SPACES-2018, Dept. of ECE, K L Deemed to be UNIVERSITY
Gain Enhancement of Patch Antenna Using L-slotted
Mushroom EBG
R Venkata Sravya, Runa Kumari
Department of Electrical and Electronics Engineering
Birla Institute of Technology and Science, Pilani
Hyderabad Campus, Hyderabad, India
rajamanurisep13@gmail.com,runakumari15@gmail.com
In [4], a cylindrical mushroom EBG is placed around a
circular patch antenna to enhance gain by 2.9 dB. The EBG
has two periodic structures: metallic rings and vias. A gain
enhancement of 4.57dB is achieved by using mushroom
EBG with a proximity fed V-band patch antenna, which is
having liquid crystal polymer as its substrate [5]. In [6], an
N-shaped coplanar EBG structure without vias is designed.
In this structure, all the EBG are interconnected. The
comparison between patch antenna with EBG and without
EBG resulted a gain of 1.9 dB, a bandwidth of 100 MHz
and -3dB enhancement in return loss. A novel uniplanar
compact EBG is designed in [7] by creating slots in it.
Using this design, a gain enhancement of 3dB is achieved.
Four layered rectangular slotted mushroom EBG is
designed in [8], where a gain enhancement of 2.5 dB is
achieved. The EBGs are arranged in chessboard format to
reduce deformations caused by first layer of EBG and also
to reduce RCS. In [9] a novel two via rectangular slot-EBG
(TVS-EBG) is designed to achieve bandwidth enhancement
by increasing effective capacitance.
In this paper a new mushroom EBG with L- slot (LSEBG) is designed. A gain enhancement of 1.2 dB is
achieved. The new EBG structure is based on mushroom
EBG. On the EBG patch, an L shaped slot is created.
The paper is organized as follows. Section II provides the
analysis and design of the rectangular patch antenna without
any EBG structure. In Section III, standard mushroom EBG
is designed and the performance of the patch antenna along
with EBG is studied. The new L-slot EBG structure design
is explained in Section IV. A comparison of the results with
mushroom EBG has been done. A conclusion is presented in
Section V. All simulations are done in Ansoft HFSS.
Abstract—Gain enhancement of patch antenna is
investigated in this paper. A rectangular patch antenna fed by
coaxial probe is designed for a resonant frequency of 5.8 GHz.
The resulted gain and bandwidth are 5.3 dB and 160 MHz
respectively. Using standard mushroom Electromagnetic
Bandgap (EBG) placed at a distance 3 mm from edge of the
patch, a bandwidth of 143 MHz and a gain of 5.5 dB is
achieved. A novel L-slot mushroom EBG (LS-EBG) is
proposed. The L-slot one layer and two layers of EBG
structures are used to further enhance the gain by 0.6 dB and
1.2 dB respectively.
Index Terms—Microstrip patch antenna, Mushroom EBG,
surface waves, gain enhancement.
I.
INTRODUCTION
Microstrip patch antennas are most commonly used for
wireless communication [1]. Few of its advantages are
compactness, less weight, low cost, ease of fabrication etc.
The major limitations of microstrip antennas are low gain (3
to 5dB) and narrow bandwidth (30MHz). In practical
applications, a finite ground plane kept at a distance less
than λ/4 from the radiating patch is used [2]. This causes
surface waves to be generated in the substrate, thereby
decreases gain and bandwidth. To suppress the surface
waves, high impedance surfaces such as EBG are used.
EBGs are periodic structures which suppress/assist the
propagation of electromagnetic waves (EM) in a specific
band of frequency for incident angles and all polarization
states [3]. EBG can be categorized based on their
geometrical configurations as: three-dimensional, twodimensional and one-dimensional. One such two
dimensional EBG structure which suppress the EM waves is
mushroom EBG. Mushroom EBGs are mostly used because
of ease of analysis and fabrication.
Mushroom EBG which is placed around the radiating
patch at some distance, consists of a patch and vias. The
vias is connected between the EBG patch and the ground
plane. The mushroom EBG can be realized using lumped
elements as LC-parallel resonance circuit where the current
passing through the vias from EBG patch to ground plane
generates inductance. The capacitance is generated because
of the dielectric between two EBG patches (metal).
II.
ANTENNA DESIGN
A microstrip patch antenna is designed at 5.6 GHz. The
FR4 sheet (ϵr = 4.4, δ=0.002) with 1.6 mm height is used as
a substrate in the proposed design The schematic of the
proposed antenna structure is shown in Fig 1.
The patch antenna dimensions are calculated using
equations given in [1] and are found to be: length (lpatch) =
11.57 mm and width (wpatch) = 15.739 mm.
37
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SPACES-2018, Dept. of ECE, K L Deemed to be UNIVERSITY
f0
(2)
(3)
Ph
L
1
2SLC
BW
K
L
C
(4)
where f0 is the resonant frequency, BW is the bandwidth, C
is the capacitance and L is the inductor in mushroom EBG
structure.
The dimensions of mushroom EBG to resonate at 5.6 GHz
are: width and length of EBG patch (w1 = L1) is 7 mm,
periodicity (w1+g) = 8 mm. The vias diameter considered as
1 mm. The distance (G) between EBG layer and patch edge
is 3 mm. The bandwidth and the gain obtained are 143 MHz
and 5.517 dB respectively, shown in Fig. 4 and Fig. 5. The
resulted gain in comparison to the patch antenna without
EBG has been enhanced by 0.2 dB.
Fig. 1.(a) Top view of rectangular patch (b) side view of Microstrip patch
antenna with coaxial feeding
Fig.3. (a) Top view of mushroom EBG (b) Schematic for Microstrip patch
antenna with mushroom EBG
Fig.2. Gain of microstrip patch antenna without EBG
A coaxial probe feed at distance 4 mm along y-axis (y)
and 2 mm along x-axis (x) from the center of the patch is
used. The size of the substrate is 50 × 50 mm2. The
bandwidth and gain obtained at 5.6 GHz is 160 MHz and
5.3 dB respectively.
Fig. 2 shows the gain of the microstrip patch antenna
without EBG. The gain of the patch antenna has been
further enhanced by 0.2 dB and 0. 6 dB by using mushroom
and L-slot mushroom EBG respectively. The design and
analysis are explained in the following sections.
III. ANALYSIS OF PATCH ANTENNA WITH MUSHROOM
EBG
A mushroom EBG shown in Fig 3 is designed using the
Equations (1)-(4) given below [3]. The substrate height (h)
is considered to be 1.6 mm and the gap between the EBG
patches (g) is considered to be 1mm.
§W g ·
WH 0 (1 H r )
(1)
¸
cosh 1 ¨
C
S
¨
©
g
Fig. 4. S11 plot for microstrip patch antenna with standard mushroom EBG
¸
¹
38
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Fig. 5. Gain of microstrip patch antenna with standard mushroom EBG
IV.
Fig.7 .Microstrip patch antenna with proposed L-slot mushroom EBG
DESIGN OF THE PROPOSED SLOTTED MUSHROOM
EBG
In the previous sections design of patch and the patch
antenna with mushroom EBG is analyzed. A new EBG
substrate using L-slot mushroom EBG is presented in this
section. The schematic of the proposed EBG substrate is
given in Fig.6 and Fig. 7.
The EBG is placed at a distance 3 mm (G, same as
mushroom EBG) from patch edge. The EBG dimensions
are: width of EBG patch (w1) = 7 mm, periodicity (w1+g) =8
mm, vias diameter (r) =1 mm, slot length (L2) =5 mm, slot
width (w2) = 1 mm. The distance between L-slot and EBG
patch center (d) is 2 mm.
Fig. 8. S11 plot for microstrip patch antenna with L-slot mushroom EBG
Fig. 9. Gain of microstrip patch antenna with L-slot mushroom EBG
Fig. 6. Schematic for L-slot mushroom EBG (a) Square L-slot mushroom
EBG with 7 mm EBG patch width (w1), 1 mm slot width (w2) and 5 mm
slot length (L2) (b) Top view of microstrip patch antenna with L-slot
mushroom EBG
Fig.8 and Fig. 9 shows the S-parameter and Gain plots of
patch antenna with L-slotted mushroom EBG.
39
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SPACES-2018, Dept. of ECE, K L Deemed to be UNIVERSITY
The gain of microstrip patch antenna with 2 layers
of L-slot mushroom EBG is given in Fig 11. A comparison
of the results has been done by tabulating the data, given in
Table I. Using a slot EBG, the gain of the simple patch
antenna can be enhanced by 1.2 dB.
V.
CONCLUSION
In this paper, a new mushroom EBG with L-slot is
designed and analyzed. The obtained gain of microstrip
patch with L-slot mushroom EBG is 5.9 dB with one layer
and 6.45 dB with two layers. The gain enhancement of 0.6
dB with one layer and 1.2 dB with two layers is achieved.
The resulted gain of one and two layers of L-slot mushroom
EBG in comparison to one and two layers of mushroom
EBG is enhanced by 0.4 dB and 0.5 dB respectively.
Fig.10. Schematic for patch antenna with two layers of L-slot EBG
structure
The bandwidth and gain obtained for patch antenna
by using one layer of L-slot mushroom EBG is 143 MHz
and 5.9 dB. The bandwidth obtained for patch with
mushroom EBG and patch antenna with L-slot mushroom
EBG is same. The patch with L-slot mushroom EBG results
in a gain enhancement of 0.6 dB. A schematic for two layers
of L-slot EBG with periodicity 8 mm is shown in Fig. 10.
Further analysis has been done by using two EBG
layers around the patch. When two layers of mushroom
EBG is used the bandwidth and gain obtained are 143 MHz
and 6 dB and with two layers of L-slot mushroom 146 MHz
bandwidth and 6.45 dB gain is obtained.
REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
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D.F. Sievenpiper, “High Impedance Electromagnetic Surfaces,” Ph.D.
dissertation, Univ. California, Los-Angeles, CA.1999.
F. Yang and Y. Rahmat-Samii, Electromagnetic Band Gap Structures
in Antenna Engineering. Cambridge University Press, 2009.
H. Boutayeb and T. A. Denidni, “Gain Enhancement of a Microstrip
Patch Antenna Using a Cylindrical Electromagnetic Crystal
Substrate,” IEEE Trans. Antennas Propag., vol. 55, no. 11, pp. 3140–
3145, Nov. 2007.
Y. Wang, J.-C. S. Chieh, and A.-V. Pham, “A wideband and high
Gain V-band EBG Patch Antenna on liquid crystal polymer,”
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on, 2011, pp. 1820–1823.
A. Ameelia Roseline, K. Malathi, and A. K. Shrivastav, “Enhanced
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Z.-J. Han, W. Song, and X.-Q. Sheng, “Gain Enhancement and RCS
Reduction for Patch Antenna by Using Polarization-Dependent EBG
Surface,” IEEE Antennas Wireless Propag. Lett., vol. 16, pp. 1631–
1634, 2017.
M.S.S. Dalenjan, P.Rezari,M.Akbari,S.H.Gupta, and A.R.Sebak,
“Radiation properties enhancement of a microstrip antenna using a
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P. P. Bhavarthe, S. S. Rathod, and K. T. V. Reddy, “A Compact Two
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Fig. 11. Gain of microstrip patch antenna with 2 layers of L-slot mushroom
EBG
S.No
1
2
3
4
5
Table 1: Summary of Results for slotted EBG
Structure
Bandwidth
Patch antenna without EBG
160MHz
Patch antenna with mushroom EBG
143MHz
Patch antenna with L-slot mushroom EBG
143MHz
Patch antenna with 2 layers mushroom
143MHz
EBG
Patch antenna with 2 layers L-slot
146MHz
mushroom EBG
Gain
5.3dB
5.5dB
5.9dB
6dB
6.5dB
40
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