR value of international standard.

Design and Specific Absorption Rate of 2.6 GHz Rectangular-Shaped Planar Inverted-F Antenna

<span lang="EN-US">This article presents the investigation of specific absorption rate (SAR) of a rectangular-shaped planar inverted-F antenna (PIFA) at frequency of 2.6 GHz. Initially, the design antenna is presented with parametric study concerning the dimensions of antenna patch length, shorting plate, ground plane and substrate. The proposed PIFA antenna has -20.46 dB reflection coefficient and 2.383 dB gain. The PIFA’s SAR is correlated with the antenna gain and excitation power. The analysis shows that higher gain contributes to a lower SAR value. While, the higher excitation power causes a higher SAR value. All the design and analysis are performed using the CST Microwave Studio</span>

The Effect of a Metamaterial Based Wearable Monopole Antenna on the Human Body

In this study, design and characterization of a wearable monopole antenna and metamaterial based electromagnetic band gap structure using conductive textile was reported. The pure copper polyester taffeta fabric was used as a conductive textile. The conductive textile based wearable antennas have attracted considerable attention for body centric technologies due to the ability of being integrated with clothes and easily worn. In this respect, the reflection coefficients, radiation pattern, and surface currents for proposed antenna were investigated and its performance was obtained. Then, we designed the electromagnetic band gap structure (3x3 unit cell) and integrated the wearable antenna with this structure. Finally, the specific absorption rate (SAR) values for wearable antenna and integrated structure were analyzed. The SAR values of wearable antenna and integrated structure were obtained as 17.4 W/kg and 0.329 W/kg, respectively. In addition, the electromagnetic band gap structure that has 4x3 unit cell was designed and again the wearable antenna was integrated with this 4x3 structure. Similarly, we obtained the SAR value of new integrated structure as 0.241 W/kg. It was demonstrated that the integrated structures have considerably favorable SAR value for human body. It can be used in many wearable antenna applications with this low SAR value.

Asymmetric Assembling of Iron Oxide Nanocubes for Improving Magnetic Hyperthermia Performance.

Magnetic hyperthermia (MH) based on magnetic nanoparticles (MNPs) is a promising adjuvant therapy for cancer treatment. Particle clustering leading to complex magnetic interactions affects the heat generated by MNPs during MH. The heat efficiencies, theoretically predicted, are still poorly understood because of a lack of control of the fabrication of such clusters with defined geometries and thus their functionality. This study aims to correlate the heating efficiency under MH of individually coated iron oxide nanocubes (IONCs) versus soft colloidal nanoclusters made of small groupings of nanocubes arranged in different geometries. The controlled clustering of alkyl-stabilized IONCs is achieved here during the water transfer procedure by tuning the fraction of the amphiphilic copolymer, poly(styrene-co-maleic anhydride) cumene-terminated, to the nanoparticle surface. It is found that increasing the polymer-to-nanoparticle surface ratio leads to the formation of increasingly large nanoclusters with defined geometries. When compared to the individual nanocubes, we show here that controlled grouping of nanoparticles—so-called “dimers” and “trimers” composed of two and three nanocubes, respectively—increases specific absorption rate (SAR) values, while conversely, forming centrosymmetric clusters having more than four nanocubes leads to lower SAR values. Magnetization measurements and Monte Carlo-based simulations support the observed SAR trend and reveal the importance of the dipolar interaction effect and its dependence on the details of the particle arrangements within the different clusters.

Evaluation of hydrocephalus patients with 3D-SPACE technique using variant FA mode at 3T.

The major advantages of three-dimensional sampling perfection with application optimized contrasts using different flip-angle evolution (3D-SPACE) technique are its high resistance to artifacts that occurs as a result of radiofrequency or static field, the ability of providing images with sub-millimeter voxel size which allows obtaining reformatted images in any plane due to isotropic three-dimensional data with lower specific absorption rate values. That is crucial during examination of cerebrospinal-fluid containing complex structures, and the acquisition time, which is approximately 5min for scanning of entire cranium. Recent data revealed that T2-weighted (T2W) 3D-SPACE with variant flip-angle mode (VFAM) imaging allows fast and accurate evaluation of the hydrocephalus patients during both pre- and post-operative period for monitoring the treatment. For a better assessment of these patients; radiologists and neurosurgeons should be aware of the details and implications regarding to the 3D-SPACE technique, and they should follow the updates in this field. There could be a misconception about the difference between T2W-VFAM and routine heavily T2W 3D-SPACE images. T2W 3D-SPACE with VFAM imaging is only a subtype of 3D-SPACE technique. In this review, we described the details of T2W 3D-SPACE with VFAM imaging and comprehensively reviewed its recent applications.

A specific absorption rate reduction method for simultaneous multislice magnetic resonance imaging.

This study proposes a modified Shinnar-Le Roux method to synthesize the excitation radio frequency (RF) pulse for a 2D gradient echo (GRE) based simultaneous multi-slice (SMS) magnetic resonance imaging (MRI) with features of low specific absorption rate (SAR) and small out-of-slice ripple. This synthesis method for SMS RF pulses employs thinner slice bandwidth and lower multislice offset frequencies to reduce SAR values and adopts a weighted Parks-McClellan algorithm to reduce sidelobes. Formulas for estimating relative SAR values of the SMS pulses are also introduced. Relative SAR values and out-of-slice ripples of the proposed and typical RF pulses with different parameters are presented. In simultaneous 5-slice phantom and 3-slice human brain imaging, SMS pulses synthesized with the proposed method achieve 32% and 28% SAR values of standard pulses while providing similar image qualities. Typical RF pulses such as sinc x cos can also take advantage of the proposed method and offer lower SAR values for SMS imaging. The RF pulse synthesized using the proposed method features low SAR, small sidelobes, and consistent image quality for 2D GRE-based SMS MRI. This method is applicable to the synthesis of typical SMS RF pulses for significant SAR reduction.

Low specific absorption rate microstrip patch antenna for cellular phone applications

The aim of this study is to design a new microstrip-fed patch antenna for cell phone applications. The antenna design is composed of slots and Flame Retardant 4 dielectric substrate fed by a partial ground plane and a microstrip line. The user's effects on antenna performances are also analysed using standard specific anthropomorphic mannequin head phantom. The specific absorption rate (SAR) values of the proposed antenna are evaluated for different frequency bands considering cheek position of talk mode. The proposed antenna has an impedance bandwidth of 230.4 MHz (0.725-0.95 GHz, lower band), and 522.24 MHz (1.74-2.25 GHz, upper band), which can cover global system for mobile (GSM) 900 MHz, digital communication system 1800 MHz, personal communications service 1900 MHz, GSM 1900 MHz, and universal mobile telecommunications service 2100 MHz bands. Moreover, the proposed antenna produces lower SAR values in the human head than that of a dipole antenna, helical antenna, and planar inverted-F antenna.

Miniature low SAR printed monopole antenna for mobile phone

ABSTRACTA multiband compact printed monopole antenna is proposed for mobile phone. In this configuration, the antenna comprises a slotted rectangular‐shaped radiator, microstrip‐fed line, and a slotted ground plane on FR‐4 substrate. The total antenna dimensions with ground plane are 78 × 40 × 0.8 mm3. The measured results show that the proposed antenna has an impedance bandwidth 358.4 MHz (0.60–0.95 GHz, lower band), and 1 GHz (1.7–2.7 GHz, upper band), which can cover GSM 900 MHz, DCS 1800 MHz, PCS 1900 MHz, GSM 1900 MHz, UMTS 2100 MHz, Bluetooth 2400 MHz, WLAN II.b (2400 MHz), and LTE (2300–2400 MHz) bands. The proposed antenna shows very good radiation efficiencies and gain values and near omnidirectional radiation patterns at those frequency bands. Moreover, the proposed antenna produces lower specific absorption rate values in the human head than that of a dipole antenna, helical antenna, and planar inverted‐F antenna. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2471–2475, 2015

Low SAR Microstrip Patch Antenna for Mobile Phone

AbstractThe aim of this article is to design a new microstrip-fed patch antenna for cell phone applications. The antenna design is composed of slots and FR-4 dielectric substrate fed by a partial ground plane and a microstrip line. The user’s effects on antenna performances are also analyzed using standard SAM phantom. The specific absorption rate (SAR) values of proposed antenna are evaluated for different frequency bands considering cheek position of talk mode. The proposed antenna has an impedance bandwidth (–10 dB reflection coefficients) 100 MHz (0.87–0.97 GHz, lower band), 50 MHz (1.47–1.52 GHz, middle band), and 150 MHz (1.78–1.93 GHz, upper band), which can cover GSM 900 MHz, GPS 1,500 MHz, DCS 1,800 MHz, PCS 1,900 MHz, and GSM 1,900 MHz bands. Moreover, the proposed antenna produces lower SAR values in the human head than that of a dipole and helical antenna.

Diminishing SAR for Wearable UHF Antennas

This letter presents a study on the specific absorption rate (SAR) evaluation of UHF wearable antennas. A planar inverted-F antenna (PIFA) intended to operate in wireless body area networks (WBANs) is taken as an example for the investigation. The presence of the ground plane introduces isolation between the body and the wearable antenna and decouples the antenna from the body, thus resulting in lower SAR values. The performed analysis of the proposed PIFA indicates increased near-field regions close to the shorting wall, which directly leads to increased SAR values. This can be avoided if alternative current paths are provided, e.g., extending the ground plane slightly. The dielectric materials used as substrates partially reduce the SAR by confining part of the fields inside the dielectric. All the suggested solutions are easily applicable for a practical implementation.