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

11

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.

INTERNATIONAL JOURNAL OF ELECTRONICS AND

COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)

ISSN 0976 – 6464(Print)

ISSN 0976 – 6472(Online)

Volume 4, Issue 3, May – June, 2013, pp. 11-23

© IAEME: www.iaeme.com/ijecet.asp

Journal Impact Factor (2013): 5.8896 (Calculated by GISI) www.jifactor.com

IJECET

© I A E M E



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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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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.



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.




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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.



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.




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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



20

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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A slotted e shaped stacked layers patch antenna for