A Low Profile CombinedArray Antenna for Wireless Application

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Internati onal e-J ournal For Technol ogy And Research-2017

A Low Profile CombinedArray Antenna for Wireless Application 1

1

S. Sudhaker,2 R. Anandan, 3 S. Saranya.

PG Student, R.Anandan,Associate Professor,3 S. Saranya,Assistant Professor.

Department of Electronics and Communication Engineering, 2

DhanalakshmiSrinivasan College of Engineering & Technology, Chennai,Tamil Nadu, India. sudhakervpm@g mail.co m,anandandscet@gmail.co m, ssaranya85@yahoo.com.

Abstract—In

wireless communication, micro strip antenna is used for various applications such as Wireless local area network, Bluetooth, Cordless Telephones and IS M band. Here a low profile microstrip antenna is to be designed. The antenna is constructed with FR4 substrate having relative permittivity of 4.4 and thickness of 1.6 mm. The unique (symmetric) array design enhances the narrow ban dwidth an d gain. The design results in extended WLANin X-band applications. Using High Frequency S tructure S imulator (HFSS ) software package, the antenna is simulated and dimensions are adjusted to achieve the desired resonant frequencies for desired operation.

achieve required operational bands. The EM simulat ion software is used to design and optimize the patch antenna.

The wide range of applicat ions in the antenna world gives the interested people to do a lot of designs and modifications. The ease of design and fabrication is a good motivation to enter such an area. The idea of this wo rk is to design unique slot with partial ground microstrip patch antenna with triple band for Wi-Fi/WiMax application, there is still the need for a solution in some areas, and the need to enhance services and applications in development in this process in techno logy.

IEEE 802.16 (W iMax) operates in more than one band and these bands are categorized in t wo ways .

Keywords—Microstrip patch antenna, Ex.WLAN, Array HFSS.

I. INTRODUCTION An antenna is an electrical device wh ich converts electric currents into radio waves, and vice versa. It is usually used with a radio t ransmitter or radio receiver. The patch antennas received considerable attention in the 1970s, although the idea was explored already in 1953 and documented in 1955.

Practical imp lementation started in the 1970s when suitable substrate materials became available. The microstrip patch antennas [9] are low profile and easy to fabricate using modern printed circuit technology. They are mostly used to enhance the bandwidth in mobile, radio and wireless communicat ion systems. Nowadays, microstrip patch antennas are used in many government and commercial sector applications [13]. Since the antennas are small they can be used in satellites and other high performance applications.

They are also practical to use in mobile applications, radars and security systems.

The microstrip patch antenna is analyzed using transmission line model. The effort has to be taken by modeling the antenna by various techniques such as slot cut, edge cut, partial ground, slotted ground, etc,. The substrate material has to be chosen carefully in the design. The mu ltiband antenna is designed and the sizes are varied to

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i. ii.

Licensed Un-licensed

Table I shows the so-called bands: TABLE I

Operational W LAN Bands S. No.

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License require d

Band

Frequencies

1

2.4 GHz

2.4 to 2.69 GHz

Yes

2

5.2 GHz

5.2 to 5.6 GHz.

Yes in some countrie s

3

8.2 GHz

8.15 to 8.25 GHz

No

Availability

Allocated in Brazil, Mexico, some Southeast Asian countries and the US In some countries, the 5.2 GHz to the 5.6 GHz band is allocated for broadband wireless.

Many countries allow higher power output (4 watts).it’s mainly used for satellite communications.

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Internati onal e-J ournal For Technol ogy And Research-2017 In recent times, the WLAN are operating at 2.4/5.2/8.2 GHz bands is becoming very popular due to its strategic features.

i.

Ground Plane Width and Length

II. PROPOSED METHOD The proposed antenna structure is achieved by cutting slots and etching out different shapes from a conventional rectangular patch. The microstrip patch antenna is analyzed through mathemat ical modeling (transmission line model).

The patch length and width for desired frequency can be calculated by utilizing the already established mathemat ical equations [4]. The antenna is constructed with FR4 substrate having relative permittivity (Îľr) of 4.4 and thickness of 1.6 mm. The design frequency of the antenna is 5.7 GHz. The length đ??ż of the radiating patch has dominating effect on the antenna performances other than the width đ?‘Š. Consider,

W= L=

c0 2f Îľ reff

c0

2

2f

Îľ r +1

Îľ r +1 2

+

Îľ r −1 2

h −1/2

w

(3)

Where h denotes the thickness of the substrate used.

Because of the effect of the fringing field surrounding the radiating patch, the electrical dimension of the antenna seems to be bigger than the physical dimension. The change of length of Δđ??ż due to the effect of fringing field can be presented by the following:

∆L = 0.412h

W +0.264 h W Îľ ref f−0.258 +0.8 h

f

iii.

Feed Width W f for an Impedance Z0 of 50 oh m Wf =

2h π

B − 1 − ln 2B − 1 +

1+ 0.39−0.61Îľr

Îľr −1 2 Îľr

x ln B −

(10) B=

iv.

v.

60 Ď€ 2 Z0 đ?œ€ đ?‘&#x;

(11)

III. DESIGN M ETHODOLOGY A. Design Formulas The other design formu las and equations used for manual calculation are listed below.

Return Loss (RL) RL = 20 log |Đ“| Where, RL is in d B Đ“ is Reflect ion coefficient Vo ltage Standing Wave Ratio (VSW R) VSW R =

(12)

1+ Γ 1− Γ

(13)

vi.

Impedance Bandwidth (BW) BW = (fH – fL ) (14) Where, BW is in MHz fH is Upper cut frequency at (RL ≈ 9.5 dB)in GHz fL is Lo wer cut frequency at(RL ≈ 9.5 dB) in GHz

vii.

Fractal Bandwidth (FB) FB = (fH – fL )/fC * 100 (15) Where, FB is in Percentage fC is Center or Resonant frequency in GHz

(4)

The available equations are applicable for conventional rectangular radiating patch; however the geometric shape and dimension of the proposed antenna have been achieved by modify, test, and run method. The dimension of the microstrip line is optimized through design and simulat ion to obtain enhanced impedance matching over the operating frequency bands.

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Feed Length Lf = Îť g / 4 (7) Îť g = Îť â „ Îľreff (8) c Îť= 0 (9)

− 2∆L (2)

1 + 12

Îľ reff +0.3

ii.

(1)

Whereas c0is the speed of light, f is the design frequency, Îľr is therelative dielectric constant, and Δđ??żis the change in length. The effective dielectric constant, Îľreff ,can be formulated as,

Îľreff =

W g = 6h + W (5) (6)

Lg = 6h + L

viii.

Antenna Efficiency

e0 = ecd (1 − Γ 2 ) ∗ 100 (16) Where, e0 is Efficiency of the Antenna in Percentage ecd is Radiation efficiency of the Antenna Đ“ is Reflect ion coefficient

B. Antenna geometry Thedesigning process of the antenna is startedwith estimating that the overall dimension of radiating patchis responsible for providing the compact size of the antenna.The designed antenna 2D v iew with dimensions is shown in Fig. 1.

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Quarter wave array Impedance line

The practical circuit realizat ion suffers with the mis match between the available source power and the power delivered.

This is known as return loss. Return loss can be expressed in terms of the reflection coefficient ‘Г’as in (12). Fig. 2 shows the return loss of the studied microstrip patch antenna, obtained from the simu lation using the HFSS software.

Return loss

HFSSDesign1

ANSOFT

0.00

Fig. 1. Designed antenna structure.

-15.00

Name m1

Table II S. No.

Dimensions of designed antenna Description

Values in mm

1

Patch dimension (L*W)

20 x 20

2

Circle patch

5

3

4 Square Array (L*W)

5x5

4

Substrate dimensions (L * W * H)

28 x 28 x 1.6

5

Ground dimension (L*W)

28

X

Y

8.0695 -19.9817 m1

-20.00 Curve Info dB(S(1,1)) Setup1 : Sw eep

-25.00

The antenna design is a unique design as the midd le circle patch and edges are in a symmetric square fashion. The antenna consists of single circle patch at the middle, 4 squarearray on each side, edge (top and down) on each side, circle ground. The microstrip feed with lu mped port is used to excite the patch antenna. The dimensions of designed antenna are given in Tab le II.

-9.3413

-9.8151

-10.00 dB(S(1,1))

MY2: -20.0833 10.0833

MY1: -10.0000

-5.00

-30.00 7.00

8.00 Frequency [GHz] MX1: 8.0308 0.0749 MX2: 8.1057

9.00

Fig. 2. Return Loss of the Simulated Antenna.

The return loss of the antenna is obtained as -22.5 dB at 8.175 GHz respectively. It is better to have the return loss less than -10 dB to make the antenna radiates well. It is noted that the multip le resonant frequencies are excited with less than 10 dB return loss.

B. VSWR The voltage standing wave ratio (VSWR) is a crucial parameter in antenna design, which means that if the transmission line is concluded with a mismatch in impedance, a portion of entered power is reflected back down, in wh ich case the incident signal will be mixed with the reverse signal.

This causes a voltage standing wave pattern, in which the ratio of maximu m to min imu m voltage is known as VSWR. The VSW R of the designed antenna is shown in Fig. 3.

The 4Square arrays are act as a director and connected with 50 oh m impedance line with middle circle gives the main resonant frequency band of operation for Extended WLAN applications. The Circle ground technique produce the circular polarization in X band application. The antenna total size is 28 x 28 x 1.6 mm3 . The geometry is said to be low profile antenna, because of the size, cost, etc. The simulat ing frequency range is 6 - 9 GHz. IV. RESULTS AND DISCUSSION A. Return Loss

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Fig. 3. VSWR of the Simulated Antenna.

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Internati onal e-J ournal For Technol ogy And Research-2017 The value of VSWR at these entire three resonating frequency band is also lies between 1 & 2. So we can say that designed antenna is resonating at 3 different resonating frequencies. The VSW R values are manually calculated by using (12) and (13) and is given by, i.

RL = -22.5; Γ = 0.243; VSW R = 1.22,

The bandwidths of three resonant frequencies are found fro m (14) and is given by, i.

Band 1 = [8105 – 8012] M Hz = 93 MHz,

D. Radiation Pattern The term radiat ion pattern refers to the directional (angular) dependence of the strength of the radio waves fro m the antenna or other source. Radiation pattern is the graphical representation radiation properties of the antenna and it shows the variation of power radiated by the antenna as a function of the direction. The radiation pattern also represents the relative strength of the radiated field in different directions fro m the antenna, at a constant distance.The far field and near field 2D radiation patterns for the proposed patch antenna are shown in Fig.6.

Fractal bandwidth (FB) is defined as the arith metic average of the upper and lower frequencies. FB for narrowband antenna in percentage is found from (15) and is given by, i.

Band 1 = [8105-8012]/8100 * 100 = 1.14 %,

Fig. 5. 2D Radiation Patterns of the Simulated Antenna.

C. Gain The 3D Gain plot is shown in Fig. 4. The gain is manually calculated using (17). The calculated gain is 5.35 d B. The measured gain is 5.35 dB

Since this microstrip patch antenna radiates normally to its patch surface, the radiation patterns of the antenna are almost omni-directional wh ich allows us to use this antenna for mobile applications E. Efficiency Usually rad iation efficiency (ecd)is very difficu lt to compute, but they can be determined experimentally. The measured value of radiation efficiency (ecd) is 0.9922 at 8.2 GHz. The efficiency of the antenna is manually calculated using (16). The reflection coefficient (Γ) is calculated by using (13) as follows, VSW R = 1.2227 at 8.2 GHz; |Γ| = 0.1625.

Efficiency (e 0 ) = gain/directivity x 100% = 96.45%

F. J-Field Current Distribution Fig. 8 shows the simu lated surface current distribution. The maximu m value of the J-field obtained is 1.12 x 102 A/m.

Fig. 4. 3D - Gain Total of the Simulated Antenna.

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Internati onal e-J ournal For Technol ogy And Research-2017 Hindawi Publishing Corporation, The Scientific World Journal, Art icle ID 183741, 10 pages.

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(Online: http://dx.doi.org/10.14257/ ijhit.2014.7.4.29).

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Fig. 6. J-Field Current Distribution of the Simulated Antenna.

V. CONCLUSION The low profile array microstrip patch antenna was designed and simulated with the High Frequency Structure Simu lator software. The simulation result shows that the microstrip patch antenna can be operated in X-band with functional bandwidth of 93MHz. The antenna exhibits an almost steady radiation pattern with acceptable gain of 5.4 dB, which can satisfactorily cover the requirement offered by Xband applications. Moreover the designed antenna concentrates on 8.2 GHz band Extended WLAN application and also achieves considerable bandwidth improvement in that band. .

VI.

ACKNOW LEGEM ENTS

The author would like to thank the management and staffs of DhanalakshmiSrinivasanEngineering and Technology for excellent encouragement during the tenure of work, and also expressmy sincere gratitude to Mrs. S. Saranya, M.E., Assistant Professor, ECE Depart ment, for her guidance and tolerance throughout the project.

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IDL - International Digital Library Of Technology & Research Volume 1, Issue 4,April 2017

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