Dual Band Electromagnetic Band Gap (EBG) Structure
Osman Ayop1, Mohamad Kamal A.Rahim1 and Thelaha Masri1
1
Wireless Communication Centre,
Faculty of Electrical Engineering,
Universiti teknologi Malaysia,
81310 Skudai Johore Baharu.
[email protected], [email protected], [email protected].
Abstract - In this paper, a 3 by 3 dual band
Electromagnetic Band Gap (EBG) structure has been
designed to cover the two frequency of unlicensed
Band at 2.4 GHz and 5.2 GHz. The characteristic of
the EBG structure is investigated by measuring the
forward transmission coefficient, S21. The discussion
of the design and the evaluation of the structure itself
have been made. The simulation process was carried
out using microwave office software. This structure
has been designed using 1.6 mm Fire Retardant-4
(FR4) board which has relative permittivity of 4.9 and
loss tangent of 0.019. The simulated result for S21
shows the band gap frequencies measured are found to
be between 2.037 GHz and 2.609 GHz with cover 2.4
GHz ISM band GHz and between 4.738 GHz and
5.492 GHz which cover 5.2 GHz UNI band.
Keywords: Dual band antenna, Electromagnetic band Gap
(EBG); ISM Band; Surface wave; radiation pattern;
1. Introduction
In recent years, there has been growing interest in
utilizing electromagnetic band-gap (EBG) structures in
the electromagnetic and antenna community. The EBG
terminology has been suggested based on the photonic
band-gap (PBG) phenomena in optics that are realized
by periodical structures [1]. This structure is compact
which has good potential to build low profile and high
efficiency antenna surface [2]. The main advantage of
EBG structure is their ability to suppress the surface
wave current [3]. The generation of surface waves
decreases the antenna efficiency and degrades the
radiation pattern [3, 4].
Surface wave are excited on microstrip antenna
when the substrate єr > 1. Besides end fire radiation,
surface wave give rise to coupling between various
elements of an array. Surface wave are launched into
the substrate at an elevation angle θ lying between π/2
and sin-1 (1/√єr). These waves are incident on the
ground plane at this angle shown, get the reflected
from there, then meet the dielectric-air interface, which
also reflect them. Following this zig-zag path, they
finally reach the boundaries of the microstrip structure
where they are reflected back and diffracted by the
edges giving rise to end-fire radiation [5].
Figure 1: Propagation of surface waves in substrate of
patch antenna [5]
The operation mechanism of EBG structure can
be explained as a distributed LC network with specific
resonant frequencies [6]. The electromagnetic
properties of the EBG unit cells can be described using
lump-circuit elements—capacitors and inductors, as
shown in Figure 2. The EBG structure for the figure
2.26 is also known as mushroom like EBG structure
[6]. This structure has frequency range where the
surface impedance is very high. The equivalent LC
circuit acts as a two-dimensional electric filter in this
range of frequency to block the flow of the surface
waves [7].
Figure 2: 2D Dipole antenna [6].
The centre frequency of the band gap
is f c = 1 (2π LC ) . The inductor L results from the
current flowing through the vias, and the capacitor C
due to the gap effect between the adjacent patches.
Thus, the approach to increase the inductance or
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capacitance will naturally result in the decrease of
band-gap position [7].
2. The Design and Construction
The 3 by 3 dual band Electromagnetic Band Gap
structure is simulated based on 1.6 mm Fire Retardant4 (FR4) board which has a relative permittivity 5.4.
The shape of the single element of the EBG structure
is shown in figure 3 below.
Figure 5: 3D view of dual band Electromagnetic band
Gap (EBG) structure
Figure 3: Single element dual band Electromagnetic
band Gap (EBG) structure
Based on figure 3, the design is initially from
mushroom like EBG structure [6]. The two slots are
introduced to make another one square patch structure
in the larger square patch shape. As a result, this
structure has successfully achieve dual band gap
frequency instead of having only one band gap
frequency for conventional square patch EBG
structure. The size of the larger square patch is 9 mm
x 9 mm while the size of the smaller square patch is 5
mm x 5 mm. The two 1 mm width slot line is
introduced to realize the dual band EBG structure.
Figure 4 shows the structure of 3 by 3 dual band
Electromagnetic Band Gap by using the transmission
line technique to measure the S21 value. Each element
is separated by 2 mm each other. The transmission line
is placed 0.5 mm on the EBG structure. Two
connectors are used to test the value of forward
transmission coefficient, S21. The size of 3 by 3 EBG
structures is 50 mm by 50 mm.
Figure 4: 2D view of dual band Electromagnetic band
Gap (EBG) structure
3. Result and Discussion
The above structure has been simulated using the
microwave office software. From the simulated S21
result, the structure is successfully achieve two band
gap frequencies at the desire frequency. Figure 6
shows the simulated S21 result.
Figure 6: Simulated S21 for dual band Electromagnetic
band Gap (EBG) structure
From the simulated result, two band gap
frequencies have been found based on -20 dB S21
value. One of the bands covers 2.4 GHz ISM band
which has band gap frequency between 2.037 GHz and
2.609 GHz. Another one band gap frequency covers
5.2 GHz ISM band between 4.738 GHz and 5.492
GHz. As long as the bandwidth of the operational
frequency fall into this band gap frequency range, the
surface wave can be suppressed if the antenna is
integrated with the dual band Electromagnetic Band
Gap structure. The performance of the dual band
antenna in term of radiation pattern is improved by
increasing the front radiation and reducing the back
and side radiation.
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References
Table 1: Properties of dual band Electromagnetic Band
Gap (EBG) structure.
Frequency Band Gap
(GHz)
2.037 – 2.609
4.738 – 5.492
Bandwidth
(MHz)
572
754
Bandwidth
(%)
24.81
14.78
[1] Fan Yang, “Applications of Electromagnetic
Band-Gap (EBG) Structures in Microwave
Antenna Designs”, Invited presentation at
Tampere University of Technology, Finland,
August 12, 2002.
[2] Li Yang, Zheng Feng, “Advanced Method to
Improve
Compactness in EBG
Design
Utilization”, IEEE Antennas and Propagation
Symp, Vol. 4, June 2004, pp. 3585-3588
[3] Fan Yang and Yahya Rahmat-Samii, “Mutual
Coupling Reduction of Microstrip Antennas Using
Electromagnetic Band-Gap Structure”,2001 IEEE
AP-S Digest, vol. 2, pp. 478-481, July 2001.
Figure 7: Simulated S11 for dual band Electromagnetic
band Gap (EBG) structure
Figure 7 shows the simulated S11 value for dual
band Electromagnetic band Gap (EBG) structure.
From the figure, the S11 value is approaches near 0 dB
in the range of the band gap frequency indicates that
the signal which operates in the range of band gap
frequency cannot propagate on the EBG structure.
[4] Fan Yang, Chul-Sik Kee, and Yahya Rahmatsamii, “Step-Like Structure and EBG Structure to
Improve the Performance of Patch Antennas on
High Dielectric Substrate”, 2001 IEEE AP-S
Digest. vol 2, pp. 482-485, July 2001.
[5] Y. Oian, R. Coccioli, D. Sievenpiper, V. Radisie,
“A microstrip patch antenna using novel photonic
band-gap structures,” Microwave Journal, vol. 42,
no. 1, pp. 66-76, Jan 1999.
[6] Fan Yang and Yahya Rahmat-Samii, “A
Mushroom-Like
Electromagnetic
Band-Gap
(EBG) Structure: Band Gap Characterization and
Antenna Applications”, 2002 URSI digest, pp.
225, June 2002.
Conclusion
From this paper, the characteristic of the dual band
Electromagnetic Band Gap (EBG) structure has been
presented. The structure can be used to increase the
performance of the dual band microstrip antenna
which operates at dual ISM band at 2.4 GHz and 5.2
GHz.
[7] F. Yang, and Y. Rahmat-Samii, “Microstrip
Antennas integrated with electromagnetic bandgap structure: a low mutual coupling design for
array application,” IEEE Trans. Antennas and
Propagation, vol. 51, pp. 2936-2946, Oct. 2003.
Acknowledgements
The authors thanks to the Ministry of Higher
Education (MOSTI) for supporting the research work,
Research Management Centre (RMC) and Wireless
Communication Centre, Universiti Teknologi Malaysia
(WCC, UTM) for the support of paper.
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