IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY, VOL. 60, NO. 6, DECEMBER 2018
2057
Letters
A Novel Compact Dual-Band Frequency Selective Surface for GSM Shielding
by Utilizing a 2.5-Dimensional Structure
Weiyang Yin, Hou Zhang, Tao Zhong, and Xueliang Min
Abstract—Based on 2.5-dimensional (2.5-D) structure, a novel
compact dual-band frequency selective surface for GSM shielding is proposed in this letter. The unit cell geometryis designed
by knitting double square-loop elements in 2.5-D which realizes
the compact dual band-stop characteristics successfully. The size
of proposed 2.5-D frequency selective surfaces (FSS) cell is only
0.072 λ0 , where λ0 corresponds to free-space wavelength of the
lower resonance frequency. The 2.5-D FSS is modeled and simulated by Microwave CST STUDIO SUITE. The simulation result
shows that the FSS offers band-stop response at 900 and 1790 MHz
with shielding effectiveness of 41.9 dB and 49.2 dB, respectively.
Furthermore, the 2.5-D FSS performs a good angle-stability under
both TE and TM polarizations. Hence, the designed 2.5-D FSS can
be used for GSM shielding effectively. A prototype of proposed
2.5-D FSS is fabricated. The measurement result proves the satisfactory consistency with the simulation results.
Index Terms—2.5-dimensional structure, dual-band, frequency
selective surfaces (FSSs), GSM shielding, shielding effectiveness
(SE).
I. INTRODUCTION
N RECENT years, with the rapid development of wireless
communication and internet technology, the mobile phones
become really universal worldwide. In the same time, the electromagnetic interference (EMI) caused by mobile phones has
become increasingly serious [1]–[3]. According to the reports
[4], the GSM 900/1800 bands at which most mobile phones operating are the main contributor of the EMI, which threaten the
security of the electronics equipment and sensitive equipment
severely [5], [6]. In order to solve this problem, frequency selective surfaces (FSSs) have been studied intensively for providing
effective shielding [7]–[9].
FSSs are usually two-dimensional (2-D) periodic metallic
patches or apertures on a dielectric substrate that can exhibit bandpass or band-stop characteristics at especial bands
[10]–[12]. Recently, FSSs used for GSM shielding have been
reported frequently. In [13], a dual-band frequency selective
I
Manuscript received December 2, 2017; accepted December 28, 2017. Date
of publication January 18, 2018; date of current version August 13, 2018.
(Corresponding author: Weiyang Yin.)
The authors are with the Air and Missile Defense College, Air Force Engineering University, Xi’an 710051, China (e-mail: 18165368761@163.com;
warmer88@163.com; ztbull001@163.com; MinXL08@163.com).
Color versions of one or more of the figures in this letter are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TEMC.2018.2790584
surface realized as wallpaper for walls is proposed for GSM
Frequency Shielding, but the size of the unit cell is 0.3 λ. In
[14], using the Jerusalem crosses to synthesize a compact FSS
that can be used to shield GSM 900/1800 bands is proposed. The
size of the FSS cell is 0.187 λ. In [7], a fractal square-loop FSS
is discussed to attenuate signals at GSM bands and the element
size is 0.14 λ. In [8], a modified double square-loop element
based FSS is designed to cover the GSM bands, the element
size is also 0.14 λ. Beside, two tri-band FSSs designed for GSM
systems are described in [15] and [16] with element size is 0.15
λ and 0.17 λ, respectively. Although many structures have been
realized for GSM shielding, the size of those proposed FSSs are
too large to embed into small electronic devices. Besides, the
large size will make it difficult to contain enough elements in
limit space to act like infinite FSSs and will move the grating
region close to the operating band. Hence, a compact frequency
selective surface used to shield GSM bands is in urgent need.
In this letter, a novel compact dual-band frequency selective
surface for GSM shielding is proposed. The structure consists
of modified double square-loop elements using 2.5-D structure. The proposed 2.5-D FSS performs dual-band characteristics at frequencies 900 and 1790 MHz and the element size is
only 0.072 λ0 . The simulation and measurement results show
that the proposed 2.5-D FSS can be used to shield GSM bands
effectively.
This letter is organized as follows. The Section II details the
geometry of proposed 2.5-D FSS and analyzes the simulation
results. The Section III shows the distribution of surface current
and equivalent circuit of 2.5-D FSS and analyzes the operating
mechanism of the miniaturized dual-band characteristics. Finally, the measurement setup is presented and the measurement
results are explained in Section IV.
II. FSS DESIGN AND ITS PERFORMANCE
The schematic of designed 2.5-D FSS is shown in Fig. 1. The
substrate of the FSS is 2-mm thick Pure Poly tetra fluoroethylene
(PTFE) with dielectric constant εr = 2.2 and loss tangent δ =
0.001.
As shown in Fig. 1, the 2.5-D FSS is a modification of double square-loop element. To increase the equivalent inductance
and capacitance and realize miniaturization characteristics, the
double square-loop element has been knitted on both sides of
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Fig. 1.
IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY, VOL. 60, NO. 6, DECEMBER 2018
Fig. 3.
Simulated SE for TE mode under different incident angles.
Fig. 4.
Simulated SE for TM mode under different incident angles.
Structure of the 2.5-D FSS element. (a) Top view. (b) Perspective view
TABLE I
PARAMETERS OF PROPOSED 2.5-D FSS
Parameters
D
L1
L2
l1
s
Value/(mm)
Parameters
Value/(mm)
24
23
17
1.9
1
l2
l3
l4
R
W
2.3
3.3
5.6
0.2
0.2
exhibits dual band-stop characteristics at 900 and 1790 MHz
with transmission coefficient well below −40 dB. Besides,
the −18 dB bandwidth at resonant frequencies 900 MHz and
1790 MHz is 91 MHz and 156 MHz, respectively. Furthermore,
the size of the proposed 2.5-D FSS cell is only 0.072 λ0 , where
λ0 corresponds to free-space wavelength of the lower resonance
frequency. When the 2.5-D FSS is used to shield the GSM
signals, the shielding effectiveness (SE) should be taken into
consideration. According to [4], the SE is defined as follows:
SE (in dB) = −20 × log10 (Stransmission /Sincidence )
Fig. 2.
Transmission and reflection coefficients of 2.5-D FSS.
the substrate and interconnected through metallic vias. Besides,
the metallic elements on the top layer of the 2.5-D FSS are convoluted to lengthen the perimeter of the square loop and adjust
operating frequency. The prototype of the 2.5-D FSS is modeled
and simulated by Microwave CST STUDIO SUITE. Following a
heuristic process, the optimized parameters are given in Table I.
The simulated transmission and reflection coefficients of proposed 2.5-D FSS are given in Fig. 2. It is clear that the 2.5-D FSS
(1)
where the Stransm ission is the transmission coefficient when the
FSS is introduced in the shielding and the Sincidence is the transmission coefficient when the FSS is taken away. To investigate
the angle-stability of 2.5-D FSS for TE and TM wave, the simulation results are given in Figs. 3 and 4. In Fig. 3, it is clear that
the 18-dB bandwidth is directly proportional to the incident angle for TE mode. In Fig. 4, for TM mode, the 18-dB bandwidth
decreased with the increase of incident angle. The phenomenon
mainly attributed to wave impedance changes, which validates
the basic theory of FSS mentioned in [10]. However, it is to
be noted that the 2.5-D FSS exhibits excellent stability for different incident angles and polarizations. Hence, the proposed
2.5-D FSS can be used to shield GSM signals effectively.
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Fig. 5.
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Fig. 7. Comparison of transmission parameters in the normal illuminated by
TE wave.
Distribution of surface current. (a) 900 MHz. (b) f = 1790 MHz.
TABLE II
COMPARISON WITH OTHER FSSS IN PREVIOUS LITERATURES
Fig. 6.
Equivalent circuit of 2.5-D FSS.
Ref
εr
Operation
Size
Angular stability
[13]
[7]
[14]
[8]
[15]
[16]
This letter
1.8
4.3
2.2
3.4
4.4
2.2
2.2
Dual-band
Dual-band
Dual-band
Dual-band
triple-band
triple-band
Dual-band
0.30 λ
0.14 λ
0.18 λ
0.14 λ
0.15 λ
0.17 λ
0.072 λ
Up to 45°
Up to 45°
Not Reported
up to 60°
Up to 45°
Not Reported
up to 60°
III. MINIATURIZED DUAL-BAND CHARACTERISTICS ANALYSIS
To explore the operating mechanism of the 2.5-D FSS, the
distribution of surface current at the resonant frequencies 900
and 1790 MHz is illustrated in Fig. 5.
In Fig. 5, the arrow represents the direction of the current flow.
It is observed that the outer 2.5-D square loop decides the lower
resonant frequency and the inner 2.5-D square loop decides the
higher resonant frequency. According to equivalent transmission line theory, the resonant frequency of dual band-stop FSS
constructed by plane double square loop can be expressed as
fi = 1/2π(Li Ci )1/2 (i = 1, 2)
(2)
where f1 is the lower resonance frequency and f2 is the higher
resonance frequency, L1 and C1 represents the inductance and
capacitance of outer metallic strip, respectively, L2 and C2 represents the inductance and capacitance of inner metallic strip,
respectively. In this letter, the thickness h of the substrate is
far less than λ0 . Then, the 2.5-D square loop can be seen as
complete plane square loop and the equivalent circuit of the
2.5-D FSS can be observed in Fig. 6. The resonant frequency of
proposed 2.5-D FSS can be expressed as [12]
fi = 1/2π[(Li + Lai ) × (Ci + Cai )]1/2 (i = 1, 2)
(3)
where La1 , Ca1 , La2 , Ca2 are introduced by the metallic vias.
In detail, La1 , La2 are contributed by vias itself and Ca1 , Ca2
are caused by the capacitive behavior of the gap between two
adjacent vias. Therefore, changing the length of metallic vias
can alter the equivalent inductance and capacitance, which can
be used to adjust the operating bands of the 2.5-D FSS.
In order to verify the analysis above, a plane double squareloop FSS is modeled and simulated. The size of the planer double
square-loop FSS is the same with proposed 2.5-D FSS. The
comparison of transmission coefficients between plane double
square-loop FSS and 2.5-D FSS illuminated by TE wave of
normal incidence is represented in Fig. 7. As shown in Fig. 7,
the two resonant frequencies of the proposed 2.5-D FSS are
lower than that of plane double square-loop FSS, which validates
the analysis above. Hence, the dual-band characteristics can be
adjusted by changing the perimeter of the 2.5-D double square
loop. Besides, the method provides a reference for designing
compact FSS for other frequency bands.
In order to exhibit the advantages of the proposed 2.5-D
FSS, the designed FSS is compared with the FSSs proposed
in previous literatures, and the comparison is shown in Table II.
From Table II, it is obvious that the proposed 2.5-D FSS exhibits
an excellent miniaturization than other FSSs proposed in the
previous literatures. Compared with the compact FSS proposed
in [14], the size of proposed 2.5-D FSS realizes the reduction
of 60%. Besides, when the incident angle is 60°, the maximum
deviation amount of the operating frequency is only 1.5%, which
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the processing error and unsteady test condition. In addition,
the finite period of the fabricated FSS also contributes to the
differences between simulation and measurement results.
V. CONCLUSION
Fig. 8.
Actual version of fabricated FSS and the measurement setup.
In this letter, a novel compact dual-band frequency selective
surface using 2.5-D structure for GSM shielding is proposed.
The 2.5-D FSS can provide attenuation of 41.9 and 49.2 dB at
resonant frequencies 900 and 1790 MHz, with 18-dB bandwidth
of 91 MHz and 156 MHz, respectively. The size of the 2.5-D FSS
cell is only 0.072 λ. Besides, the 2.5-D FSS performs excellent
angle-stability up to 60° with respect to different polarizations.
The operating mechanism of the 2.5-D FSS is analyzed and the
prototype is fabricated and measured. The measurement results
prove the accuracy of the simulation. Hence, the proposed 2.5-D
FSS has great potential in shielding GSM 900/1800 bands for
small electronic devices.
REFERENCES
Fig. 9.
Measured and simulated result of SE values under oblique incidence.
is less than the maximum deviation amount of FSS proposed in
[8] when the incident angle is 60°.
IV. MEASUREMENT SETUP AND RESULTS
A prototype of the proposed 2.5-D FSS is fabricated and
measured. The fabricated 2.5-D FSS is 19.2 × 19.2 cm and
contains an array of 8 × 8 elements. The substrate is 2-mm
thick Pure PTFE with εr = 2.2 and loss tangent δ = 0.001.
The measurement is implemented in anechoic chamber which
can mimic a relatively quiet environment. In the measurement,
two horn antennas connected to the Agilent N5230A network
analyzer are placed in the opposite direction of the 2.5-D FSS.
The actual version of the fabricated 2.5-D FSS and the setup is
illustrated in Fig. 8. The measurement results of the SE value
under different incident angles for TE wave are shown in Fig. 9.
It is observed in the Fig. 9 that the measurement results of the
fabricated 2.5-D FSS are in good agreement with the simulation
results. The fabricated 2.5-D FSS can provide the maximum
SE value of 37 and 43 dB at frequencies 880 and 1800 MHz,
which means the fabricated 2.5-D FSS can be used to shield the
GSM signals in practical application. The small deviation and
lack of smoothness in the measurement results may come from
[1] E. J. van Lieshout et al., “Interference by new-generation mobile phones
on critical care medical equipment,” Critical Care, vol. 11, no. 5, 2007,
Art. no. R98.
[2] M. Periyasamy and R. Dhanasekaran, “Electromagnetic interference on
critical medical equipments by RF devices,” in Proc. Int. Conf. Commun.
Signal Process., Apr. 3–5, 2013, pp. 78–82.
[3] M. Kaur, S. Kakar, and D. Mandal, “Electromagnetic interference,” in
Proc. Int. Conf. Electron. Comput. Technol., 2011, vol. 4, no. 1, pp. 1–5.
[4] E. Unal, A. Gokcen, and Y. Kutlu, “Effective electromagnetic shielding,”
IEEE Microw. Mag., vol. 7, no. 4, pp. 48–54, Aug. 2006.
[5] G. Calcagnini et al., “Electromagnetic interference to infusion pumps
from GSM mobile phones,” in Proc. Int. Conf. IEEE Eng. Med. Biol. Soc.,
2008, pp. 4503–4506.
[6] S. Iskra, B. W. Thomas, R. McKenzie, and J. Rowley, “Potential GPRS
900/180-MHz and WCDMA 1900-MHz interference to medical devices,”
IEEE Trans. Biomed. Eng., vol. 54, no. 10, pp. 1858–1866, Oct. 2007.
[7] F. C. Seman and N. K. Khalid, “Investigations on fractal square loop FSS
at oblique incidence for GSM applications,” in Proc. 2014 Elect. Power,
Electron., Commun., Control Informat. Seminar, 2014, pp. 62–66.
[8] R. Sivasamy, L. Murugasamy, M. Kanagasabai, E. F. Sundarsingh, and M.
Gulam Nabi Alsath, “A low-profile paper substrate-based dual-band FSS
for GSM shielding,” IEEE Trans. Electromagn. Compat., vol. 58, no. 2,
pp. 611–614, Apr. 2016.
[9] L. Zhang, G. Yang, Q. Wu, and J. Hua, “A novel active frequency selective surface with wideband tuning range for EMC purpose,” IEEE Trans.
Magn., vol. 48, no. 11, pp. 4534–4537, Nov. 2012.
[10] B. A. Munk, Frequency Selective Surfaces: Theory and Design. New York,
NY, USA: Wiley, 2000
[11] Y. Shi, W. Tang, W. Zhuang, and C. Wang, “Miniaturised frequency selective surface based on 2.5-dimensional closed loop,” Electron. Lett., vol. 50,
no. 23, pp. 1656–1658, Nov. 2014.
[12] T. Hussain, Q. Cao, J. Khan Kayani, and I. Majid, “Miniaturization of frequency selective surfaces using 2.5-dimensional knitted structures: Design
and synthesis,” IEEE Trans. Antenna Propag., vol. 65, no. 5, pp. 2405–
2412, May 2017.
[13] W. Kiermeier and E. Biebl, “New dual-band frequency selective surfaces
for GSM frequency shielding,” in Proc. 37th Eur. Microw. Conf., Oct.
2007, pp. 222–225.
[14] M. M. Masud, B. Ijaz, I. Ullah, and B. Braaten, “A compact dual-band
emi metasurface shield with an actively tunable polarized lower band,”
IEEE Trans. Electromagn. Compat., vol. 54, no. 5, pp. 1182–1185, Oct.
2012.
[15] M. Kartal, J. J. Golezani, and B. Doken, “A triple band frequency selective
surface design for GSM systems by utilizing a novel synthetic resonator,”
IEEE Trans. Antennas Propag., vol. 65, no. 5, pp. 2724–2727, May 2017.
[16] L. B. Wan et al., “Tri-band frequency selective band-stop shield using
screen printing technique,” in Proc. 2012 Asia-Pac. Symp. Electromagn.
Compat., Jul. 2012, pp. 21–24.
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