scholarly journals Evaluation of 8-Channel Radiative Antenna Arrays for Human Head Imaging at 10.5 Tesla

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6000
Author(s):  
Myung Kyun Woo ◽  
Lance DelaBarre ◽  
Matt Thomas Waks ◽  
Young Woo Park ◽  
Russell Luke Lagore ◽  
...  
Keyword(s):  
Antenna Array ◽  
Antenna Arrays ◽  
Specific Absorption Rate ◽  
Human Head ◽  
Dipole Antenna ◽  
Monopole Antenna ◽  
Human Model ◽  
Head Model ◽  
Coaxial Feed ◽  
Substantial Drop

For human head magnetic resonance imaging at 10.5 tesla (T), we built an 8-channel transceiver dipole antenna array and evaluated the influence of coaxial feed cables. The influence of coaxial feed cables was evaluated in simulation and compared against a physically constructed array in terms of transmit magnetic field (B1+) and specific absorption rate (SAR) efficiency. A substantial drop (23.1% in simulation and 20.7% in experiment) in B1+ efficiency was observed with a tight coaxial feed cable setup. For the investigation of the feed location, the center-fed dipole antenna array was compared to two 8-channel end-fed arrays: monopole and sleeve antenna arrays. The simulation results with a phantom indicate that these arrays achieved ~24% higher SAR efficiency compared to the dipole antenna array. For a human head model, we observed 30.8% lower SAR efficiency with the 8-channel monopole antenna array compared to the phantom. Importantly, our simulation with the human model indicates that the sleeve antenna arrays can achieve 23.8% and 21% higher SAR efficiency compared to the dipole and monopole antenna arrays, respectively. Finally, we obtained high-resolution human cadaver images at 10.5 T with the 8-channel sleeve antenna array.

scholarly journals A 16-Channel Dipole Antenna Array for Human Head Magnetic Resonance Imaging at 10.5 Tesla

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7250
Author(s):  
Myung Kyun Woo ◽  
Lance DelaBarre ◽  
Matt Waks ◽  
Jerahmie Radder ◽  
Uk-Su Choi ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Antenna Array ◽  
Antenna Arrays ◽  
Human Head ◽  
Biological Tissues ◽  
Dipole Antenna ◽  
Human Model ◽  
Resonance Imaging ◽  
Array Configuration

For ultra-high field and frequency (UHF) magnetic resonance imaging (MRI), the associated short wavelengths in biological tissues leads to penetration and homogeneity issues at 10.5 tesla (T) and require antenna transmit arrays for efficiently generated 447 MHz B1+ fields (defined as the transmit radiofrequency (RF) magnetic field generated by RF coils). Previously, we evaluated a 16-channel combined loop + dipole antenna (LD) 10.5 T head array. While the LD array configuration did not achieve the desired B1+ efficiency, it showed an improvement of the specific absorption rate (SAR) efficiency compared to the separate 8-channel loop and separate 8-channel dipole antenna arrays at 10.5 T. Here we compare a 16-channel dipole antenna array with a 16-channel LD array of the same dimensions to evaluate B1+ efficiency, 10 g SAR, and SAR efficiency. The 16-channel dipole antenna array achieved a 24% increase in B1+ efficiency in the electromagnetic simulation and MR experiment compared to the LD array, as measured in the central region of a phantom. Based on the simulation results with a human model, we estimate that a 16-channel dipole antenna array for human brain imaging can increase B1+ efficiency by 15% with similar SAR efficiency compared to a 16-channel LD head array.

scholarly journals Design and SAR assessment of three compact 5G antenna arrays

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. Lak ◽  
Z. Adelpour ◽  
H. Oraizi ◽  
N. Parhizgar
Keyword(s):  
Antenna Arrays ◽  
Millimeter Waves ◽  
Reasonable Agreement ◽  
Specific Absorption Rate ◽  
Human Head ◽  
Head Model ◽  
Measurement Results ◽  
Exposure Source ◽  
Simulation Results ◽  
The Brain

AbstractIn this paper three different multi stub antenna arrays at 27–29.5 GHz are designed. The proposed antenna arrays consist of eight single elements. The structure of feeding parts is the same but the radiation elements are different. The feeding network for array is an eight way Wilkinson power divider (WPD). To guarantee the simulation results, one of the proposed structures is fabricated and measured (namely the characteristics of S11, E-, and H-plane patterns) which shows acceptable consistency with measurement results. The simulation results by CST and HFSS show reasonable agreement for reflection coefficient and radiation patterns in the E- and H- planes. The overall size of the proposed antenna in maximum case is 29.5 mm × 52 mm ×  0.38 mm  (2.8 $${{\varvec{\lambda}}}_{0}$$ λ 0 × 4.86$${{\varvec{\lambda}}}_{0}$$ λ 0 × 0.036$${{\varvec{\lambda}}}_{0}$$ λ 0 ). Moreover, for Specific Absorption Rate (SAR) estimation, a three-layer spherical human head model (skin, skull, and the brain) is placed next to the arrays as the exposure source. The simulation results show that the performance of proposed antennas as low-SAR sources makes them ideal candidates for the safe usage and lack of impact of millimeter waves (mmW) on the human health. In all three cases of SAR simulations the value of SAR1g and SAR10g are below the standard limitations.

scholarly journals Analysis of Specific Absorption Rate on Six Layer Human Head Model

2020 ◽  
Author(s):  
Anand Swaminathan ◽  
Ramprakash A ◽  
Dhejonithan K
Keyword(s):  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Mass Density ◽  
Human Head ◽  
Federal Communications Commission ◽  
Head Model ◽  
Health Issues ◽  
Specific Absorption ◽  
Proposed Model ◽  
The Impact

Despite numerous advantages, mobile phones cause serious health issues to people due to electromagnetic radiation. Various head models already exist to study the impact of radiation on a human head. The accuracy of the measurement of power absorbed by different layers of a head should be high. A new head model with six layers is proposed in this paper. Parameters such as dielectric constant, conductivity and mass density of different tissue layers skin, fat, bone, Dura, cerebrospinal fluid (CSF), and brain are extracted from the Federal Communications Commission (FCC) database. To study the impact of radiation in the proposed model, standard planar inverted F-antennas (PIFA) capable to radiate at 1.7 GHz and 2.4 GHz are used. Simulations are performed using ANSYS Electromagnetics Suite. The analysis shows that the specific absorption rate (SAR) in the brain layer decreased in the proposed model when compared to the existing model.

scholarly journals Dual Band and Dual Diversity Four-Element MIMO Dipole for 5G Handsets

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 767
Author(s):  
Muhammad Ali Jamshed ◽  
Masood Ur-Rehman ◽  
Jaroslav Frnda ◽  
Ayman A. Althuwayb ◽  
Ali Nauman ◽  
...  
Keyword(s):  
Multiple Input Multiple Output ◽  
Human Head ◽  
Dipole Antenna ◽  
Base Station ◽  
Dual Band ◽  
Head Model ◽  
Antenna Element ◽  
Total Efficiency ◽  
Large Space ◽  
Mobile Handset

The increasing popularity of using wireless devices to handle routine tasks has increased the demand for incorporating multiple-input-multiple-output (MIMO) technology to utilize limited bandwidth efficiently. The presence of comparatively large space at the base station (BS) makes it straightforward to exploit the MIMO technology’s useful properties. From a mobile handset point of view, and limited space at the mobile handset, complex procedures are required to increase the number of active antenna elements. In this paper, to address such type of issues, a four-element MIMO dual band, dual diversity, dipole antenna has been proposed for 5G-enabled handsets. The proposed antenna design relies on space diversity as well as pattern diversity to provide an acceptable MIMO performance. The proposed dipole antenna simultaneously operates at 3.6 and 4.7 sub-6 GHz bands. The usefulness of the proposed 4×4 MIMO dipole antenna has been verified by comparing the simulated and measured results using a fabricated version of the proposed antenna. A specific absorption rate (SAR) analysis has been carried out using CST Voxel (a heterogeneous biological human head) model, which shows maximum SAR value for 10 g of head tissue is well below the permitted value of 2.0 W/kg. The total efficiency of each antenna element in this structure is −2.88, −3.12, −1.92 and −2.45 dB at 3.6 GHz, while at 4.7 GHz are −1.61, −2.19, −1.72 and −1.18 dB respectively. The isolation, envelope correlation coefficient (ECC) between the adjacent ports and the loss in capacity is below the standard margin, making the structure appropriate for MIMO applications. The effect of handgrip and the housing box on the total antenna efficiency is analyzed, and only 5% variation is observed, which results from careful placement of antenna elements.

scholarly journals A Study of specific absorption rate in human head due to electromagnetic exposure to 4G signals

2019 ◽  
Vol 13 (3) ◽  
pp. 1161
Author(s):  
Siti Rokiah Abdul Mutalik ◽  
Mohd Hafizuddin Mat ◽  
Muzammil Jusoh ◽  
A. W. N. Husna
Keyword(s):  
Electromagnetic Field ◽  
Numerical Analysis ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Human Head ◽  
Dipole Antenna ◽  
Specific Absorption ◽  
Phantom Model

<span>This paper presents a numerical analysis of the specific absorption rate in SAM phantom exposed to electromagnetic field. A two set dipole antenna operating with 1800MHz and 2600MHz were placed parallel to the z-axis and rotated in clockwise from 0<sup>o</sup> (vertical) to 180<sup>o</sup> in steps of 30<sup>o</sup> to investigate the effect of frequency and polarization. The maximum average of 1gram and 10gram of tissue have been presented to show the effect of SAR in SAM phantom model. A comparison of the mass average SAR in head shows the 1g of SAR at 2600MHz is double to 1800MHz frequency. While for 10g of SAR, slightly different for both 1800MHz and 2600MHz.</span>

scholarly journals SIMULATION OF A FLEXIBLE LINEAR GRAPHENE ANTENNA ARRAY ON A PAPER SUBSTRATE

2021 ◽  
Vol 8 ◽  
pp. 307-313
Author(s):  
Alexander G. Cherevko ◽  
Yury V. Morgachev
Keyword(s):  
Antenna Array ◽  
Radiation Pattern ◽  
Antenna Arrays ◽  
Dipole Antenna ◽  
Paper Substrate ◽  
Final Shape ◽  
Flexible Antenna ◽  
Folded Dipole

The article presents an analysis of flexible graphene antenna arrays, which has shown the promise of using a folded dipole antenna as an element of such array. The structure of the flexible folded dipole operating at a frequency of 5,8 GHz on a photo-paper substrate is considered. Simulation yields a gain of 2,53 dBi with a final efficiency of 75% and | S 11| -31,82 dB. The influence of bending on the final shape of the radiation pattern is considered, as well as the value and position of the minimum of the | S 11|. The gain of a linear three-element graphene flexible antenna array based on a folded flexible dipole is 5,78 dBi.

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