BIO-INSPIRED RED-BAY LEAF SHAPED ANTENNA FOR NARROW BAND APPLICATIONS

Dr. V. Latha, Professor- Electronics and Communication Engineering, Velammal Engineering College, Chennai-66,

India.Divya Rajagopal, B.E.Electronics and Communication Engineering, Velammal Engineering College, Chennai-66,

R. Kiruthika, B.E.Electronics and Communication Engineering, Velammal Engineering College, Chennai-66,

L. Reshma, B.E.Electronics and Communication Engineering,Velammal Engineering College, Chennai-66,

Abstract: In this paper, a new bio inspired design for a microstrip patch antenna is discussed. The antenna is designed using RT Duroid 5880 substrate and a slotted ground plane. The objective of the antenna is to work around a frequency of 2.512GHz with a bandwidth of 38MHz.The Return loss, Radiation efficiency, Gain and VSWR simulation results for the antenna are extracted. The fabricated antenna is tested in the physical environment and the results shows that the antenna performance is suitable for several military, medical and monitoring applications. The extracted parameters are compared with the test results of the fabricated antenna.

Keywords: Antenna, CST software, Frequency domain, ISM band, Microstrip patch antenna, RTDuroid 5880, Slotted antenna.

1. INTRODUCTION

Wireless communication is one of the key areas in the

growing technology. It finds its application in almost every

discipline of technology. It is now applied in the field of

medicine, defence, communication, environmental studies etc.

The antennas are finding major applications in bio imaging

[3], Bio monitoring as in the case of RFID, telemetry,

monitoring of flora and fauna, Military [10] etc. Hence, the

need for developing new antenna designs which are

application specific is becoming important.

The microstrip patch antenna is one of the antenna types that

is finding application in latest inventions for its small size and

planar structure. It is also highly regarded for its low

fabrication cost and its capability to support the dual

polarisation and high frequency applications. The structure of

patch antenna is composed of three layers namely the Ground

plane, Substrate and the Patch. The patch can take any shape

and the dimensions of the patch also contributes to the amount

of energy that is radiated. The feeding point to the patch also

characterises the loss of the antenna due to impedance

matching. Three types of feeding methods can be

implemented namely, the corner feed, Inset feed, coaxial feed.

The substrate holds the fringing fields which are responsible

of radiation of electromagnetic waves. The selection of

substrate and its thickness [7] plays an important role in

deciding the parameters of the antenna. A good dielectric

constant is characterised with low dielectric constant and

should aid at low loss, good radiation of antenna and larger

bandwidth and low return loss.

The ground plane confines the electric fields due to the

fringing effect from the underside of the antenna. The

characteristics of the ground plane also influences the antenna

performance parameters. The ground plane dimensions must

be carefully selected. Hence, the proposed leaf shaped patch

antenna [8] is designed to be used for applications like

environmental monitoring such as animal monitoring using

RFID tags and for monitoring the number of trees in the

particular radius of area using RFID [6] to keep a check on the

illegal timber extraction. This paper deals with improvisation

of [2] to obtain improved return loss. The return loss

improvement is brought about by including slots in the ground

plane. The shape and size of the slot and its position around

the patch alters the effect of the slot on the bandwidth and

return loss value.

2. ANTENNA DESIGN

The length and width of the ground plane and the substrate are

the same having dimensions of 60mm x 40mm.The ground

plane is made out of copper annealed material with a thickness

of 0.3mm. The ground plane is designed with two slots to

improve the antenna gain and performance [4]. The substrate

material is selected to be RT Duroid 5880 (Rogers Duroid

5880 (Lossy) as in CST Software) with a thickness of 1.5mm.

The substrate material chosen has a dielectric constant of

2.2[9]. The patch is made Leaf shaped with Copper annealed

material with a thickness of 1mm. The patch is corner fed and

the feed line dimensions are 12mm x 4mm x 1mm.

International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 6, 2019 (Special Issue) © Research India Publications. http://www.ripublication.com

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Fig. 1: Shape of antenna [ Red-bay leaf]

Fig. 2: Antenna dimensions [ Front view]

Fig. 3: Ground plane [ Back view]

Fig. 1shows the leaf shaped patch (front view of the antenna)

in comparison with the Red-Bay (Perseaborbonia) leaf which

served as a bio-inspiration for the patch shape. Fig. 2 depicts

the dimensions of the antenna and Fig. 3 shows the ground

plane with slots (back view) of the antenna.The circular and

square slots cut in the ground plane have the following

dimensions.

Table 1. Square slot

Parameters Dimensions Xmin 4

Xmax 16

Ymin -16

Ymax -28

Zmin 1.5

Zmax 1.8

Table 2. Circular slot

Parameters Dimensions Outer radius 6

Inner radius 0

X center -10

Y center 22

Zmin 1.5

Zmax 1.8

Segments 0

3. SIMULATION RESULTS

3.1. Far-Field Radiation (f = 2.5) The Fig. 4 and Fig. 5 are the 2D and 3D plots of the far-field

pattern. The far-field directivity is 4.169dBi at 2.5GHz

frequency.

Fig. 4: Far-field [2-D view]

Fig. 5: Far-field [3-D view]

3.2 S-Parameter (Return Loss 𝐒𝟏𝟏) This is the one of the most important parameters to be

analysed for construction of an antenna with satisfactory gain.

S11 is sometimes also called the Reflection coefficient since it

quantifies the amount of power that is reflected back at the

antenna and transmission line junction due to impedance

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mismatch. It is analysed at the antenna port using a network

analyser. Low S11 value indicated high radiated power by the

antenna implying good antenna performance. It is measured in

Decibels.

The return loss plot for the frequency range of 1GHz to 3GHz

is shown below:

Fig. 6: S-parameter [software results]

The plot shown in Fig. 6 indicates a steep fall of about -41.12

dB around 2.518GHz. It reaches back to 0dB around 3GHz.

From the plot, it can be found that the cut off frequency of the

antenna to be 2.518GHz. The bandwidth of the antenna is

determined to be 38MHz.

3.3 Efficiency

Efficiency is the power fed to the antenna by the power

radiated from the antenna ratio.A desirable efficiency implies

greater amount of radiated power over absorbed power.

Efficiency of the antenna can eb increased through proper

impedance matching.

Fig. 7: Efficiency

The above plot (Fig. 7) indicates a total efficiency of -32.89dB

at 1GHz and -9.4467dB at 3GHz and radiation efficiency of -

8.4696dB at 1GHz and -0.39862dB at 3GHz.

4. FABRICATION AND TEST

RESULTSCOMPARISON

The fabricated antenna images are shown in the Fig. 8 shown

below. The antenna was tested in anechoic chamber.

Fig. 8: Fabricated antenna

Fig. 9: S-parameter [test result]

The test result (Fig. 9) shows that the antenna’s return loss is -

24.247dB on fabrication an improved bandwidth of 500 MHz

also is seen. The antenna is also found to operate in two other

frequencies as 3.6GHz and 7.9GHz showing a return loss of -

12.484dB and -10.247dB respectively.

5. CONCLUSION

Thus, this paper throws light on the performance of a newly

designed leaf shaped antenna through comparison between the

simulation and test results. The antenna designed using the

CST software shows a return loss of -41.1dB in simulation

and the return loss on fabrication is 60% (-24.247dB) of the

obtained simulation value. The frequency of operation in

simulation is 2.52GHz while on testing the antenna was found

to operate in three frequencies as 2.5 GHz, 3.6 GHz and

7.9GHz. This shows that the antenna can be used for three

different applications in these frequencies. At 2.5GHz, the

antenna can be used for medical [12] and RFID purposes as in

development of Medical implants [5] and RFID animal

monitoring devices and tags [11]. At 3.6GHz, the antenna can

be used for radio location service and Fixed Satellite Services.

It can be allocated for both Federal and Non-federal use. At

frequency 7.9GHz (X band), the antenna can be used for

government and military purposes. It can also facilitate radar,

satellite communication and wireless and Computer

Networking in that frequency.

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