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Design and Simulation of Single patch and Linear

Array (1x3) for Smart Antenna Applications V.S. Prabhu, R. Archana, A.M. Fiearlin Mercy, G. Bhavya Sree,

Assistant Professor, Dept of ECE, Dept of ECE, Dept of ECE,

Dept. of ECE, R.M.D. Engg.College, R.M.D.Engg. College, R.M.D. Engg. College,

R.M.D. Engg. College, Thiruvallur, India. Thiruvallur, India Thiruvallur, India.

Thiruvallur, India

Abstract—The design of smart antenna for cellular networks

can be implemented with single microstrip patch antenna.

But in some cases the radiation pattern, gain and directivity

requirement for certain applications were unable to meet by

the single element antenna. Suitable solutions can be

obtained by combining more than one antenna which is

generally called as the antenna array. In this paper, a

microstripsingle patch antenna and a linear microstrip patch

antenna array of (1x3) was designed and simulated to meet

tripleISM frequency band of 2.45GHz, 4.5GHz and 7.1GHz.

Thus due to this multiband frequencies the smart antenna

designed can be used for multiple applications. The return

loss obtained in S11 plot is -35 dB at 4.5GHz and 7.9GHz for

single patch antenna and linear array antenna respectively.

The microstrip patch and linear antenna array was designed

and simulated in ADS software. The radiation pattern

obtained was found to be narrow and thus can be

implemented for smart antenna applications.

Keywords-- linear array, microstrip patch antenna, ISM

band.

I. INTRODUCTION

The development recently made in the field of antenna has

lead to the need of high gain, narrow band radiation pattern

and directivity. Usually the radiation pattern of a single

element is relatively wide, and each element provides low

values of directivity and gain. In many applications it is

necessary to design antennas with very high directive

characteristics to meet the demand of long distance

communication. This can be accomplished by multi-elements

which is referred to as arrays [1]. The antenna arrays can be of

any forms like linear, circular, rectangular, spherical, etc. The

design and simulation of microstrip patch and a linear array of

(1x3) was done in this paper.

The arrays are equally spaced and are placed in a straight

line for linear arrays.However, if some of the manifold vectors

are linearlydependent, then the ambiguity problem is said to

arise,implying a need to identify array geometries that are free

ofsome type of ambiguities, as well as estimating the set

ofambiguous directions associated with a given geometry

[3].The main problem in designing the antenna array was

instrumental in selecting elements which conform to the

geometry of the device, and an array architecture that could

control the radiation pattern in both the azimuth and elevation

directions [4].

The preliminary design was to select the dimensions of the

rectangular patch. And for the antenna array the preliminary

design resulted in the selection of microstrip patches,

arranged in a linear array configuration. In addition, the

number of radiating elements was chosen to meet beam width

requirements. Mutual-coupling effects between the antenna

elements were also considered, as they affect the overall

performance of the antenna array. Mutual couplingresults in

radiation patterns that have shallower and shifted nulls,

and less accurate angles of arrival, thus causing a

deterioration in the overall performance of antenna system.

Figure 1. Rectangular microstrip antenna element

The antenna array is designed from the rectangular

microstrip patch antenna. The design of single patch antenna

was discussed in section 1. Microstrip patch antenna consists

of a radiating patch on one side of a dielectric substrate with

acontinuous metal layer bonded to the opposite side of the

substrate which forms a ground plane.The patch is generally

made of conducting material such as copper or gold and can

take anypossible shape. [5]. The major advantages of selecting

microstrip patches are very low cost, reduction in weight,

planar or conformal and ability of integration with electronic

or signal processing circuitry. Microstrip antenna array

consists of microstrip antenna elements, feed and phasing

networks. Designing microstrip structure requires

understanding of both mathematical relatives and its

application [6].

In most microstrip end fed antennas the feed line

impedance (50) is always the sameas the radiation resistance

at the edge of the patch, which is usually a few hundred

ohmsdepending on the patch dimensions and the substrate

used. As a result this inputmismatch will affect the antenna

performance because maximum power is not beingtransferred.

When a matching network is implemented on the feed network

thisimproves the performance of the antenna as there are less

reflections [7]. A typical method used to match the antenna is

the use of an inset feed, because theresistance varies as a

cosine squared function along the length of the patch a 50

can befound which is a distance from the edge of the patch

[8].The emphasis on theoretical and practical design

techniques of available substrate materials are reviewed along

with the relation between dielectric constant tolerance and

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resonant frequency of microstrip patches [9]. Practical procedures are given for standard rectangular patches, as wellas variations on those designs are summarized [10].The design of linear microstrip array is explained in section 3.

II.SINGLE PATCH ANTENNA DESIGN

The microstrip patch antenna was designed in ADS

software. Microstrip patch antenna is made up of two sides.

One side is the ground plane and the other side is the radiating

patch with a continuous metal layer. The patch is made up of

gold or copper and it can take any shape.

The design equations of the single patch are given below.It

was considered that the relative permittivity, r =8 and height

h=0.15 cm.

The width of microstrip patch antenna is given by the

equation (1),

1

2

2

rr

o

f

vW

(1)

W= 2.946 for 2.45GHz ; 1.57 for 4.5 GHz ; 0.995 for 7.1 GHz

The Effective relative dielectric permittivity is given by

the equation (2),

2/1

1212

1

2

1

W

hrrreff

(2)

reff =7.257 for 2.45 GHz; 6.88 for 4.5GHz ; 6.588 for

7.1GHz

The change in length is given by the equation (3),

8.0258.0

264.03.0

412.0

h

W

h

W

hL

reff

reff

(3)

L = 0.06 for 2.45GHz ;0.06 for 4.5GHz; 0.06 for 7.1GHz

The actual length of the Patch is given by the equation (4),

𝐿 = Lf ooreffr

22

1

(4)

L= 2.15cm for 2.45GHz ;1.15cm for 4.5GHz ; 0.703cm for

7.1GHz

The effective Length of the Patch is given by the

equation(5),

ef fL = LL 2 (5)

ef fL = 2.27cm for 2.45GHz ;1.27 for 4.5GHz ; 0.823 for

7.1GHz

A method used to match the microstrip patch antenna is by

an inset feed. In the inset feed the resistance varies as a cosine

squared function along the length of the patch. The input

resistance of the inset feed is found by the formula given

below.

Rin = 1

2 𝐺1±𝐺12 𝑐𝑜𝑠2(

∏

𝐿𝑦𝑜) (6)

yois the depth of the inset feed into the rectangular patch.

Generally yois taken as half the total length of the rectangular

patch.

Where G1 is the conductance of slot 1 and G12 is the mutual

conductance between slot 1 and 2 of the microstrip antenna.

𝐺1 =

𝑊2

90 х 𝜆2 𝑓𝑜𝑟𝑊 ≪ 𝜆

𝑊2

120 х 𝜆2 𝑓𝑜𝑟𝑊 ≫ 𝜆

(7)

The dielectric substrate of appropriate tangential loss and

thickness „h‟must be selected. Substrates of high thickness are

mechanically strong, and it will increase the radiated power,

reduceconductor loss and improve the impedance

bandwidth.A high loss tangent increases thedielectric loss and

therefore reduces antenna efficiency.

Figure 2.Single Patch Antenna Model and design in ADS

For the calculated design parameters, antenna design is

proceeded with ADS Software. After creating a new project,

the initialization steps like grid spacing, and layout units are

defined. Here the substrate is selected as 60 mil thick and loss

tangent of 0.002 for the operating frequency of 2.4GHz. Patch

width has a minor effect on the resonant frequency and

radiation pattern of the antenna.With the proper excitation, a

patch width „W‟ is obtained which is greater than the patch

length „L‟, without excitingundesired modes. In this paper, a

broadband rectangular microstrip patch antenna is designed

using the permittivity r of 3.4 and log tan δ of 0.002. The

width and height of the patch is 30mm and 34mm

respectively. The single patch antenna designed in the ADS

software with its feeding structure, by means of a microstrip

line was shown in the Fig. 2.The width and height of

microstrip line is 3.5mm and 31mm respectively.

The loss in the signal power due to the reflections caused at

a discontinuity in a transmission line is generally called the

return loss. The return loss plot for the designed single patch

antenna was shown in fig 3.

Directivity is a measure of isotropic antenna. The gain of

the antenna directly dependson the radiation efficiency and the

directivity of the antenna.

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Figure 3: Return loss plot for single patch antenna

From the figure 3, the return loss of -6dB, -35dB and –13

dB occurs at 2.4GHz, 4.4GHz and 7.2GHz respectively.

Normally, while supplying power to the antenna, reflection of

power takes place. For better efficiency, this reflected power

should be as low as possible. The „0‟ dB in the graph shows

that 100% of the power is reflected. As it goes on decreasing,

it clearly indicates that there is minimum reflection of power.

The S11 plot in the figure3 shows, minimum amount of power

is reflected in the above mentioned frequencies.

It is observed that directivityincreases with increase of

substrate thickness and patch width. Conversely, the

beamwidth isexpected to decrease for higher values of „h „and

„W‟. The simulation of the antenna model was done in ADS

software by the pre-processing step. By computing the far

field, antenna parameters such as gain, directivity, effective

angle are calculated. High directivity shows that antenna is

directed in the direction of strongest emission. And by the

post-processing step, the three dimensional view and the

animated view of radiation pattern is obtained.

III. LINEAR ANTENNA ARRAY

The 1x3 linear patch antenna was designed by connecting

three single patch antennas to the matching circuits.The height

and width of the single patches in the linear array antenna

were similar as that of single patch antenna discussed in the

section1.The matching circuit for the array is developed in the

schematic window of ADS and then produced to the layout

window. The uniform linear array of patches with spacing of

λ/2 is arranged as shown in figure 3.

Figure 4. 1x3 linear patch antenna designed in ADS

Figure 5: Return loss plot for linear antenna array

The S11 plot in the figure 5 shows, minimum amount of power

is reflected in the frequencies 2.6GHz, 5.0 GHz and

7.9GHz.When an antenna is connected by a feed line,

the impedance of the antenna and feed line must match exactly

for maximum energy transfer from the feed line to the antenna

to be possible.Return loss is the loss of signal power resulting

from the reflection caused at a discontinuity in a transmission

line.From the fig 5, it is clearly shown that the return loss lies

around -20dB for the linear array antenna. Thus the designed

linear array has high resistance to reflection.

IV. RESULTS AND DISCUSSIONS

The most important characteristics of the antenna array

include the radiation pattern. The radiation pattern implies the

gain, directivity and the beamwidth. Radiation pattern is

computed using method of moments in ADS. The radiation

pattern for the single patch and uniform linear antenna array

for the three frequencies are shown in below Figures. Also by

the post processing step the animated view of radiation

patterns are obtained shown in fig 9 and fig 13.

The radiation pattern plays a vital role in antenna array. It

is observed that the radiation pattern of the linear array is

found to be narrow and thus useful in various smart antenna

applications. The gain of the antenna is the quality which

describes the performance of the antenna to concentrate

energy through the direction to to give a better picture of the

radiation performance.The below tabulation shows the antenna

parameters like Directivity, Gain, Power radiated for the three

different frequency ranges.

Operating

frequency

Directivity Gain Power radiated

Single

patch

Linear

array

Single

patch

Linear

array

Single

patch

Linear

array

2.4 GHz to

2.6GHz

5.434

9.547

3.089

6.553

0.582

0.501

4.4 GHz to

5 GHz

7.074

11.552

6.697

7.817

0.917

0.423

7 GHz to 8

GHz

8.557

11.492

6.935

9.808

0.688

0.678

Table1 Performance comparision of single patch & linear array antenna

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Figure 6: Radiation pattern of single patch antenna at 2.4 GHz

Figure 7: Radiation pattern of single patch antenna at 4.4 GHz

Figure 8: Radiation pattern of single patch antenna at 7.4 GHz

Figure 9: Animated view of single patch antenna

Figure 10: Radiation pattern of 1x3 antenna array at 2.6 GHz

Figure 11: Radiation pattern of 1x3 antenna array at 4.9 GHz

Figure 12: Radiation pattern of 1x3 antenna array at 8 GHz

Figure 13: Animated view of Linear array antenna

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VI. CONCLUSION

The antenna array designed with linear microstrip patch antenna provides narrow radiation pattern and have better directivity compared to that of single patch microstrip antenna.The designed linear antenna array has high resistance to reflection. The reason that patch antenna arrays are employed for wireless applications are due to their high gain even at their low profiles as inferred from the above tabulation. Due to better antenna parameters, narrow beamwidth and multiple operating frequencies, linear array antenna can be used for applications like Bluetooth at 2.4 GHz, Mobile Wi-Fi at 2.45 GHz and C - Band applications which includes commercial Wi-Fi , Satellite communications, Broadcasting etc in the range of 4 to 8 GHz.From the results obtained it is concluded that the linear array can be used in smart antenna system with triple band applications. This triple band frequency applications are used for cellular networks particularly in adhoc networks as it gives a satisfactory performance.

VII. REFERENCES

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[3] Simon Haykin, “Adaptive Filter Theory”, Fourth edition , 2002.

[4] AthanassiosManikas, Christos Proukakis, and VasileiosLefkaditis, “ Investigative study of planar array ambiguitiesbased on hyperhelical parameterization”, IEEE transactions on Signal processing, vol. 47, no. 6, june 1999

[5] K.Meena alias Jeyanthi and A.P.Kabilan, “Modeling and simulation of Microstrip patch array for smartAntennas” , International Journal of Engineering,IJE volume(3),Issue(6), 2006

[6] Ramesh Gharg, PrakashBhartia, ”Microstrip Antenna design Handbook”, Artech House, 2000.

[7] Mr. Martin Leung, “Microstrip Antenna Design Using Mstrip40”, Nov.2002.

[8] Z.Rostamy, “Determination of resonant frequency of dominant and higher order modes in thin and thick circular mcrostrip patch antennas with superstrate by MWM”, International journal of Engineering,volume 16, November 2003.

[9] K.R. Carver and J.W. Mink, “Microstrip Antenna Technology,” IEEE Trans.Antennas Propagat., vol. AP-29, no.1, pp 2-24, Jan. 1981.

[10] NiruthPrombutr, PrayootAkkaraaektharm, ”Analysis and design of Hilbert curve fractal antenna feed with coplanar wave guide for multiband wireless communications”, International Journal of Engineering, volume 2, Issue 3, 2003.

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