A slotted e shaped stacked layers patch antenna for
Transcript of A slotted e shaped stacked layers patch antenna for
International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 3, May – June (2013), © IAEME
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A SLOTTED E-SHAPED STACKED LAYERS PATCH ANTENNA FOR
5.15-5.85 GHZ FREQUENCY BAND APPLICATIONS
Uma Shankar Modani1, Gajanand Jagrawal
2
1(Govt. Engg. College, Ajmer, Rajasthan, India)
2(Govt. Engg. College, Ajmer, Rajasthan, India)
ABSTRACT
The design of a slotted E-shaped microstrip patch antenna for wideband operation has
been presented in this paper. It has been demonstrated that by adding slots to E-shaped
rectangular patch and applying stacked layers technique for broad banding, wideband
operation can be satisfactorily achieved which is suitable for WiMax, WLAN, high- speed
networks and other wireless communication systems operating in 5.15-5.85GHz frequency
band. The ANSOFT HFSS software has been used for designing the antenna. The patch
element is being placed on Roger RO4350 substrate of 1.6mm height with relative
permittivity of 3.66 and dielectric loss tangent of 0.004. The antenna is coaxial probe feeded.
High performance characteristics and good return loss values for 5.15-5.85 GHz frequency
band have been obtained for the proposed antenna. The development of the design and
parametric study has also been presented in this paper.
Keywords: Slotted patch, E-shaped, WiMax, WLAN, Stacked layers.
1. INTRODUCTION
Microstrip patch antennas are widely used in wireless communications due to their
inherent advantages of low profile, less weight, low cost, and ease of integration with
microstrip circuits [1]. However, the main disadvantage of microstrip antennas is the small
bandwidth. Many methods have been proposed to improve the bandwidth. These include the
use of a thick substrate and cutting slots in the design [2-6]. Improvement of broader
bandwidth becomes an important need for many applications such as for high speed
networks.
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Recently, high-speed wireless computer networks have attracted the attention of
researchers, especially in the 5-6 GHz band (e. g. WiMax and IEEE 802.11a Indoor and
Outdoor WLAN). Such networks have the ability to provide high- speed connectivity (>50
Mb/s) between notebook computers, PCs, personal organizers and other wireless digital
appliances. Although current 5 GHz wireless computer network systems operate in the 5.15-
5.35 GHz band, future systems may make use of the 5.72-5.85 GHz band in addition to the
5.15-5.35 GHz band, for even faster data rates.
Many novel antenna designs have been proposed to suit the standard for high-speed
wireless computer networks. Some approaches resulted in the probe-fed U-slot patch
antennas [7-11], the E- shaped patch antennas [12-19].
In this paper, a slotted E-shaped patch antenna with an air gap of 1mm inserted
between ground plane and the substrate to improve the bandwidth, which was introduced in
[13], has been presented with the parametric study. The various parameters of the design have
been varied and their effects on return loss have been studied. The technique of stacked layer
structure using an air box sandwiched between substrate and ground has been reported in [20-
23]. Ansoft HFSS which is the industry standard simulation tool for 3D full-wave
electromagnetic field simulation based on Finite Element Method (FEM) has been used for
simulation purposes [24], [25].
2. ANTENNA DESIGN
The side view of the proposed antenna structure has been shown in Fig. 1. The broad
banding technique of stacked layers is used to improve the bandwidth. An air box of height
1mm is inserted between substrate and the ground. The Roger RO4350 of 1.6mm thickness
having relative permittivity of 3.66 and dielectric loss tangent of 0.004 has been used as
substrate. The substrate and ground size has been considered as 33.2mm x 27.2mm. The
antenna is probe feeded. The feeding method is easy to fabricate but difficult to model
accurately and have low spurious radiation and narrow bandwidth of impedance matching
[26]. The location of the feed element with respect to the patch also plays a role in the
antenna performance. The patch geometry has been shown in Fig. 2. The optimized
dimensions of the patch to cover the required bandwidth are listed in TABLE I. The two
rectangular slots, one in each upper and lower edge of the main E-shaped patch have been
introduced and two rectangular slot strips symmetrical and parallel to the y-axis have been
cut from the main patch. The two square slots are embedded at the two corners of the left
edge of the patch. All these slots have been included in the design to achieve the desired
antenna performance. The feed point is located at (-1mm, -7mm).
Fig. 1 Proposed antenna structure
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Fig. 2 Slotted E-shaped patch geometry
TABLE I DIMENSIONS OF THE OPTIMIZED PATCH
Parameters
Dimensions
(mm)
L1 23.6
W1 17.6
W2 16.2
W3 1.4
L2 3
L3 7.6
L4 5
W4 5
L5 3
L6 1.5
L7 1
W5 6
W6 1
3. DEVELOPMENT OF THE ANTENNA DESIGN
The proposed antenna design is a modified standard rectangular patch. The various
steps in the designing of the antenna shape have been shown in Fig. 3. In step 1, a rectangular
patch has been designed to resonate at 5.2 GHz by using standard equations given in [1]. The
feed point is located at (-1mm, -7mm). In step 2, two rectangular shaped patches of L2*W2
have been removed from the right edge of the main patch. These rectangular patches have
been cut at a distance of L2 from both the top and bottom edges of the main patch. This step
has resulted in E-shaped design. In step 3, two vertical strips each of L5*W6 dimensions
have been removed from the top and bottom edges of the patch at a distance of 2.8mm from
the left edge of the patch. In next step, two horizontal strips each of L7*W5 dimensions have
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been removed from the patch at a distance of 2.3mm from the left edge of the patch. In final
step, two rectangular patches of L6*W3 dimensions have been removed from two left edge
corners of the patch. The final design has resulted in required lower and higher cut off
frequencies as well as the bandwidth. The return loss plots of all the steps have been shown in
Fig.4.
Fig.3 Development of the design
Fig.4 Return loss plots for various steps in development of the design
TABLE III RESULTS OF RETURN LOSS PLOTS FOR DEVELOPMENT OF THE DESIGN
Design Step fr[GHz] fL[GHz] fH[GHz] Bandwidth[MHz]
Step 1 5.2318 5.020 5.461 441
Step 2 5.3273 5.145 5.542 397
5.8591 5.778 5.925 147
Step 3 5.2727 5.063 5.484 421
5.8318 5.785 5.880 095
Step 4 5.2591 5.058 5.467 409
5.7909 5.729 5.8540 125
Step 5 5.3682 5.143 5.8580 715
5.7636
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4. PARAMETRIC STUDY
The slots W3, W4, L4, W5, L5, W6, L6, L7, and feed point location are set as
variables and their effects on the impedance bandwidth have been studied. The study has
been carried out for the final design as obtained after the step 5 in the development of the
design. The patch design parameters are varied about the optimized values shown in Table I.
Fig.5 shows the effect of changes in W3 while keeping all the other parameters same
as shown in Table I. All the results in these figures show that this antenna has two resonant
frequencies: f1 and f2. As shown in Fig.5, with the increase in W3, f1and f2 increase and with
decrease in W3, f1 and f2 both decrease and also the bandwidth.
Fig.5 Return loss plots for variations in W3
Fig.6 shows the effect of changes in L4 while keeping all the other parameters same
as shown in Table I. As shown in Fig.6, when L4 is increased then both resonant frequency f1
and f2 are decreased. When L4 is decreased then f1 is decreased but f2 is increased. The
bandwidth is also reduced as L4 is decreased.
Fig.6 Return loss plots for variations in L4
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Fig.7 shows the effect of changes in W4 while keeping all the other parameters same
as shown in Table I. When W4 is increased then only one resonant frequency is remaining
and bandwidth is also reduced. As shown in Fig.7, when W4 is decreased, then f1 is
decreased, f2 increased and bandwidth is also reduced.
Fig.7 Return loss plots for variations in W4
Fig.8 shows the effect of changes in L5 while keeping all the other parameters same
as shown in Table I. When L5 is increased then both resonant frequencies f1 and f2 are
decreased and bandwidth is also reduced. When L5 is decreased then also both resonant
frequencies f1 and f2 are decreased. When L5 is decreased then it does not cover the entire
frequency band from 5.15GHz to 5.85 GHz.
Fig.8 Return loss plots for variations in L5
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Fig.9 shows the effect of changes in W5 while keeping all the other parameters same
as shown in Table I. when W5 is increased then both resonant frequency f1 and f2 are
decreased and is not cover the frequency band from 5.15 GHz to 5.85GHz. When W5 is
decreased then f1 is decreased and f2 is increased but bandwidth is reduced.
Fig.9 Return loss plots for variations in W5
Fig.10 shows the effect of changes in L6 while keeping all the other parameters same
as shown in Table I. In both cases, when L6 increased and decreased then bandwidth is
reduced. Fig.11 shows the effect of changes in W6 while keeping all the other parameters
same as shown in Table I. When W6 is increased then the antenna does not cover the
frequency band from 5.15GHz to 5.85GHz. When W6 is decreased then bandwidth is
reduced. Fig.12 shows the effect of changes in L7 while keeping all the other parameters
same as shown in Table I. When L7 is increased then both resonant frequencies f1 and f2 are
decreased. When L7 is decreased then bandwidth is reduced. Fig.13 shows the return loss
plots for different feed locations. As shown in Fig.13 we get optimized result in step5.
Fig.10 Return loss plots for variations in L6
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Fig.11 Return loss plots for variations in W6
Fig.12 Return loss plots for variations in L7
Fig.13 Return loss plots for variation in feed locations
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5. RESULTS AND DISCUSSION
Fig. 14 shows the return loss plot of the proposed antenna with optimized parameters
as shown in Table I. The lower -10dB frequency at 5.15GHz and upper -10dB frequency at
5.85GHz have been obtained which covers the entire range of WiMax and WLAN
applications. In fact, there are two bands resonating at 5.35GHz and 5.75GHz which are
stagger coupled to result in such response. Fig. 15 presents the E-plane and H-plane radiation
patterns which are almost omnidirectional in shape. The maximum gain of 4.7dB has been
obtained in both the planes. The smith chart has been shown in Fig. 16. Fig. 17 shows the 3D
polar plot obtained at 5.5GHz. Fig. 18 shows the variations in the gain with respect to
frequency. It has revealed that the gain performance of the proposed antenna is satisfactory
within the desired frequency range. The other parameters such as peak directivity, peak gain
and radiation efficiency are shown in TABLE III.
3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 8.00Freq [GHz]
-25.00
-20.00
-15.00
-10.00
-5.00
0.00
Re
turn
Lo
ss (
dB
)
XY Plot 31
-10.0096 -10.0974
MX2: 5.1507
MX1: 5.8547
Fig. 14 Return loss plot of the optimized antenna design
-5.20
-2.40
0.40
3.20
90
60
30
0
-30
-60
-90
-120
-150
-180
150
120
m1m2
Name Theta Ang Mag
m1 -90.0000 0.0000 4.7212
m2 -92.0000 -2.0000 4.7310
Curve Info
dB(GainTotal)
Phi='0deg'
dB(GainTotal)
Phi='90deg'
Fig. 15 E-plane and H-plane radiation patterns
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5.002.001.000.500.20
5.00
-5.00
2.00
-2.00
1.00
-1.00
0.50
-0.50
0.20
-0.20
0.00-0.000
10
20
30
40
50
60
708090100
110
120
130
140
150
160
170
180
-170
-160
-150
-140
-130
-120
-110-100 -90 -80
-70
-60
-50
-40
-30
-20
-10
Fig. 16 Smith chart
Fig. 17 3D polar plot at 5.5GHz
3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 8.00Freq [GHz]
-4.00
-3.00
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
dB
(Ga
inT
ota
l)
XY Plot 34
Fig. 18 Gain v/s frequency curve
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TABLE IIII OTHER SIMULATED RESULTS
Parameters Simulated
Results
Peak Directivity 1.6208
Peak Gain 1.5965
Radiation Efficiency 0.985
6. CONCLUSION AND FUTURE WORK
A novel compact slotted E-shaped microstrip patch antenna has been designed for
WiMax, WLAN and other high-speed wireless communication systems operating within
5.15GHz to 5.85GHz frequency band. The simulated results have demonstrated satisfactory
radiation performance of the antenna across the entire operating frequency range. These
features are very useful for worldwide portability of wireless communication equipment. The
proposed antenna design will be helpful for antenna design engineers to design and optimize
the antennas for other wireless applications. The future works include fabrication of the
antenna, measurements of antenna performance parameters with the industry standard
equipments and comparison of simulated and measured results.
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