Proceeding of the 2011 IEEE Students' Technology Symposium

14-16 January, 2011, lIT Kharagpur

Compact CPW- Fed Antenna for Wideband application

1. Balakrishna, R. Malmathanraj and S.Raghavan Department of Electronics and Communication Engineering

National Institute of Technology,Tiruchirappalli, Tamilnadu, INDIA Email: balakrishna.402@gmail.com. rmathan@nitt.edu, raghavan@nitt.edu

Abstract-- This paper presents a CPW-fed antenna for wideband

application. This Antenna satisfies the licensed frequency band of

WLAN (5.15-5.85)GHz and X-Band(8-12)GHz application. A

resonant frequency for WLAN at 5.57GHz and 11.27GHz for

h=lmm having return loss lower than -IOdB. This antenna is

designed on a substrate with dielectric constant &r=4.4. With a size

15.2mmx15.6mmxlmm the antenna operates for wideband

application. The effects of shape, length, size, and location of

feeding point, substrate and their thickness have been evaluated.

And obtained 2D radiation patterns with elevation, VSWR,

Return loss, gain and antenna efficiency. The simulation results of

this antenna are analyzed by using Method of Moment (MoM)

from IE3D software.

Key words - CPW-fed slot antenna, wireless LAN applications. I. INTRODUCTION

With the development of the modem supply chain, radio frequency identification (RFIO) and wireless local area network (WLAN) systems have been paid more and more attention, and have a huge potential market. Several frequency bands have been assigned to RFID and WLAN applications: 125 kHz, 13.56 MHz, 869 MHz, 902-928 MHz, 2.450 (2.400-2.483) GHz and 5.800 (5.725-5.875) GHz. The design of RFID[l,IO] antenna becomes more complicated and critical when the operating frequency rises into the microwave region. A design example for providing a wide operating bandwidth covering the 5 GHz WLAN band (5.15-5.825)GHz, wireless local area network band) or the 5 GHz license-exempt WiMAX[3-9] band (Worldwide Interoperability for Microwave Access) which is allocated the 2.5-2.69/3.4-3.69/5.25-5.85GHz is demonstrated [2]. X-Band (8-12) GHz is used for Short-range tracking, missile guidance, mapping, marine radar, airborne intercept. Where Ku-Band is typically used for High resolution mapping, satellite altimetry etc. Here in X-Band 8GHz-IOGHz is also used as I-Band in military electronic counter measures band designation. Most of the military applications are covered by X-Band and rest of the applications in this band are taken for services like police radar[12] which uses 10.525GHz and 11.7GHz to 12.5GHz is used for Direct broadcast satellite TV downlink (Europe). Ku-Band comes under l-Band in military electronic counter measures band designation. It covers some major known application like Direct broadcast satellite TV downlink (US) for example, EchoStar's Dish Network at 12.2-12.7 GHz. Wide band

antennas[11,13] are designed such that it covers all the important applications and it can be easily fabricated.

Now a day's CPW FED antennas have many attractive features like low radiation loss, less dispersion, easy integration for monolithic integrated circuits, so these types of antennas have recently become more and more attractive[7]. In addition, the CPW feed is particularly suitable for millimetre wave applications because of reduced surface wave excitation in electrically thick substrates. Printed slot antennas fed by a coplanar waveguide (CPW) have many advantages over microstrip antennas. Besides small size, light weight, low cost, good performance, ease of fabrication and installation, and low profile, they exhibit wider bandwidth, lower dispersion and lower radiation loss than microstrip antennas besides the ease of being shunted with active and passive elements required for matching and gain improvement [6]. The shape inside the aperture looks like triangle on rectangular patch with a rectangular slot in resonating element.

In this paper, a novel antenna with CPW-fed structure is proposed, which has many advantages. The proper shape of the patch is designed to meet the requirements of broadband and compact size simultaneously. Both simulated and test results are presented, which are in good agreement.

II. ANTENNA STRUCTURE AND DESIGN

y

z

'-------________ e. ________ ---.JI :1> Fig. I Layout of the proposed antenna

TSIICOMSOP027 978-1-4244-8943-5/11/$26.00 ©2011 IEEE 109

x

In this paper the proposed antenna exhibits a Voltage standing wave ratio (VSWR) of less than 2 and the Fig. 4 and 5 shows the radiation patterns at the resonate frequency 5.57GHz and 11.27GHz. The commercial simulator IE3D[14] is used to simulate and optimize the proposed antenna, Relative Omni

directional and stable radiation patterns are achieved.

III. DESIGN OF ANTENNA

The geometrical configuration of the proposed antenna is shown in Fig. 1. The parameters of the antenna are M=15.2mm, N=15.6mm,Ll=5.5mm,L2=3mm,L3=6mm,L4=6.3mm,Wl=7 mm, W2=2mm, W3=2mm, W 4=1 mm,S 1 =5mm,S2=1 mm,G=1.5 mm and g=O.6mm. The scheme of the proposed small CPW­fed patch antenna for wideband application is shown in Fig.l. Its simple structure is based on a one-layer FR4 dielectric substrate only, which has thickness as h=lmm and permittivity of 4.4. The whole antenna structure is symmetrical about the y­axis in Fig. 1 Based on systematic comparative studies by means of simulation using Method of Moment (MoM) from IE3D software. A set of suitable geometric parameters for the antenna is designed and then checked and adjusted by experimental test. The dimensions of the antenna are given in Fig. 1. The simulation of this antenna has been done and obtained a wide band application which covers some wireless applications and licensed frequency band for WLAN (5.15-5.85) GHz.

IV. SIMULATION RESULTS

A prototype of the Compact CPW-fed antenna for wideband has been simulated. From fig 2 we can see the simulated curve of return loss for the frequency range 5GHz to 12.2GHz is lower than -1 OdS. Return loss of -24dB is observed at resonant frequency 5.57GHz and -38dB at resonant frequency 11.27GHz. However it covers both WLAN frequency band and X-Band where the maximum return loss of -38dB is observed at resonant frequency 11.27GHz. It is clear from the fig 3 the simulated voltage standing wave ratio (VSWR) of the wireless LAN aperture antenna is less than 2 for entire frequency range of 5GHz to 12.2GHz.

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Proceeding of the 2011 IEEE Students' Technology Symposium 14-16 January, 2011, liT Kharagpur

-4--r P0I11 5.5.-------------------;-------------, 5.5

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1.5 1.5

5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5 11 11.5 12 12.5 Fre(IUellcy (GHz)

Fig. 3 VSWR curve of the antenna

The Figures shows the simulated radiation patterns with Elevation and azimuthal at a resonant frequency by using ZELAND IE3D software. The simulated radiation patterns of antenna in the E-plane (XZ-plane) and H-plane (YZ-plane) for 5.57GHz and 11.27GHz are shown in Fig. 4 and Fig. 5. The patterns and other curves are obtained at the time of simulation.

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�f-5.57595(GHZ). E.total,l)hl-O (deg) -e--f""""f-5.57595(GHz). E.lotal.,)hl-90 (deg)

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(180-cp) 4.0

o. �

0'08 � Elevation Pattern Gaill Disl>lay

(dBI) Fig. 4a E-plane 2D Radiation pattern at 5.57 GHz

�f-11.2785(GHZ). E •• oml. phi-O (deg) -----r- .-11.2785(GHz). E.to'al.l)hi-90 (deg)

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Fre(llIelicy (GHz) Fig. 2 Return loss of the antenna

TS 11 COMSOP027

Elev� ... tioll Panern Gain DiSI)lay (dBi)

Fig. 4b E-plane 2d Radiation pattern at 11.278GHz

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Azimuth Pattern Gain OiSI)lay (dBi)

Fig. 5a H-Plane Radiation pattern at 5.57 GHz

�f:11.2785(GHZ). E.total, theta:O (deg) � f:11.2785(GHz), E·total. theta:90 (deg)

0.0

Azimuth Pattern Gain Display (dBi)

Fig. 5b H-Plane Radiation pattern at 11.278GHz

Far field radiation characteristics were also studied. In the above fig's Black colour indicates the co-polarisation ,the Pink colour indicates the cross-polarisation .The Fig 4[a,b] and 5[a,b] show co-polarization and cross polarization radiation patterns in E and H-planes at 5.57 OHz and 11.27 OHz.

TS11COMSOP027

Proceeding of the 2011 IEEE Students' Technology Symposium

14-16 January, 2011, lIT Kharagpur

Total Field Gain vs. Frequency �r MOlxinllllll Tot..,' Field G..,in 3.9 . f';' 'f 'T : : . �"'� 'I 3.9 3.6 � .. � . . � .. ; .. . ;. : . : .: 1 3.6

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2.4 2.1 ... : . .. :. '�"'."' . .. .... .. ;. � .. � .. I 2.1 i 1.8 . , . . .�- -� :--- � --�--- � - 1.8 � 1.5 . . . : .. : ... : ..... : : ; : : : : 1 1 5 ::. 1.2 ; .; .l.l j :::.:: : :·}:::.·. : : '11 2 :�IIII�EiFjTT! l i ++ 1 �: ·0.3 . . . . . . . . . . . . . . . . 1

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Fig. 6 GAIN curve

Finally the antenna gain is observed and displayed in Fig 6 the antenna gain is observed 2.7dBi at 5.57 OHz owing to return loss of -24dB and 2.1dBi at 11.270Hz owing to high return loss of -38dB the gain is above 2.5dBi at 5 to 6.50Hz and the maximum gain 3.6dBi we can observe at a frequency of 5.850Hz and we can observe the decrease in gain from 2dBi from frequency (7-7.5)OHz. However for the WLAN and resonant frequency in X-Band the gain is more than 2. The efficiency of the antenna is observed in Fig 7. Here we can see efficiency of the antenna is more than 80% from 50Hz to 6.50Hz and it reaches a maximum of 99% at first resonant frequency and at second resonant frequency it shows 62%. The smith chart of the antenna is also plotted and observed an impedance of 50.7 at 5.50Hz and 51.1 at 11.280Hz which is shown in Fig 8.

Efficiency Vs. Frequency ----g.-r A'I'eml<.l Efficienc'y --r Radl4;"rtinu EfflclellCY

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Fig. 7 EFFICIENCY vs FREQUENCY curve of the antenna

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Fig. 8 Smith chart of the proposed antenna

V. CONCLUSION

New slot antennas with an extended ground have been proposed. Following the design guidelines, the proposed antenna structures can be applied for WLAN, RFIO, X-Band and other wireless applications. The observed results are VSWR < 2, Gain> 2 and efficiency> 75%. Advantages of these antenna are easy to construct, simple structure, and low cost.

VI. ACKNOWLEDGEMENT

I would like to thank Professor Dr. S. Raghavan (NITT) for his constant support on this work.

REFERENCE

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[3] Chien-Yuan Pan, Tzyy-Sheng Horng, Wen-Shan Chen, and Chien­Hsiang Huang,"Dual Wideband Printed Monopole Antenna for WLAN/WiMAX Applications," IEEE Antennas and Wireless Propagation Letters, vol.6, pp.149-151, 2007.

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[7] C. A Balanis, "Antenna Theory Analysis and Design," 2nd ed., New York: IEEE Press, 1997.

[8] C.1. Lin, K.L. Wong, and S.H. Yeh, "Wideband EMC chip antenna for

TS11COMSOP027

Proceeding of the 2011 IEEE Students' Technology Symposium

14-16 January, 2011, lIT Kharagpur

WLANlWiMAX operation in the sliding mobile phone," Microwave Opt Technol Lett 48. 1362-1366 ,2006.

[9] Y. Ding, Z. Du, and Z. Feng, "A novel dual-band printed diversity antenna for mobile terminals," IEEE Trans. Antennas Propag, vol. 55, no. 7, pp. 2088-2096, Jul. 2007.

[10] Tseng C.F, Huang and Hsu, "A wideband planar inverted-F dielectric resonator antenna for RFID system applications ", Microw. Opt. Techno/. Lett.48, (7), pp. 1302-1305, 2006.

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[12] AA Eldek, AZ. Elsherbeni, and C.E. Smith, "Wideband bow-tie slot antennas for radar applications," IEEE Topical ConjJ. Wireless Commun. Technol, Honolulu, Hawai, 2003.

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