new multi-band microstrip antenna design for wireless

Naftali (Tuli) HeracoviciLincoln Laboratory - Group 61Massachusetts Institute of Technology244 Wood StreetLexington, MA 02420-9108 USATel: +1 (781) 981-0801Fax: +1 (928) 832-4025SkypeIAOL: tuliOlE-mail: [email protected]

Christos ChristodoulouDepartment of Electrical andComputer EngineeringUniversity of New MexicoAlbuquerque, NM 87131-1356 USATel: +1 (505) 277 6580Fax: +1 (505) 277 1439E-mail: [email protected]

New Multi-Band Microstrip Antenna Designfor Wireless Communications

Joseph Costan tine1, Karim Y. Kabalan 2 1 Al EI-Hajj, and Mohammad Rammal 3

'Electrical and Computer Engineering DepartmentUniversity of New MexicoAlbuquerque, NMV USA

2 Elcrcland Computer Engineering DepartmentAmerican University of Beirut

P0 Box 11-0236, Beirut, LebanonE-mail: [email protected]

3 Lebanese UniversityIUT, Saida, Lebanon

AbstractThis paper presents a new approach for the design of a multi-wideband microstrip-patch antenna. The radiating elements inthis antenna are composed of rectangular slots following a Chebyshev distribution of order 10 around a center rectangularslot, and an additional triangular slot. These slots are engraved in the rectangular and triangular patch, joined together in onestructure, and fed by one probe feed. A sample antenna was analyzed, simulated, fabricated, and tested. There was goodagreement between the computed and test results. The new antenna can be used for several applications, especially in theGSM domain, and for Wi-Fi, Bluetooth, and several other applications, as detailed in this paper.

Keywords: Microstrip antennas; multifrequency antennas; mobile antennas; WLAN; GSM; Bluetooth; wideband antennas

IEEE Antennas and Propagation Magazine, Vol. 49, No. 6, December 200718

Wireless Corner

181

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1. Introduction

S everal methods for obtaining multi-band and/or widebandantenna characteristics have been developed. In [1], a dual

wideband folded microstrip-patch antenna was introduced for pos-

sible wireless local-area network (WLAN) applications in the 3.5-

4 GHz frequency range. The proposed antenna operated in a wide

frequency band by utilizing a unique coupling mechanism between

the radiating elements and the ground plane. In [2], a novel recon-

figurable patch antenna with switchable slots (PASS) was pro-

posed to realize various functionalities, such as dual-frequency

operation, dual-band circularly polarized (CP) performance, and

polarization diversity with only one patch and a single feed. A

cavity-model-based simulation tool, along with a genetic optimiza-

tion algorithm, was presented in [3] for the design of dual-band

microstrip antennas. This used multiple slots in the patch, or multi-

ple shorting strips between the patch and the ground plane. The

optimization of the positions of the slots and shorting strips was

then performed via a genetic optimization algorithm to achieve

acceptable antenna operation over the desired frequency bands. A

similar approach was presented in [4], where a single low-profile

printed antenna, which provided dual-band operation by having

loading from two-step slots embedded close to the radiating edge.

In [4], it was also shown that the ratio of the two frequencies can

be well controlled by the aspect ratio of the step-loading dimen-sion.

A low-profile cylindrical monopole with a top-loaded mean-

der-line patch, for K-PCS operation, and a corner-truncated square-

ring microstrip-patch antenna with four slits for GPS operation,

were presented in [5]. In [6], an antenna was presented consisting

of two parts: a fundamental-mode truncated square patch antenna,

and a higher-order-mode annular-ring patch antenna. The truncated

square patch operated with right-hand circular polarization at

1575 MHz with and 8 MHz CP bandwidth, making the desigu suit-

able for GPS applications. Furthermore, more slots were embedded

into a ground plane to meander the current path of the annular-ring

patch at the TM mode, which considerably lowered the resonant

frequency, and effectively increased the impedance bandwidth. In

[7], a multi-band microstrip antenna operating at frequencies of

2.4 GHz and 5.2 GHz was presented. The dimensions of the single

elements of the operating frequencies were calculated using the

transmission-line model. Two elements of an inset-fed microstrip

antenna were used for each frequency band. In [8], microstrip-line-

fed, printed isosceles-triangular slot antennas, with a small rectan-

gular slot for broadband operation, were proposed and experimen-

tally investigated. Experimental results indicated that a 2:1 VSWRwas achieved over a bandwidth of 2.9 GHz, between 2.33 and

5.23 GHz. This was nearly 4.6 times that of a conventional micro-

strip-line-fed, printed isosceles-triangular slot.

This paper presents a multi-band antenna-design approach

based on inserting rectangular slots, following a Chebyshev distri-

bution, in addition to a triangular slot into the patch, which repre-

sents a combination of a rectangular and an isosceles-tri angular

patch. The part of the patch formed by the isosceles triangle has the

same area as the part formed by the rectangle. The triangular slot is

inserted into the isosceles-triangular part, and the rectangular slots

are inserted into the rectangular part of the patch. The whole sys-

tem is fed by a coaxial probe into the substrate, with an input

impedance of 50 Q. A sample antenna was analyzed, simulated,

fabricated, and tested. The agreement between the computed and

experimental results was very good.

182

The proposed antenna has many applications, and can be used

to cover GSM, GPS, Wi-Fi, WiMax, video wireless communica-

tion, and Bluetooth applications. The concept of inserting slot array

following a known antenna-array distribution has proven to give

remarkable functionality to an antenna. It causes it to radiate sig-

nificantly at different ranges of frequencies, using only one single

feed point.

2. Geometry and Formulationof the Problem

The proposed antenna geometry is based on joining a rectan-

gular patch and a triangular patch, in order to increase the radiation

area, as shown in Figure 1. The structure is fed by a 50 Q2 coaxial

probe. The radiation pattern of the proposed structure with this

feeding technique is determined by adding the fields radiated by

the rectangular patch to those radiated by the triangular patch. The

substrate used in the formulation process was of thickness

h =0.32 cm. The far electric fields of the rectangular patch were

given in [9] as

E e-kr Cos (koh_[_ cs

sin 7 sin 0sin qj )Cos ( AO sin 0cos q') cos~o

1 (I)sin~sinq'

-Ke jkorEý, r Cos (koh~e Cos 0)

sinf'AO sin 0 sin (p )Costj 4sinocos~p)Cos 0

sin Os

Figure 1. A rectangle added to an equilateral triangle patch,fed by a probe.



In Equations (1) and (2), Ic0 is the wavenumber, ,4 is the wave-

length, e, is the dielectric permittivity, and W and L are the widthand the length dimensions of the rectangular patch, respectively.Moreover, the far electric fields radiated from an equilateral trian-gle were given in [10] as

E0 = -joeqo (F, cos Ocos V+ FY cos Osin ýo), (3)

E( - i 0)7o( -Fsi n (p+ FYco s (P). (4)

In Equations (3) and (4), )7 = 120)r Q, and the terms F, and Fare the electric potential components. These latter were given indetail in [10], and will not be repeated here, for convenience. Byspecifying the lowest-order mode, TM010, for approximating therectangular dimensions to a length, L, of 4 cm and width, W, of3 cm, and for an equilateral triangle 3 cm on a side, for an operat-ing frequency, fo, of 3.24 GHz, Equations (1) and (2) become

Ke- JKotE9 = cos (0.322 cos90)

rsin (0.9448 sin 0 sin r)cos (0.7086 sin 9 cos (p) cos 9 , (5)

sin 9 sin V9

E Ke-.o cos(0.322cos9)r

sn(0.9448 sin 9 cos v)cos (0.707 sin 9 cos (p) cos 9. (6)sin 9

It is clear from Equation (5) that for V = 0' and (p =90', bothcomponents of the electric field vanish, due to the terms sin (p andcos ýo, respectively. Moreover, for (p = 90', Equation (6) becomes

Ep=Ke-.o co(.22oO sin (0.9448 sin 9) cos9. (7)

r co(.2cs) sin90

For an equilateral triangular patch, the 4p components of the elec-tric field are given by the product of the terms A and C, given by

study, shown in Figure 3, clearly indicated dual-band operation ofthe new structure, as was indicated earlier.

3. Antenna Structure and Results

The basic structure of the proposed antenna, shown in Fig-ure 4, consists of three layers. The lower layer, which constitutesthe ground plane, covers all the substrate and has a width of 6 cmand a length of 15 cm. The middle substrate, which is PolyflonNorclad, has a dielectric constant c, 2.55 and a height of

0

300

ISOEplu simulated for phi=90 degrees

Figure 2a. The simulated electric field, to be compared to Fig-ure 2b.

30 330

A:f 21(139.6258 + j39. 1789 sin 0) rsin (1.01 789 sinO)

I. 6498.455 -1534.986 sin 2 9

+2jcos (1.01789 sin90) -2j+ 39.1789sin9 (8)

C= -jo0 17o [(47rr)- 1 e0he-jKOr ] e -j39.1 789sing Costp 2 jwf Co I

(9)

C01I is a constant defined in [10]. The total electric field of the new

structure is obtained by adding the electric field radiated from therectangular patch, defined in Equation (7), to that of the triangularpatch, derived in Equations (8) and (9). A comparison between cal-culated and simulated results is shown in Figure 2.

In order to prove that joining a triangular and a rectangularpatch increases the radiation area and provides a multi-resonatingantenna, the S, parameter of a simple rectangular patch of dimen-sions similar to those of the structure of Figure 1 was compared tothe S, I parameter of the combined structure. The comparative


'I ~

60 \ - s - 3013

40 ~'30 - .~

go ~~~ 20 ~Q 720I

0 -- -- - - --

-2 0

120 S-~. , 240

15~11 I210

180

Ephi ".cubt~ed of the structure

Figure 2b. The calculated electric field, to be compared to Fig-ure 2a.

183

'0


0 antenna, and to monitor the effect of both the triangular and the

Chebyshev apertures, At first, the feeding point was chosen near

the edge of the rectangle on its left-hand side. Results showed the-5- non-functioning of the antenna under 2 GHz, and wideband opera-

-~ U tion at 2.8 GHz. This result was expected, since the feeding pointwas a bit far from the radiating elements represented by the

to -10- Chebyshev distributed rectangular slots, and also very far from the

I, triangular slot, where the multi-band operation is triggered. Sec-CL ond, the feeding point was moved close to the radiating elements,

7 is- in order to obtain optimum operation of the antenna. If the feedingpoint was placed just at the edge of the rectangular slots, where

radiation should be optimum, then the S, t parameter results

-20 -obtained showed a clear resonance at 1.6-1.7 GHz, close to the

Nbaja~Pc GSM 1.8 GHz operation; at 2.4 GHz, the Bluetooth operation; and

-25NNm~r wideband operation at 2.8 GHz for wireless video operation. More

12 1!5 2 2.5 3 35 results on this feeding point can be found in [ 13].

FrecercVin hz X1(?At this point, it became clear that moving the feed deeper into

Figure 3. The S, parameter of a simple rectaagular patch, the structure and putting it closer to the triangular slot made the

and the S, parameter of the structure shown in Figure 1. functioning of that triangular slot more effective, and gave the totalresponse. Figure 4 shows the final position of the feeding point,and the results obtained are shown in Figure 5. Figure 5 shows

clear GSM 900 MHz wideband operation, in addition to operationat 2.8 GHz and 3.5 GHz. It is also clear from Figure 5, and by

varying the geometry, that the resonant frequencies below 2 GRz

were severely affected by the presence of the tri angular slot and the

position of the feed, closer or further from the triangle. However,the rectangular Chebyshev slots were responsible for the wideband

operation at the frequencies above 2 GHz and, in particular, at

2.8 GHz. The resonant frequency at 3.5 GHz was also affected bythe presence of the feed near the triangular slot, where the S1

parameter suddenly decreased to under -10 dB. The input imped-

ance of the antenna is shown in Figure 6, where the solid linerepresents the real part of the impedance, and the dashed line

shows the imaginary part. The return to zero of the imaginary part

revealed the resonances of the antenna, and the clear functioning.

4. Experimental Results:Fabrication and Testing

Figure 4. The new antenna structure. The antenna was fabricated and tested in the facilities of thehigh-frequency institute of Munich University of Technology

0.32 cm. The upper layer, which is the patch, consists of a rectan- cgle with a width of 3 cmn and a length of 4 cm, joined with an isos-

celes triangle having the same area as the rectangular patch and a

base of 3cm. and a height h =8 cm. -6-

Inside the rectangular patch, ten rectangular slots, following a-1Chebyshev distribution around a center rectangular slot, were

inserted. According to Babinet's principle [I11], the pattern of the t

slot was identical in shape to that of a dipole, except that the E and -16

H fields were interchanged. Moreover, as was shown in [12], a

Chebyshev distribution applied to an antenna array decreases

sidelobes and increases directivity. Accordingly, a slot array fol- -2-

lowing the Chebyshev distribution inserted into a structure will

increase the beamwidth and increase resonances. Also, inside the -25

triangular patch, a triangular slot with a base of 1.5 cm and a height

of 1 .2124 cm was inserted. __________0________1___

0.6 1 1.5 2 25 3 3.6 4

A parametric study and an optimization were done, in order Freqcieny in G~zX1

to find the best feeding point of the structure. Several points were

tested in order to get an overview of the defined functioning of the Figure 5. The S, parameter of the new antenna structure.

184 IEEE Antennas and Propagation Magazine, Vol. 49, No. 6, December 2007184


'JOLURealpart(TUM) in Munich, Germany. The antenna was based on the sub-IrnadnaiyPart strate Polyflon Norclad, and was fabricated using the printed-

- -00r circuit technique. The testing took into consideration the S, I

parameter of the antenna, where a complete analogy was foundbetween simulation results and fabrication results. A picture of the

500 fabricated antenna and the testing process is given in Figure 7.

Figure 8 shows a comparison between the tested and the0 - simulated S, parameter of this antenna. The results obtained in

Figure 8 emphasized the correctness of the simulated results. Theyproved that the functioning envisioned was accurate, and demon-

em00 strated a great similarity between the simulated and the fabricatedresults.

Frequecy in G~n x 1(? 5. Antenna ApplicationsFigure 6. The antenna's input impedance.

Various applications can be the subject for this newlydesigned antenna, since it is a multi-functional and multi-resonantantenna, according to simulation and fabrication results. Eachresonant frequency can be the subject of various applications intoday's modem wireless communication world. The S, I parametergoing under -10 dB; in Figure 8 also indicated the presence of threeresonant frequencies. This new wideband operation of the antennashares the presence of resonances at the wireless CCTV applicationat 2.8 GHz, and two other completely new applications:

I1. 900 MHz. GSM, ISM, WLAN, RFID applications

2. 2.8 GHz: wireless CCTV and wireless video links,WLAN applications

3. 3.5 GHz: WLAN, WiMax, wireless WiMax,802.1 6a applications

As shown and discussed, the designed antenna has multiple bandsof operation and a wide range of applications. By a simple change

Figure 7. The fabricated antenna, and testing the S, parame- of feeding position, the functioning of the antenna varies com-ter. pletely, while maintaining certain constant applications.

Me-~jasured

0 Simulated

Id 6. Conclusion-5

A new multi-band antenna design has been presented. The-10 design consists of joining a rectangular and a triangular patch

together in one patch, and inserting several forms of slots. The new- -15idea behind this design also includes the insertion of rectangular

slots following a Chebyshev distribution around a central rectan--2 gular slot, in addition to a triangular slot inserted into the triangle,

I which has the same area as the rectangular patch. The concept of-25 inserting slot arrays following a known antenna-array distribution

has proven to give remarkable functionality to an antenna. It causes

-30 1it to be highly radiating in different frequency ranges, using only0 0.5 1 1.5 2 25 3 3.5 4 one single feed, represented by a 50 Q2 SMA connector, where the

Frequency in Gi x 0 position has been optimized.

Figure 8. A comparison between the simulated and measured The antenna has many applications, such as GSM, GPS, Wi-S1 parameter, with feeding at a point with coordinates Fi, WiMax, video wireless communication, and Bluetooth applica-(x= 2.1,y =-). tions, in one single instrument, using this type of antenna.

IEEE Antennas and Propagation Magazine, Vol. 49, No. 6, December 200715 185


7. Acknowledgment

The authors would like to acknowledge Prof. Peter Russer

from the High-Frequency Institute of Munich University of Tech-

nology (TUM) for providing the facilities to fabricate and test the

antenna.

12. S. Jazi, "A New Formulation for the Design of Chebyshev

Arrays," IEEE Transactions on Antennas and Propagation, AP-42,

3, March 1994, pp. 439-443.

13. J. Costantine, New Multi Wide Band Design for a Microstrip

Patch Antenna Masters thesis, American University of Beirut,

October 2006.

8. References

1. T. Sittironnarit and M. Ali, "Analysis and Design of a Dual-

Band Folded Microstrip, Patch Antenna for Handheld Device

Application," IEEE Southeast Conference Proceedings, 2002, pp.

255-258.

2. F. Yang and Y. Rahmat-Samii, "A Compact Dual Band Circu-

larly Polarized Antenna Design For Mars Rover Mission," IEEE

International Symposium on Antennas and Propagation Digest, 3,

June 22-27, 2003, pp. 858-861.

3. 0. Oziemn, M. Selma, M. 1. Aksun, and L. Alatan, "Design of

Dual-Frequency Probe Fed Microstrip Antennas with Genetic

Algorithm," IEEE Transactions on Antennas and Propagation,

AP-51, 8, August 2003, pp. 19 47 -1 95 4 .

4. M. Khairul, H. Ismail, and M. Esa, "Low Profile Printed

Antenna With A Pair Of Step Loading For Dual-Frequency Opera-

tion," Proceedings of the 2003 Asia Pacific Conference On

Applied Electromagnetics (APACE 2003), Shah Alamn, Malaysia,

2003.

5. H. Y. Kim, Y. A. Lee, C. H. Won, and H. M. Lee, "Design of a

Compact Dual-Band Microstrip Patch Antenna for GPS/K-PCS

Operation," IEEE International Symposium on Antennas and

Propagation Digest, 4, June 2004, pp. 3529-3532.

6. S. Y. Lin and K. C. Huang, "A Compact Microstrip Antenna for

GPS and DCS Application," IEEE Transactions on Antennas and

Propagation, AP-53, 3, March 2005, pp. 1227-1229.

7. A. Asrokin, M. K. A. Rahim, and M. Z. A. Abd Aziz, "Dual

Band Microstrip Antenna for Wireless LAN Application," Pro-

ceedings of the 2005 Asia Pacific Conference on Applied Electro-

magnetics, Johor Bahru, Johor, Malaysia, December, 2005, pp.

10698-10701.

8. W. S. Chen and F. M. Hsieh, "A Broadband Design for a

Printed Isosceles Triangular Slot Antenna for Wireless Communi-

cations," Microwave Journal, 48, 7, July 2005, pp. 98-112.

9. C. A. Balanis, Antenna Theory Analysis and Design, Second

Edition, New York, Wiley, 1997.

10. K. F. Lee, K. M. Luk, and J. S. Dahele, "Characteristics of the

Equilateral Triangular Patch Antenna," IEEE Transactions on

Antennas and Propagation, AP-36, 10, November 1988, pp. 15 10-

1518.

11. R. F. Harrngton, Time-Harmonic Electromagnetic Fields, New

York, IEEE Press, 2001.

Introducing the Authors

Joseph Costantine was born in Saida, Lebanon. He received

the BE degree in Electrical, Electronic, Computer and Communi-

cation Engineering from the second branch of the Faculty of Engi-

neering in the Lebanese University in 2004, and the ME in Com-

puter and Communication Engineering from the American Univer-

sity in Beirut in 2006. He started his PhD degree in Electrical and

Computer Engineering at the University of New Mexico in January

2007. He received the Abdul Hadi Debs award for academic

excellence from the American University in Beirut for the year

2007. He was chosen during his masters degree to spend a six-

month semester at the Munich University of Technology, as part of

the TEMPUS program. His research interests are reconfigurable

systems and antennas, antenna designs applied to wireless commu-

nications, electromagnetic fields, and communication systems.

Karim Y. Kabalan was born in Jbeil, Lebanon. He received

the BS degree in Physics from the Lebanese University in 1979,

and the MS and PhD degrees in Electrical and Computer Engi-

neering from Syracuse University in 1983 and 1985, respectively.

During the 1986 fall semester, he was a visiting Assistant Professor

of Electrical and Computer Engineering at Syracuse University.

Currently, he is a Professor of Electrical and Computer Engineer-

ing with the Electrical and Computer Engineering Department,

Faculty of Engineering and Architecture, American University of

Beirut. His research interests are numerical solution of electromag-

netic-field problems and software development.

All EI-Hajj was born in Aramnta, Lebanon, in 1959. He

received the Lisense degree in Physics from the Lebanese Univer-

sity, Lebanon in 1979; the degree of lngenieur from L'Ecole

Superieure d'Electricite, France, in 1981; and the Docteur

Ingenieur degree from the University of Rennes 1, France, in 1983.

From 1983 to 1987, he was with the Electrical Engineering

Department at the Lebanese University. In 1987, he joined the

American University of Beirut, where he is currently Professor of

Electrical and Computer Engineering. His research interests are

numerical solution of electromagnetic-field problems and engi-

neering education.

Mohamed Rammal was born in Lebaonon. He received his

BE in Engineering from the Lebanese University in 1988, his DEA

from the University de Limoges in 1989, and his PhD from the

same university in 1993. Currently, he is an Associate Professor at

the Lebanese University, and the Director of the Radio Communi-

cation Lab. His areas of interest are numerical solutions of EM

problems, antenna design, and numerical filters.'1



new multi-band microstrip antenna design for wireless

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