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Hindawi Publishing Corporation International Journal of Antennas and Propagation Volume 2013, Article ID 365719, 7 pages http://dx.doi.org/10.1155/2013/365719 Research Article Multiband MIMO Antenna System with Parasitic Elements for WLAN and WiMAX Application Reza Karimian and Hamed Tadayon Antenna and Microwave Research Laboratory, EE Department, Iran University of Science and Technology, 1684613114 Tehran, Iran Correspondence should be addressed to Reza Karimian; [email protected] Received 10 July 2013; Revised 5 November 2013; Accepted 8 November 2013 Academic Editor: Ahmad Safaai-Jazi Copyright © 2013 R. Karimian and H. Tadayon. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A new microstrip slot antenna with parasitic elements has been presented in this paper. e proposed antenna is composed of a microstrip feed line, a ground plane on which some simple slots are etched, and parasitic elements. Simulation results show that the antenna structure allows for the independent adjustment of each frequency. A two-element array configuration of this antenna for MIMO application is investigated as well. For comparison between simulation and measurement result both single and array configurations have been fabricated. e measurement result exhibits good radiation performance in terms of return loss, low mutual coupling, and compactness. 1. Introduction Recent researches show that MIMO system can provide substantial improvement in system capacity with the tradi- tional SISO communication systems [1]. e recent increase in demand for high quality wireless communications has induced the development of various multiantennas systems for WLAN and WiMAX applications such as diversity and MIMO systems. Because of the advantages of low manufac- turing cost, light weight, easy integration, and easy fabrica- tion, the printed antenna becomes a good candidate for these applications. In order to meet the WLAN and WiMAX standards simu- ltaneously, multiband antennas are required. Many related researches have been done for such demands. Slot antennas are oſten adopted to realize multiband operation owing to their easy integrating with ground plane, such as inverted U- shaped slot [2] and triband slot antenna with the pair of T- shaped strips [3]. Patch antennas for multiband operations were also presented [48]. Coplanar waveguide antennas (CPW), such as dual-band rhombus slot [9], monopole antenna employing T-shaped quasi-self-complimentary res- onators [10], parasitically loaded CPW-fed [11], and planar monopole [12], are also applied to realize multiband oper- ation due to their low cost and omni-directional radiation pattern. Various printed antennas suitable for MIMO applications have been proposed as well [1316]. e design of a triband E- shaped monopole antenna loaded with narrow slots is given in [13]. A four-element L-shaped slot antenna with L-shaped slit has been presented in [14]. Also a two-element MIMO antenna for wireless applications is presented in [16]. In this paper, a new design of planar antenna with para- sitic strip suitable for MIMO application is presented. Com- pared to the antennas in [212], the proposed antenna in this paper not only achieves triple bands simultaneously but also has a rather simple structure that is easy to fabricate. Mean- while, the proposed antenna structure also allows for the independent adjustment or tuning of each frequency of interest within certain limits, which is important aspect for manufacturing. Also in comparison with [1315] the pro- posed array offers an enhanced performance in terms of ope- ration frequency bands with better isolation in addition to the advantage of smaller size. Details of the proposed design are described. Simulation and measurement result for both single and array antenna is presented. e measured results show good agreement with the simulated ones. 2. Antenna Geometry and Design Procedure Figure 1 shows the geometry with design parameters of the proposed multiband antenna which is printed on a low
8

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May 28, 2018

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Page 1: Research Article Multiband MIMO Antenna System …downloads.hindawi.com/journals/ijap/2013/365719.pdfResearch Article Multiband MIMO Antenna System with Parasitic Elements for WLAN

Hindawi Publishing CorporationInternational Journal of Antennas and PropagationVolume 2013 Article ID 365719 7 pageshttpdxdoiorg1011552013365719

Research ArticleMultiband MIMO Antenna System with Parasitic Elements forWLAN and WiMAX Application

Reza Karimian and Hamed Tadayon

Antenna and Microwave Research Laboratory EE Department Iran University of Science and Technology 1684613114 Tehran Iran

Correspondence should be addressed to Reza Karimian rezabahnemirigmailcom

Received 10 July 2013 Revised 5 November 2013 Accepted 8 November 2013

Academic Editor Ahmad Safaai-Jazi

Copyright copy 2013 R Karimian and H TadayonThis is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in anymedium provided the originalwork is properly cited

A new microstrip slot antenna with parasitic elements has been presented in this paper The proposed antenna is composed of amicrostrip feed line a ground plane on which some simple slots are etched and parasitic elements Simulation results show thatthe antenna structure allows for the independent adjustment of each frequency A two-element array configuration of this antennafor MIMO application is investigated as well For comparison between simulation and measurement result both single and arrayconfigurations have been fabricated The measurement result exhibits good radiation performance in terms of return loss lowmutual coupling and compactness

1 Introduction

Recent researches show that MIMO system can providesubstantial improvement in system capacity with the tradi-tional SISO communication systems [1] The recent increasein demand for high quality wireless communications hasinduced the development of various multiantennas systemsfor WLAN and WiMAX applications such as diversity andMIMO systems Because of the advantages of low manufac-turing cost light weight easy integration and easy fabrica-tion the printed antenna becomes a good candidate for theseapplications

In order tomeet theWLANandWiMAX standards simu-ltaneously multiband antennas are required Many relatedresearches have been done for such demands Slot antennasare often adopted to realize multiband operation owing totheir easy integrating with ground plane such as inverted U-shaped slot [2] and triband slot antenna with the pair of T-shaped strips [3] Patch antennas for multiband operationswere also presented [4ndash8] Coplanar waveguide antennas(CPW) such as dual-band rhombus slot [9] monopoleantenna employing T-shaped quasi-self-complimentary res-onators [10] parasitically loaded CPW-fed [11] and planarmonopole [12] are also applied to realize multiband oper-ation due to their low cost and omni-directional radiationpattern

Various printed antennas suitable forMIMO applicationshave been proposed as well [13ndash16]The design of a triband E-shaped monopole antenna loaded with narrow slots is givenin [13] A four-element L-shaped slot antenna with L-shapedslit has been presented in [14] Also a two-element MIMOantenna for wireless applications is presented in [16]

In this paper a new design of planar antenna with para-sitic strip suitable for MIMO application is presented Com-pared to the antennas in [2ndash12] the proposed antenna in thispaper not only achieves triple bands simultaneously but alsohas a rather simple structure that is easy to fabricate Mean-while the proposed antenna structure also allows for theindependent adjustment or tuning of each frequency ofinterest within certain limits which is important aspect formanufacturing Also in comparison with [13ndash15] the pro-posed array offers an enhanced performance in terms of ope-ration frequency bandswith better isolation in addition to theadvantage of smaller size Details of the proposed design aredescribed Simulation andmeasurement result for both singleand array antenna is presented The measured results showgood agreement with the simulated ones

2 Antenna Geometry and Design Procedure

Figure 1 shows the geometry with design parameters of theproposed multiband antenna which is printed on a low

2 International Journal of Antennas and Propagation

a

Ls

Ws

(a)

X

Y

ZWp

Wf

Lf

Lp

(b)

Figure 1 Configuration of an antenna element (a) front view and (b) back view

cost FR4 substrate with dielectric 120576119903= 44 loss tangent

tan 120575 = 002 and thickness 16mm The overall dimen-sion of the antenna is 28 times 28mm2 Figure 2 exhibits thedesign evolution of the proposed multiband antenna onsimulated frequency response of return loss It begins witha conventional slot antenna 25(a) times 25(a)mm2 (denoted asCase I) which is about 1205822 = 62mm with respect to thefirst operation band Due to higher resonant mode (secondresonant frequency in this case) in Case I in addition ofdesired frequency at 24 GHz there is another resonantfrequency at the frequency of 43 GHz cong 085120582 As it has beendiscussed in [14] at the second resonance the pattern startsto undulateTherefore the second resonant frequency cannotbe used for omni-directional goals

The second resonant frequency at 35 GHz can beachieved with introducing a pair of symmetrical horizontalstrips at the middle of wide slot The strips generate currentflow path at the second resonant frequency which can beassumed as [17]

119891 =

119888

4119871119904sdot radic120576

120576 =

120576119903+ 1

2

(1)

where 119871119904is the length of horizontal strip 120576 is the effective

dielectric constant and 119888 is the speed of light in free spaceCase II in Figure 2 represents that the second resonant fre-quency at 35 GHz is achieved with little impact on the firstdesigned frequency Two-strip patch as parasitic element isetched on the bottom portion of FR4 substrate in order toachieve third resonant frequency at 58GHz Case III in Fig-ure 2 depicts that the third resonant has been achieved whileother frequencies are almost constant Note that at all threecases the antennas are fed through a 50 ohmmicrostrip patchat the bottom side of antenna

Figure 3 represents surface current distribution at24GHz and 43GHz The difference between 05120582 and

085120582 can be clearly seen from the figure Surface currentdistribution at 24GHz has two maximum and a minimumrepresenting half-wave slot antenna (Figures 3(a) and3(b)) representing 085120582 (almost two maximum and twominimum) Note that this figure is related to Case II

In Figure 4(a) the current flows along the edge of thestrips upward to the upper side of the rectangular slotThere-fore the embedded strips in the slotmainly generate themid-dle frequency Similarly in Figure 4(b) the current centralizesin the region nearby the parasitic strip that generates thehighest frequency

A comprehensive parametric study was carried out to getinsight on the effect of various antenna parameters that enableoptimization of the antennarsquos performance

The return loss characteristics of different 119871119904are demon-

strated in Figure 5 As the length of horizontal strip (119871119904)

increases from 6mm to 9mm the upper edge frequency ofthe antenna shifts down while leaving the lower and upperedge frequency almost unchanged The parasitic elementshave a strong effect on the upper frequency characteristic ofthe antenna Figure 6 displays that the upper resonance fre-quency is mainly determined by the dimension of 119871

119901 while

the other resonant frequencies are almost unchanged Thelonger the 119871

119901is the lower the upper resonance frequencywill

beBy fixing the optimum parameters of the proposed

antenna good impedance matching through the operationbands for WLAN andWiMAX applications can be achievedThe parameters are set as follows 119886 = 25mm 119871

119904= 86mm

119882119904= 04mm 119871

119901= 13mm119882

119901= 03mm 119871

119891= 115mm

and119882119891= 3mm

The comparison between the simulated and measuredreflection coefficient characteristic of the proposed antennaobtained by using CST2010 and the Agilent E8361C vectornetwork analyzer is shown in Figure 7 Apparently the mea-sured return losses below minus10 dB bandwidth range between

International Journal of Antennas and Propagation 3

0 1 2 3 4 5 6minus50

minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

WO patch and parasitic elementsWith patch and WO parasitic elementsProposed antenna

Case I Case II

Case III(front view)

Case III(back view)

Figure 2 Design procedure of the proposed antenna Case I single band Case II dual-band and Case III triband operation

254

190

127

634

0

(Am

)

(a)

254

190

127

634

0

(Am

)

(b)

Figure 3 Surface current distribution (a) 24GHz and (b) 43 GHz

254

190

127

634

0

(Am

)

(a)

254

190

127

634

0

(Am

)

(b)

Figure 4 Surface current distribution (a) 35 GHz and (b) 58GHz

4 International Journal of Antennas and Propagation

1 15 2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

Ls = 6mmLs = 7mm

Ls = 8mmLs = 9mm

Figure 5 Simulated return loss with different 119871119904

1 15 2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

Lp = 12mmLp = 133mm

Lp = 146mmLp = 16mm

Figure 6 Simulated return loss with different 119871119901

2 25 3 35 4 45 5 55 6minus30

minus25

minus20

minus15

minus10

minus5

0

Frequency (GHz)

SimulationMeasurement

Refle

ctio

n co

effici

ent (

dB)

Figure 7 Simulated and measured reflection coefficient characteristic of proposed antenna element

23ndash252GHz 34ndash362GHz and 56ndash595GHz which showapproximate agreementwith the simulated result Some slightdiscrepancies between them may be attributed to measure-ment errors inaccuracies in the fabrication process and theeffect of the SMA connector

3 Integration of Two MIMO Element

The antenna element presented in Section 2 shows that itis suitable for WLAN and WiMAX application and can bearrayed for use in MIMO application

The primary aim of MIMO antenna design is to reducecorrelation between received signals A significant parameterfor the correlation is the mutual coupling One of the most

critical parameters affecting mutual coupling and correlationis due to common ground plane sharing the surface currentwhich can be reduced by etching slot into the ground planeamong the slot antennaThe second parameter that affects thecorrelation between the received signals is the polarization ofthe antennas polarization diversity

This paper based on orthogonal polarization diversityand separated common ground plane introduces a new lowprofile two-element MIMO antenna with good isolation andsimple to fabricate

31 Impedance Performance Figure 8 depicts a photographof the fabricated proposed array antenna The antennaelements are orthogonal to each other in order to make

International Journal of Antennas and Propagation 5

(a)

(b)

Figure 8 Prototype of fabricated MIMO antenna (a) front view and (b) bottom view

2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S11 simulationS21 simulationS22 simulation

S11 measurementS21 measurementS22 measurement

Scat

terin

g pa

ram

eter

s (dB

)

Figure 9 Comparison between simulated and measured scattering parameters for the proposed MIMO array

polarization diversity A rectangular slot with the widthof less than 01120582 (120582 is the wavelength of lowest resonantfrequency) has been etched on ground plane of the antennaarray to separate the common ground plane The simulatedand measured 119878-parameters are in a good agreement asobserved in Figure 9 An E8361C vector network analyzerwas used to measure the scattering parameters characteristicof the fabricated MIMO array in an anechoic chamber Inthis measurement one port is excited and the other port wasterminated by a 50Ω matching load Mutual coupling betterthan minus22 dB has been achieved for the antenna spacing lessthan 01120582 (10mm) In comparison with [13] this antennaarray configuration improved isolation more than 8 dB withthe advantage of compact size

32 Radiation Performance Measured radiation pattern forthree principal planes and for three resonant frequencieswhen one element was excited and the other antenna elementwas matched by a standard 50Ω matching load has beendemonstrated in Figure 10 The orientation of the antennawith respect to coordinate system is clarified in Figure 1 Onecan see that nearly omnidirectional pattern has been achievedat all three frequencies (Table 1) There are no deep nulls inany direction This is an important factor when antenna hasbeen used for MIMO application [14]

Table 1 Simulated peak gain and radiation efficiency results

Frequency (GHz) 24 35 52Gain (dBi) 198 31 16Efficiency () 75 87 64

33 Diversity Performance Envelope correlation coefficientis an important parameter to measure the diversity gain ofa MIMO system Generally low envelope correlation alwaysleads to high diversity gain [14] For a two-antenna system asimple formula can be used to calculate envelope correlationcoefficient [18] as follows

120588 =

1003816100381610038161003816Slowast11S12+ Slowast21S22

1003816100381610038161003816

2

(1 minus1003816100381610038161003816S11

1003816100381610038161003816

2

minus1003816100381610038161003816S21

1003816100381610038161003816

2

) (1 minus1003816100381610038161003816S22

1003816100381610038161003816

2

minus1003816100381610038161003816S12

1003816100381610038161003816

2

)

(2)

The calculated result of the proposed antenna is exhibitedin Figure 11 It shows that the desired operation band of theproposed antenna has an envelope correlation coefficient lessthan 004 which is practically acceptable

Low mutual coupling good impedance matching lowenvelope correlation and stable radiation patterns in threeprincipal planes confirm that the proposed MIMO array is

6 International Journal of Antennas and Propagation

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(a)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(b)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(c)

Figure 10 Measured radiation pattern for three principle planes (a) 24GHz (b) 35 GHz and (c) 58 GHz

a good candidate for use in WLAN and WiMAX MIMOsystems

4 Conclusion

A compact planar multiband antenna is developed in thiswork The proposed antenna utilized a pair of horizontalstrips and a pair of vertical strips patch as parasitic element

to achieve second and third resonant frequency whilethe wideband slot provides the first resonant frequency at24GHz The current distributions excited at resonant fre-quency reveals that the proposed antenna operates at half-wave guided length mode Parametric study shows thatthe proposed antenna structure allows for the independentadjustment or tuning of each frequency of interest withincertain limits A particular combination of two such elements

International Journal of Antennas and Propagation 7

0 1 2 3 4 5 60

005

01

015

02

Frequency (GHz)

Enve

lope

coeffi

cien

t

Figure 11 Measured envelope correlation of the proposed multi-band antenna

has been used for MIMO application The measured returnloss complies with the frequency of WLAN and WiMAXapplication The MIMO antenna array provides better thanminus22 dB mutual coupling envelope correlation of lower than001 and stable omnidirectional patterns at all three frequen-cies

References

[1] Y Ding Z Du K Gong and Z Feng ldquoA novel dual-bandprinted diversity antenna for mobile terminalsrdquo IEEE Transac-tions onAntennas and Propagation vol 55 no 7 pp 2088ndash20962007

[2] L Xiong and P Gao ldquoA compact triple-band wide-slot antennafor WLANWiMAX applicationsrdquo Journal of ElectromagneticWave and Application vol 26 no 7 pp 895ndash903 2012

[3] X Q Zhang Y C Jiao and W H Wang ldquoCompact wide tri-band slot antenna forWLANWiMAX applicationsrdquoElectronicsLetters vol 48 no 2 pp 64ndash65 2012

[4] K He R-X Wang Y-F Wang and B-H Sun ldquoCompacttri-band claw-shaped monopole antenna for WLANWiMAXapplicationsrdquo Journal of Electromagnetic Waves and Applica-tions vol 25 no 5-6 pp 869ndash877 2011

[5] YHan Y-Z Yin Y-QWei Y Zhao B Li andX-N Li ldquoAnoveltriple-band monopole antenna with double coupled C-shapedstrips for WLANWiMAX applicationsrdquo Journal of Electro-magneticWaves and Applications vol 25 no 8-9 pp 1308ndash13162011

[6] W-C Liu M Ghavami and W-C Chung ldquoTriple-frequencymeandered monopole antenna with shorted parasitic strips forwireless applicationrdquo IET Microwaves Antennas and Propaga-tion vol 3 no 7 pp 1110ndash1117 2009

[7] L Peng C-L Ruan and X-H Wu ldquoDesign and operationof dualtriple-band asymmetric M-shaped microstrip patchantennasrdquo IEEE Antennas andWireless Propagation Letters vol9 pp 1069ndash1072 2010

[8] J Pei A-G Wang S Gao and W Leng ldquoMiniaturized triple-band antenna with a defected ground plane for WLANWiMAX applicationsrdquo IEEE Antennas andWireless PropagationLetters vol 10 pp 298ndash301 2011

[9] C-C Lin E-Z Yu and C-Y Huang ldquoDual-band rhombus slotantenna fed by CPW for WLAN applicationsrdquo IEEE Antennasand Wireless Propagation Letters vol 11 pp 362ndash364 2012

[10] W Hu Y-Z Yin S-T Fan X Yang Y Zhao and J-H YangldquoCompact octagonal monopole antenna employing T-shapedquasi-self-complimentary resonators for tri-band operationrdquo

Journal of Electromagnetic Waves and Applications vol 25 no14-15 pp 1953ndash1962 2011

[11] W-C Liu C-M Wu and Y-J Tseng ldquoParasitically loadedCPW-fed monopole antenna for broadband operationrdquo IEEETransactions on Antennas and Propagation vol 59 no 6 pp2415ndash2419 2011

[12] H-W Liu C-H Ku and C-F Yang ldquoNovel CPW-fed planarmonopole antenna for WiMAXWLAN applicationsrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 240ndash2432010

[13] S M A Nezhad and H R Hassani ldquoA novel triband E-shapedprintedmonopole antenna forMIMOapplicationrdquo IEEEAnten-nas and Wireless Propagation Letters vol 9 pp 576ndash579 2010

[14] R Karimian M Soleimani and S M Hashemi ldquoTri-band fourelementsMIMOantenna system forWLANandWiMAXappli-cationrdquo Journal of Electromagnetic Waves and Applications vol26 no 17-18 pp 2348ndash2357 2012

[15] R Karimian H Oraizi S Fakhte and M Farahani ldquoNovelF-shaped quad-band printed slot antenna for WLAN andWiMAX MIMO systemsrdquo IEEE Antennas and Wireless Propa-gation Letters vol 12 pp 405ndash408 2013

[16] M S Sharawi A B Numan andD N Aloi ldquoIsolation improve-ment in a dual-band dual-element mimo antenna system usingcapacitively loaded loops loaded loopsrdquo Progress in Electromag-netic Research vol 134 pp 247ndash266 2013

[17] C M Li K Wang and C K Chen ldquoSmall tri-band monopoleantenna for WLANWiMAX applicationsrdquo Journal of Electro-magnetic Waves and Applications vol 25 pp 1297ndash1307 2011

[18] J Thaysen and K B Jakobsen ldquoEnvelope correlation in (N N)mimo antenna array from scattering parametersrdquo Microwaveand Optical Technology Letters vol 48 no 5 pp 832ndash834 2006

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Page 2: Research Article Multiband MIMO Antenna System …downloads.hindawi.com/journals/ijap/2013/365719.pdfResearch Article Multiband MIMO Antenna System with Parasitic Elements for WLAN

2 International Journal of Antennas and Propagation

a

Ls

Ws

(a)

X

Y

ZWp

Wf

Lf

Lp

(b)

Figure 1 Configuration of an antenna element (a) front view and (b) back view

cost FR4 substrate with dielectric 120576119903= 44 loss tangent

tan 120575 = 002 and thickness 16mm The overall dimen-sion of the antenna is 28 times 28mm2 Figure 2 exhibits thedesign evolution of the proposed multiband antenna onsimulated frequency response of return loss It begins witha conventional slot antenna 25(a) times 25(a)mm2 (denoted asCase I) which is about 1205822 = 62mm with respect to thefirst operation band Due to higher resonant mode (secondresonant frequency in this case) in Case I in addition ofdesired frequency at 24 GHz there is another resonantfrequency at the frequency of 43 GHz cong 085120582 As it has beendiscussed in [14] at the second resonance the pattern startsto undulateTherefore the second resonant frequency cannotbe used for omni-directional goals

The second resonant frequency at 35 GHz can beachieved with introducing a pair of symmetrical horizontalstrips at the middle of wide slot The strips generate currentflow path at the second resonant frequency which can beassumed as [17]

119891 =

119888

4119871119904sdot radic120576

120576 =

120576119903+ 1

2

(1)

where 119871119904is the length of horizontal strip 120576 is the effective

dielectric constant and 119888 is the speed of light in free spaceCase II in Figure 2 represents that the second resonant fre-quency at 35 GHz is achieved with little impact on the firstdesigned frequency Two-strip patch as parasitic element isetched on the bottom portion of FR4 substrate in order toachieve third resonant frequency at 58GHz Case III in Fig-ure 2 depicts that the third resonant has been achieved whileother frequencies are almost constant Note that at all threecases the antennas are fed through a 50 ohmmicrostrip patchat the bottom side of antenna

Figure 3 represents surface current distribution at24GHz and 43GHz The difference between 05120582 and

085120582 can be clearly seen from the figure Surface currentdistribution at 24GHz has two maximum and a minimumrepresenting half-wave slot antenna (Figures 3(a) and3(b)) representing 085120582 (almost two maximum and twominimum) Note that this figure is related to Case II

In Figure 4(a) the current flows along the edge of thestrips upward to the upper side of the rectangular slotThere-fore the embedded strips in the slotmainly generate themid-dle frequency Similarly in Figure 4(b) the current centralizesin the region nearby the parasitic strip that generates thehighest frequency

A comprehensive parametric study was carried out to getinsight on the effect of various antenna parameters that enableoptimization of the antennarsquos performance

The return loss characteristics of different 119871119904are demon-

strated in Figure 5 As the length of horizontal strip (119871119904)

increases from 6mm to 9mm the upper edge frequency ofthe antenna shifts down while leaving the lower and upperedge frequency almost unchanged The parasitic elementshave a strong effect on the upper frequency characteristic ofthe antenna Figure 6 displays that the upper resonance fre-quency is mainly determined by the dimension of 119871

119901 while

the other resonant frequencies are almost unchanged Thelonger the 119871

119901is the lower the upper resonance frequencywill

beBy fixing the optimum parameters of the proposed

antenna good impedance matching through the operationbands for WLAN andWiMAX applications can be achievedThe parameters are set as follows 119886 = 25mm 119871

119904= 86mm

119882119904= 04mm 119871

119901= 13mm119882

119901= 03mm 119871

119891= 115mm

and119882119891= 3mm

The comparison between the simulated and measuredreflection coefficient characteristic of the proposed antennaobtained by using CST2010 and the Agilent E8361C vectornetwork analyzer is shown in Figure 7 Apparently the mea-sured return losses below minus10 dB bandwidth range between

International Journal of Antennas and Propagation 3

0 1 2 3 4 5 6minus50

minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

WO patch and parasitic elementsWith patch and WO parasitic elementsProposed antenna

Case I Case II

Case III(front view)

Case III(back view)

Figure 2 Design procedure of the proposed antenna Case I single band Case II dual-band and Case III triband operation

254

190

127

634

0

(Am

)

(a)

254

190

127

634

0

(Am

)

(b)

Figure 3 Surface current distribution (a) 24GHz and (b) 43 GHz

254

190

127

634

0

(Am

)

(a)

254

190

127

634

0

(Am

)

(b)

Figure 4 Surface current distribution (a) 35 GHz and (b) 58GHz

4 International Journal of Antennas and Propagation

1 15 2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

Ls = 6mmLs = 7mm

Ls = 8mmLs = 9mm

Figure 5 Simulated return loss with different 119871119904

1 15 2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

Lp = 12mmLp = 133mm

Lp = 146mmLp = 16mm

Figure 6 Simulated return loss with different 119871119901

2 25 3 35 4 45 5 55 6minus30

minus25

minus20

minus15

minus10

minus5

0

Frequency (GHz)

SimulationMeasurement

Refle

ctio

n co

effici

ent (

dB)

Figure 7 Simulated and measured reflection coefficient characteristic of proposed antenna element

23ndash252GHz 34ndash362GHz and 56ndash595GHz which showapproximate agreementwith the simulated result Some slightdiscrepancies between them may be attributed to measure-ment errors inaccuracies in the fabrication process and theeffect of the SMA connector

3 Integration of Two MIMO Element

The antenna element presented in Section 2 shows that itis suitable for WLAN and WiMAX application and can bearrayed for use in MIMO application

The primary aim of MIMO antenna design is to reducecorrelation between received signals A significant parameterfor the correlation is the mutual coupling One of the most

critical parameters affecting mutual coupling and correlationis due to common ground plane sharing the surface currentwhich can be reduced by etching slot into the ground planeamong the slot antennaThe second parameter that affects thecorrelation between the received signals is the polarization ofthe antennas polarization diversity

This paper based on orthogonal polarization diversityand separated common ground plane introduces a new lowprofile two-element MIMO antenna with good isolation andsimple to fabricate

31 Impedance Performance Figure 8 depicts a photographof the fabricated proposed array antenna The antennaelements are orthogonal to each other in order to make

International Journal of Antennas and Propagation 5

(a)

(b)

Figure 8 Prototype of fabricated MIMO antenna (a) front view and (b) bottom view

2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S11 simulationS21 simulationS22 simulation

S11 measurementS21 measurementS22 measurement

Scat

terin

g pa

ram

eter

s (dB

)

Figure 9 Comparison between simulated and measured scattering parameters for the proposed MIMO array

polarization diversity A rectangular slot with the widthof less than 01120582 (120582 is the wavelength of lowest resonantfrequency) has been etched on ground plane of the antennaarray to separate the common ground plane The simulatedand measured 119878-parameters are in a good agreement asobserved in Figure 9 An E8361C vector network analyzerwas used to measure the scattering parameters characteristicof the fabricated MIMO array in an anechoic chamber Inthis measurement one port is excited and the other port wasterminated by a 50Ω matching load Mutual coupling betterthan minus22 dB has been achieved for the antenna spacing lessthan 01120582 (10mm) In comparison with [13] this antennaarray configuration improved isolation more than 8 dB withthe advantage of compact size

32 Radiation Performance Measured radiation pattern forthree principal planes and for three resonant frequencieswhen one element was excited and the other antenna elementwas matched by a standard 50Ω matching load has beendemonstrated in Figure 10 The orientation of the antennawith respect to coordinate system is clarified in Figure 1 Onecan see that nearly omnidirectional pattern has been achievedat all three frequencies (Table 1) There are no deep nulls inany direction This is an important factor when antenna hasbeen used for MIMO application [14]

Table 1 Simulated peak gain and radiation efficiency results

Frequency (GHz) 24 35 52Gain (dBi) 198 31 16Efficiency () 75 87 64

33 Diversity Performance Envelope correlation coefficientis an important parameter to measure the diversity gain ofa MIMO system Generally low envelope correlation alwaysleads to high diversity gain [14] For a two-antenna system asimple formula can be used to calculate envelope correlationcoefficient [18] as follows

120588 =

1003816100381610038161003816Slowast11S12+ Slowast21S22

1003816100381610038161003816

2

(1 minus1003816100381610038161003816S11

1003816100381610038161003816

2

minus1003816100381610038161003816S21

1003816100381610038161003816

2

) (1 minus1003816100381610038161003816S22

1003816100381610038161003816

2

minus1003816100381610038161003816S12

1003816100381610038161003816

2

)

(2)

The calculated result of the proposed antenna is exhibitedin Figure 11 It shows that the desired operation band of theproposed antenna has an envelope correlation coefficient lessthan 004 which is practically acceptable

Low mutual coupling good impedance matching lowenvelope correlation and stable radiation patterns in threeprincipal planes confirm that the proposed MIMO array is

6 International Journal of Antennas and Propagation

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(a)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(b)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(c)

Figure 10 Measured radiation pattern for three principle planes (a) 24GHz (b) 35 GHz and (c) 58 GHz

a good candidate for use in WLAN and WiMAX MIMOsystems

4 Conclusion

A compact planar multiband antenna is developed in thiswork The proposed antenna utilized a pair of horizontalstrips and a pair of vertical strips patch as parasitic element

to achieve second and third resonant frequency whilethe wideband slot provides the first resonant frequency at24GHz The current distributions excited at resonant fre-quency reveals that the proposed antenna operates at half-wave guided length mode Parametric study shows thatthe proposed antenna structure allows for the independentadjustment or tuning of each frequency of interest withincertain limits A particular combination of two such elements

International Journal of Antennas and Propagation 7

0 1 2 3 4 5 60

005

01

015

02

Frequency (GHz)

Enve

lope

coeffi

cien

t

Figure 11 Measured envelope correlation of the proposed multi-band antenna

has been used for MIMO application The measured returnloss complies with the frequency of WLAN and WiMAXapplication The MIMO antenna array provides better thanminus22 dB mutual coupling envelope correlation of lower than001 and stable omnidirectional patterns at all three frequen-cies

References

[1] Y Ding Z Du K Gong and Z Feng ldquoA novel dual-bandprinted diversity antenna for mobile terminalsrdquo IEEE Transac-tions onAntennas and Propagation vol 55 no 7 pp 2088ndash20962007

[2] L Xiong and P Gao ldquoA compact triple-band wide-slot antennafor WLANWiMAX applicationsrdquo Journal of ElectromagneticWave and Application vol 26 no 7 pp 895ndash903 2012

[3] X Q Zhang Y C Jiao and W H Wang ldquoCompact wide tri-band slot antenna forWLANWiMAX applicationsrdquoElectronicsLetters vol 48 no 2 pp 64ndash65 2012

[4] K He R-X Wang Y-F Wang and B-H Sun ldquoCompacttri-band claw-shaped monopole antenna for WLANWiMAXapplicationsrdquo Journal of Electromagnetic Waves and Applica-tions vol 25 no 5-6 pp 869ndash877 2011

[5] YHan Y-Z Yin Y-QWei Y Zhao B Li andX-N Li ldquoAnoveltriple-band monopole antenna with double coupled C-shapedstrips for WLANWiMAX applicationsrdquo Journal of Electro-magneticWaves and Applications vol 25 no 8-9 pp 1308ndash13162011

[6] W-C Liu M Ghavami and W-C Chung ldquoTriple-frequencymeandered monopole antenna with shorted parasitic strips forwireless applicationrdquo IET Microwaves Antennas and Propaga-tion vol 3 no 7 pp 1110ndash1117 2009

[7] L Peng C-L Ruan and X-H Wu ldquoDesign and operationof dualtriple-band asymmetric M-shaped microstrip patchantennasrdquo IEEE Antennas andWireless Propagation Letters vol9 pp 1069ndash1072 2010

[8] J Pei A-G Wang S Gao and W Leng ldquoMiniaturized triple-band antenna with a defected ground plane for WLANWiMAX applicationsrdquo IEEE Antennas andWireless PropagationLetters vol 10 pp 298ndash301 2011

[9] C-C Lin E-Z Yu and C-Y Huang ldquoDual-band rhombus slotantenna fed by CPW for WLAN applicationsrdquo IEEE Antennasand Wireless Propagation Letters vol 11 pp 362ndash364 2012

[10] W Hu Y-Z Yin S-T Fan X Yang Y Zhao and J-H YangldquoCompact octagonal monopole antenna employing T-shapedquasi-self-complimentary resonators for tri-band operationrdquo

Journal of Electromagnetic Waves and Applications vol 25 no14-15 pp 1953ndash1962 2011

[11] W-C Liu C-M Wu and Y-J Tseng ldquoParasitically loadedCPW-fed monopole antenna for broadband operationrdquo IEEETransactions on Antennas and Propagation vol 59 no 6 pp2415ndash2419 2011

[12] H-W Liu C-H Ku and C-F Yang ldquoNovel CPW-fed planarmonopole antenna for WiMAXWLAN applicationsrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 240ndash2432010

[13] S M A Nezhad and H R Hassani ldquoA novel triband E-shapedprintedmonopole antenna forMIMOapplicationrdquo IEEEAnten-nas and Wireless Propagation Letters vol 9 pp 576ndash579 2010

[14] R Karimian M Soleimani and S M Hashemi ldquoTri-band fourelementsMIMOantenna system forWLANandWiMAXappli-cationrdquo Journal of Electromagnetic Waves and Applications vol26 no 17-18 pp 2348ndash2357 2012

[15] R Karimian H Oraizi S Fakhte and M Farahani ldquoNovelF-shaped quad-band printed slot antenna for WLAN andWiMAX MIMO systemsrdquo IEEE Antennas and Wireless Propa-gation Letters vol 12 pp 405ndash408 2013

[16] M S Sharawi A B Numan andD N Aloi ldquoIsolation improve-ment in a dual-band dual-element mimo antenna system usingcapacitively loaded loops loaded loopsrdquo Progress in Electromag-netic Research vol 134 pp 247ndash266 2013

[17] C M Li K Wang and C K Chen ldquoSmall tri-band monopoleantenna for WLANWiMAX applicationsrdquo Journal of Electro-magnetic Waves and Applications vol 25 pp 1297ndash1307 2011

[18] J Thaysen and K B Jakobsen ldquoEnvelope correlation in (N N)mimo antenna array from scattering parametersrdquo Microwaveand Optical Technology Letters vol 48 no 5 pp 832ndash834 2006

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 3: Research Article Multiband MIMO Antenna System …downloads.hindawi.com/journals/ijap/2013/365719.pdfResearch Article Multiband MIMO Antenna System with Parasitic Elements for WLAN

International Journal of Antennas and Propagation 3

0 1 2 3 4 5 6minus50

minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

WO patch and parasitic elementsWith patch and WO parasitic elementsProposed antenna

Case I Case II

Case III(front view)

Case III(back view)

Figure 2 Design procedure of the proposed antenna Case I single band Case II dual-band and Case III triband operation

254

190

127

634

0

(Am

)

(a)

254

190

127

634

0

(Am

)

(b)

Figure 3 Surface current distribution (a) 24GHz and (b) 43 GHz

254

190

127

634

0

(Am

)

(a)

254

190

127

634

0

(Am

)

(b)

Figure 4 Surface current distribution (a) 35 GHz and (b) 58GHz

4 International Journal of Antennas and Propagation

1 15 2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

Ls = 6mmLs = 7mm

Ls = 8mmLs = 9mm

Figure 5 Simulated return loss with different 119871119904

1 15 2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

Lp = 12mmLp = 133mm

Lp = 146mmLp = 16mm

Figure 6 Simulated return loss with different 119871119901

2 25 3 35 4 45 5 55 6minus30

minus25

minus20

minus15

minus10

minus5

0

Frequency (GHz)

SimulationMeasurement

Refle

ctio

n co

effici

ent (

dB)

Figure 7 Simulated and measured reflection coefficient characteristic of proposed antenna element

23ndash252GHz 34ndash362GHz and 56ndash595GHz which showapproximate agreementwith the simulated result Some slightdiscrepancies between them may be attributed to measure-ment errors inaccuracies in the fabrication process and theeffect of the SMA connector

3 Integration of Two MIMO Element

The antenna element presented in Section 2 shows that itis suitable for WLAN and WiMAX application and can bearrayed for use in MIMO application

The primary aim of MIMO antenna design is to reducecorrelation between received signals A significant parameterfor the correlation is the mutual coupling One of the most

critical parameters affecting mutual coupling and correlationis due to common ground plane sharing the surface currentwhich can be reduced by etching slot into the ground planeamong the slot antennaThe second parameter that affects thecorrelation between the received signals is the polarization ofthe antennas polarization diversity

This paper based on orthogonal polarization diversityand separated common ground plane introduces a new lowprofile two-element MIMO antenna with good isolation andsimple to fabricate

31 Impedance Performance Figure 8 depicts a photographof the fabricated proposed array antenna The antennaelements are orthogonal to each other in order to make

International Journal of Antennas and Propagation 5

(a)

(b)

Figure 8 Prototype of fabricated MIMO antenna (a) front view and (b) bottom view

2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S11 simulationS21 simulationS22 simulation

S11 measurementS21 measurementS22 measurement

Scat

terin

g pa

ram

eter

s (dB

)

Figure 9 Comparison between simulated and measured scattering parameters for the proposed MIMO array

polarization diversity A rectangular slot with the widthof less than 01120582 (120582 is the wavelength of lowest resonantfrequency) has been etched on ground plane of the antennaarray to separate the common ground plane The simulatedand measured 119878-parameters are in a good agreement asobserved in Figure 9 An E8361C vector network analyzerwas used to measure the scattering parameters characteristicof the fabricated MIMO array in an anechoic chamber Inthis measurement one port is excited and the other port wasterminated by a 50Ω matching load Mutual coupling betterthan minus22 dB has been achieved for the antenna spacing lessthan 01120582 (10mm) In comparison with [13] this antennaarray configuration improved isolation more than 8 dB withthe advantage of compact size

32 Radiation Performance Measured radiation pattern forthree principal planes and for three resonant frequencieswhen one element was excited and the other antenna elementwas matched by a standard 50Ω matching load has beendemonstrated in Figure 10 The orientation of the antennawith respect to coordinate system is clarified in Figure 1 Onecan see that nearly omnidirectional pattern has been achievedat all three frequencies (Table 1) There are no deep nulls inany direction This is an important factor when antenna hasbeen used for MIMO application [14]

Table 1 Simulated peak gain and radiation efficiency results

Frequency (GHz) 24 35 52Gain (dBi) 198 31 16Efficiency () 75 87 64

33 Diversity Performance Envelope correlation coefficientis an important parameter to measure the diversity gain ofa MIMO system Generally low envelope correlation alwaysleads to high diversity gain [14] For a two-antenna system asimple formula can be used to calculate envelope correlationcoefficient [18] as follows

120588 =

1003816100381610038161003816Slowast11S12+ Slowast21S22

1003816100381610038161003816

2

(1 minus1003816100381610038161003816S11

1003816100381610038161003816

2

minus1003816100381610038161003816S21

1003816100381610038161003816

2

) (1 minus1003816100381610038161003816S22

1003816100381610038161003816

2

minus1003816100381610038161003816S12

1003816100381610038161003816

2

)

(2)

The calculated result of the proposed antenna is exhibitedin Figure 11 It shows that the desired operation band of theproposed antenna has an envelope correlation coefficient lessthan 004 which is practically acceptable

Low mutual coupling good impedance matching lowenvelope correlation and stable radiation patterns in threeprincipal planes confirm that the proposed MIMO array is

6 International Journal of Antennas and Propagation

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(a)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(b)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(c)

Figure 10 Measured radiation pattern for three principle planes (a) 24GHz (b) 35 GHz and (c) 58 GHz

a good candidate for use in WLAN and WiMAX MIMOsystems

4 Conclusion

A compact planar multiband antenna is developed in thiswork The proposed antenna utilized a pair of horizontalstrips and a pair of vertical strips patch as parasitic element

to achieve second and third resonant frequency whilethe wideband slot provides the first resonant frequency at24GHz The current distributions excited at resonant fre-quency reveals that the proposed antenna operates at half-wave guided length mode Parametric study shows thatthe proposed antenna structure allows for the independentadjustment or tuning of each frequency of interest withincertain limits A particular combination of two such elements

International Journal of Antennas and Propagation 7

0 1 2 3 4 5 60

005

01

015

02

Frequency (GHz)

Enve

lope

coeffi

cien

t

Figure 11 Measured envelope correlation of the proposed multi-band antenna

has been used for MIMO application The measured returnloss complies with the frequency of WLAN and WiMAXapplication The MIMO antenna array provides better thanminus22 dB mutual coupling envelope correlation of lower than001 and stable omnidirectional patterns at all three frequen-cies

References

[1] Y Ding Z Du K Gong and Z Feng ldquoA novel dual-bandprinted diversity antenna for mobile terminalsrdquo IEEE Transac-tions onAntennas and Propagation vol 55 no 7 pp 2088ndash20962007

[2] L Xiong and P Gao ldquoA compact triple-band wide-slot antennafor WLANWiMAX applicationsrdquo Journal of ElectromagneticWave and Application vol 26 no 7 pp 895ndash903 2012

[3] X Q Zhang Y C Jiao and W H Wang ldquoCompact wide tri-band slot antenna forWLANWiMAX applicationsrdquoElectronicsLetters vol 48 no 2 pp 64ndash65 2012

[4] K He R-X Wang Y-F Wang and B-H Sun ldquoCompacttri-band claw-shaped monopole antenna for WLANWiMAXapplicationsrdquo Journal of Electromagnetic Waves and Applica-tions vol 25 no 5-6 pp 869ndash877 2011

[5] YHan Y-Z Yin Y-QWei Y Zhao B Li andX-N Li ldquoAnoveltriple-band monopole antenna with double coupled C-shapedstrips for WLANWiMAX applicationsrdquo Journal of Electro-magneticWaves and Applications vol 25 no 8-9 pp 1308ndash13162011

[6] W-C Liu M Ghavami and W-C Chung ldquoTriple-frequencymeandered monopole antenna with shorted parasitic strips forwireless applicationrdquo IET Microwaves Antennas and Propaga-tion vol 3 no 7 pp 1110ndash1117 2009

[7] L Peng C-L Ruan and X-H Wu ldquoDesign and operationof dualtriple-band asymmetric M-shaped microstrip patchantennasrdquo IEEE Antennas andWireless Propagation Letters vol9 pp 1069ndash1072 2010

[8] J Pei A-G Wang S Gao and W Leng ldquoMiniaturized triple-band antenna with a defected ground plane for WLANWiMAX applicationsrdquo IEEE Antennas andWireless PropagationLetters vol 10 pp 298ndash301 2011

[9] C-C Lin E-Z Yu and C-Y Huang ldquoDual-band rhombus slotantenna fed by CPW for WLAN applicationsrdquo IEEE Antennasand Wireless Propagation Letters vol 11 pp 362ndash364 2012

[10] W Hu Y-Z Yin S-T Fan X Yang Y Zhao and J-H YangldquoCompact octagonal monopole antenna employing T-shapedquasi-self-complimentary resonators for tri-band operationrdquo

Journal of Electromagnetic Waves and Applications vol 25 no14-15 pp 1953ndash1962 2011

[11] W-C Liu C-M Wu and Y-J Tseng ldquoParasitically loadedCPW-fed monopole antenna for broadband operationrdquo IEEETransactions on Antennas and Propagation vol 59 no 6 pp2415ndash2419 2011

[12] H-W Liu C-H Ku and C-F Yang ldquoNovel CPW-fed planarmonopole antenna for WiMAXWLAN applicationsrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 240ndash2432010

[13] S M A Nezhad and H R Hassani ldquoA novel triband E-shapedprintedmonopole antenna forMIMOapplicationrdquo IEEEAnten-nas and Wireless Propagation Letters vol 9 pp 576ndash579 2010

[14] R Karimian M Soleimani and S M Hashemi ldquoTri-band fourelementsMIMOantenna system forWLANandWiMAXappli-cationrdquo Journal of Electromagnetic Waves and Applications vol26 no 17-18 pp 2348ndash2357 2012

[15] R Karimian H Oraizi S Fakhte and M Farahani ldquoNovelF-shaped quad-band printed slot antenna for WLAN andWiMAX MIMO systemsrdquo IEEE Antennas and Wireless Propa-gation Letters vol 12 pp 405ndash408 2013

[16] M S Sharawi A B Numan andD N Aloi ldquoIsolation improve-ment in a dual-band dual-element mimo antenna system usingcapacitively loaded loops loaded loopsrdquo Progress in Electromag-netic Research vol 134 pp 247ndash266 2013

[17] C M Li K Wang and C K Chen ldquoSmall tri-band monopoleantenna for WLANWiMAX applicationsrdquo Journal of Electro-magnetic Waves and Applications vol 25 pp 1297ndash1307 2011

[18] J Thaysen and K B Jakobsen ldquoEnvelope correlation in (N N)mimo antenna array from scattering parametersrdquo Microwaveand Optical Technology Letters vol 48 no 5 pp 832ndash834 2006

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 4: Research Article Multiband MIMO Antenna System …downloads.hindawi.com/journals/ijap/2013/365719.pdfResearch Article Multiband MIMO Antenna System with Parasitic Elements for WLAN

4 International Journal of Antennas and Propagation

1 15 2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

Ls = 6mmLs = 7mm

Ls = 8mmLs = 9mm

Figure 5 Simulated return loss with different 119871119904

1 15 2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S 11

(dB)

Lp = 12mmLp = 133mm

Lp = 146mmLp = 16mm

Figure 6 Simulated return loss with different 119871119901

2 25 3 35 4 45 5 55 6minus30

minus25

minus20

minus15

minus10

minus5

0

Frequency (GHz)

SimulationMeasurement

Refle

ctio

n co

effici

ent (

dB)

Figure 7 Simulated and measured reflection coefficient characteristic of proposed antenna element

23ndash252GHz 34ndash362GHz and 56ndash595GHz which showapproximate agreementwith the simulated result Some slightdiscrepancies between them may be attributed to measure-ment errors inaccuracies in the fabrication process and theeffect of the SMA connector

3 Integration of Two MIMO Element

The antenna element presented in Section 2 shows that itis suitable for WLAN and WiMAX application and can bearrayed for use in MIMO application

The primary aim of MIMO antenna design is to reducecorrelation between received signals A significant parameterfor the correlation is the mutual coupling One of the most

critical parameters affecting mutual coupling and correlationis due to common ground plane sharing the surface currentwhich can be reduced by etching slot into the ground planeamong the slot antennaThe second parameter that affects thecorrelation between the received signals is the polarization ofthe antennas polarization diversity

This paper based on orthogonal polarization diversityand separated common ground plane introduces a new lowprofile two-element MIMO antenna with good isolation andsimple to fabricate

31 Impedance Performance Figure 8 depicts a photographof the fabricated proposed array antenna The antennaelements are orthogonal to each other in order to make

International Journal of Antennas and Propagation 5

(a)

(b)

Figure 8 Prototype of fabricated MIMO antenna (a) front view and (b) bottom view

2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S11 simulationS21 simulationS22 simulation

S11 measurementS21 measurementS22 measurement

Scat

terin

g pa

ram

eter

s (dB

)

Figure 9 Comparison between simulated and measured scattering parameters for the proposed MIMO array

polarization diversity A rectangular slot with the widthof less than 01120582 (120582 is the wavelength of lowest resonantfrequency) has been etched on ground plane of the antennaarray to separate the common ground plane The simulatedand measured 119878-parameters are in a good agreement asobserved in Figure 9 An E8361C vector network analyzerwas used to measure the scattering parameters characteristicof the fabricated MIMO array in an anechoic chamber Inthis measurement one port is excited and the other port wasterminated by a 50Ω matching load Mutual coupling betterthan minus22 dB has been achieved for the antenna spacing lessthan 01120582 (10mm) In comparison with [13] this antennaarray configuration improved isolation more than 8 dB withthe advantage of compact size

32 Radiation Performance Measured radiation pattern forthree principal planes and for three resonant frequencieswhen one element was excited and the other antenna elementwas matched by a standard 50Ω matching load has beendemonstrated in Figure 10 The orientation of the antennawith respect to coordinate system is clarified in Figure 1 Onecan see that nearly omnidirectional pattern has been achievedat all three frequencies (Table 1) There are no deep nulls inany direction This is an important factor when antenna hasbeen used for MIMO application [14]

Table 1 Simulated peak gain and radiation efficiency results

Frequency (GHz) 24 35 52Gain (dBi) 198 31 16Efficiency () 75 87 64

33 Diversity Performance Envelope correlation coefficientis an important parameter to measure the diversity gain ofa MIMO system Generally low envelope correlation alwaysleads to high diversity gain [14] For a two-antenna system asimple formula can be used to calculate envelope correlationcoefficient [18] as follows

120588 =

1003816100381610038161003816Slowast11S12+ Slowast21S22

1003816100381610038161003816

2

(1 minus1003816100381610038161003816S11

1003816100381610038161003816

2

minus1003816100381610038161003816S21

1003816100381610038161003816

2

) (1 minus1003816100381610038161003816S22

1003816100381610038161003816

2

minus1003816100381610038161003816S12

1003816100381610038161003816

2

)

(2)

The calculated result of the proposed antenna is exhibitedin Figure 11 It shows that the desired operation band of theproposed antenna has an envelope correlation coefficient lessthan 004 which is practically acceptable

Low mutual coupling good impedance matching lowenvelope correlation and stable radiation patterns in threeprincipal planes confirm that the proposed MIMO array is

6 International Journal of Antennas and Propagation

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(a)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(b)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(c)

Figure 10 Measured radiation pattern for three principle planes (a) 24GHz (b) 35 GHz and (c) 58 GHz

a good candidate for use in WLAN and WiMAX MIMOsystems

4 Conclusion

A compact planar multiband antenna is developed in thiswork The proposed antenna utilized a pair of horizontalstrips and a pair of vertical strips patch as parasitic element

to achieve second and third resonant frequency whilethe wideband slot provides the first resonant frequency at24GHz The current distributions excited at resonant fre-quency reveals that the proposed antenna operates at half-wave guided length mode Parametric study shows thatthe proposed antenna structure allows for the independentadjustment or tuning of each frequency of interest withincertain limits A particular combination of two such elements

International Journal of Antennas and Propagation 7

0 1 2 3 4 5 60

005

01

015

02

Frequency (GHz)

Enve

lope

coeffi

cien

t

Figure 11 Measured envelope correlation of the proposed multi-band antenna

has been used for MIMO application The measured returnloss complies with the frequency of WLAN and WiMAXapplication The MIMO antenna array provides better thanminus22 dB mutual coupling envelope correlation of lower than001 and stable omnidirectional patterns at all three frequen-cies

References

[1] Y Ding Z Du K Gong and Z Feng ldquoA novel dual-bandprinted diversity antenna for mobile terminalsrdquo IEEE Transac-tions onAntennas and Propagation vol 55 no 7 pp 2088ndash20962007

[2] L Xiong and P Gao ldquoA compact triple-band wide-slot antennafor WLANWiMAX applicationsrdquo Journal of ElectromagneticWave and Application vol 26 no 7 pp 895ndash903 2012

[3] X Q Zhang Y C Jiao and W H Wang ldquoCompact wide tri-band slot antenna forWLANWiMAX applicationsrdquoElectronicsLetters vol 48 no 2 pp 64ndash65 2012

[4] K He R-X Wang Y-F Wang and B-H Sun ldquoCompacttri-band claw-shaped monopole antenna for WLANWiMAXapplicationsrdquo Journal of Electromagnetic Waves and Applica-tions vol 25 no 5-6 pp 869ndash877 2011

[5] YHan Y-Z Yin Y-QWei Y Zhao B Li andX-N Li ldquoAnoveltriple-band monopole antenna with double coupled C-shapedstrips for WLANWiMAX applicationsrdquo Journal of Electro-magneticWaves and Applications vol 25 no 8-9 pp 1308ndash13162011

[6] W-C Liu M Ghavami and W-C Chung ldquoTriple-frequencymeandered monopole antenna with shorted parasitic strips forwireless applicationrdquo IET Microwaves Antennas and Propaga-tion vol 3 no 7 pp 1110ndash1117 2009

[7] L Peng C-L Ruan and X-H Wu ldquoDesign and operationof dualtriple-band asymmetric M-shaped microstrip patchantennasrdquo IEEE Antennas andWireless Propagation Letters vol9 pp 1069ndash1072 2010

[8] J Pei A-G Wang S Gao and W Leng ldquoMiniaturized triple-band antenna with a defected ground plane for WLANWiMAX applicationsrdquo IEEE Antennas andWireless PropagationLetters vol 10 pp 298ndash301 2011

[9] C-C Lin E-Z Yu and C-Y Huang ldquoDual-band rhombus slotantenna fed by CPW for WLAN applicationsrdquo IEEE Antennasand Wireless Propagation Letters vol 11 pp 362ndash364 2012

[10] W Hu Y-Z Yin S-T Fan X Yang Y Zhao and J-H YangldquoCompact octagonal monopole antenna employing T-shapedquasi-self-complimentary resonators for tri-band operationrdquo

Journal of Electromagnetic Waves and Applications vol 25 no14-15 pp 1953ndash1962 2011

[11] W-C Liu C-M Wu and Y-J Tseng ldquoParasitically loadedCPW-fed monopole antenna for broadband operationrdquo IEEETransactions on Antennas and Propagation vol 59 no 6 pp2415ndash2419 2011

[12] H-W Liu C-H Ku and C-F Yang ldquoNovel CPW-fed planarmonopole antenna for WiMAXWLAN applicationsrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 240ndash2432010

[13] S M A Nezhad and H R Hassani ldquoA novel triband E-shapedprintedmonopole antenna forMIMOapplicationrdquo IEEEAnten-nas and Wireless Propagation Letters vol 9 pp 576ndash579 2010

[14] R Karimian M Soleimani and S M Hashemi ldquoTri-band fourelementsMIMOantenna system forWLANandWiMAXappli-cationrdquo Journal of Electromagnetic Waves and Applications vol26 no 17-18 pp 2348ndash2357 2012

[15] R Karimian H Oraizi S Fakhte and M Farahani ldquoNovelF-shaped quad-band printed slot antenna for WLAN andWiMAX MIMO systemsrdquo IEEE Antennas and Wireless Propa-gation Letters vol 12 pp 405ndash408 2013

[16] M S Sharawi A B Numan andD N Aloi ldquoIsolation improve-ment in a dual-band dual-element mimo antenna system usingcapacitively loaded loops loaded loopsrdquo Progress in Electromag-netic Research vol 134 pp 247ndash266 2013

[17] C M Li K Wang and C K Chen ldquoSmall tri-band monopoleantenna for WLANWiMAX applicationsrdquo Journal of Electro-magnetic Waves and Applications vol 25 pp 1297ndash1307 2011

[18] J Thaysen and K B Jakobsen ldquoEnvelope correlation in (N N)mimo antenna array from scattering parametersrdquo Microwaveand Optical Technology Letters vol 48 no 5 pp 832ndash834 2006

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 5: Research Article Multiband MIMO Antenna System …downloads.hindawi.com/journals/ijap/2013/365719.pdfResearch Article Multiband MIMO Antenna System with Parasitic Elements for WLAN

International Journal of Antennas and Propagation 5

(a)

(b)

Figure 8 Prototype of fabricated MIMO antenna (a) front view and (b) bottom view

2 25 3 35 4 45 5 55 6minus40

minus30

minus20

minus10

0

Frequency (GHz)

S11 simulationS21 simulationS22 simulation

S11 measurementS21 measurementS22 measurement

Scat

terin

g pa

ram

eter

s (dB

)

Figure 9 Comparison between simulated and measured scattering parameters for the proposed MIMO array

polarization diversity A rectangular slot with the widthof less than 01120582 (120582 is the wavelength of lowest resonantfrequency) has been etched on ground plane of the antennaarray to separate the common ground plane The simulatedand measured 119878-parameters are in a good agreement asobserved in Figure 9 An E8361C vector network analyzerwas used to measure the scattering parameters characteristicof the fabricated MIMO array in an anechoic chamber Inthis measurement one port is excited and the other port wasterminated by a 50Ω matching load Mutual coupling betterthan minus22 dB has been achieved for the antenna spacing lessthan 01120582 (10mm) In comparison with [13] this antennaarray configuration improved isolation more than 8 dB withthe advantage of compact size

32 Radiation Performance Measured radiation pattern forthree principal planes and for three resonant frequencieswhen one element was excited and the other antenna elementwas matched by a standard 50Ω matching load has beendemonstrated in Figure 10 The orientation of the antennawith respect to coordinate system is clarified in Figure 1 Onecan see that nearly omnidirectional pattern has been achievedat all three frequencies (Table 1) There are no deep nulls inany direction This is an important factor when antenna hasbeen used for MIMO application [14]

Table 1 Simulated peak gain and radiation efficiency results

Frequency (GHz) 24 35 52Gain (dBi) 198 31 16Efficiency () 75 87 64

33 Diversity Performance Envelope correlation coefficientis an important parameter to measure the diversity gain ofa MIMO system Generally low envelope correlation alwaysleads to high diversity gain [14] For a two-antenna system asimple formula can be used to calculate envelope correlationcoefficient [18] as follows

120588 =

1003816100381610038161003816Slowast11S12+ Slowast21S22

1003816100381610038161003816

2

(1 minus1003816100381610038161003816S11

1003816100381610038161003816

2

minus1003816100381610038161003816S21

1003816100381610038161003816

2

) (1 minus1003816100381610038161003816S22

1003816100381610038161003816

2

minus1003816100381610038161003816S12

1003816100381610038161003816

2

)

(2)

The calculated result of the proposed antenna is exhibitedin Figure 11 It shows that the desired operation band of theproposed antenna has an envelope correlation coefficient lessthan 004 which is practically acceptable

Low mutual coupling good impedance matching lowenvelope correlation and stable radiation patterns in threeprincipal planes confirm that the proposed MIMO array is

6 International Journal of Antennas and Propagation

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(a)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(b)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(c)

Figure 10 Measured radiation pattern for three principle planes (a) 24GHz (b) 35 GHz and (c) 58 GHz

a good candidate for use in WLAN and WiMAX MIMOsystems

4 Conclusion

A compact planar multiband antenna is developed in thiswork The proposed antenna utilized a pair of horizontalstrips and a pair of vertical strips patch as parasitic element

to achieve second and third resonant frequency whilethe wideband slot provides the first resonant frequency at24GHz The current distributions excited at resonant fre-quency reveals that the proposed antenna operates at half-wave guided length mode Parametric study shows thatthe proposed antenna structure allows for the independentadjustment or tuning of each frequency of interest withincertain limits A particular combination of two such elements

International Journal of Antennas and Propagation 7

0 1 2 3 4 5 60

005

01

015

02

Frequency (GHz)

Enve

lope

coeffi

cien

t

Figure 11 Measured envelope correlation of the proposed multi-band antenna

has been used for MIMO application The measured returnloss complies with the frequency of WLAN and WiMAXapplication The MIMO antenna array provides better thanminus22 dB mutual coupling envelope correlation of lower than001 and stable omnidirectional patterns at all three frequen-cies

References

[1] Y Ding Z Du K Gong and Z Feng ldquoA novel dual-bandprinted diversity antenna for mobile terminalsrdquo IEEE Transac-tions onAntennas and Propagation vol 55 no 7 pp 2088ndash20962007

[2] L Xiong and P Gao ldquoA compact triple-band wide-slot antennafor WLANWiMAX applicationsrdquo Journal of ElectromagneticWave and Application vol 26 no 7 pp 895ndash903 2012

[3] X Q Zhang Y C Jiao and W H Wang ldquoCompact wide tri-band slot antenna forWLANWiMAX applicationsrdquoElectronicsLetters vol 48 no 2 pp 64ndash65 2012

[4] K He R-X Wang Y-F Wang and B-H Sun ldquoCompacttri-band claw-shaped monopole antenna for WLANWiMAXapplicationsrdquo Journal of Electromagnetic Waves and Applica-tions vol 25 no 5-6 pp 869ndash877 2011

[5] YHan Y-Z Yin Y-QWei Y Zhao B Li andX-N Li ldquoAnoveltriple-band monopole antenna with double coupled C-shapedstrips for WLANWiMAX applicationsrdquo Journal of Electro-magneticWaves and Applications vol 25 no 8-9 pp 1308ndash13162011

[6] W-C Liu M Ghavami and W-C Chung ldquoTriple-frequencymeandered monopole antenna with shorted parasitic strips forwireless applicationrdquo IET Microwaves Antennas and Propaga-tion vol 3 no 7 pp 1110ndash1117 2009

[7] L Peng C-L Ruan and X-H Wu ldquoDesign and operationof dualtriple-band asymmetric M-shaped microstrip patchantennasrdquo IEEE Antennas andWireless Propagation Letters vol9 pp 1069ndash1072 2010

[8] J Pei A-G Wang S Gao and W Leng ldquoMiniaturized triple-band antenna with a defected ground plane for WLANWiMAX applicationsrdquo IEEE Antennas andWireless PropagationLetters vol 10 pp 298ndash301 2011

[9] C-C Lin E-Z Yu and C-Y Huang ldquoDual-band rhombus slotantenna fed by CPW for WLAN applicationsrdquo IEEE Antennasand Wireless Propagation Letters vol 11 pp 362ndash364 2012

[10] W Hu Y-Z Yin S-T Fan X Yang Y Zhao and J-H YangldquoCompact octagonal monopole antenna employing T-shapedquasi-self-complimentary resonators for tri-band operationrdquo

Journal of Electromagnetic Waves and Applications vol 25 no14-15 pp 1953ndash1962 2011

[11] W-C Liu C-M Wu and Y-J Tseng ldquoParasitically loadedCPW-fed monopole antenna for broadband operationrdquo IEEETransactions on Antennas and Propagation vol 59 no 6 pp2415ndash2419 2011

[12] H-W Liu C-H Ku and C-F Yang ldquoNovel CPW-fed planarmonopole antenna for WiMAXWLAN applicationsrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 240ndash2432010

[13] S M A Nezhad and H R Hassani ldquoA novel triband E-shapedprintedmonopole antenna forMIMOapplicationrdquo IEEEAnten-nas and Wireless Propagation Letters vol 9 pp 576ndash579 2010

[14] R Karimian M Soleimani and S M Hashemi ldquoTri-band fourelementsMIMOantenna system forWLANandWiMAXappli-cationrdquo Journal of Electromagnetic Waves and Applications vol26 no 17-18 pp 2348ndash2357 2012

[15] R Karimian H Oraizi S Fakhte and M Farahani ldquoNovelF-shaped quad-band printed slot antenna for WLAN andWiMAX MIMO systemsrdquo IEEE Antennas and Wireless Propa-gation Letters vol 12 pp 405ndash408 2013

[16] M S Sharawi A B Numan andD N Aloi ldquoIsolation improve-ment in a dual-band dual-element mimo antenna system usingcapacitively loaded loops loaded loopsrdquo Progress in Electromag-netic Research vol 134 pp 247ndash266 2013

[17] C M Li K Wang and C K Chen ldquoSmall tri-band monopoleantenna for WLANWiMAX applicationsrdquo Journal of Electro-magnetic Waves and Applications vol 25 pp 1297ndash1307 2011

[18] J Thaysen and K B Jakobsen ldquoEnvelope correlation in (N N)mimo antenna array from scattering parametersrdquo Microwaveand Optical Technology Letters vol 48 no 5 pp 832ndash834 2006

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 6: Research Article Multiband MIMO Antenna System …downloads.hindawi.com/journals/ijap/2013/365719.pdfResearch Article Multiband MIMO Antenna System with Parasitic Elements for WLAN

6 International Journal of Antennas and Propagation

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(a)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(b)

900

60

30

0

330

300

270

240

210

180

150

120

minus20

minus10

XZ (120579 component)YZ (120579 component)XY (Φ component)

(c)

Figure 10 Measured radiation pattern for three principle planes (a) 24GHz (b) 35 GHz and (c) 58 GHz

a good candidate for use in WLAN and WiMAX MIMOsystems

4 Conclusion

A compact planar multiband antenna is developed in thiswork The proposed antenna utilized a pair of horizontalstrips and a pair of vertical strips patch as parasitic element

to achieve second and third resonant frequency whilethe wideband slot provides the first resonant frequency at24GHz The current distributions excited at resonant fre-quency reveals that the proposed antenna operates at half-wave guided length mode Parametric study shows thatthe proposed antenna structure allows for the independentadjustment or tuning of each frequency of interest withincertain limits A particular combination of two such elements

International Journal of Antennas and Propagation 7

0 1 2 3 4 5 60

005

01

015

02

Frequency (GHz)

Enve

lope

coeffi

cien

t

Figure 11 Measured envelope correlation of the proposed multi-band antenna

has been used for MIMO application The measured returnloss complies with the frequency of WLAN and WiMAXapplication The MIMO antenna array provides better thanminus22 dB mutual coupling envelope correlation of lower than001 and stable omnidirectional patterns at all three frequen-cies

References

[1] Y Ding Z Du K Gong and Z Feng ldquoA novel dual-bandprinted diversity antenna for mobile terminalsrdquo IEEE Transac-tions onAntennas and Propagation vol 55 no 7 pp 2088ndash20962007

[2] L Xiong and P Gao ldquoA compact triple-band wide-slot antennafor WLANWiMAX applicationsrdquo Journal of ElectromagneticWave and Application vol 26 no 7 pp 895ndash903 2012

[3] X Q Zhang Y C Jiao and W H Wang ldquoCompact wide tri-band slot antenna forWLANWiMAX applicationsrdquoElectronicsLetters vol 48 no 2 pp 64ndash65 2012

[4] K He R-X Wang Y-F Wang and B-H Sun ldquoCompacttri-band claw-shaped monopole antenna for WLANWiMAXapplicationsrdquo Journal of Electromagnetic Waves and Applica-tions vol 25 no 5-6 pp 869ndash877 2011

[5] YHan Y-Z Yin Y-QWei Y Zhao B Li andX-N Li ldquoAnoveltriple-band monopole antenna with double coupled C-shapedstrips for WLANWiMAX applicationsrdquo Journal of Electro-magneticWaves and Applications vol 25 no 8-9 pp 1308ndash13162011

[6] W-C Liu M Ghavami and W-C Chung ldquoTriple-frequencymeandered monopole antenna with shorted parasitic strips forwireless applicationrdquo IET Microwaves Antennas and Propaga-tion vol 3 no 7 pp 1110ndash1117 2009

[7] L Peng C-L Ruan and X-H Wu ldquoDesign and operationof dualtriple-band asymmetric M-shaped microstrip patchantennasrdquo IEEE Antennas andWireless Propagation Letters vol9 pp 1069ndash1072 2010

[8] J Pei A-G Wang S Gao and W Leng ldquoMiniaturized triple-band antenna with a defected ground plane for WLANWiMAX applicationsrdquo IEEE Antennas andWireless PropagationLetters vol 10 pp 298ndash301 2011

[9] C-C Lin E-Z Yu and C-Y Huang ldquoDual-band rhombus slotantenna fed by CPW for WLAN applicationsrdquo IEEE Antennasand Wireless Propagation Letters vol 11 pp 362ndash364 2012

[10] W Hu Y-Z Yin S-T Fan X Yang Y Zhao and J-H YangldquoCompact octagonal monopole antenna employing T-shapedquasi-self-complimentary resonators for tri-band operationrdquo

Journal of Electromagnetic Waves and Applications vol 25 no14-15 pp 1953ndash1962 2011

[11] W-C Liu C-M Wu and Y-J Tseng ldquoParasitically loadedCPW-fed monopole antenna for broadband operationrdquo IEEETransactions on Antennas and Propagation vol 59 no 6 pp2415ndash2419 2011

[12] H-W Liu C-H Ku and C-F Yang ldquoNovel CPW-fed planarmonopole antenna for WiMAXWLAN applicationsrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 240ndash2432010

[13] S M A Nezhad and H R Hassani ldquoA novel triband E-shapedprintedmonopole antenna forMIMOapplicationrdquo IEEEAnten-nas and Wireless Propagation Letters vol 9 pp 576ndash579 2010

[14] R Karimian M Soleimani and S M Hashemi ldquoTri-band fourelementsMIMOantenna system forWLANandWiMAXappli-cationrdquo Journal of Electromagnetic Waves and Applications vol26 no 17-18 pp 2348ndash2357 2012

[15] R Karimian H Oraizi S Fakhte and M Farahani ldquoNovelF-shaped quad-band printed slot antenna for WLAN andWiMAX MIMO systemsrdquo IEEE Antennas and Wireless Propa-gation Letters vol 12 pp 405ndash408 2013

[16] M S Sharawi A B Numan andD N Aloi ldquoIsolation improve-ment in a dual-band dual-element mimo antenna system usingcapacitively loaded loops loaded loopsrdquo Progress in Electromag-netic Research vol 134 pp 247ndash266 2013

[17] C M Li K Wang and C K Chen ldquoSmall tri-band monopoleantenna for WLANWiMAX applicationsrdquo Journal of Electro-magnetic Waves and Applications vol 25 pp 1297ndash1307 2011

[18] J Thaysen and K B Jakobsen ldquoEnvelope correlation in (N N)mimo antenna array from scattering parametersrdquo Microwaveand Optical Technology Letters vol 48 no 5 pp 832ndash834 2006

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 7: Research Article Multiband MIMO Antenna System …downloads.hindawi.com/journals/ijap/2013/365719.pdfResearch Article Multiband MIMO Antenna System with Parasitic Elements for WLAN

International Journal of Antennas and Propagation 7

0 1 2 3 4 5 60

005

01

015

02

Frequency (GHz)

Enve

lope

coeffi

cien

t

Figure 11 Measured envelope correlation of the proposed multi-band antenna

has been used for MIMO application The measured returnloss complies with the frequency of WLAN and WiMAXapplication The MIMO antenna array provides better thanminus22 dB mutual coupling envelope correlation of lower than001 and stable omnidirectional patterns at all three frequen-cies

References

[1] Y Ding Z Du K Gong and Z Feng ldquoA novel dual-bandprinted diversity antenna for mobile terminalsrdquo IEEE Transac-tions onAntennas and Propagation vol 55 no 7 pp 2088ndash20962007

[2] L Xiong and P Gao ldquoA compact triple-band wide-slot antennafor WLANWiMAX applicationsrdquo Journal of ElectromagneticWave and Application vol 26 no 7 pp 895ndash903 2012

[3] X Q Zhang Y C Jiao and W H Wang ldquoCompact wide tri-band slot antenna forWLANWiMAX applicationsrdquoElectronicsLetters vol 48 no 2 pp 64ndash65 2012

[4] K He R-X Wang Y-F Wang and B-H Sun ldquoCompacttri-band claw-shaped monopole antenna for WLANWiMAXapplicationsrdquo Journal of Electromagnetic Waves and Applica-tions vol 25 no 5-6 pp 869ndash877 2011

[5] YHan Y-Z Yin Y-QWei Y Zhao B Li andX-N Li ldquoAnoveltriple-band monopole antenna with double coupled C-shapedstrips for WLANWiMAX applicationsrdquo Journal of Electro-magneticWaves and Applications vol 25 no 8-9 pp 1308ndash13162011

[6] W-C Liu M Ghavami and W-C Chung ldquoTriple-frequencymeandered monopole antenna with shorted parasitic strips forwireless applicationrdquo IET Microwaves Antennas and Propaga-tion vol 3 no 7 pp 1110ndash1117 2009

[7] L Peng C-L Ruan and X-H Wu ldquoDesign and operationof dualtriple-band asymmetric M-shaped microstrip patchantennasrdquo IEEE Antennas andWireless Propagation Letters vol9 pp 1069ndash1072 2010

[8] J Pei A-G Wang S Gao and W Leng ldquoMiniaturized triple-band antenna with a defected ground plane for WLANWiMAX applicationsrdquo IEEE Antennas andWireless PropagationLetters vol 10 pp 298ndash301 2011

[9] C-C Lin E-Z Yu and C-Y Huang ldquoDual-band rhombus slotantenna fed by CPW for WLAN applicationsrdquo IEEE Antennasand Wireless Propagation Letters vol 11 pp 362ndash364 2012

[10] W Hu Y-Z Yin S-T Fan X Yang Y Zhao and J-H YangldquoCompact octagonal monopole antenna employing T-shapedquasi-self-complimentary resonators for tri-band operationrdquo

Journal of Electromagnetic Waves and Applications vol 25 no14-15 pp 1953ndash1962 2011

[11] W-C Liu C-M Wu and Y-J Tseng ldquoParasitically loadedCPW-fed monopole antenna for broadband operationrdquo IEEETransactions on Antennas and Propagation vol 59 no 6 pp2415ndash2419 2011

[12] H-W Liu C-H Ku and C-F Yang ldquoNovel CPW-fed planarmonopole antenna for WiMAXWLAN applicationsrdquo IEEEAntennas and Wireless Propagation Letters vol 9 pp 240ndash2432010

[13] S M A Nezhad and H R Hassani ldquoA novel triband E-shapedprintedmonopole antenna forMIMOapplicationrdquo IEEEAnten-nas and Wireless Propagation Letters vol 9 pp 576ndash579 2010

[14] R Karimian M Soleimani and S M Hashemi ldquoTri-band fourelementsMIMOantenna system forWLANandWiMAXappli-cationrdquo Journal of Electromagnetic Waves and Applications vol26 no 17-18 pp 2348ndash2357 2012

[15] R Karimian H Oraizi S Fakhte and M Farahani ldquoNovelF-shaped quad-band printed slot antenna for WLAN andWiMAX MIMO systemsrdquo IEEE Antennas and Wireless Propa-gation Letters vol 12 pp 405ndash408 2013

[16] M S Sharawi A B Numan andD N Aloi ldquoIsolation improve-ment in a dual-band dual-element mimo antenna system usingcapacitively loaded loops loaded loopsrdquo Progress in Electromag-netic Research vol 134 pp 247ndash266 2013

[17] C M Li K Wang and C K Chen ldquoSmall tri-band monopoleantenna for WLANWiMAX applicationsrdquo Journal of Electro-magnetic Waves and Applications vol 25 pp 1297ndash1307 2011

[18] J Thaysen and K B Jakobsen ldquoEnvelope correlation in (N N)mimo antenna array from scattering parametersrdquo Microwaveand Optical Technology Letters vol 48 no 5 pp 832ndash834 2006

International Journal of

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RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Control Scienceand Engineering

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International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Page 8: Research Article Multiband MIMO Antenna System …downloads.hindawi.com/journals/ijap/2013/365719.pdfResearch Article Multiband MIMO Antenna System with Parasitic Elements for WLAN

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of