This paper is intended to investigate intensely the impact of multipossible hand-hold positions on the electromagnetic (EM) interaction of handset antennas and a human by using a finite-difference time-domain (FDTD) method. Candy-bar handsets with different external and internal antenna positions operating in the GSM900, GSM1800/DCS, and UMTS/IMT-2000 bands are hereby simulated with configuration of the most parts in order to achieve the commercially available handset model design. Homogeneous and heterogeneous phantoms both are used to simulate the human head, whereas, a semirealistic model with three different tissues is designed to simulate a human hand holding a set. Both of the antenna performance including the total isotropic sensitivity (TIS) and the specific absorption rate (SAR) in tissues are examined for the different suggested applicable cases, where various positions of antenna, handset and hand are considered in simulations. This simulation study determines that both of the antenna performance and the SAR in tissues significantly alter owing to the positioning of the handset against user's head at different hand levels; where a maximum alteration is observed due to the exposure of handset with internal antenna, as compared with the handset having external antenna.
The possible health hazard of cellular communication handsets due to their electromagnetic (EM) interaction with human and the means of reducing the impact of this interaction have appeared as a public concern. It is noticeable that while using cellular handset in close proximity to head, many factors may affect on the EM interaction, among them is the hand-hold position.
Measuring the specific absorption rate (SAR) in human
head exposed to the handset antenna radiation, most standards (IEEE-1528, EN
50360/1, IEC 62209, ARIB STD-T56, FCC, ACA) [
Although over the
last fifteen years many authors have investigated the interaction between
the EM field radiated by the cellular hand-held and human head [
In [
Specifically in [
(1) In [
(2) In [
(3) In [
(4) In [
(5) In [
(6) In [
(7) In [
In this research, a semirealistic right-hand model with
three tissues [
In view of the fact that the external antenna position on a
handset has a considerable impact on the EM interaction [
The prediction of the EM interaction is based on evaluating
the handset antenna performance including the total isotropic sensitivity (TIS)
as well as the SAR and power absorbed in tissues.
Both
All simulations are achieved at 900, 1800, and 2025 MHz, which represent the GSM-family standards including E-GSM900 (880–960 MHz), GSM1800/DCS (1710–1880 MHz), and UMTS/IMT-2000 (1885–2200 MHz), respectively. For the later, the frequency of 2025 MHz represents the upper edge of the transmitting band of the IMT-2000 (1885–2025 MHz) also within the range of UMTS band.
The finite-difference
time-domain (FDTD) method proposed by Yee in 1966 [
For the handset with external antenna, a candy-bar handset
operating at 900 MHz [
The considered electromechanical parts of the
proposed handset models with external and internal antennas are
The main dielectric parts of the handset CAD models and the corresponding material parameters.
Part | ||
---|---|---|
Antenna cover and bushing | 2.5 | 0.003 |
PCB dielectric | 4.5 | 0.07 |
LCD glass | 4.5 | 0.01 |
LCD dielectric | 3.0 | 0.01 |
Housing and covers | 3.5 | 0.02 |
Keypad/buttons | 3.5 | 0.02 |
Battery case | 3.5 | 0.02 |
A short-whip antenna top-loaded with a small
cylinder [
The
Many
techniques were suggested to make the microstrip patch antenna (MPA) suitable
in size for the mobile communication terminals. One of the effective ways to
reduce the patch size of the microstrip antenna is to introduce a shorting pin
at the edge of the
patch [
In this work, a semirealistic handset model using a single-band probe-fed rectangular patch antenna with shorting plate at the edge is designed. Six different handset models are simulated with top and bottom-mounted patch antennas operating at different frequencies, that is, 900, 1800, and 2025 MHz.
The handset parts and components are not located identically
in all models due to the different antenna position and size regarding each
different operating frequency. Figure
The
The numerical structure of the rectangular patch antenna with shorting plate, used for the handset with internal antenna, and its dimensions at 900, 1800, and 2025 MHz.
A semirealistic hand model consisting of three
tissues (skin, muscle, and bone) [
Values of hand, HR-EFH, and SAM
material parameters (relative permittivity
Hand Tissue | 900 MHz | 1800 MHz | 2025 MHz | ||||
---|---|---|---|---|---|---|---|
Hand skin | 41.41 | 0.87 | 38.87 | 1.18 | 38.53 | 1.28 | 1100 |
Hand muscle | 55.03 | 0.94 | 53.55 | 1.34 | 53.26 | 1.47 | 1041 |
Hand bone | 12.45 | 0.14 | 11.78 | 0.28 | 11.64 | 0.31 | 1990 |
HR-EFH Tissue | |||||||
Air | 1.000 | 0.00 | 1.00 | 0.000 | 1.00 | 0.000 | 1.16 |
Blood vessel | 44.78 | 0.70 | 43.34 | 1.07 | 43.06 | 1.18 | 1050 |
Bone (ramus of mandible) | 12.45 | 0.14 | 11.78 | 0.28 | 11.64 | 0.31 | 1990 |
Brain/gray matter | 52.73 | 0.94 | 50.08 | 1.39 | 49.65 | 1.53 | 1039 |
Brain/white matter | 38.89 | 0.59 | 37.01 | 0.91 | 36.70 | 1.01 | 1043 |
Cerebellum | 49.44 | 1.26 | 46.11 | 1.71 | 45.62 | 1.84 | 1040 |
Cerebro Spinal Fluid (CSF) | 68.64 | 2.41 | 67.20 | 2.92 | 66.87 | 3.09 | 1007 |
Ear (cartilage) | 42.65 | 0.78 | 40.22 | 1.29 | 39.70 | 1.44 | 1100 |
Eye-cornea | 55.24 | 1.39 | 52.77 | 1.86 | 52.34 | 2.00 | 1032 |
Eye-lens | 46.57 | 0.79 | 45.35 | 1.15 | 45.10 | 1.26 | 1090 |
Eye-vitreous body | 68.90 | 1.64 | 68.57 | 2.03 | 68.46 | 2.17 | 1009 |
Fat (average infiltrated) | 11.33 | 0.11 | 11.02 | 0.19 | 10.95 | 0.22 | 916 |
Jaw bone (mandible) | 12.45 | 0.14 | 11.78 | 0.28 | 11.64 | 0.31 | 1990 |
Mastoid cells (bones) | 5.50 | 0.04 | 5.370 | 0.07 | 5.340 | 0.08 | 980 |
Midbrain (mesencephalon) | 45.79 | 0.76 | 43.00 | 1.20 | 43.00 | 1.00 | 1039 |
Muscles | 55.03 | 0.94 | 53.55 | 1.34 | 53.26 | 1.47 | 1041 |
Nasal cavity (mucous membrane) | 46.08 | 0.84 | 43.85 | 1.23 | 43.48 | 1.35 | 1050 |
Parotid gland | 59.68 | 1.04 | 58.14 | 1.50 | 57.81 | 1.65 | 1050 |
Skin | 41.41 | 0.87 | 38.87 | 1.18 | 38.53 | 1.28 | 1100 |
Skull | 16.62 | 0.24 | 15.56 | 0.43 | 15.35 | 0.49 | 1645 |
Spinal cord | 32.53 | 0.57 | 30.87 | 0.84 | 30.60 | 0.92 | 1038 |
Spine | 12.45 | 0.14 | 11.78 | 0.28 | 11.64 | 0.31 | 1990 |
Thalamus | 45.79 | 0.76 | 43.00 | 1.20 | 43.00 | 1.00 | 1039 |
Tongue | 55.27 | 0.94 | 53.57 | 1.37 | 53.23 | 1.51 | 1041 |
Ventricles (brain) | 68.64 | 2.41 | 67.20 | 2.92 | 66.87 | 3.09 | 1007 |
SAM phantom material | |||||||
SAM head shell | 5.0 | 0.0016 | 5.0 | 0.0016 | 5.0 | 0.0016 | 1030 |
SAM head liquid | 41.5 | 0.97 | 40.0 | 1.4 | 40.0 | 1.4 | 1030 |
A heterogeneous high-resolution European female head (HR-EFH) model with pressed ears
[
For comparison, an SAM phantom developed by
different standard committees [
Figure
Different CAD representations of the handset in hand against HR-EFH at
The simulation platform
To align the simulated handset components to the
FDTD grid accurately, a minimum spatial resolution of
Table
The generated FDTD grid cell size of the studied handset models in free space and in hand close to HR-EFH at different positions operating at 900, 1800, and 2025 MHz.
FDTD-grid cell size (Mcells) | 900 MHz | 1800 MHz | 2025 MHz | |||||
---|---|---|---|---|---|---|---|---|
Handset model | A1 | A2 | A1 | A2 | A1 | A2 | ||
In free space | 0.73372 | 0.73372 | 0.47925 | 0.47925 | 0.89113 | 0.89113 | ||
HR-EFH | Hand1 | 19.841 | 19.9055 | 18.07 | 18.1998 | 12.9027 | 13.1749 | |
Hand2 | 18.513 | 18.7085 | 16.6208 | 16.2842 | 11.8514 | 12.3738 | ||
Hand1 | 20.7561 | 20.9639 | 19.3401 | 19.2665 | 18.9213 | 18.695 | ||
Hand2 | 19.6181 | 19.6262 | 17.852 | 17.6552 | 17.4448 | 17.4434 | ||
Handset model | B1 | B2 | B1 | B2 | B1 | B2 | ||
In free space | 1.176 | 1.20755 | 1.04378 | 1.22912 | 1.04378 | 1.08768 | ||
HR-EFH | Hand1 | 19.4184 | 18.7987 | 19.2137 | 19.9362 | 19.0769 | 19.0168 | |
Hand2 | 17.6703 | 17.6138 | 17.1771 | 19.0242 | 17.1164 | 18.2577 | ||
Hand1 | 21.8594 | 22.0785 | 20.9776 | 21.93 | 21.1931 | 21.4403 | ||
Hand2 | 20.3798 | 20.8524 | 19.0882 | 19.7979 | 19.2979 | 19.4936 |
The EM
interaction between handset antenna and human is evaluated, firstly, by
assessing the effect of human head and hand on the handset antenna performance
through computing the antenna parameters including the input impedance
The results in Table
Computational results of the
antenna input impedance,
Parameter | Frequency/900 MHz | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
Handset model | A1 | A2 | A1 | A2 | A1 | A2 | A1 | A2 | ||
No head | In free space | 44.5 + j0.86 | 44.5 + j0.86 | −24.4 | −24.4 | 77.8 | 77.8 | 77.6 | 77.6 | |
In hand1 | 49.2 − j8.17 | 51.3 − j9.55 | −21.6 | −20.5 | 89.8 | 60.3 | 87.2 | 59.8 | ||
In hand2 | 78.5 + j37.4 | 58.36 − j3.5 | −9.1 | −21.5 | 30.7 | 36.5 | 26.9 | 36.3 | ||
HR-EFH | Hand1 | 42.7 + j4.63 | 42.6 + j4.27 | −20.6 | −20.8 | 18.7 | 21.2 | 18.5 | 21.0 | |
Hand2 | 57.7 + j46.9 | 44.1 + j10.9 | −7.9 | −17.6 | 10.3 | 10.7 | 8.60 | 10.6 | ||
Hand1 | 48.1 + j2.25 | 47.0 − j0.49 | −30.4 | −30.1 | 29.1 | 30.7 | 29.1 | 30.7 | ||
Hand2 | 66.7 + j46.7 | 52.2 + j10.1 | −8.1 | −19.9 | 16.2 | 17.1 | 13.6 | 16.9 | ||
Handset model | B1 | B2 | B1 | B2 | B1 | B2 | B1 | B2 | ||
No head | In free space | 49.6 – j11.7 | 50.6 – j6.92 | −18.7 | −23.2 | 83.2 | 83.9 | 82.1 | 83.5 | |
In hand1 | 60.4 – j0.32 | 24.4 + j11.7 | −20.5 | −8.5 | 64.5 | 62.6 | 63.9 | 53.8 | ||
In hand2 | 17.0 + j36.2 | 17.7 + j34.6 | −3.8 | −4.1 | 35.5 | 37.5 | 20.9 | 23.0 | ||
HR-EFH | Hand1 | 57.7 – j17.5 | 30.1 + j13.5 | −15.1 | −10.6 | 25.5 | 35.6 | 24.7 | 32.5 | |
Hand2 | 22.6 + j 32.6 | 17.9 + j32.6 | −5.4 | −4.3 | 14.6 | 19.8 | 10.4 | 12.5 | ||
Hand1 | 57.2 – j13.4 | −17.0 | −10.5 | 37.9 | 44.5 | 37.1 | 40.5 | |||
Hand2 | 19.6 + j32.9 | 15.4 + j33.9 | −4.7 | −3.6 | 19.4 | 27.4 | 12.8 | 15.5 |
Computational results of the
antenna input impedance,
Parameter | Frequency/1800 MHz | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
Handset model | A1 | A2 | A1 | A2 | A1 | A2 | A1 | A2 | ||
No head | In free space | 38.7 + j9.92 | 38.7 + j9.92 | −15.5 | −15.5 | 89.8 | 89.8 | 87.3 | 87.3 | |
In hand1 | 38.5 + j9.07 | 56.2 + j0.82 | −15.6 | −24.6 | 52.2 | 62.1 | 50.8 | 61.9 | ||
In hand2 | 98.7 + j26.4 | 41.7 + j5.52 | −8.7 | −19.3 | 27.8 | 42.4 | 24.8 | 41.9 | ||
HR-EFH | Hand1 | 43.9 + j17.9 | 61.7 + j18.1 | −14.1 | −14.4 | 17.5 | 30.1 | 16.8 | 29.0 | |
Hand2 | 106 + j47.2 | 45.6 + j16.3 | −7.0 | −15.2 | 9.6 | 20.0 | 7.6 | 19.4 | ||
Hand1 | 43.7 + j22.5 | 64.1 + j22.0 | −12.3 | −13.0 | 20.1 | 30.1 | 18.9 | 28.6 | ||
Hand2 | 106 + j50.3 | 44.5 + j18.2 | −6.8 | −14.1 | 11.1 | 19.1 | 8.8 | 18.3 | ||
Handset model | B1 | B2 | B1 | B2 | B1 | B2 | B1 | B2 | ||
No head | In free space | 33.3 – j9.97 | 38.9 – j8.72 | −12.7 | −16.0 | 90.0 | 86.4 | 85.1 | 84.2 | |
In hand1 | 36.7 – j6.13 | 58.7 + j23.3 | −15.5 | −13.0 | 54.0 | 41.2 | 52.4 | 39.1 | ||
In hand2 | 49.2 + j36.5 | 42.9 + j6.88 | −9.2 | −19.5 | 31.1 | 37.2 | 27.4 | 36.7 | ||
HR-EFH | Hand1 | 37.9 + j7.64 | 61.1 + j25.5 | −15.8 | −12.3 | 22.9 | 22.9 | 22.3 | 21.5 | |
Hand2 | 48.6 + j52.0 | 52.8 + j6.65 | −6.6 | −23.1 | 15.6 | 13.9 | 12.2 | 13.8 | ||
Hand1 | 32.9 – j1.25 | 59.3 + j24.9 | −13.6 | −12.5 | 24.4 | 26.5 | 23.3 | 25.0 | ||
Hand2 | 42.0 + j41.4 | 40.3 + j9.6 | −7.6 | −16.5 | 17.7 | 22.3 | 14.6 | 21. 8 |
Computational results of the
antenna input impedance,
Parameter | Frequency/2025 MHz | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
Handset model | A1 | A2 | A1 | A2 | A1 | A2 | A1 | A2 | ||
No head | In free space | 41.8 + j12.3 | 41.8 + j12.3 | −15.9 | −15.9 | 92.0 | 92.0 | 89.6 | 89.6 | |
In hand1 | 37.6 + j11.2 | 49.4 + j2.06 | −14.4 | −33.3 | 55.4 | 65.5 | 53.5 | 65.4 | ||
In hand2 | 72.4 + j28.4 | 36.4 + j10.1 | −10.8 | −14.2 | 32.0 | 46.1 | 29.3 | 44.3 | ||
HR-EFH | Hand1 | 42.3 + j16.8 | 61.5 + j8.64 | −14.1 | −17.8 | 19.1 | 32.0 | 18.4 | 31.4 | |
Hand2 | 82.8 + j40.9 | 45.4 + j17.0 | −8.5 | −14.8 | 10.5 | 19.0 | 9.0 | 18.3 | ||
Hand1 | 43.6 + j20.9 | 60.1 + j9.4 | −12.8 | −18.1 | 22.3 | 33.0 | 21.1 | 32.5 | ||
Hand2 | 82.1 + j44.6 | 45.7 + j18.1 | −8.1 | −14.4 | 11.9 | 20.1 | 10.1 | 19.3 | ||
Handset model | B1 | B2 | B1 | B2 | B1 | B2 | B1 | B2 | ||
No head | In free space | 42.7 – j1.80 | 45.5 + j4.0 | −21.8 | −23.9 | 94.6 | 94.0 | 94.0 | 93.6 | |
In hand1 | 49.4 – j0.33 | 70.1 + j36.5 | −43.1 | −9.6 | 67.0 | 32.8 | 67.0 | 29.2 | ||
In hand2 | 73.4 + j62.7 | 50.6 + j25.3 | −6.3 | −12.2 | 33.0 | 38.6 | 25.3 | 36.3 | ||
HR-EFH | Hand1 | 49.9 + j5.50 | 73.2 + j38.6 | −25.2 | −9.1 | 26.8 | 16.7 | 26.7 | 14.6 | |
Hand2 | 74.5 + j75.0 | 59.3 + J21.1 | −5.3 | −13.7 | 12.0 | 16.6 | 8.5 | 15.4 | ||
Hand1 | 40.7 + j2.92 | 72.6 + j37.6 | −19.3 | −9.3 | 28.8 | 20.9 | 28.5 | 18.5 | ||
Hand2 | 63.4 + J67.5 | 50.4 + j38.6 | −5.6 | −9.1 | 14.2 | 25.0 | 10.3 | 23.2 |
The three-dimensional far-field radiation patterns of the handset model-A1 in free space, in hand1 close to SAM and in hand1 close to HR-EFH at 900, 1800, and 2025 MHz.
Model-A1 in free-space, 900 MHz
Model-A1 in free-space, 1800 MHz
Model-A1 in free-space, 2025 MHz
Model-A1 in hand1 close to SAM,
Model-A1 in hand1 close to SAM,
Model-A1 in hand1 close to SAM,
Model-A1 in hand1 close to
HR-EFH,
Model-A1 in hand1 close to
HR-EFH,
Model-A1 in hand1 close to
HR-EFH,
The three-dimensional far-field radiation beam patterns of the handset model-B1 in free space, in hand1 close to SAM and in hand1 close to HR-EFH at 900, 1800, and 2025 MHz.
Model-B1 in free-space, 900 MHz
Model-B1 in free-space, 1800 MHz
Model-B1 in free-space, 2025 MHz
Model-B1 in hand1 close to SAM,
Model-B1 in hand1 close to SAM,
Model-B1 in hand1 close to SAM,
Model-B1 in hand1 close to
HR-EFH,
Model-B1 in hand1 close to
HR-EFH,
Model-B1 in hand1 close to
HR-EFH,
The TIS
is a measure of the handset receiving performance, where both TIS and total
radiated power (TRP) together determine effectiveness of the handset as a piece
of radio equipment, in particular, the maximum range at which the handset can
operate from the base station with some given level of performance [
The total isotropic sensitivity (TIS) levels of the handset models for different setups at 900, 1800, and 2025 MHz.
TIS (dBm) | 900 MHz | 1800 MHz | 2025 MHz | |||||
---|---|---|---|---|---|---|---|---|
Handset model | A1 | A2 | A1 | A2 | A1 | A2 | ||
In free space | −104.9 | −104.9 | −105.4 | −105.4 | −105.5 | −105.5 | ||
In hand1 | −103.6 | −103.8 | −103.1 | −103.9 | −103.3 | −104.2 | ||
In hand2 | −100.3 | −101.6 | −99.8 | −102.2 | −100.7 | −102.5 | ||
HR−EFH | Hand1 | −98.7 | −99.2 | −98.3 | −100.6 | −98.7 | −101.0 | |
Hand2 | −95.4 | −96.3 | −94.9 | −98.9 | −95.6 | −98.6 | ||
Hand1 | −100.6 | −100.9 | −98.8 | −100.6 | −99.3 | −101.1 | ||
Hand2 | −97.4 | −98.3 | −95.5 | −98.7 | −96.0 | −98.9 | ||
Handset model | B1 | B2 | B1 | B2 | B1 | B2 | ||
In free space | −105.2 | −105.2 | −105.3 | −105.3 | −105.7 | −105.7 | ||
In hand1 | −104.2 | −103.3 | −103.2 | −101.9 | −104.3 | −100.7 | ||
In hand2 | −99.1 | −99.6 | −100.4 | −101.7 | −100 | −101.6 | ||
HR-EFH | Hand1 | −100 | −101.1 | −99.5 | −99.3 | −100.3 | −97. 7 | |
Hand2 | −96.2 | −97.0 | −96.9 | −97.4 | −95.2 | −97. 9 | ||
Hand1 | −101.7 | −102.1 | −99.7 | −100 | −100.6 | −98.7 | ||
Hand2 | −97.1 | −97.9 | −97.7 | −99.4 | −96.2 | −99. 7 |
The influence
of the EM wave irradiation on the living body is measured by evaluating the SAR,
where SAR is defined as the amount of EM energy absorption in the unit mass as
follows [
The spatial-peak SAR should be evaluated in a cubical volume of the body
tissues that is within 5% of the required mass [
The computed values of the peak SAR (averaged
over 1 g and 10 g) and power absorption in tissues owing to handsets exposure in
different conditions at 900, 1800, and 2025 MHz are listed in Tables
Pooled statistics of peak 1 and 10 g SAR in tissues, radiated power, absorbed power in tissues, dielectric loss, and power budget error for the handset models in hand closed to HR-EFH at different positions operating at 900 MHz.
Handset model | Frequency/900 MHz | ||||||||
---|---|---|---|---|---|---|---|---|---|
A1 | A2 | B1 | B2 | ||||||
Hand position | hand1 | hand2 | hand1 | hand2 | hand1 | hand2 | hand1 | hand2 | |
Antenna input power (mW) | 600 | 600 | 600 | 600 | 600 | 600 | 600 | 600 | |
3.38 | 2.52 | 2.77 | 2.51 | 4.87 | 3.23 | 2.21 | 3.07 | ||
1.90 | 1.76 | 2.01 | 1.94 | 2.52 | 2.37 | 1.74 | 2.42 | ||
1.54 | 5.16 | 1.46 | 3.62 | 0.79 | 6.37 | 4.06 | 5.47 | ||
Radiated power (mW) | 111.0 | 51.6 | 125.9 | 63.4 | 148.6 | 62.6 | 194.8 | 75.2 | |
Absorbed power in head (mW) | 250.4 | 209.1 | 247.3 | 214.7 | 280.3 | 229.3 | 183.3 | 245.3 | |
Absorption rate in head (%) | 41.7 | 34.8 | 41.2 | 35. 8 | 46.7 | 38.2 | 30.5 | 40. 9 | |
Absorbed power in hand (mW) | 97.5 | 208.3 | 86.4 | 182.6 | 48.6 | 260.2 | 146.2 | 229.8 | |
Dielectric loss (mW) | 135.0 | 119.6 | 134.5 | 131.5 | 115.6 | 36.1 | 63.7 | 36.9 | |
Power budget error (%) | 1.01 | 1.90 | 0.98 | 1.30 | 1.15 | 1.94 | 1.99 | 2.13 | |
2.61 | 1.99 | 2.04 | 1.90 | 3.19 | 2.04 | 0.91 | 1.52 | ||
1.10 | 0.97 | 1.17 | 1.10 | 1.45 | 1.36 | 0.73 | 1.20 | ||
1.86 | 5.11 | 1.72 | 4.40 | 1.12 | 7.00 | 4.25 | 7.30 | ||
Radiated power (mW) | 174.4 | 81.9 | 184.3 | 101.4 | 222.7 | 76.9 | 243.3 | 93.1 | |
Absorbed power in head (mW) | 184.6 | 159.2 | 185.3 | 160.6 | 193.8 | 195.6 | 130.3 | 166.0 | |
Absorption rate in head (%) | 30.8 | 26.5 | 30.9 | 26.8 | 32.3 | 32.6 | 21.7 | 27.7 | |
Absorbed power in hand (mW) | 114.0 | 237.1 | 99.4 | 213.5 | 77.0 | 280.0 | 159.0 | 291.4 | |
Dielectric loss (mW) | 122.5 | 110.0 | 126.2 | 117.3 | 104.8 | 35.0 | 63.9 | 38.7 | |
Power budget error (%) | 0.75 | 1.97 | 0.80 | 1.19 | 0.28 | 2.08 | 0.58 | 1.80 |
Pooled statistics of peak 1 and 10 g SAR in tissues, radiated power, absorbed power in tissues, dielectric loss, and power budget error for the handset models in hand closed to HR-EFH at different positions operating at 1800 MHz.
Handset model | Frequency/1800 MHz | ||||||||
---|---|---|---|---|---|---|---|---|---|
A1 | A2 | B1 | B2 | ||||||
Hand position | hand1 | hand2 | hand1 | hand2 | hand1 | hand2 | hand1 | hand2 | |
Antenna input power (mW) | 125 | 125 | 125 | 125 | 125 | 125 | 125 | 125 | |
1.48 | 0.85 | 1.16 | 1.10 | 2.67 | 1.81 | 0.84 | 1.49 | ||
0.66 | 0.41 | 0.67 | 0.55 | 1.74 | 0.85 | 0.51 | 0.90 | ||
1.28 | 3.87 | 1.21 | 2.01 | 0.84 | 1.82 | 1.65 | 1.06 | ||
Radiated power (mW) | 21.0 | 9.55 | 36.2 | 24.2 | 27.9 | 15.3 | 26.9 | 17.3 | |
Absorbed power in head (mW) | 53.7 | 36.2 | 45.7 | 38.9 | 61.7 | 44.6 | 27.8 | 47.7 | |
Absorption rate in head (%) | 43.0 | 29.0 | 36.6 | 31.2 | 49.4 | 35.7 | 22.3 | 38.2 | |
Absorbed power in hand (mW) | 36.6 | 63.9 | 31.1 | 50.0 | 24.3 | 58.2 | 60.8 | 47.0 | |
Dielectric loss (mW) | 13.4 | 12.8 | 11.8 | 11.4 | 10.9 | 5.30 | 9.30 | 12.3 | |
Power budget error (%) | 0.18 | 2.00 | 0.16 | 0.33 | 0.10 | 1.27 | 0.12 | 0.58 | |
1.54 | 0.89 | 0.93 | 1.06 | 2.46 | 1.66 | 0.42 | 0.77 | ||
0.60 | 0.35 | 0.53 | 0.49 | 1.10 | 0.72 | 0.26 | 0.45 | ||
1.25 | 3.80 | 1.60 | 2.24 | 1.12 | 2.17 | 1.94 | 1.36 | ||
Radiated power (mW) | 23.6 | 11.0 | 35.7 | 22.9 | 29.2 | 18.3 | 31.3 | 27.2 | |
Absorbed power in head (mW) | 50.5 | 35.7 | 42.4 | 36.1 | 52.2 | 37.9 | 17.4 | 26.8 | |
Absorption rate in head (%) | 40.4 | 28.6 | 34.0 | 28.9 | 41.8 | 30.4 | 13.9 | 21.4 | |
Absorbed power in hand (mW) | 37.0 | 63.1 | 34.2 | 53.6 | 29.7 | 60.3 | 65.1 | 58.0 | |
Dielectric loss (mW) | 13.2 | 12.7 | 12.0 | 11.4 | 13.6 | 6.46 | 10.6 | 12.8 | |
Power budget error (%) | 0.44 | 1.96 | 0.54 | 0.74 | 0.21 | 1.62 | 0.45 | 0.17 |
Pooled statistics of peak 1 and 10 g SAR in tissues, radiated power, absorbed power in tissues, dielectric loss, and power budget error for the handset models in hand closed to HR-EFH at different positions operating at 2025 MHz.
Handset model | Frequency/2025 MHz | ||||||||
---|---|---|---|---|---|---|---|---|---|
A1 | A2 | B1 | B2 | ||||||
Hand position | hand1 | hand2 | hand1 | hand2 | hand1 | hand2 | hand1 | hand2 | |
Antenna input power (mW) | 125 | 125 | 125 | 125 | 125 | 125 | 125 | 125 | |
1.85 | 1.09 | 1.39 | 1.64 | 3.78 | 2.40 | 0.71 | 1.32 | ||
0.77 | 0.50 | 0.77 | 0.78 | 1.70 | 1.15 | 0.43 | 0.80 | ||
2.12 | 4.10 | 1.98 | 1.95 | 0.58 | 2.10 | 1.83 | 2.17 | ||
Radiated power (mW) | 23.0 | 11.3 | 39.3 | 22.9 | 33.4 | 10.6 | 18.3 | 19.2 | |
Absorbed power in head (mW) | 53.7 | 36.7 | 44.8 | 43.7 | 68.6 | 49.4 | 26.0 | 44.0 | |
Absorption rate in head (%) | 43.0 | 29.3 | 35.8 | 35.0 | 54.9 | 39.5 | 20.8 | 35.2 | |
Absorbed power in hand (mW) | 36.7 | 64.4 | 30.0 | 47.3 | 14.5 | 59.3 | 68.0 | 51.0 | |
Dielectric loss (mW) | 11.0 | 10.0 | 10.7 | 10.8 | 8.00 | 3.10 | 10.4 | 10.0 | |
Power budget error (%) | 0.48 | 2.00 | 0.14 | 0.12 | 0.36 | 2.06 | 1.86 | 0.62 | |
1.91 | 1.15 | 1.17 | 1.58 | 3.80 | 2.20 | 0.38 | 0.71 | ||
0.67 | 0.42 | 0.60 | 0.69 | 1.54 | 0.93 | 0.23 | 0.40 | ||
2.17 | 4.18 | 2.31 | 1.98 | 0.92 | 2.16 | 2.10 | 2.72 | ||
Radiated power (mW) | 26.4 | 12.6 | 40.6 | 24.2 | 35.6 | 12.9 | 23.1 | 29.0 | |
Absorbed power in head (mW) | 50.7 | 35.0 | 40.8 | 40.1 | 59.0 | 43.2 | 17.6 | 26.2 | |
Absorption rate in head (%) | 40.6 | 28.0 | 32.6 | 32.0 | 47.2 | 34. 6 | 14.1 | 21.0 | |
Absorbed power in hand (mW) | 36.8 | 64.9 | 32.9 | 50.1 | 22.0 | 62.7 | 71.5 | 58.0 | |
Dielectric loss (mW) | 10.8 | 9.8 | 9.8 | 10.2 | 8.2 | 3.6 | 10.6 | 9.8 | |
Power budget error (%) | 0.18 | 2.12 | 0.7 | 0.38 | 0.13 | 2.06 | 1.78 | 1.60 |
Figures
Sliced distribution of the averaged-peak
Sliced distribution of the averaged-peak
Sliced distribution of the averaged-peak
Sliced distribution of the averaged-peak
The power
budget error is defined as
The hand impact on the EM interaction between handset antennas and human is investigated profoundly in this paper. Owing to hand-hold alteration under different usage patterns, handsets with external and internal antennas show a significant deviation in their performance as well as in their EM radiation impact on head. Although the user’s hand has a negative impact on the antenna performance of a handset in-use, changing its position may reduce the amount of the SAR and power absorption in head tissues.
The results listed in Tables
(1) The significant degradation in internal patch antenna performance due to the different hand positions, as compared with the external antenna, is because the patch antenna is sandwiched between hand and head tissues during the practical usage, where the hand tissues act as the antenna upper dielectric layers. This may shift the tuning frequency as well as decrease the radiation efficiency.
(2) Based on the relation between the
absolute difference in antenna total efficiency due to hand-hold alteration
(from hand1 to hand2) and the antenna/handset position, as shown in Figure
Absolute difference in the antenna total efficiency owing to hand-hold alteration at different antenna/handset positions against HR-EFH in GSM900, GSM1800, and UMTS/IMT-2000 bands.
Models-A1 and A2 against HR-EFH
Models-B1 and B2 against HR-EFH
Absolute difference in the TIS levels owing to hand-hold alteration at different antenna/handset positions against HR-EFH in GSM900, GSM1800, and UMTS/IMT-2000 bands.
Models-A1 and A2 against HR-EFH
Models-B1 and B2 against HR-EFH
Percentage difference in the averaged-peak
Models-A1 and A2 against HR-EFH
Models-B1 and B2 against HR-EFH
(3) Although the interference of the
external noisy components (i.e., display and camera, as well as their
associated feed circuits) is not considered in simulation, the drop in TIS
specification of handsets while in-use, as shown in Table
(4) Figure
(5) Figures
Tables
(1)
More SAR
variation in HR-EFH tissues is perceived owing to the internal antenna
exposure, as compared with the external antenna exposure. Figure
(2) The direction of arrows shown in
Figure
(3) In [
(4) It is clear from Figure
(5) The percentage values of power
absorption in head (SAM and HR-EFH) at different antenna/handset positions in
GSM900, GSM1800, and UMTS/IMT-2000 bands are narrated and illustrated in Figure
Percentage power absorption in head tissues at different antenna/handset positions in GSM900, GSM1800, and UMTS/IMT-2000 bands.
Models-A1 and A2 at 900 MHz
Models-B1 and B2 at 900 MHz
Models-A1 and A2 at 1800 MHz
Models-B1 and B2 at 1800 MHz
Models-A1 and A2 at 2025 MHz
Models-B1 and B2 at 2025 MHz
(6) To some context, the power absorption in hand tissues behaves inversely to that in head.
The power loss in handset materials is corresponded
to the dielectric loss (since all the metal parts are considered as PEC in
simulations and consequently the metallic ohmic-loss equal to zero). Tables
The dielectric loss of the
handset with internal antenna gets decreased while shifting the hand from hand1
to hand2, where a maximum percentage difference of −68.8% is recorded at 900 MHz for model-B1 at
Many researchers have investigated the SAR in
both SAM- and MRI-based human head due to the handset antennas exposure. Study
by some researchers concluded that SAM underestimates SAR in adult MRI-based head,
whereas, some other researchers concluded that SAM overestimates SAR in MRI-based adult head.
Simultaneously, some researchers have presented mixed results. Light has been shed
in detail on all these three states in [
The simulations carried out in
this work bring to light SAR difference in SAM and HR-EFH as explained here. According
to the adopted handset positions with respect to head, inclusion of the pinna
in the 1 and 10 g SAR averaging volumes for the HR-EFH and the database used to
define the tissues parameters, the SAM has always been found underestimating
SAR in HR-EFH by a factor ranging from 1.0 to 2.0, with the exception of the
handset models being at
SAM and HR-EFH get different
SAR values and absorb different amount of powers because of the differences
between their volumes, masses, and homogeneities. The volume and mass of the
SAM phantom are approximately 5825
Figures
For the same FDTD-grid setting, handset in hand
close to HR-EFH needs more number of grid cells to be simulated, as compared
with handset close to SAM. It is true even with duplicating the refining factor
of SAM solid regions (shell and liquid). It is because of homogeneous property
of the SAM phantom in which the spatial resolution along the head tissue gradually
increases from the minimum to maximum in short distance at each axis. As concerning
the heterogeneous HR-EFH model, the minimum spatial resolution has no big
chances to reach the maximum value at each axis owing to the existence of the twenty
five different tissues. Consequently, for the same FDTD-grid setting, the power
budget error in cases with the HR-EFH is less than in cases with the SAM. As
revealed in Tables
All computations were performed on a 2 GHz Intel centrino Laptop machine (Dell, inspiron-630 m) with 2 GB memory and a 1.6 GHz dual core Intel Pentium machine (Acer, Aspire M1600) with 4 GB memory.
The
runtime and memory requirements depend on the simulation space as well as the
refinement factor for each solid region. Less memory and runtime were required
for the handset simulation in free space, whereas more memory and runtime were
required for the handset in hand close to head. The maximum number of FDTD-grid
cells that can be achieved with the adopted simulating machines is about 24 Mcells, where a hardware accelerator aXware [
On the
bases of the handset, hand, and head models used in this research, it has been significantly
elaborated that the hand-hold position has a considerable impact on the EM
interaction between cellular handset and human. Other related factors such as the
operating frequency, antenna type/position, and the handset position against
head were assessed while anticipating the hand impact. To achieve realistic in-use
conditions, different candy-bar handset models having external and internal
antennas operating in GSM900, GSM1800, and UMTS/IMT-2000 bands were simulated, whereas
semirealistic hand model of three tissues, MRI-based adult female head model of
twenty five tissues, and SAM phantom were selected for evaluating the EM
interaction. Owing to the hand-hold alteration, more differences in values of
the antenna total efficiency, total isotropic sensitivity, and both SAR and
power absorption in tissues were recorded with the handset models having
internal patch antenna, as compared with the handset models having external
loaded short-whip antenna. This paper showed interesting results; in a certain
usage pattern of a handset having left-side external antenna, the maximum
percentage difference of spatial-peak
The authors would like to thank reverent Wayne Jennings, Application Engineer, SPEAG Schmid & Partner Engineering AG for the kind assistance in providing the numerical corrected model of a human head (HR-EFH). They would like to express their gratitude to Professor M. L. Chaudhary, the Higher Institute of Electronics for his kind assistance in removing the linguistic errors in this article.