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Recent Trend in Electromagnetic Radiation and Compliance Assessments for 5G Communication

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The deployment of the 5G networks will feature high proliferation of radio base station (RBS) in order to meet the increasing demand for bandwidth and also to provide wider coverage that will support more mobile users and the internet-of-things (IoT). The radio frequency (RF) waves from the large-scale deployment of the RBS and mobile devices will raise concerns on the level of electromagnetic (EM) radiation exposure to the public. Hence, in this paper, we provide an overview of the exposure limits, discuss some of the effects of the EM emission, reduction techniques and compliance assessment for the 5G communication systems. We discuss the open issues and give future directions. Copyright © 2017 Institute of Advanced Engineering and Science. All rights reserved.
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International Journal of Electrical and Computer Engineering (IJECE)
Vol.7, No.2, April 2017, pp. 912~918
ISSN: 2088-8708, DOI: 10.11591/ijece.v7i2.pp912-918 912
Journal homepage: http://iaesjournal.com/online/index.php/IJECE
Recent Trend in Electromagnetic Radiation and Compliance
Assessments for 5G Communication
Nor Adibah Ibrahim, Tharek Abd. Rahman, Olakunle Elijah
Wireless Communication Center, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, Malaysia
Article Info
ABSTRACT
Article history:
Received Sep 12, 2016
Revised Nov 30, 2016
Accepted Dec 15, 2016
The deployment of the 5G networks will feature high proliferation of
radio base station (RBS) in order to meet the increasing demand for
bandwidth and also to provide wider coverage that will support more
mobile users and the internet-of-things (IoT). The radio frequency
(RF) waves from the large-scale deployment of the RBS and mobile
devices will raise concerns on the level of electromagnetic (EM)
radiation exposure to the public. Hence, in this paper, we provide an
overview of the exposure limits, discuss some of the effects of the
EM emission, reduction techniques and compliance assessment for
the 5G communication systems. We discuss the open issues and give
future directions.
Keyword:
5G
Electromagnetic radiation
EMF assessment
Power density
SAR
Copyright © 2017 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
Olakunle Elijah,
Wireless Communication Center,
Universiti Teknologi Malaysia, P15a, 81310, Skudai, Malaysia.
Email: elij_olak@yahoo.com
1. INTRODUCTION
The deployment of the 5G networks would feature high proliferation of base station (BS) in order to
meet the increasing demand for bandwidth and provide wider coverage that will support more mobile users
and internet of things (IoT). Apart from that, transmission using the millimeter wave bands and deployment
of BS with massive antenna configurations, ultra-high densification of small cells access points and
heterogeneous networks are expected to be part of the 5G networks. The millimeter-wave (mmWave) band is
part of the radio frequency (RF) spectrum, comprised of frequencies between 30 GHz and 300 GHz.
However, the recommended International Telecommunication Union- Radio have selected 24 GHz to 86
GHz for study purposes. The radio frequency (RF) waves from the large scale deployment of the BS and
mobile devices will raise the level of electromagnetic (EM) radiation exposure to the public. This raises
concern about the possible adverse health effects due to exposure of RF radiation from mobile
communication systems. Subsequently, several studies have been carried out to investigate the effect of the
EM emission, reduction techniques and compliance test for the communication systems. The EM radiation is
considered carcinogenic to humans and it has been classified as Group 2B under the international agency for
research on cancer (IARC) of the world health organization as reported in the 2011 [1]. The emission from
mobile phones can cause health hazards due to the proximity of the antennas to the human body especially
the head. Moreover, there are also concerns about EM exposure from BS. As a result, there exist several
international and national EM radiation exposure guidelines, limits and compliance tests which have been
introduced by relevant regulatory bodies. EM radiation metrics such as the specific absorption rate (SAR)
and power density are used to measure the EM radiation in the near-field and far-field, respectively.
The SAR measurement is the merit that is currently used to regulate the safety limits for the
exposure of the mobile phone radiation. It is a measure of the rate of absorbed energy inside the human body
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Recent Trend in Electromagnetic Radiation and Compliance Assessments for 5G, (Nor Adibah Ibrahim)
913
and it requires either expensive measurement systems or advanced numerical simulations. The power density
on the other hand, is defined as the power per unit area normal to the direction of propagation. At frequency
between 10 MHz and 10 GHz, the International Commission on Non-Ionizing Radiation Protection (ICNIRP)
basic restrictions are given in terms of SAR while for higher frequencies from 10 GHz to 300 GHz the basic
restrictions are given in terms of free space power density.
Some of the projects which are involved in the investigation of possible health hazards, reduction of
EM radiation and the transmit power of mobile communication systems are listed and discussed in [2]. They
include the international EMF project [3], low EMF exposure future networks (LEXNET), energy aware
radio and also neTwork tecHnologies (EARTH) and greentouch [4]. These projects consist of industrial
partners, network operators, research centers and universities. Some of their aims incorporate reduction of
EM radiation exposure, reduction of energy consumption, improvement in energy efficiency and
development of international acceptable standards. Consequently, guidelines on the limits of EM exposure
from mobile phones, BSs, and other source of EM radiation exposure have been reported in [5], [6]. These
guidelines which are based on laboratory and epidemiological studies specify the maximum admissible
exposure of people to EM waves of up to 300 GHz. The guidelines are applicable to both occupational and
public exposure. The public exposure refers to members of the public who are of all ages and are unaware of
such exposures. Thus, they take less precautions to minimize the EMF exposure. On the other hand, the
occupational exposure refers to the EM exposure of adults who are not only trained and aware of the possible
harzards, but also has taken the necessary precautions. The exposure limits for occupational and public
exposures specified by different standardization bodies such as ICNIRP, FCC and National Radiological
Protection Board (NRPB) are summarized in Table 1 for various frequency ranges.
Table 1. Summary of Exposure Limits
Body
Metric
Public values
Occupational values
Remarks
ICNIRP
SAR
0.08 W/kg
0.4W/kg
Whole body
averaged over
10g,
SAR
2 W/kg
10 W/kg
Localized
head/trunk
SAR
4W/kg
20W/kg
Localized limbs
Power density
10 W/m2
50 W/m2
Averaged over
20cm2
Body
Metric
Public values
Occupational values
Remarks
FCC
SAR
0.08 W/kg
0.4W/kg
Averaged over 1g
Power density
10 W/m2
Averaged over
1cm2
Body
Metric
Public values
Occupational values
Remarks
NRPB
SAR
0.1 W/kg
0.4W/kg
Whole body
SAR
2 W/kg
10 W/kg
Localized
There are different methods that have been proposed to reduce the EM radiation of 5G
communication systems. Some of these methods which have been identified in the literature include SAR
shielding, power control, beamforming and massive MIMO. In addition, product compliance assessment
tests are required for the telecommunication products emitting RF EMFs in order to comply with the relevant
regulatory exposure limits. Compliance assessment method for 5G radio BS is currently an active research
area. Hence, in this paper, we provide an overview of some of the effects of the EM emission, reduction
techniques and compliance test for the 5G communication systems. We discuss the open issues and future
direction for EMF assessment and compliance test. The rest of this paper is organized as follows. In Section
2, the methods for EM radiation metrics are presented. Methods to reduced EM radiation exposure for 5G
networks are discussed followed by EMF compliance assemment methods. Section 3 takes a look at the open
issues and future directions. Section 4 concludes this paper.
2. METHOD AND EM RADIATION METRICS
2.1. EM Radiation Metrics
Physical quantities like the SAR, electric field strength, magnetic field strength and power density
are used to specify EM radiation exposure. In literature, the popular metrics used are the SAR and power
density for the near-field and far-field, respectively. The near-field and far-field are two different regions that
define the electric and magnetic fields based on distance from the antenna as shown in Figure 1.
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The near field region begins from the antenna up to
2
2/D
and it is divided into two areas which
are the reactive and radiative areas (where D is largest dimension of the antenna). The reactive near-field
region begins from the antenna up to the distance
/2

, where
is the wavelength. The SAR, in watts
per kilogramme of body weight (W/kg), is typically used to measure the EM radiation exposure level in the
near-field region averaged over time, (minutes). SAR is mathematically expressed as:
WW
SAR t m t V
 
   





 
(1)
where
W
,
m
,
V
, and
are the energy absorbed by the body, mass, volume and density of the body,
respectively.
The far-field region begins at a distance greater than
2
2/D
from the transmitting antenna. The
EM radiation in the far-field is commonly measured in terms of power density in W / m2 and is expressed as
22
377
o
EE
S HE Z
 
(2)
Where Z0 is the characteristic impedance and H,E denote the magnetic and electric fields,
Respectively.
Near-field Far-field
Reactive field Radiative field
2
2/D
/2

.
Antenna
Figure 1. Illustration of EM radiation fields
2.2. Biological Effects of EM Radiation
In order to create an effect in the biological material, EM wave needs to deposit enough energy
above the thermal kinetic energy to alter some structure significantly. The biological and health effects of
EM radiation on human body have been investigated in several literatures. These include investigation in
different parts of the human body such as head [7-10], and also fetus[11], [12]. The effect can be assessed by
observing the increase in temperature using the SAR when the exposure is more than 6 minutes.The effect on
a fetus in a maternal abdomen which is exposed to EM wave from a portable antenna shows that the SAR is
affected by distance and penetration path from the antenna [11]. However, the SARs in the fetus are lower
than the RF safety guideline for occupational exposure. The simulation results in [10] demonstrate that the
existence of a metallic object between mobile phone and human head can cause the increase of SAR in the
head. Other works have examined the effects of EMF on both children and adults[13]. These studies employ
different types of antennas and different operating frequencies.
2.3. EMF Reduction Techniques
The BS communicates with the mobile phones wirelessly over an RF channel and the operating
frequency used by a network depends on the technology and operational license. The evolution of the cellular
networks over the years from 1G, 2G, 3G, 4G to 5G has brought about reduction in transmission power of the
BS resulting to lower reduced EM radiation exposure levels and increased throughput. Different techniques
have been developed to reduce the EM radiation exposure. Some of the techniques are massive MIMO,
power control, SAR shielding, and beamforming.
Massive MIMO - is a communication system where a BS with a few hundred antennas array
simultaneously serve many tens of UTs, each having a single antenna, in the same time frequency
resource [14], [15]. In massive MIMO, the BS employs large array of active antennas in order to achieve
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directional beam towards UTs. The benefit of the massive MIMO system is the reduction in the transmit
power. Power Control is a process that involves the adjustment of the output transmit power levels of BSs
or mobile stations in order to maximize the received power of the desired signals. This helps to reduce power
consumption as well as interference. The reduction in power helps to reduce the EM exposure levels.
SAR Shielding is a process that involves the use of metamaterial attachment or ferrite materials
between mobile phone and head to reduce SAR. The use of ferrite materials and metamaterials in the
reduction of SAR has been reported in [16-18]. The ferrite materials are characterised by low conductivity
which leads to smaller induced currents when exposed to EM waves while the metamaterials have special
resonant characteristics that produce a negative permittivity or negative permeability.
Beamforming is a process where RF radiation is focused in a particular direction through the use
of large antenna arrays. This can be done through switch beamforming or adaptive array beamforming. The
ability to focus signals towards desired users is considered to have the advantage of minimizing or
eliminating EM radiation towards unintended users. The study on effect of beamforming for SAR mitigation
is reported in [19], [20].
2.4. EMF Compliance Assessment
Manufacturers are concerned with the risk of non-compliance to EM exposure limits. Hence, the
manufacturers carry out product compliance test to determine the compliance boundary outside of which the
RF EMF exposure is below the relevant limits. The evaluation of EM radiation exposure in a body can be
categorized into physical model and computational techniques [2]. The physical model encompasses the use
of a phantom to simulate SAR or current density in the body while the numerical model encompasses
theoretical calculation such as the finite-difference-time-domain method (FDTD) [21-23], [13]. Furthermore,
the European standard CENELEC EN 50383 [24] has provided a guideline on how to combine exposures on
multiple electromagnetic (EM) sources in terms of SAR and power density antenna systems and the product
compliance assessment methods. The different approaches for combined exposure are categorized into
experimental and numerical/computational techniques. Numerical simulations have been employed to
conduct compliance assessment of a BS antenna using electromagnetic simulation software (example
FEKO). The model of the BS antenna is created and meshed according to the numerical algorithm
employed. The simulation can be conducted by using different numerical methods or solvers such as the
(method of moments) MoM, multi-level fast multipole method (MLFMM), finite element method (FEM),
finite difference time domain (FDTD), physical optics (PO), and uniform theory of diffraction (UTD). The
choice of solvers determine the performance accuracy in terms of reduction of side lobes, directivity gains
and amount of resources used during simulation (such as simulation time, computational memory and disc
storage requirements). Meticulous selection in numerical methods is required for appropriate antenna types
and sizes.
The use of large array BS antennas and the application of millimetre wave band for 5G networks
pose new challenge in RF EMF assessments. One of the challenges is the mutual coupling between the
antenna arrays and determination of the field distributions. In RF EMF assessments for large array multiport
antennas, the combined exposure from all ports needs to be considered. Hence, different assessment methods
for antenna array intended for beamforming applications have been investigated in [25-29]. The author in
[25] shows that accurate and efficient EMF compliance assessments can be conducted by using embedded
element approach. In the embedded element approach, each array element is excited sequentially while other
elements are terminated in matched loads. This approach is suitable for small array antennas like the current
4G communication MIMO systems which require maximum of eight antennas. In [27], numerical EMF
exposure assessment are carried out by using a conservative field procedure and combined with the
embedded element approach in EMF assessment.The numerical results are in agreement with reference
measurements. While this particular procedure is suitable for MIMO arrays, it is rather costly in terms of
assessment time and resources for very large array antennas. Degirmenci et al.[29], proposes approximate
methods for EMF compliance assessments of large array antennas. The accuracy of the approximate
methods in terms of front compliance distance is measured as the relative difference with respect to the
reference method results and expressed as [29]:
( , ) 100
ref
ref ref
CD CD
RD CD CD CD

(3)
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where CD is the compliance is distance of the approximate method and, CD ref is the compliance distance
of the reference method.
The approximate method is motivated by the impedance characteristics of the sum of the embedded
fields of all array elements. The result in [28], [29] shows that the approximate method has significantly
improved the assessment time when compared to the embedded element approach combined with a
conservative field combining technique.
3. OPEN ISSUES AND FUTURE DIRECTION
In this section, we discuss the open issues and provide future direction in EM radiation and
compliance assessment for 5G communication systems. Some of the open issues discussed are compliance
assessment, proliferation of mobile devices and small cell access points and millimetre wave. In addition,
future direction is also presented.
3.1. Compliance Assessment
Accurate determination of compliance boundary may be quite complex for large array of RBS.The
combination of massive MIMO transmitting at millimetre wave bands will introduce different configurations
and array sizes of BS. Different array shapes and sizes such as cylindrical, spherical, circular, rectangular and
linear, have been proposed for massive MIMO BSs as shown in Figure 2. The simplified and accurate
method to determine compliance boundary that is applicable to all large antenna array needs to be
considered. Furthermore, simplified methods for EMF exposure of this large arrays antennas also need to be
further investigated.
Figure 2. Illustration of massive MIMO antennas
3.2. Proliferation of Mobile Devices and Small Cell Access Points
The introduction of internet of things and increased number of mobile devices using RF
communications will continue to raise concerns on health hazards due to EMF exposure. More studies based
on practical measurements are needed to examine these effects.
3.4. Millimetre Wave
The effect of EM radiation for 5G communication systems in the millimetre wave has been
investigated in [30]. A temperature based technique for the evaluation of safety compliance is proposed. The
result of the study shows that about 34% to 42% of the incident power is reflected at the skin surface at 60
GHz. More work concerning the millimetre wave are needed to establish the effect on human body and
different transmit power and different antenna types.
3.5. Future Direction
In the future, more work are expected in analysing the effects of EM radiation form massive
deployment of IoT and proliferation of mobile devices. In addition, more work on the numerical efficient
methods for compliance assessment of EMF exposures for RBS with large antenna arrays needs to be carried
out. The choice of methods need to take into consideration the accuracy and effect of antenna correlation of
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determining the compliance boundary of the RBS operating with large array at millimetre wave. More
measurement campigns are expected in order to verify the proposed numerical methods.
4. CONCLUSION
An overview of EM radiation and compliance assessments for 5G communication systems have
been presented in this paper. Other than that, the description of the EM radiation metrics which include SAR
and power density, near-field and far-field have also been discussed in this paper. Apart from the summary of
the effects of EM radiation from publish works that have been cited in this paper, methods to reduce EM
exposure and EMF compliance assessment have also been discussed. Finally, open issues and future direction
have also been presented.
ACKNOWLEDGEMENTS
The authors would like to express utmost gratitude to the ministry of higher education (MOHE) in
Malaysia and Universiti Teknologi Malaysia (UTM) for providing the financial support for this research
through the GUP grant (R.J130000.7809.4F589). The grant is managed by Research Management Centre
(RMC) at UTM.
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BIOGRAPHIES OF AUTHORS
Nor Adibah Binti Ibrahim received the Bachelor degree of electrical engineering from
Universiti Teknologi Malaysia (UTM) in 2011. From April until July 2010, she was trainee for
telecommunication company in Malaysia. She also received Master in Electrical Engineering
from same University in 2015. Currently, she is a PhD student in Wireless Communication
Center, Faculty of Electrical Engineering, UTM and conducting research on EMF radiation and
compliance assessment for radio base station for 5G communication systems. Her research
interest include coding in Matlab and OFDM modulation technique, the performance analysis of
Inter Carrier Interference (ICI) by using pulse shaping in OFDM systems and radio frequency
exposure.
Prof. Dr. Tharek Abd Rahman is a Professor at Faculty of Electrical Engineering, Universiti
Teknologi Malaysia (UTM). He obtained his BSc. In Electrical & Electronic Engineering from
University of Strathclyde UK in 1979, MSc in Communication Engineering from UMIST
Manchester UK and PhD in Mobile Radio Communication Engineering from University of
Bristol, UK in 1988. He is the Director of Wireless Communication Centre (WCC), UTM. His
research interests are radio propagation, antenna and RF design and indoors and outdoors
wireless communication. He has also conducted various short courses related to mobile and
satellite communication to the Telecommunication Industry and government body since 1990.
He has a teaching experience in the area of mobile radio, wireless communication system and
satellite communication. He has published more than 250 papers related to wireless
communication in national/international journal and conference.
Olakunle Elijah received the B.Eng. degree from Federal University of Technology Minna,
Minna, Nigeria, the M.Sc. degree in micro-electronics and computing from Bournemouth
University, Poole, U.K., and the postgraduate certificate in advance microelectronics from
Bolton University, Bolton, U.K., in 2003, 2008, and 2010, respectively. He is currently pursuing
the Ph.D. degree at the Universiti Teknologi Malaysia, Johor Bahru, Malaysia, and is conducting
research in the field of wireless communications. He worked as a Field Engineer for Kuyet
Nigeria Ltd., Lagos, Nigeria, in 2006. From 2011 to 2013, he was the MD/CEO at Microscale
Embedded Limited, Abuja, Nigeria. His research interests include embedded systems, wireless
communication, massive MIMO, radio frequency exposure for 5G, and interference mitigation.
He is the receipent of IEEE Malaysia ComSoc and VTS society joint chapter best paper award
2016.
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The fifth-generation (5G) network has been broadly investigated by many researchers. The capabilities of 5G include massive system capacity, incredibly high data rates everywhere, very low latency and the most important point is that it is exceptionally low device cost and low energy consumption. A key technology of 5G is the millimeter wave operating at 28 GHz and 38 GHz frequency bands which enable massive MIMO and small cell base station densification. However, there has been public concern associated with human exposure to electromagnetic fields (EMF) from 5G communication devices. Hence, this paper studies the power density of a 5G antenna array that can be used for the indoor base station. The power density is the amount of power or signal strength absorbed by a receiver such as the human body located a distance from the base station. To achieve this, the design of array antennas using CST software at 28 GHz, fabrication and measurement were carried out in an indoor and hallway environment. The measurement processes were set up at IC5G at UTM Kuala Lumpur in which the distance of the transmitter to receiver where 1 m, 4 m, 8 m, and 10 m. In this study, the measured power density is found to be below the set limit by ICNIRP and hence no health implication is feared. Regardless, sufficient act of cautionary has to be applied by those staying close to small cell base stations and more studies are still needed to ensure the safety of use of 5G base stations.
... A third factor concerns the scale and who is the driving force behind the 5G campaign. The level of marketing activity is a key, with intense lobbying of governments by equipment suppliers and operatorsand also of the public by governments [10]. ...
... Particularly, in fifth-generation (5G) networks, the current major concern is the green communications without making a tradeoff with other performance metrics like spectrum efficiency (SE) and latency [5][6][7][8][9][10][11][12][13][14]. Millimeter wave (mm-wave) solution is adopted in concentrated-coverage base stations (BSs) for loading the massive backhaul traffic [15][16][17][18][19]. Nonetheless, it is a significant contribution to realize such traffic load in a low energy consumption way [20]. ...
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... If you're using VMware Cloud Foundation technologies on premises today, you can also simplify your hybrid IT operations by using those same technologies including vSphere, vSAN, NSX, and vCenter Server across your on-premises data centers and on the AWS cloud, Google GCP, or Microsoft Azure. VMware Cloud on public cloud providers are mentioned lets you maintain consistent operations across your hybrid cloud architecture, without having to purchase any new or custom hardware or rewrite applications [14]- [16]. ...
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... The most important requirements are wideband spectrum and higher frequency. Some frequencies have been proposed to be a candidate for the 5G spectrum, covering 6-100 GHz, i.e. 6-10 GHz, 27-29 GHz, 37-40 GHz, 50-52 GHz, 66-74 GHz, 81-86 GHz [9], [10]. The 5G antenna system that covers its wideband spectrum is continuously improved. ...
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p>This paper presents a half triangular Comb-shaped slits edge Antipodal Vivaldi Antenna (Comb-AVA) as compared to the conventional Antipodal Vivaldi Antenna (AVA) design. This proposed antenna covers 20-40 GHz spectrum. This Comb-AVA antenna is designed for the 5G application which is addressed to cover a dualband 28/38 GHz frequencies. A half triangular comb-shaped slits edge structure is employed to investigate its effects on antenna parameters. This proposed Comb-AVA occupies a 25x8 mm2 of FR 4 substrate (𝜀𝛾 = 4.4, tan δ=0.02, thinkness 1.6 mm). It has impedance bandwidth (S11≤-10 dB) along 20-40 GHz spectrum and fractional bandwidth (FBW) ≥0.5. It means that the bandwidth is categorized as ultra wideband (UWB). In addition, there is 11 dB refinement of return loss in the CombAVA design at 38 GHz frequency. VSWR value is in range of 1.054 to 1.396. This proposed antena also has a wider angular width (3 dB) than the AVA. Higher directivity and gain is generated by Comb-AVA at 28 GHz. This proposed antenna has good performances and suitable for 5G application. </p
... The most important requirements are wideband spectrum and higher frequency. Some frequencies have been proposed to be a candidate for the 5G spectrum, covering 6-100 GHz, i.e. 6-10 GHz, 27-29 GHz, 37-40 GHz, 50-52 GHz, 66-74 GHz, 81-86 GHz [9], [10]. The 5G antenna system that covers its wideband spectrum is continuously improved. ...
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This paper presents a half triangular Comb-shaped slits edge Antipodal Vivaldi Antenna (Comb-AVA) as compared to the conventional Antipodal Vivaldi Antenna (AVA) design. This proposed antenna covers 20-40 GHz spectrum. This Comb-AVA antenna is designed for the 5G application which is addressed to cover a dualband 28/38 GHz frequencies. A half triangular comb-shaped slits edge structure is employed to investigate its effects on antenna parameters. This proposed Comb-AVA occupies a 25×8 mm² of FR 4 substrate (ϵγ tan δ=0.02, thinkness 1.6 mm). It has impedance bandwidth (S11≤-10 dB) along 20-40 GHz spectrum and fractional bandwidth (FBW) ≥0.5. It means that the bandwidth is categorized as ultra wideband (UWB). In addition, there is 11 dB refinement of return loss in the Comb-AVA design at 38 GHz frequency. VSWR value is in range of 1.054 to 1.396. This proposed antena also has a wider angular width (3 dB) than the AVA. Higher directivity and gain is generated by Comb-AVA at 28 GHz. This proposed antenna has good performances and suitable for 5G application. Copyright © 2018 Institute of Advanced Engineering and Science. All rights reserved.
... These antennas seamlessly emit the electromagnetic field (EMF) radiation in the form of non-ionizing radiation (NIR) [5], which can cause the thermal effect to human body. Thus, the interaction relations between the EMF emission from these multiple antennas and human tissue is significant to be studied [6], [7]. ...
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