This document investigates the performance of a dipole textile antenna in relation to human body orientation and the specific absorption rate (SAR) when the antenna is worn. It highlights the significant influence of antenna orientation and position on SAR values, noting that horizontally oriented antennas present greater SAR compared to vertical ones. The study concludes that careful selection of antenna orientation and placement on the body is essential for optimizing performance and safety compliance.

1. Effects of Human Body and Antenna Orientation
on Dipole Textile Antenna Performance and SAR

2. PRESENTATION OUTLINE
INTRODUCTIONS
BACKGROUND
PROBLEM STATEMENT
OBJECTIVES
METHODOLOGY
RESULTS AND DISCUSSIONS
CONCLUSIONS

3.  Specific Absorption Rate (SAR)
3
INTRODUCTIONS

4. 4
 Wearable Antennas
 Utilization of textile materials for the development of flexible
wearable systems is rapid due to the recent miniaturization of
wireless devices for body-centric networks communications
technology [2-8].
 The textile antennas can be constructed using ordinary fabric as
dielectric and e.g. conductive tape or fabric as conducting
elements. This enables the antenna to be flexible and
lightweight
 The wearable antenna structure is easy to attach to clothing
and the structure does not limit the possible antenna
placements.
 Antennas that are rigid and massive have limited amount of
places they can be attached to without being uncomfortable to
the user.

5. 5
 Recently, wearable antennas have received growing interest due to the
introduction of personal and body-centric networks communications
technology. Therefore, additional factors and scenarios must be considered for
SAR compliance testing since the antenna is worn closely to human body.
 The influence of different types body models on SAR values has been treated
in the literature [9]. The variation of SAR values with the distance between the
wearable antenna and the human phantom has also been investigated in
some additional studies [9,10].
 Author [13] has discussed the effect of human body towards the SAR
distribution in the human head induced by planar inverted F antenna (PIFA)
and monopole antenna. The effects of antenna orientation were also
considered. The author concluded that human body plays a significant role on
the SAR value in the head and particularly important for the vertical
orientation cases for both antennas investigated.

PROBLEM STATEMENT

6. 6
 However, there is no research to date reported on the effect of the antenna
orientation towards the SAR values in other body part. Most of the previous
research only focused on the effect of the antenna orientation on the antenna
performance and SAR inside the human head only.
 Therefore, this project tends to focus on the SAR values and the energy
absorption when the antenna is placed at several positions in two different
orientations. The results will be discussed in terms of antenna resonant
frequency, radiation pattern, gain and SAR.
PROBLEM STATEMENT (cont.)

7. OBJECTIVES
1. To investigate the interaction between a single band
textile antenna with human body at 2.4 GHz.
2. To examine the effects of antenna orientation towards
the antenna performance and Specific Absorption Rate
(SAR), considering different antenna positions and
distances between the antenna and voxel human body
model.

8. Simulation of antenna in free space
Fabricate and measure antenna in free space
Satisfied
Analysis results
No
No
Simulate antenna+body (horizontally position)
Yes
Satisfied
Yes
8
middle chest right chest right waist stomach
METHODOLOGY
Back of body
Simulate 4 different antenna-body distance
Change to vertical position
Satisfied
No
Yes

9. Frequency (GHz)
1.5 2.0 2.5 3.0 3.5
S
11
(dB)
-50
-40
-30
-20
-10
0
simulation
measurement-
shieldit
measurement-
copper tape
METHODOLOGY
denim textile
εr=1.7
tan d=0.025
Substrate:
Fig. 1. (a) The fabricated antenna, (b) Front view,
(c) Back view. Antenna dimensions are in [mm].
(d) the antenna resonance frequency in free space.
(a)
(b)
(c)

10. METHODOLOGY (cont. )
10
d = 1, 5, 10 and 20mm
Gustav voxel model (38 years old male)
Human body
(a) (b)
(d)
(c)
(e)
(a)
(e)
(d)
(c)
(b)
Fig. 2. Depictions of horizontally and vertically orientated antenna locations. (a) Middle chest, (b) Right
chest, (c) Back, (d) Right Waist, (e) Stomach.
Horizontally Orientated Vertically Orientated

11. RESULTS
AND
DISCUSSIONS

12. RESULTS AND DISCUSSIONS
 The worst case is observed when the horizontally orientated antenna
is placed at 1 mm from the stomach.
Antenna
Position
Horizontal Orientation Vertical Orientation
Antenna-body distance,d Antenna-body distance,d
1 mm 5 mm 10 mm 20 mm 1 mm 5 mm 10 mm 20 mm
Middle
Chest
2.44 -16.35 2.44 -16.84 2.40 -16.97 2.36 -
25.71 2.38 -
24.34 2.36 -
30.69 2.35 -
42.26 2.36 -
23.74
Right
Chest
2.54 -33.77 2.49 -20.06 2.44 -18.75 2.40 -
22.87 2.46 -
18.56 2.44 -
18.44 2.41 -
19.52 2.38 -
29.02
Stomach 2.48 -8.20 2.59 -26.07 2.50 -16.38 2.42 -
14.47 2.46 -
19.25 2.44 -
15.88 2.40 -
16.61 2.35 -
29.48
Back 2.62 -22.73 2.54 -14.42 2.46 -17.21 2.40 -
19.54 2.54 -
13.99 2.45 -
18.51 2.42 -
18.11 2.37 -
24.75
Right
Waist
2.50 -25.49 2.48 -18.79 2.45 -17.46 2.40 -
21.81 2.49 -
16.46 2.45 -
14.78 2.41 -
15.78 2.36 -
23.58
TABLE I. Antenna Resonant Frequency (fr in GHz/S11 in dB)

13. Horizontal vs. Vertical
Frequency (GHz)
1.5 2.0 2.5 3.0 3.5
S
11
(dB)
-50
-40
-30
-20
-10
0
antenna-free space
antenna+stomach (d=5mm)-H
antenna+back (d=5mm)-H
antenna+stomach (d=20mm)-H
antenna+back (d=20mm)-H
antenna+stomach (d=5mm)-V
antenna+back (d=5mm)-V
antenna+stomach (d=20mm)-V
antenna+back (d=20mm)-V

14. RESULTS AND DISCUSSIONS
 The gain for horizontally orientated antenna placed at 1 mm from the
stomach and back of the body is negative value which is -7.26 dB and
-3.35 dB respectively. Whereas, the gain value increase for the entire
vertically polarized antenna case investigated.
Fig. 3. Gain of the antenna in horizontal and vertical orientation on
the voxel phantom.

15. RESULTS AND DISCUSSIONS (cont. )
Middle Chest
-40 -30 -20 -10 0 10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
0
30
60
90
120
150
180
210
240
270
300
330
Stomach
-
40 -
30 -
20 -
10 0 10
-
40
-
30
-
20
-
10
0
10
-
40
-
30
-
20
-
10
0
10
-
40
-
30
-
20
-
10
0
10
0
30
60
90
120
150
180
210
240
270
300
330
Right Chest
-40 -30 -20 -10 0 10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
0
30
60
90
120
150
180
210
240
270
300
330
Back
-40 -30 -20 -10 0 10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
0
30
60
90
120
150
180
210
240
270
300
330
Right Waist
-40 -30 -20 -10 0 10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
0
30
60
90
120
150
180
210
240
270
300
330
Right Chest
-40 -30 -20 -10 0 10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
0
30
60
90
120
150
180
210
240
270
300
330
Middle Chest
-40 -30 -20 -10 0 10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
0
30
60
90
120
150
180
210
240
270
300
330
Back
-40 -30 -20 -10 0 10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
0
30
60
90
120
150
180
210
240
270
300
330
Stomach
-40 -30 -20 -10 0 10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
0
30
60
90
120
150
180
210
240
270
300
330
Right Waist
-40 -30 -20 -10 0 10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
-40
-30
-20
-10
0
10
0
30
60
90
120
150
180
210
240
270
300
330
Fig. 4. Simulated radiation patterns for antenna placed 1mm from stomach, middle chest, back,
right chest and right waist. (a) E-plane. (b) H-plane.
(a) (b)
Stomach Middle chest
Back
Right waist
Right chest
Stomach Middle chest
Back Right chest
Right waist

16. CONCLUSIONS
 The presence of the human body significantly detuned the
antenna resonance frequency and altered the antenna
radiation pattern. However, the effects become more
pronounced when the antenna is curved.
 Besides, the antenna orientations and locations produce a
prominent effect on SAR value. SAR is increased up to 16 %
when the textile antenna is horizontally orientated compared
to antenna in vertical orientation.
 Furthermore, the SAR value is significantly influenced by the
antenna locations on the human body and separation distance
between the antenna and human body.
 Therefore, due to this orientation effect, it is better to carefully
choose the best orientation and position to place the antenna
on the human body.

17. 1) I. C. o. N.-I. R. P. (ICNIRP), "Guidelines For Limiting Exposure To Time-Varying
Electric, Magnetic, And Electromagnetic Fields (Up To 300 GHz)," ed: Health
Physics Society, 1998.
2) M. A. R. Osman, et al., "Design and analysis UWB wearable textile antenna," 2011,
pp. 530-533.
3) M. A. R. Osman, M. K. A. Rahim, M. Azfar, N. A. Samsuri, F. Zubir, and K.
Kamardin, "Design, implementation and performance of ultra-wideband textile
antenna," Progress In Electromagnetics Research B, vol. 27, pp. 307-325, 2011.
4) N. Chahat, et al., "Design and characterization of an UWB wearable antenna,"
2010, pp. 461-464.
5) M. A. R. Osman, et al., "Embroidered fully textile wearable antenna for medical
monitoring applications," Progress in Electromagnetics Research, vol. 117, pp.
321-337, 2011.
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