Research ArticleLow-Profile Dual-Wideband MIMO Antenna with Low ECC forLTE and Wi-Fi Applications

Gye-Taek Jeong1 Sunho Choi2 Kyoung-hak Lee3 and Woo-Su Kim4

1 RampD Center WAVE TECH BD 15 iljik-ro 94-gil Seoksu-dong Anyang Gyeonggi-do 430-040 Republic of Korea2 RampD Center GoerTek Korea Co Ltd 607 A-dong Digital Empire BD 1556 Deogyeong-daero Yeongtong-guSuwon Gyeonggi-do 443-812 Republic of Korea

3 Industry-Academic Cooperation Foundation NamSeoul University 91 Daehakro Seonghwan-eup Seobuk-guCheonan 331-707 Republic of Korea

4 Planning and Budget Team KEIT 10F KOTECH Building 305 Teheran-Ro Gangnam-Gu Seoul 135-080 Republic of Korea

Correspondence should be addressed to Woo-Su Kim kwskeitrekr

Received 3 March 2014 Revised 5 May 2014 Accepted 6 May 2014 Published 22 May 2014

Academic Editor Byungje Lee

Copyright copy 2014 Gye-Taek Jeong et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

This paper presents a low-profile dual-wideband multiple input multiple output (MIMO) antenna with low envelop correlationcoefficient (ECC) for long-term evolution (LTE) and wireless fidelity (Wi-Fi) applicationsThe antenna covers LTE band 7 andWi-Fi as well as wireless broadband (Wibro) and Worldwide Interoperability for Microwave Access (WiMax) (except for the 35-GHzband) To aid with integration of a practical mobile terminal the MIMO antenna elements are placed at appropriate locations byanalyzing the surface current distribution and without using any additional isolation techniques The measured bandwidths withreflection coefficients of ltminus10 dB are 368 in the range 202ndash293GHz and 234 in the range 510ndash645GHz Isolation is satisfiedto be gt20 dB in the operating frequency ranges of both LTE band 7 and Wi-Fi Additionally the calculated ECC is in the range0005 lt 120588 lt 0025 which is considerably lower than the 120588 lt 05 required for MIMO applications The measured radiation patternsare appropriate for mobile terminals and omnidirectional radiation patterns are obtained

1 Introduction

Wireless communications systems should be of high qualityand should provide services with a high data rate Antennadiversity using MIMO is a well-known technique to improvethe performance of wireless communications systems byreducing multipath-induced fading and cross-channel inter-ference [1] In a MIMO system multiple antennas are used toincrease channel capacity without requiring additional powersources [2] It is relatively simple to implement a wirelesscommunications system at a base station using antennaseparation into many wavelengths however for high-qualitywireless download signals more than one antenna is requiredon the terminal side In this type of mobile terminalstwo or more antenna elements are employed and herethe restricted space available for the antenna is an issueof achieving channel separation [3] Low-profile dual-bandcomponents are preferred because many communications

systems operate in dual bands However it is difficult toclosely integrate multiple antennas into a compact spacewhile maintaining good isolation between antenna elementsto achieve channel separation particularly for dual-bandantenna arrays and the efficiency of a MIMO communi-cations system is affected by spatial correlations due to themutual coupling of array elements [4ndash6]

AMIMO antenna system requires a high level of isolationbetween antenna elements however in a typical MIMO sys-tem the space limitationsmean that antennasmust be placedclose to each other Therefore we should investigate optimallocations for closely spaced antenna elements to achievechannel separation [7] Some attempts have been madeto design arrays with little interference using mushroom-like electromagnetic band-gap structures ground structurescontaining defects and parasitic elements [8ndash10] Howeverthese techniques cannot be employed in a practical mobileterminal with a printed circuit board (PCB) along with other

Hindawi Publishing CorporationInternational Journal of Antennas and PropagationVolume 2014 Article ID 158028 6 pageshttpdxdoiorg1011552014158028

2 International Journal of Antennas and Propagation

70 m

m

50 mm

15 m

m

Port 2

Port 1

Ground stub

AB

D C

xz

y

Gx

Gy

(a)

H

Branch 1 Branch 2

W3

W2

W1

L2

L3

L1

(b)

Figure 1 Proposed WLAN antenna (a) geometry and (b) radiator

electronic components because these techniques requireadditional areas where the solid ground plane is modifiedor removed Recently the MIMO antennas yielding goodisolation performances without the use of extra isolationenhancement element have been studied [11 12] Howeverthey have a high profile 6 dB return loss bandwidth and highECC

In this paper we propose a low-profile dual-widebandMIMO antenna for long-term evolution (LTE) band 7 andWi-Fi applications A single antenna with a wide bandwidththat exhibited a reflection coefficient of S

11lt minus10 dB using a

ground stub is designed the locations of the antenna elementswere adjusted to achieve minimal interference through thecurrent distribution analysis without employing additionalisolation techniques which may not be practicable CSTMicrowave Studio was used for the design and analysisof the structure which was subsequently fabricated andcharacterized

2 Antenna Design

The MIMO antenna should cover all frequency bandsrequired for LTE band 7 and Wi-Fi applications Figure 1presents the geometry of the proposed MIMO antenna Theprototype of the antenna is the two-strip monopole antennaAfter satisfying the S

11characteristic of the antenna element

the optimal position of the MIMO antenna is identifiedThe current path length of branch 1 is set at approxi-

mately 30mm which corresponds to a quarter-wavelengthof 25 GHz Thereafter the length of branch 2 is set not onlyto ensure the resonance is 52 GHz as in branch 1 but alsoto ensure narrow impedance bandwidths To improve thebandwidth a ground stub (119866

119909= 15mm times 119866

119910= 50mm)

is inserted This ground stub increased the lower bandwidthfrom 216 (206sim256GHz) to 283 (209sim278GHz) and

Frequency (GHz)1 2 3 4 5 6 7

S p

aram

eter

s (dB

)

minus70

minus60

minus50

minus40

minus30

minus20

minus10

0

A-B deployment SA-B deployment SA-C deployment S

A-C deployment SA-D deployment SA-D deployment S

21

11

2111

21

11

Figure 2The 119878-parameters of the MIMO antennas separated alongthe lines A-B A-C and A-D

increased the higher bandwidth from 41 (472sim492GHz)to 241 (475sim605GHz)

Figure 2 presents the S11

and S21

characteristics of theproposed MIMO antenna elements A-B A-C and A-D S

22

and S12do not appear because the proposed MIMO antenna

elements are deployed symmetrically One might expect thatS21

would perform best when the MIMO antenna elementsare deployed in an A-D configuration because the distancebetween the antenna elements is the greatest among theseconfigurations However results reveal that S

21performs best

in the A-C configuration at the low operating frequencybands S

21performs satisfactorily above 7 dB 17 dB and

International Journal of Antennas and Propagation 3

(a)

(b) (c)

(d)

(e) (f)

Figure 3 The current distribution at 25 GHz and 55GHz in the MIMO antennas separated along (a) the width (A-B) (b) the length (A-C)and (c) the diagonal (A-D) at 25 GHz (d) the width (A-B) (e) the length (A-C) and (f) the diagonal (A-D) at 55 GHz

10 dB respectively for the A-B A-C and A-D configurationsBoth the distance between the antenna elements and thecurrent distribution are important characteristics of S

21 The

amount of coupling between the two adjacent antennaedepends on both the direction of the current flow on thesurface and the distance between the two antennae If the

current direction is the same on the adjacent sides of bothantennae the mutual coupling increases if the current flowis opposite then induced mutual coupling is cancelled Asshown in Figure 3 in the A-B and A-D configurationsthe current direction is the same In contrast in an A-Cconfiguration it is the opposite

4 International Journal of Antennas and Propagation

Frequency (dB)2 3 4 5 6 7

S p

aram

eter

s (dB

)

minus60

minus50

minus40

minus30

minus20

minus10

0

Simulated SSimulated S

Measured SMeasured S

202 GHz 293 GHz

510 GHz

645 GHz

11

21

11

21

Figure 4 Simulated and measured reflection and transmissioncoefficients of the MIMO antennas

3 Measurement Results

The MIMO antennas were fabricated using the optimizedparameters from the simulation analysis described abovewhich are listed in Table 1 A 08mm thick FR4 substrate withdimensions of 50 times 100mm and relative permittivity of 120576

119903=

44 was used The overall volume of the antenna array wasless than 12 times 8 times 1mm3 Identical antennas were deployedsymmetrically along the diagonal A-C The MIMO antennaswere characterized using an HP 8719ES network analyzer

Figure 4 shows the simulated and measured reflectioncoefficients as well as the transmission coefficients S

21 which

show the isolation of the antennas The measurement resultsare in good agreement with the simulation analysis albeitwith a small shift in the resonance frequency which isattributed to the fabrication tolerances at the feed pointsThe fractional bandwidth of the fabricated antenna wherethe reflection coefficient was S

11lt minus10 dB was 368

in the range of 202ndash293GHz and 234 in the range of510ndash645GHz The measured isolation was favorable andno additional area or removal of the solid ground plane ofthe PCB was required The isolation was less than minus20 dBacross the operating frequencies of LTE band 7 and Wi-Fi applications and therefore these results are of practicalutility

Another important parameter of MIMO antennas is theenvelope correlation coefficient (ECC) The diversity of aMIMO system can be evaluated using ECC For a two-elementMIMO system ECC can be calculated as follows [13]

120588 =

1003816100381610038161003816119878lowast

1111987812+ 119878lowast

2111987822

1003816100381610038161003816

2

(1 minus (100381610038161003816100381611987811

1003816100381610038161003816

2

+100381610038161003816100381611987821

1003816100381610038161003816

2

)) (1 minus (100381610038161003816100381611987822

1003816100381610038161003816

2

+100381610038161003816100381611987812

1003816100381610038161003816

2

))

(1)

The ECC values at various frequencies are listed inTable 2 For aMIMO systemwe require 120588 lt 05 [14]The datalisted in Table 2 reveal that our fabricated MIMO antennaseasily satisfy this criterion

Table 1 Optimized parameters of the MIMO antenna

Parameter Value (mm)1198821

151198822

1201198823

90119866119909

15119867 101198711

201198712

801198713

55119866119910

50Ground 50 times 70

Table 2 ECC for our fabricated MIMO antennas at variousfrequencies

Freq (GHz) ECC24 00083425 00167426 00144727 00052252 00124154 00241956 00096858 002151

Figure 5 shows the measured radiation patterns at25 GHz and 55GHz The data shown are for the antenna inpositionAwhich is identical to the other antennae because ofthe symmetry of the systemThemeasured radiation patternswere nearly omnidirectional The small degree of directivityresults from the119910119911-plane at high frequencies and is attributedto the large ground plane The measured gain of the antennawas 409 dBi at 25 GHz and 432 dBi at 55 GHz

4 Conclusion

We have described a compact multiband MIMO antennawith low ECC for LTE band 7 and Wi-Fi applications Themeasured reflection coefficients of a single antenna were368 in the range of 202 to 293GHz and 234 in the rangeof 510 to 645GHz Isolation was satisfied to be above 20 dBacross the operating frequency ranges for LTE band 7 andWi-Fi applications This was achieved without requiring anadditional area or the removal of any of the solid groundplanes of the PCB based on an analysis of the distributionof the surface currents The calculated ECC was in the range0005 lt 120588 lt 0025 which is considerably lower than the120588 lt 05 required for MIMO applications The measuredradiation patterns were appropriate formobile terminals andomnidirectional radiation patterns were obtained The mea-sured gain was 409 dBi at 25 GHz and 432 dBi at 55 GHzBased on these metrics the MIMO antennas reported hereare suitable for practical mobile terminals for both LTE band7 and Wi-Fi applications

International Journal of Antennas and Propagation 5

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

xz-plane

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

yz-plane

(a)

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

xz-plane

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

yz-plane

(b)

Figure 5 Measured radiation patterns of the antenna at (a) 25 GHz and (b) 55 GHz

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] R G Vaughan and J B Andersen ldquoAntenna diversity in mobilecommunicationsrdquo IEEE Transactions on Vehicular Technologyvol VT-36 no 4 pp 149ndash172 1987

[2] R D Murch and K Ben Letaief ldquoAntenna systems for broad-band wireless accessrdquo IEEE Communications Magazine vol 40no 4 pp 76ndash83 2002

[3] D Gesbert M Shafi D-S Shiu P J Smith and A NaguibldquoFrom theory to practice an overview of MIMO space-timecoded wireless systemsrdquo IEEE Journal on Selected Areas inCommunications vol 21 no 3 pp 281ndash302 2003

[4] H Li J Xiong and S L He ldquoExtremely compact dual-bandPIFAs for MIMO applicationrdquo Electronics Letters vol 45 no 17pp 869ndash870 2009

6 International Journal of Antennas and Propagation

[5] M A Jensen and J W Wallace ldquoA review of antennas andpropagation for MIMOwireless communicationsrdquo IEEE Trans-actions on Antennas and Propagation vol 52 no 11 pp 2810ndash2824 2004

[6] A M Tulino A Lozano and S Verdu ldquoImpact of antennacorrelation on the capacity of multiantenna channelsrdquo IEEETransactions on InformationTheory vol 51 no 7 pp 2491ndash25092005

[7] S Karimkashi A A Kishk and D Kajfez ldquoAntenna arrayoptimization using dipole models for MIMO applicationsrdquoIEEE Transactions on Antennas and Propagation vol 59 no 8pp 3112ndash3116 2011

[8] K Payandehjoo and R Abhari ldquoEmploying EBG structuresin multiantenna systems for improving isolation and diversitygainrdquo IEEE Antennas and Wireless Propagation Letters vol 8pp 1162ndash1165 2009

[9] F-G Zhu J-D Xu and Q Xu ldquoReduction of mutual cou-pling between closely-packed antenna elements using defectedground structurerdquo Electronics Letters vol 45 no 12 pp 601ndash602 2009

[10] R Karimian and H Tadayon ldquoMultiband MIMO antennasystem with parasitic elements for WLAN and WiMAX appli-cationrdquo International Journal of Antennas and Propagation vol2013 Article ID 365719 7 pages 2013

[11] X Zhao Y Lee and J Choi ldquoDesign of a compact MIMOantenna using coupled feed for LTE mobile applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 837643 8 pages 2013

[12] B Mun F J Harackiewicz B Kim et al ldquoNew configurationof handset MIMO antenna for LTE 700 band applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 850489 6 pages 2013

[13] S Blanch J Romeu and I Corbella ldquoExact representation ofantenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003

[14] A N Kulkami and S K Sharma ldquoA multiband antenna withMIMO implementation for USB dongle size wireless devicesrdquoMicrowave and Optical Technology Letters vol 54 pp 1990ndash1994 2012

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Chemical EngineeringInternational Journal of Antennas and

Propagation

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International Journal of

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DistributedSensor Networks

International Journal of

2 International Journal of Antennas and Propagation

70 m

m

50 mm

15 m

m

Port 2

Port 1

Ground stub

AB

D C

xz

y

Gx

Gy

(a)

H

Branch 1 Branch 2

W3

W2

W1

L2

L3

L1

(b)

Figure 1 Proposed WLAN antenna (a) geometry and (b) radiator

electronic components because these techniques requireadditional areas where the solid ground plane is modifiedor removed Recently the MIMO antennas yielding goodisolation performances without the use of extra isolationenhancement element have been studied [11 12] Howeverthey have a high profile 6 dB return loss bandwidth and highECC

In this paper we propose a low-profile dual-widebandMIMO antenna for long-term evolution (LTE) band 7 andWi-Fi applications A single antenna with a wide bandwidththat exhibited a reflection coefficient of S

11lt minus10 dB using a

ground stub is designed the locations of the antenna elementswere adjusted to achieve minimal interference through thecurrent distribution analysis without employing additionalisolation techniques which may not be practicable CSTMicrowave Studio was used for the design and analysisof the structure which was subsequently fabricated andcharacterized

2 Antenna Design

The MIMO antenna should cover all frequency bandsrequired for LTE band 7 and Wi-Fi applications Figure 1presents the geometry of the proposed MIMO antenna Theprototype of the antenna is the two-strip monopole antennaAfter satisfying the S

11characteristic of the antenna element

the optimal position of the MIMO antenna is identifiedThe current path length of branch 1 is set at approxi-

mately 30mm which corresponds to a quarter-wavelengthof 25 GHz Thereafter the length of branch 2 is set not onlyto ensure the resonance is 52 GHz as in branch 1 but alsoto ensure narrow impedance bandwidths To improve thebandwidth a ground stub (119866

119909= 15mm times 119866

119910= 50mm)

is inserted This ground stub increased the lower bandwidthfrom 216 (206sim256GHz) to 283 (209sim278GHz) and

Frequency (GHz)1 2 3 4 5 6 7

S p

aram

eter

s (dB

)

minus70

minus60

minus50

minus40

minus30

minus20

minus10

0

A-B deployment SA-B deployment SA-C deployment S

A-C deployment SA-D deployment SA-D deployment S

21

11

2111

21

11

Figure 2The 119878-parameters of the MIMO antennas separated alongthe lines A-B A-C and A-D

increased the higher bandwidth from 41 (472sim492GHz)to 241 (475sim605GHz)

Figure 2 presents the S11

and S21

characteristics of theproposed MIMO antenna elements A-B A-C and A-D S

22

and S12do not appear because the proposed MIMO antenna

elements are deployed symmetrically One might expect thatS21

would perform best when the MIMO antenna elementsare deployed in an A-D configuration because the distancebetween the antenna elements is the greatest among theseconfigurations However results reveal that S

21performs best

in the A-C configuration at the low operating frequencybands S

21performs satisfactorily above 7 dB 17 dB and

International Journal of Antennas and Propagation 3

(a)

(b) (c)

(d)

(e) (f)

Figure 3 The current distribution at 25 GHz and 55GHz in the MIMO antennas separated along (a) the width (A-B) (b) the length (A-C)and (c) the diagonal (A-D) at 25 GHz (d) the width (A-B) (e) the length (A-C) and (f) the diagonal (A-D) at 55 GHz

10 dB respectively for the A-B A-C and A-D configurationsBoth the distance between the antenna elements and thecurrent distribution are important characteristics of S

21 The

amount of coupling between the two adjacent antennaedepends on both the direction of the current flow on thesurface and the distance between the two antennae If the

current direction is the same on the adjacent sides of bothantennae the mutual coupling increases if the current flowis opposite then induced mutual coupling is cancelled Asshown in Figure 3 in the A-B and A-D configurationsthe current direction is the same In contrast in an A-Cconfiguration it is the opposite

4 International Journal of Antennas and Propagation

Frequency (dB)2 3 4 5 6 7

S p

aram

eter

s (dB

)

minus60

minus50

minus40

minus30

minus20

minus10

0

Simulated SSimulated S

Measured SMeasured S

202 GHz 293 GHz

510 GHz

645 GHz

11

21

11

21

Figure 4 Simulated and measured reflection and transmissioncoefficients of the MIMO antennas

3 Measurement Results

The MIMO antennas were fabricated using the optimizedparameters from the simulation analysis described abovewhich are listed in Table 1 A 08mm thick FR4 substrate withdimensions of 50 times 100mm and relative permittivity of 120576

119903=

44 was used The overall volume of the antenna array wasless than 12 times 8 times 1mm3 Identical antennas were deployedsymmetrically along the diagonal A-C The MIMO antennaswere characterized using an HP 8719ES network analyzer

Figure 4 shows the simulated and measured reflectioncoefficients as well as the transmission coefficients S

21 which

show the isolation of the antennas The measurement resultsare in good agreement with the simulation analysis albeitwith a small shift in the resonance frequency which isattributed to the fabrication tolerances at the feed pointsThe fractional bandwidth of the fabricated antenna wherethe reflection coefficient was S

11lt minus10 dB was 368

in the range of 202ndash293GHz and 234 in the range of510ndash645GHz The measured isolation was favorable andno additional area or removal of the solid ground plane ofthe PCB was required The isolation was less than minus20 dBacross the operating frequencies of LTE band 7 and Wi-Fi applications and therefore these results are of practicalutility

Another important parameter of MIMO antennas is theenvelope correlation coefficient (ECC) The diversity of aMIMO system can be evaluated using ECC For a two-elementMIMO system ECC can be calculated as follows [13]

120588 =

1003816100381610038161003816119878lowast

1111987812+ 119878lowast

2111987822

1003816100381610038161003816

2

(1 minus (100381610038161003816100381611987811

1003816100381610038161003816

2

+100381610038161003816100381611987821

1003816100381610038161003816

2

)) (1 minus (100381610038161003816100381611987822

1003816100381610038161003816

2

+100381610038161003816100381611987812

1003816100381610038161003816

2

))

(1)

The ECC values at various frequencies are listed inTable 2 For aMIMO systemwe require 120588 lt 05 [14]The datalisted in Table 2 reveal that our fabricated MIMO antennaseasily satisfy this criterion

Table 1 Optimized parameters of the MIMO antenna

Parameter Value (mm)1198821

151198822

1201198823

90119866119909

15119867 101198711

201198712

801198713

55119866119910

50Ground 50 times 70

Table 2 ECC for our fabricated MIMO antennas at variousfrequencies

Freq (GHz) ECC24 00083425 00167426 00144727 00052252 00124154 00241956 00096858 002151

Figure 5 shows the measured radiation patterns at25 GHz and 55GHz The data shown are for the antenna inpositionAwhich is identical to the other antennae because ofthe symmetry of the systemThemeasured radiation patternswere nearly omnidirectional The small degree of directivityresults from the119910119911-plane at high frequencies and is attributedto the large ground plane The measured gain of the antennawas 409 dBi at 25 GHz and 432 dBi at 55 GHz

4 Conclusion

We have described a compact multiband MIMO antennawith low ECC for LTE band 7 and Wi-Fi applications Themeasured reflection coefficients of a single antenna were368 in the range of 202 to 293GHz and 234 in the rangeof 510 to 645GHz Isolation was satisfied to be above 20 dBacross the operating frequency ranges for LTE band 7 andWi-Fi applications This was achieved without requiring anadditional area or the removal of any of the solid groundplanes of the PCB based on an analysis of the distributionof the surface currents The calculated ECC was in the range0005 lt 120588 lt 0025 which is considerably lower than the120588 lt 05 required for MIMO applications The measuredradiation patterns were appropriate formobile terminals andomnidirectional radiation patterns were obtained The mea-sured gain was 409 dBi at 25 GHz and 432 dBi at 55 GHzBased on these metrics the MIMO antennas reported hereare suitable for practical mobile terminals for both LTE band7 and Wi-Fi applications

International Journal of Antennas and Propagation 5

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

xz-plane

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

yz-plane

(a)

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

xz-plane

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

yz-plane

(b)

Figure 5 Measured radiation patterns of the antenna at (a) 25 GHz and (b) 55 GHz

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] R G Vaughan and J B Andersen ldquoAntenna diversity in mobilecommunicationsrdquo IEEE Transactions on Vehicular Technologyvol VT-36 no 4 pp 149ndash172 1987

[2] R D Murch and K Ben Letaief ldquoAntenna systems for broad-band wireless accessrdquo IEEE Communications Magazine vol 40no 4 pp 76ndash83 2002

[3] D Gesbert M Shafi D-S Shiu P J Smith and A NaguibldquoFrom theory to practice an overview of MIMO space-timecoded wireless systemsrdquo IEEE Journal on Selected Areas inCommunications vol 21 no 3 pp 281ndash302 2003

[4] H Li J Xiong and S L He ldquoExtremely compact dual-bandPIFAs for MIMO applicationrdquo Electronics Letters vol 45 no 17pp 869ndash870 2009

6 International Journal of Antennas and Propagation

[5] M A Jensen and J W Wallace ldquoA review of antennas andpropagation for MIMOwireless communicationsrdquo IEEE Trans-actions on Antennas and Propagation vol 52 no 11 pp 2810ndash2824 2004

[6] A M Tulino A Lozano and S Verdu ldquoImpact of antennacorrelation on the capacity of multiantenna channelsrdquo IEEETransactions on InformationTheory vol 51 no 7 pp 2491ndash25092005

[7] S Karimkashi A A Kishk and D Kajfez ldquoAntenna arrayoptimization using dipole models for MIMO applicationsrdquoIEEE Transactions on Antennas and Propagation vol 59 no 8pp 3112ndash3116 2011

[8] K Payandehjoo and R Abhari ldquoEmploying EBG structuresin multiantenna systems for improving isolation and diversitygainrdquo IEEE Antennas and Wireless Propagation Letters vol 8pp 1162ndash1165 2009

[9] F-G Zhu J-D Xu and Q Xu ldquoReduction of mutual cou-pling between closely-packed antenna elements using defectedground structurerdquo Electronics Letters vol 45 no 12 pp 601ndash602 2009

[10] R Karimian and H Tadayon ldquoMultiband MIMO antennasystem with parasitic elements for WLAN and WiMAX appli-cationrdquo International Journal of Antennas and Propagation vol2013 Article ID 365719 7 pages 2013

[11] X Zhao Y Lee and J Choi ldquoDesign of a compact MIMOantenna using coupled feed for LTE mobile applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 837643 8 pages 2013

[12] B Mun F J Harackiewicz B Kim et al ldquoNew configurationof handset MIMO antenna for LTE 700 band applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 850489 6 pages 2013

[13] S Blanch J Romeu and I Corbella ldquoExact representation ofantenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003

[14] A N Kulkami and S K Sharma ldquoA multiband antenna withMIMO implementation for USB dongle size wireless devicesrdquoMicrowave and Optical Technology Letters vol 54 pp 1990ndash1994 2012

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

International Journal of Antennas and Propagation 3

(a)

(b) (c)

(d)

(e) (f)

Figure 3 The current distribution at 25 GHz and 55GHz in the MIMO antennas separated along (a) the width (A-B) (b) the length (A-C)and (c) the diagonal (A-D) at 25 GHz (d) the width (A-B) (e) the length (A-C) and (f) the diagonal (A-D) at 55 GHz

10 dB respectively for the A-B A-C and A-D configurationsBoth the distance between the antenna elements and thecurrent distribution are important characteristics of S

21 The

amount of coupling between the two adjacent antennaedepends on both the direction of the current flow on thesurface and the distance between the two antennae If the

current direction is the same on the adjacent sides of bothantennae the mutual coupling increases if the current flowis opposite then induced mutual coupling is cancelled Asshown in Figure 3 in the A-B and A-D configurationsthe current direction is the same In contrast in an A-Cconfiguration it is the opposite

4 International Journal of Antennas and Propagation

Frequency (dB)2 3 4 5 6 7

S p

aram

eter

s (dB

)

minus60

minus50

minus40

minus30

minus20

minus10

0

Simulated SSimulated S

Measured SMeasured S

202 GHz 293 GHz

510 GHz

645 GHz

11

21

11

21

Figure 4 Simulated and measured reflection and transmissioncoefficients of the MIMO antennas

3 Measurement Results

The MIMO antennas were fabricated using the optimizedparameters from the simulation analysis described abovewhich are listed in Table 1 A 08mm thick FR4 substrate withdimensions of 50 times 100mm and relative permittivity of 120576

119903=

44 was used The overall volume of the antenna array wasless than 12 times 8 times 1mm3 Identical antennas were deployedsymmetrically along the diagonal A-C The MIMO antennaswere characterized using an HP 8719ES network analyzer

Figure 4 shows the simulated and measured reflectioncoefficients as well as the transmission coefficients S

21 which

show the isolation of the antennas The measurement resultsare in good agreement with the simulation analysis albeitwith a small shift in the resonance frequency which isattributed to the fabrication tolerances at the feed pointsThe fractional bandwidth of the fabricated antenna wherethe reflection coefficient was S

11lt minus10 dB was 368

in the range of 202ndash293GHz and 234 in the range of510ndash645GHz The measured isolation was favorable andno additional area or removal of the solid ground plane ofthe PCB was required The isolation was less than minus20 dBacross the operating frequencies of LTE band 7 and Wi-Fi applications and therefore these results are of practicalutility

Another important parameter of MIMO antennas is theenvelope correlation coefficient (ECC) The diversity of aMIMO system can be evaluated using ECC For a two-elementMIMO system ECC can be calculated as follows [13]

120588 =

1003816100381610038161003816119878lowast

1111987812+ 119878lowast

2111987822

1003816100381610038161003816

2

(1 minus (100381610038161003816100381611987811

1003816100381610038161003816

2

+100381610038161003816100381611987821

1003816100381610038161003816

2

)) (1 minus (100381610038161003816100381611987822

1003816100381610038161003816

2

+100381610038161003816100381611987812

1003816100381610038161003816

2

))

(1)

The ECC values at various frequencies are listed inTable 2 For aMIMO systemwe require 120588 lt 05 [14]The datalisted in Table 2 reveal that our fabricated MIMO antennaseasily satisfy this criterion

Table 1 Optimized parameters of the MIMO antenna

Parameter Value (mm)1198821

151198822

1201198823

90119866119909

15119867 101198711

201198712

801198713

55119866119910

50Ground 50 times 70

Table 2 ECC for our fabricated MIMO antennas at variousfrequencies

Freq (GHz) ECC24 00083425 00167426 00144727 00052252 00124154 00241956 00096858 002151

Figure 5 shows the measured radiation patterns at25 GHz and 55GHz The data shown are for the antenna inpositionAwhich is identical to the other antennae because ofthe symmetry of the systemThemeasured radiation patternswere nearly omnidirectional The small degree of directivityresults from the119910119911-plane at high frequencies and is attributedto the large ground plane The measured gain of the antennawas 409 dBi at 25 GHz and 432 dBi at 55 GHz

4 Conclusion

We have described a compact multiband MIMO antennawith low ECC for LTE band 7 and Wi-Fi applications Themeasured reflection coefficients of a single antenna were368 in the range of 202 to 293GHz and 234 in the rangeof 510 to 645GHz Isolation was satisfied to be above 20 dBacross the operating frequency ranges for LTE band 7 andWi-Fi applications This was achieved without requiring anadditional area or the removal of any of the solid groundplanes of the PCB based on an analysis of the distributionof the surface currents The calculated ECC was in the range0005 lt 120588 lt 0025 which is considerably lower than the120588 lt 05 required for MIMO applications The measuredradiation patterns were appropriate formobile terminals andomnidirectional radiation patterns were obtained The mea-sured gain was 409 dBi at 25 GHz and 432 dBi at 55 GHzBased on these metrics the MIMO antennas reported hereare suitable for practical mobile terminals for both LTE band7 and Wi-Fi applications

International Journal of Antennas and Propagation 5

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

xz-plane

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

yz-plane

(a)

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

xz-plane

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

yz-plane

(b)

Figure 5 Measured radiation patterns of the antenna at (a) 25 GHz and (b) 55 GHz

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] R G Vaughan and J B Andersen ldquoAntenna diversity in mobilecommunicationsrdquo IEEE Transactions on Vehicular Technologyvol VT-36 no 4 pp 149ndash172 1987

[2] R D Murch and K Ben Letaief ldquoAntenna systems for broad-band wireless accessrdquo IEEE Communications Magazine vol 40no 4 pp 76ndash83 2002

[3] D Gesbert M Shafi D-S Shiu P J Smith and A NaguibldquoFrom theory to practice an overview of MIMO space-timecoded wireless systemsrdquo IEEE Journal on Selected Areas inCommunications vol 21 no 3 pp 281ndash302 2003

[4] H Li J Xiong and S L He ldquoExtremely compact dual-bandPIFAs for MIMO applicationrdquo Electronics Letters vol 45 no 17pp 869ndash870 2009

6 International Journal of Antennas and Propagation

[5] M A Jensen and J W Wallace ldquoA review of antennas andpropagation for MIMOwireless communicationsrdquo IEEE Trans-actions on Antennas and Propagation vol 52 no 11 pp 2810ndash2824 2004

[6] A M Tulino A Lozano and S Verdu ldquoImpact of antennacorrelation on the capacity of multiantenna channelsrdquo IEEETransactions on InformationTheory vol 51 no 7 pp 2491ndash25092005

[7] S Karimkashi A A Kishk and D Kajfez ldquoAntenna arrayoptimization using dipole models for MIMO applicationsrdquoIEEE Transactions on Antennas and Propagation vol 59 no 8pp 3112ndash3116 2011

[8] K Payandehjoo and R Abhari ldquoEmploying EBG structuresin multiantenna systems for improving isolation and diversitygainrdquo IEEE Antennas and Wireless Propagation Letters vol 8pp 1162ndash1165 2009

[9] F-G Zhu J-D Xu and Q Xu ldquoReduction of mutual cou-pling between closely-packed antenna elements using defectedground structurerdquo Electronics Letters vol 45 no 12 pp 601ndash602 2009

[10] R Karimian and H Tadayon ldquoMultiband MIMO antennasystem with parasitic elements for WLAN and WiMAX appli-cationrdquo International Journal of Antennas and Propagation vol2013 Article ID 365719 7 pages 2013

[11] X Zhao Y Lee and J Choi ldquoDesign of a compact MIMOantenna using coupled feed for LTE mobile applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 837643 8 pages 2013

[12] B Mun F J Harackiewicz B Kim et al ldquoNew configurationof handset MIMO antenna for LTE 700 band applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 850489 6 pages 2013

[13] S Blanch J Romeu and I Corbella ldquoExact representation ofantenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003

[14] A N Kulkami and S K Sharma ldquoA multiband antenna withMIMO implementation for USB dongle size wireless devicesrdquoMicrowave and Optical Technology Letters vol 54 pp 1990ndash1994 2012

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

4 International Journal of Antennas and Propagation

Frequency (dB)2 3 4 5 6 7

S p

aram

eter

s (dB

)

minus60

minus50

minus40

minus30

minus20

minus10

0

Simulated SSimulated S

Measured SMeasured S

202 GHz 293 GHz

510 GHz

645 GHz

11

21

11

21

Figure 4 Simulated and measured reflection and transmissioncoefficients of the MIMO antennas

3 Measurement Results

The MIMO antennas were fabricated using the optimizedparameters from the simulation analysis described abovewhich are listed in Table 1 A 08mm thick FR4 substrate withdimensions of 50 times 100mm and relative permittivity of 120576

119903=

44 was used The overall volume of the antenna array wasless than 12 times 8 times 1mm3 Identical antennas were deployedsymmetrically along the diagonal A-C The MIMO antennaswere characterized using an HP 8719ES network analyzer

Figure 4 shows the simulated and measured reflectioncoefficients as well as the transmission coefficients S

21 which

show the isolation of the antennas The measurement resultsare in good agreement with the simulation analysis albeitwith a small shift in the resonance frequency which isattributed to the fabrication tolerances at the feed pointsThe fractional bandwidth of the fabricated antenna wherethe reflection coefficient was S

11lt minus10 dB was 368

in the range of 202ndash293GHz and 234 in the range of510ndash645GHz The measured isolation was favorable andno additional area or removal of the solid ground plane ofthe PCB was required The isolation was less than minus20 dBacross the operating frequencies of LTE band 7 and Wi-Fi applications and therefore these results are of practicalutility

Another important parameter of MIMO antennas is theenvelope correlation coefficient (ECC) The diversity of aMIMO system can be evaluated using ECC For a two-elementMIMO system ECC can be calculated as follows [13]

120588 =

1003816100381610038161003816119878lowast

1111987812+ 119878lowast

2111987822

1003816100381610038161003816

2

(1 minus (100381610038161003816100381611987811

1003816100381610038161003816

2

+100381610038161003816100381611987821

1003816100381610038161003816

2

)) (1 minus (100381610038161003816100381611987822

1003816100381610038161003816

2

+100381610038161003816100381611987812

1003816100381610038161003816

2

))

(1)

The ECC values at various frequencies are listed inTable 2 For aMIMO systemwe require 120588 lt 05 [14]The datalisted in Table 2 reveal that our fabricated MIMO antennaseasily satisfy this criterion

Table 1 Optimized parameters of the MIMO antenna

Parameter Value (mm)1198821

151198822

1201198823

90119866119909

15119867 101198711

201198712

801198713

55119866119910

50Ground 50 times 70

Table 2 ECC for our fabricated MIMO antennas at variousfrequencies

Freq (GHz) ECC24 00083425 00167426 00144727 00052252 00124154 00241956 00096858 002151

Figure 5 shows the measured radiation patterns at25 GHz and 55GHz The data shown are for the antenna inpositionAwhich is identical to the other antennae because ofthe symmetry of the systemThemeasured radiation patternswere nearly omnidirectional The small degree of directivityresults from the119910119911-plane at high frequencies and is attributedto the large ground plane The measured gain of the antennawas 409 dBi at 25 GHz and 432 dBi at 55 GHz

4 Conclusion

We have described a compact multiband MIMO antennawith low ECC for LTE band 7 and Wi-Fi applications Themeasured reflection coefficients of a single antenna were368 in the range of 202 to 293GHz and 234 in the rangeof 510 to 645GHz Isolation was satisfied to be above 20 dBacross the operating frequency ranges for LTE band 7 andWi-Fi applications This was achieved without requiring anadditional area or the removal of any of the solid groundplanes of the PCB based on an analysis of the distributionof the surface currents The calculated ECC was in the range0005 lt 120588 lt 0025 which is considerably lower than the120588 lt 05 required for MIMO applications The measuredradiation patterns were appropriate formobile terminals andomnidirectional radiation patterns were obtained The mea-sured gain was 409 dBi at 25 GHz and 432 dBi at 55 GHzBased on these metrics the MIMO antennas reported hereare suitable for practical mobile terminals for both LTE band7 and Wi-Fi applications

International Journal of Antennas and Propagation 5

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

xz-plane

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

yz-plane

(a)

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

xz-plane

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

yz-plane

(b)

Figure 5 Measured radiation patterns of the antenna at (a) 25 GHz and (b) 55 GHz

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] R G Vaughan and J B Andersen ldquoAntenna diversity in mobilecommunicationsrdquo IEEE Transactions on Vehicular Technologyvol VT-36 no 4 pp 149ndash172 1987

[2] R D Murch and K Ben Letaief ldquoAntenna systems for broad-band wireless accessrdquo IEEE Communications Magazine vol 40no 4 pp 76ndash83 2002

[3] D Gesbert M Shafi D-S Shiu P J Smith and A NaguibldquoFrom theory to practice an overview of MIMO space-timecoded wireless systemsrdquo IEEE Journal on Selected Areas inCommunications vol 21 no 3 pp 281ndash302 2003

[4] H Li J Xiong and S L He ldquoExtremely compact dual-bandPIFAs for MIMO applicationrdquo Electronics Letters vol 45 no 17pp 869ndash870 2009

6 International Journal of Antennas and Propagation

[5] M A Jensen and J W Wallace ldquoA review of antennas andpropagation for MIMOwireless communicationsrdquo IEEE Trans-actions on Antennas and Propagation vol 52 no 11 pp 2810ndash2824 2004

[6] A M Tulino A Lozano and S Verdu ldquoImpact of antennacorrelation on the capacity of multiantenna channelsrdquo IEEETransactions on InformationTheory vol 51 no 7 pp 2491ndash25092005

[7] S Karimkashi A A Kishk and D Kajfez ldquoAntenna arrayoptimization using dipole models for MIMO applicationsrdquoIEEE Transactions on Antennas and Propagation vol 59 no 8pp 3112ndash3116 2011

[8] K Payandehjoo and R Abhari ldquoEmploying EBG structuresin multiantenna systems for improving isolation and diversitygainrdquo IEEE Antennas and Wireless Propagation Letters vol 8pp 1162ndash1165 2009

[9] F-G Zhu J-D Xu and Q Xu ldquoReduction of mutual cou-pling between closely-packed antenna elements using defectedground structurerdquo Electronics Letters vol 45 no 12 pp 601ndash602 2009

[10] R Karimian and H Tadayon ldquoMultiband MIMO antennasystem with parasitic elements for WLAN and WiMAX appli-cationrdquo International Journal of Antennas and Propagation vol2013 Article ID 365719 7 pages 2013

[11] X Zhao Y Lee and J Choi ldquoDesign of a compact MIMOantenna using coupled feed for LTE mobile applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 837643 8 pages 2013

[12] B Mun F J Harackiewicz B Kim et al ldquoNew configurationof handset MIMO antenna for LTE 700 band applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 850489 6 pages 2013

[13] S Blanch J Romeu and I Corbella ldquoExact representation ofantenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003

[14] A N Kulkami and S K Sharma ldquoA multiband antenna withMIMO implementation for USB dongle size wireless devicesrdquoMicrowave and Optical Technology Letters vol 54 pp 1990ndash1994 2012

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

International Journal of Antennas and Propagation 5

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

xz-plane

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

yz-plane

(a)

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

xz-plane

minus40 minus30 minus20 minus10 0

minus40

minus30

minus20

minus10

0

minus50minus40minus30minus20minus100minus50

minus40

minus30

minus20

minus10

0

minus180

minus150

minus120minus90

minus60

minus30

0

30

60

90120

150

yz-plane

(b)

Figure 5 Measured radiation patterns of the antenna at (a) 25 GHz and (b) 55 GHz

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] R G Vaughan and J B Andersen ldquoAntenna diversity in mobilecommunicationsrdquo IEEE Transactions on Vehicular Technologyvol VT-36 no 4 pp 149ndash172 1987

[2] R D Murch and K Ben Letaief ldquoAntenna systems for broad-band wireless accessrdquo IEEE Communications Magazine vol 40no 4 pp 76ndash83 2002

[3] D Gesbert M Shafi D-S Shiu P J Smith and A NaguibldquoFrom theory to practice an overview of MIMO space-timecoded wireless systemsrdquo IEEE Journal on Selected Areas inCommunications vol 21 no 3 pp 281ndash302 2003

[4] H Li J Xiong and S L He ldquoExtremely compact dual-bandPIFAs for MIMO applicationrdquo Electronics Letters vol 45 no 17pp 869ndash870 2009

6 International Journal of Antennas and Propagation

[5] M A Jensen and J W Wallace ldquoA review of antennas andpropagation for MIMOwireless communicationsrdquo IEEE Trans-actions on Antennas and Propagation vol 52 no 11 pp 2810ndash2824 2004

[6] A M Tulino A Lozano and S Verdu ldquoImpact of antennacorrelation on the capacity of multiantenna channelsrdquo IEEETransactions on InformationTheory vol 51 no 7 pp 2491ndash25092005

[7] S Karimkashi A A Kishk and D Kajfez ldquoAntenna arrayoptimization using dipole models for MIMO applicationsrdquoIEEE Transactions on Antennas and Propagation vol 59 no 8pp 3112ndash3116 2011

[8] K Payandehjoo and R Abhari ldquoEmploying EBG structuresin multiantenna systems for improving isolation and diversitygainrdquo IEEE Antennas and Wireless Propagation Letters vol 8pp 1162ndash1165 2009

[9] F-G Zhu J-D Xu and Q Xu ldquoReduction of mutual cou-pling between closely-packed antenna elements using defectedground structurerdquo Electronics Letters vol 45 no 12 pp 601ndash602 2009

[10] R Karimian and H Tadayon ldquoMultiband MIMO antennasystem with parasitic elements for WLAN and WiMAX appli-cationrdquo International Journal of Antennas and Propagation vol2013 Article ID 365719 7 pages 2013

[11] X Zhao Y Lee and J Choi ldquoDesign of a compact MIMOantenna using coupled feed for LTE mobile applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 837643 8 pages 2013

[12] B Mun F J Harackiewicz B Kim et al ldquoNew configurationof handset MIMO antenna for LTE 700 band applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 850489 6 pages 2013

[13] S Blanch J Romeu and I Corbella ldquoExact representation ofantenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003

[14] A N Kulkami and S K Sharma ldquoA multiband antenna withMIMO implementation for USB dongle size wireless devicesrdquoMicrowave and Optical Technology Letters vol 54 pp 1990ndash1994 2012

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

6 International Journal of Antennas and Propagation

[5] M A Jensen and J W Wallace ldquoA review of antennas andpropagation for MIMOwireless communicationsrdquo IEEE Trans-actions on Antennas and Propagation vol 52 no 11 pp 2810ndash2824 2004

[6] A M Tulino A Lozano and S Verdu ldquoImpact of antennacorrelation on the capacity of multiantenna channelsrdquo IEEETransactions on InformationTheory vol 51 no 7 pp 2491ndash25092005

[7] S Karimkashi A A Kishk and D Kajfez ldquoAntenna arrayoptimization using dipole models for MIMO applicationsrdquoIEEE Transactions on Antennas and Propagation vol 59 no 8pp 3112ndash3116 2011

[8] K Payandehjoo and R Abhari ldquoEmploying EBG structuresin multiantenna systems for improving isolation and diversitygainrdquo IEEE Antennas and Wireless Propagation Letters vol 8pp 1162ndash1165 2009

[9] F-G Zhu J-D Xu and Q Xu ldquoReduction of mutual cou-pling between closely-packed antenna elements using defectedground structurerdquo Electronics Letters vol 45 no 12 pp 601ndash602 2009

[10] R Karimian and H Tadayon ldquoMultiband MIMO antennasystem with parasitic elements for WLAN and WiMAX appli-cationrdquo International Journal of Antennas and Propagation vol2013 Article ID 365719 7 pages 2013

[11] X Zhao Y Lee and J Choi ldquoDesign of a compact MIMOantenna using coupled feed for LTE mobile applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 837643 8 pages 2013

[12] B Mun F J Harackiewicz B Kim et al ldquoNew configurationof handset MIMO antenna for LTE 700 band applicationsrdquoInternational Journal of Antennas and Propagation vol 2013Article ID 850489 6 pages 2013

[13] S Blanch J Romeu and I Corbella ldquoExact representation ofantenna system diversity performance from input parameterdescriptionrdquo Electronics Letters vol 39 no 9 pp 705ndash707 2003

[14] A N Kulkami and S K Sharma ldquoA multiband antenna withMIMO implementation for USB dongle size wireless devicesrdquoMicrowave and Optical Technology Letters vol 54 pp 1990ndash1994 2012

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

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