Ultra Wideband Tapered Microstrip Antenna with

Modified Ground plane

Archana Agarwal

Electronics & Communication Institute of Technology and Management

Bhilwara, India

Abstract- since the release by the Federal Communications Commission (FCC) of a bandwidth of 7 .5GHz (from 3 . 1 GHz to 1O .6GHz) for ultra-wideband (UWB) wireless communication, UWB is rapidly advancing as a high data rate wireless communication technology. This paper focuses on UWB rectangular tapered microstrip patch antenna design with modification in ground plane to acquire UWB frequency range. Firstly the ground plane of micros trip patch antenna is cut to approximate L-shape with the optimization of feed line width and length to obtain the bandwidth from 3 .73GHz to 7 .67GHz. Later on by tapering the microstrip patch the ultra­wideband is obtained. Simulation result shows that the proposed UWB antenna have a bandwidth ranging from 3 .4GHz - 1O .6GHz which satisfies the system requirements for S-DMB, WIBRO, WLAN, CMMB and the entire UWB.

Keywords- Ultra wideband (UWB), Tapering, Bandwidth,

Microstrip Patch antenna

I . INTRODUCTION

In February 14 , 2002, the Federal Communications commission (FCC) amended the Part 1 5 rules which govern unlicensed radio devices to include the operation of UWB devices. The FCC also allocated a bandwidth of 7 .5GHz, i .e . from 3 . I GHz to I O .6GHz to UWB applications [ 1 ] , by far the largest spectrum allocation for unlicensed use the FCC has ever granted.

Ultra-wideband (UWB), a radio transmission technology which occupies an extremely wide bandwidth exceeding the minimum of 500MHz or at least 20% of the centre frequency [ 1 ] , is a revolutionary approach for short range high­bandwidth wireless communication. UWB systems transmit information by generating radio energy at specific time instants in the form of very short pulses thus occupying very large bandwidth and enabling time modulation. Due to the transmission of non-successive and very short pulses, UWB radio propagation will provide very high data rate which may be up to several hundred Megabytes per second, highly ensures the data security, power consumption of UWB systems is also extremely low and avoid multipath fading etc. Because of these alluring properties, UWB technology is widely employed in many applications such as indoor positioning, radar/medical imaging and target sensor data collection [2-5] . One of the challenges for the implementation

978-1 -4799-1 607-8/1 3/$31 .00©201 3 IEEE 33

Manish kumar, Priyanka Jain, Shagun maheshwari

Electronics & Communication Engineering 1. TM University Gurgaon, India

of UWB system is the development of suitable or optimal antennas .

Basically, the minimum achievable data rate or capacity for the ideal band-limited additive white Gaussian noise (A WGN) channel is related to the bandwidth and the signal­to-noise ratio through Shannon-Nyquist criterion [6,7] :

C = B log2 ( 1 + SNR) ( 1 )

Where C denotes the maximum transmit data rate, B stands for the channel bandwidth, and SNR is the signal-to-noise ratio. From this principle, the transmit data rate can be enhanced by increasing either the bandwidth occupation or the transmission power. However, the transmission power cannot be readily increased since many portable devices are battery powered and the potential interference should also be avoided. Thus a large frequency bandwidth seems to be the proper solution to achieve a high data rate.

The main goal of this paper is to present a new antenna configuration with combined effect of modified ground plane and use of tapering to provide low profile, ultra wide band and high gain antenna [8] . In this article, fustly the rectangular micro-strip patch antenna with a 50-Q micro-strip feed line is fabricated on the FR4 substrate. To improve the bandwidth, we modified the original ground plane to an approximate L­shape to obtain the bandwidth from 3 .43GHz to 5 . 88GHz which was further enhanced to 3 .73-7 .67GHz by optimizing the feed dimensions . Later on by tapering the microstrip patch an Ultra wideband is obtained ranging from 3 .4 GHz - 10 .6 GHz.

The detail of antenna design and preliminary result from simulation are described in Section 2, and Section 3 .This work concludes in Section 4 .

II. ANTENNA DESIGN

The geometry of the normal rectangular patch antenna with microstrip feed line for parametric study is shown in Fig. l . The rectangular patch is fabricated on a 3 8 mmx36 mmx 1 .6 mm FR -4 board (cr = 4.4, thickness = 1 .6 mm and loss tangent = 0 .02) with a feed line and a fmite ground plane . The optimized dimensions of ground plane are : WI =36m, L l=3 8mm and of patch are W2= I 5mm, L2=I Omm. The width

and length of feed line is designed to be W3=4mm and L3= 14mm for the impedance of 50n.

WI

W2 I

I: -i------1

W3 (a) Top view (b) Bottom view

Fig. 1 . Geometry of normal shaped Rectangular Patch antenna.

We use the micro-strip structure because it offers many advantages, such as being compact, inexpensive, and light weight. On the other hand, a lower bandwidth is a shortcoming for the structure . Our objectives are to modify the structure and incorporate the techniques to improve the bandwidth. In what follows, brief analysis of the parametric studies to achieve the optimum values of return loss and bandwidth is discussed.

XI

-f--I W3 WI

(a) Top view (b) Bottom view

Fig. 2. Geometry of modified ground plane Patch antenna.

A. Antenna Design with Modified Ground plane Fig.2 shows the top and bottom views of the proposed

antenna as well as its dimensions . In order to obtain a wide bandwidth, the ground plane is cut to nearly about L shape as shown .The cut dimensions are varied and the optimum dimensions are found to be Xl = 29 mm, Y1 = 23 .2 mm, X2 = l 3 .5 mm, Y2 = 1 . 8 mm. The results are shown in Fig.4.

B. Effect of change in feed dimention The next tuning parameter is the change in dimensions of

microstrip feed line . The parameter L3 is varied to get the maximum bandwidth the optimized dimension of L3 is found to be L3 ' = 9 . 8 mm. It is being observed that as the length of feed line is reduced the bandwidth is enhanced. The resulting bandwidth is from 3 .73GHz to 7 .67GHz as shown in Fig. 5 . It is worth noticing that the impedance matching is very sensitive to the dimension of the antenna. For different stages, the antenna dimension should be slightly reoptimized to achieve impedance matching.

34

C. integrating the feature of modified ground plane and tapering to obtained ultra wide band

To obtain the UWB characteristics the top patch as shown in Fig. 3 is tapered from its comer. By doing so the multi band characteristic is obtained and the dimensions of these cut are modified to obtain these bands very close to each other thereby providing the return loss below - 1 0dB and thus large bandwidth is obtained. The dimensions of the cut are G= 1 mm, H= 1 . 5 mm, S= 4 mm.

XI

W2

� N -' I � :; M '(2 -'

t-1 W3

WI (a) Top view (b) Bottom view

Fig. 3 . Geometry o f modified Tapered Patch UWB antenna.

III. SIMULA nON RESULTS

The simulated return loss of the modified ground plane patch antenna is shown in Fig.4. It is clearly indicated that the antenna has the - 1 0dB impedance bandwidth from about 3 .43GHz to 5 . 88GHz. The figure also shows that the curve touches the - 1 0dB line at a resonant frequency of 4 .85GHz. The resonant frequency is located at 3 . 83GHz.

·5 t·· · . .. . . . . . . .. . . . ,\, . .. . . . · . . . . . . · , . . . . . . . . . . . . · · . . , . . · . . .. · ... . . . . . ·,· . . · . . . . . . . . . . . . . . , .... .. . . ........ : ......... ......... ,./

� '10 . h t . . . . · · . . . . . . · . . . . , . . . . . . . . · ·\ . . . . . . , ·j

� 'UO t . . . . . . . . · . . .. ··.. ,. . . · . . . . . . . . \ . . . . . . . . . . . . . . . �. .... } ............... } ............... : . . . . .

·1S t . . . . . . . . . . . . . . .. · : . . . . . . . . . . . . ·\!

��---r----r----r--�----1---�----T----T--� 1 6 7

Fr�f Glz 10 11

Fig. 4. Return loss vs. frequency curve for modified ground plane patch antenna.

To further improve the bandwidth the feed dimensions were varied and optimized. Fig .5 shows the simulated result which shows that by shortening the feed length, the impedance bandwidth is increased from 3 .73GHz to 7 .67GHz.

o.-----�----�----�----�----�----�----_,

;:=\\- -, - - -- -- - --- - --------- i - --- - - --- -:fi/�--- - ------ - \- -+---_,.'/(----- --/-- �, - - - - - - - - -,,--- :�---------- - - - - j

\ ; /'J \ ( -15

: : • • • • •• •• -•• • -_ • • • _

•• • • - ::/(-- - - ------- ----- ,---------------------- : -------------- - - - +: • • • • -•••• _ ••• -_ ••• -••• • : -••• -•••• • • • • -••• -••••• • �-•• • -•• • • • • • • -••• --••• - : -J0 1 - --- - ---- -- ------ - -- -HI,I- ---- - ---- -- --- -+--- -- -- ------- --- ---+_-- ---- - - -- ------ - --+_--- -- -- -- -- - --- - - -+ ---- -- -- -- ---- -- - -- -- -:-- - --- - --- -- - -- - ---- -- 1

V -J5

l__-----T--------T---------;---------T-----_____;.----------;---------I

1 8 10 11 14 16 �"""", / GI!

Fig. 5 . Return loss vs. frequency curve for change in feed dimensions .

Further to obtain the ultra-wide band the top patch is tapered. Fig. 6 shows its return loss curve . This antenna can be used from 3 .4GHz - 10 .6GHz providing a bandwidth of 7.2 GHz. Fig. 7 illustrates the simulated voltage standing wave ratio (VSWR) for the proposed antenna. VSWR of the antenna is closely related to the return loss. Return loss below - 1 0 dB is also represented by VSWR from 1 to 2 in the frequency range of 3 .4 GHz to 1O .6GHz

� - -- --------" / � . /

!-to ' : ; / : l" \ //" /:�+ f\\ ----i!-- /- - -------- - -- --i- --- ---- ------ --- - --- --'i---------- ---- - - - -- j J ::: I / V 1, __ .. ____________________ ; _______________________ ; __ ---- ---------------j

-18 • -20 -12 -� l__----�----�----____T_----_____;.----______;------�--� , 8 to " 16

ff� / GH1

Fig. 6. Return loss vs. frequency curve for UWB Antenna_

8 10 �"""", ( GI!

11

Fig. 7. VSWR vs. frequency curve for UWB Antenna.

14 16

35

IV. CONCLUSION

Ultra wide band is rapidly advancing as a high data rate wireless communication technology. First the planar PCB antenna design to obtain wide band characteristic is introduced and described. Next the technique for obtaining ultra wide band is discussed. Based on the simulated results, the proposed antenna exhibits good UWB characteristics and operates from 3 .4 GHz to 1 0 .6 GHz, having fractional bandwidth of 1 02 . 85%. It complies with the VSWR range from 1 to 2 throughout the impedance bandwidth. The proposed antenna, with good UWB characteristics and geometrically small nature, is suitable for wireless communication like S-DMB, WIBRO, WLAN, CMMB and the entire UWB systems.

REFERENCES

[ I ] Federal Communications Commission, Washington, DC, "FCC report and order on ultra wideband technology", 2002.

[2] W_ Pam Siriwongpairat and KJ. Ray Liu, "Ultra-Wideband Communication Systems," John Wiley & Sons Publication, 2008.

[3] G.Z. Rafi and L. Shafai, "Wideband V -slotted diamond-shaped microstrip patch antenna," Electronics Letters, vol. 40, no. 1 9, pp. 1 1 66-1 1 67, 2004.

[4] Yashar Zehforoosh, Changiz Ghobadi and Javad Nourinia, "Antenna design for Ultra Wideband application using a new multilayer structure" .

[5 ] Progress In Electromagnetics Research Symposium 2007, Beijing, China, March 26-30, 2007 .

[6] K.N. Modha, B. Hayes-Gill, I . Harrison, "A Compact, Low Loss lee Cream Cone Ultra Wideband Antenna," The Institution of Engineering and Technology Seminar on Ultra Wideband Systems, Technologies and Applications, 2006, April 2006.

[6] 1. G. Proakis, digital communication, McGraw-Hili, New York, NY, USA, 1 989.

[7] C . E. Shannon, "A mathematical theory of communication," The BellsystemtechnicalJournal, vol. 27, PP. 379-423, 623-656, 1948.

[8] Kuo, 1. S . and K. L . Wong, "A compact microstrip antenna with meandering slots in the ground plane," Microwave and Opt. Technol. Lett . , Vol. 29, 95 -97, Apr. 20, 200 1 .

[9] M.A. Matin, "Stacked E-shaped patch antenna for lower band Ultrawideband (UWB) Applications," iET international Conference on Wireless, Mobile and Multimedia Networks, 2008, Jan 2008.