Rectangular Patch Antenna Array with Defect Ground ... 3/Issue 5/IJEIT1412201311_61.pdf · a single...

ISSN: 2277-3754

ISO 9001:2008 Certified International Journal of Engineering and Innovative Technology (IJEIT)

Volume 3, Issue 5, November 2013

365

Abstract—In this work, replacement antenna arrays, based on

a single rectangular patch antenna designed at 2.4 GHz, are

presented. The dual antenna arrays have Coupled Microstrip

Antenna configuration. Circular defects on the ground were

implemented to increase the gain. Two defects configuration were

proposed to choose the most appropriate one. The antennas were

designed and simulated using FEKO software to verify the

performance of the proposed geometries.

Index Terms— Component, Coupled Microstrip Antenna,

Current distribution, Gain, Microstrips, S11 parameter.

I. INTRODUCTION

Wi-Fi (Wireless Fidelity) is a connection mechanism of

electronic devices, such as personal computers, videogames

panels, smartphones or digital sound reproducers. They can

be connected to internet by means of an access point of a

wireless network, which generally operates at 2.4 GHz or 5

GHz. 2. 4 GHz is considered as one of the most used ranges

for wireless LAN (Local Area Network) [1].

In Mexico, the “Comisión Federal de Telecomunicaciones”

has the liability since 1996 of planning, management, and

control of the radio electric spectrum [2]. This dependence

also realizes the updating of the National Chart of

Frequencies. The frequency range 2360–2450 MHz,

corresponds to fixed and mobile services, radio localization

and amateurs. 4990–5000 MHz range corresponds to fixed

and mobile services, except aeronautical mobile, radio

astronomy and spatial research (passive) [3].

Detail information about the Wi-Fi requirements can be

found in [4], while in [5], the necessity to develop antennas to

replace the original ones of some specific equipment is

commented.

Widely information about patch antenna configurations of

COMA (Coupled Microstrip Antenna) resonators can be

found in [6]. Usually, only the central resonator is connected

to a fed line. The coupling between the driver and the parasitic

patches is basically, by proximity of the close edges, or using

short microstrip sections. The feeding is analyzed in [7],

showing it as one of the most complex aspects of the antenna

design, because it occupies a considerable space, irradiates

spurious signals and consumes power from Ohmic losses.

Using COMA, it is possible to transfer part of the power

division tasks from the network feeding to the radiating

elements.

On the other hand, different defected ground structure DGS

geometries are presented in [8, 9]. Some general applications

of defected ground structure (DGS) are also described in [8].

Specific applications can be found in [10-13].

DGS or slotted ground planes are used in [10] to achieve

dual-band operation with appreciable impedance bandwidth,

producing a novel multistrip monopole antenna fed. In [11],

DGS is used to improve the electrical performance of an

antenna as well as reducing its dimension. DGS is also used to

reduce the cross-polarized (XP) radiation of a microstrip

patch antenna [12]. DGSs tend to lessen the surface waves and

consequently increase the antenna efficiency. They are also

used to enhance the properties of the proposed microstrip

antenna structure [13].

DGSs are made to counter the generation of surface waves

and also reduce the size of a microstrip antenna with parasitic

elements. DGSs have an excellent capability of harmonic

rejection [14, 15], reducing mutual coupling between antenna

array elements, reducing unwanted responses, and tuning

[16].

DGS is motivated by a study of Photonic/Electromagnetic

Band gap structures; with an equivalent L-C resonator circuit

easy to obtain [17].

In this work, the interest is focused on the development of

patch antenna arrays for Wi-Fi, using an advanced material as

substrate, considering the gain as the performance parameter

to review. The antennas design will be described in section II.

The corresponding simulations results are provided in section

III. Finally, in section IV, some concluding remarks are given.

II. ANTENNA ARRAY DESIGN

The design of the rectangular patch antennas used to

assemble the patch antenna array was designed considering

2.4 GHz as the operation frequency. The rectangular antenna

was designed, using the following equations [18, 19]. For the

patch width:

2

12

rof

cW

, (1)

where c is the constant speed of light in vacuum, r the

dielectric constant substrate and f0, the operating frequency.

An advanced material with dielectric constant r=11.2 is used.

The effective dielectric constant:

21

1212

1

2

1

W

hrrreff

if 1

h

W

. (2)

Rectangular Patch Antenna Array with Defect

Ground Structure for Wi-Fi M. Tecpoyotl-Torres, J. G. Vera Dimas, R. Castañeda-Sotelo and R. Cabello-Ruiz

Centro de Investigación en Ingeniería y Ciencias Aplicadas, CIICAp

Universidad Autónoma del Estado de Morelos, UAEM Cuernavaca, Morelos, México

ISSN: 2277-3754



366

The effective length is calculated using:

reffof

c

effL

2

. (3)

The two increments in the length, which are generated by

the fringing fields, make electrical length slightly larger than

the physical length of the patch:

8.0258.0

264.03.0

412.0

h

W

reff

h

W

reff

hL

. (4)

The patch length is given by:

L

effLL 2

. (5)

The length and width of ground plane (and the substrate),

gL and gW are:

LhgL 6 and WhgW 6 . (6)

The calculated sizes of the individual rectangular patch

antenna (Figure 1) are shown in Table 1. The height of the

substrate is h=0.64 mm. Cuts on the corners of the rectangular

antenna are implemented in order to increase its gain, with a

depth of g/16, where g is the wavelength group.

Table I. Size of Individual Antennas

Sizes

PARAMETERS Length (mm)

Lp 20.1416

Wp 27.2034

Ls 23.9816

Ws 31.0434

At first, a DGS was implemented in the individual patch

antenna (Figure 2).

Later, several arrays were designed and simulated in order

to analyze their performance, all them coupled by micro strips

of length equal to g/16 and a width of 1 mm. The first array

was implemented using 5 rectangular patch antennas (Figure

3), with a total size of 93.8498 x 71.3535 mm2. In order to

increase the obtained gain, a new array of 9 rectangular

patches was also designed (Figure 4), with a total size of

93.9635x71.4352 mm2.

DGSs were implemented only for the COMA of 9 patches

in order to observe its effect on its antenna performance,

under two configurations. The first one is composed by

defects underneath of all patches, called DGS1 (Figure 5) and

a second one, where defects are applied underneath to the

driver patch, call DGS2 (Figure 6), the total size is the array is

95.1767x72.3066 mm2 in both cases. The diameters of defects

are of g/16. In all cases, short pines were used through the

parasitic patches.

Fig. 1. Rectangular patch antenna.

Fig. 2. DGS of the rectangular patch antenna.

Fig. 3. COMA with 5 parches.

Fig. 4. COMA with 9 patches.

Fig. 5. DGS1.

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367

Fig. 6. DGS2.

The coordinates of the feed point and the shorting pin were

established in order to have the necessary impedance

coupling.

III. SIMULATION RESULTS

For the individual antenna, the current is distributed from

the feed point (Figure 7), as it was expected.

Fig. 7. 3D current distribution on the individual patch

antenna.

Unfortunately, the gain is -2.68 dBi (see Figure 8 and 9),

this value is lower than other rectangular antenna gains using

other substrates, such as FR-4. Where the disadvantage is

their larger sizes. On the other hand, the reflection coefficient

has a value of -27.71 at 2.41 GHz (Figure 10), very near to the

design frequency. This value is widely acceptable.

When DGS is applied to the single rectangular antenna, the

current distribution shows a similar pattern to the case without

it (Figure 11). The obtained gain was of -0.742 dBi (see

Figure 8 and 9). Again, this value is lower than the

corresponding to rectangular antenna using other substrates,

such as FR-4, but it is better than the case without DGS. On

the other hand, the reflection coefficient has a value of -21.44

at 2.429 GHz (Figure 10), very near to the design frequency

and in the Wi-Fi range.

Fig. 8. Individual antenna gain, under 2D representation

Fig. 9. Individual antenna gain, under 3D representation

Fig. 10. S11 parameter of the individual antenna.

Fig. 11. 3D current distribution on a single patch with DGS.

Fig. 12. Gain of the individual antenna with DGS, under 2D

representation.

Fig. 13. Gain of the individual antenna with DGS, under 3D

representation.

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368

The small gain value of the individual antennas made

necessary to implement an array in order to improve their

performance.

For the antenna array based on five rectangular patches, the

current is distributed since the feed point (Figure 15), where it

can be observed a non-uniform distribution, very poor on the

array width. But in Figure 16 and 17, a notably gain increment

can be appreciated, reaching a value gain of 4.993 dBi. The

S11 parameter value also decreases until -17.6 dB, providing

a better response compared with the individual case (Figure

18).

Fig. 14. S11 parameter of the individual antenna with DGS.

Fig. 15. 3D current distribution in the COMA with 5

rectangular patches.

Fig. 16. 2D gain of the COMA with 5 rectangular patches.


Fig. 18. S11 of the COMA with 5 rectangular patches.

After, for the case of the antenna array based on nine

rectangular patches, the current distribution shows a more

distributed pattern (Figure 19 and 20). A notably gain

increment can be also appreciated (Figure 21 and 22),

reaching a value gain of 5.19 dBi at 6.4 deg. The S11

parameter value decreases until -9.496 dB (Figure 23),

improving the response.

Fig. 19. 3D front view of the current distribution on the

COMA with 9 rectangular patches.

Fig. 20. 3D rear view of the current distribution on the

COMA with 9 rectangular patches.

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Fig. 23. S11 parameter of the COMA with 9 rectangular

patches.

After to observe the better performance of COMA with 9

patches, DGS1 was implemented beneath of all patches

(Figure 24 and 25). A gain increment can be also appreciated

(Figure 26 and 27), compared with the case without DGS.

Fig. 24. 3D front view of the current distribution on the

COMA with DGS1.

Fig. 25. 3D rear view of the current distribution in the COMA

with DGS1.

A value gain of 7.01 dBi in the main lobe is obtained. The

S11 parameter value increases to -4.01 dB (Figure 28),

decreasing the response significantly, which is not suitable for

the array antenna operation.

Fig. 26. 3D gain of the COMA with 9 rectangular patches,

with DGS1.

Fig. 27. 2D gain of the COMA with DGS1.

Fig. 28. S11 parameter of the COMA with DGS1.

Finally, in order to improve the S11 response, DGS2 was

implemented, which allows obtaining an almost uniform

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current distribution (Figure 29 and 30). A notably gain

increment can also be appreciated (Figure 31 and 32),

reaching a gain value of 15.33 dBi at 50 deg. The S11

parameter value also decreases until -23.24 dB (Figure 33),

improving the response, as it was expected.

Fig. 29. 3D front view of the current distribution in the

COMA with DGS2

Fig. 30. 3D rear view of the current distribution in the COMA

with DGS2

Fig. 31. 2D gain of the COMA with DGS2

Fig. 32. 3D gain of the COMA with DGS2

Fig. 33. S11 parameter of the COMA with DGS2

Table II shows the parameter values of all analyzed cases,

where it is easy to compare their performance.

Table II. Parameter Values of the Implemented Antennas

Gain

[dBi]

BW

[MHz

]

S11

[dB]

Fo

[GHz]

Individual -2.68 10 -27.7

1 2.41

Individual with

defects -0.742 7.5

-21.4

4 2.429

COMA with 5

rectangular patches 4.993 12.23 -17.6 2.402

COMA with 9

rectangular patches 5.19 1

-9.49

6 2.448

COMA with DGS1 7.01 0 -4.05 2.39

COMA with DGS2 15.33 6.913 -23.2

4 2.403

IV. CONCLUSION

From the obtained results, it can be remarked that the use of

9 patches has a more uniform current distribution pattern than

in the other analyzed cases, improving considerably not only

the gain value, but also decreasing the S11 parameter value

for all considered cases without DGS. The improvement in

the gain value is considerable.

When DGSs are implemented to COMA with 9 patches, in

particular DGS2 configuration produced a notable increment

in gain. It was also showed an almost uniform distribution

current.

The next step is the implementation of this array in order to

experimentally prove its performance.

ACKNOWLEDGMENT

The authors would like to thank the partial support of

UAEM, under Ref. 07, 2013. J. G. Vera-Dimas and R.

Cabello-Ruíz express their sincere thanks to CONACyT for

the postgraduate scholarship under grants 270210/219230,

376566/248576, respectively.

REFERENCES [1] Kekun Chang, Guan-Yu Chen, Jwo-Shiun Sun, and Y. D.

Chen, “WLAN and Bluetooth Antenna Design,” PIERS

Proceedings, Beijing, China, March 23-27, 2009.

[2] “Cuadro Nacional de Frecuencias, COFETEL, 2012”, from

http://conapptel.org.mx/radioc /cnaf2012.pdf. August 2013.

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[3] S. Jalife-Villalón, “Las bandas de uso libre… no tan libre”. 29

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[9] G. Debatosh and M.M. Yahia “Microstrip and Printed

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AUTHOR BIOGRAPHY

Margarita Tecpoyotl Torres (corresponding

author) received the Mathematician degree from

the Autonomous University of Puebla (UAP),

Mexico, in 1991. In this University, she was

graduated as Electronic Engineer in 1993. She

received the M.Sc. and Ph.D. degrees in

Electronics from National Institute of

Astrophysics, Optics and Electronics (INAOE),

México, in 1997 and 1999, respectively. Dr.

Tecpoyotl works, since 1999, at CIICAp of UAEM, Mexico, where she is

currently titular professor. Her main research interest includes MEMS and

Microwave devices. She holds the status of National Researcher (SNI, level

1).

José Gerardo Vera Dimas was graduated

from the Technologic of Morelia as Electronic

Engineer. Member IEEE since January 2005. He

received the award "EGRETEC 2009" by the

Association of Graduates from the Technological

Institute of Morelia. He received the M.Sc.

degree in Electronics from the UAEM.

Nowadays, he is a Ph. D. student in the CIICAp

at UAEM. He has currently two registered

patents.

Raul Castañeda Sotelo is a B. Eng. student in

FCQeI at UAEM. He also has experience in home

electrical installation and elaboration of electrical

planes.

Ramón Cabello Ruíz obtained the Bs. Sc. and the

M. Sc. from Universidad Autónoma del Estado de

Morelos, UAEM, México in 2009 and 2012,

respectively. His interest is focused on Mechanics,

Microelectromechanic and Microwave devices. He

is currently a Ph. D student in UAEM.

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