Reconfigurable Magneto-Electric Dipole Antennas for Base …downloads.hindawi.com/journals/wcmc/2018/2408923.pdf · Reconfigurable Magneto-Electric Dipole Antennas for Base Stations

Review ArticleReconfigurable Magneto-Electric Dipole Antennas forBase Stations in Modern Wireless Communication Systems

Lei Ge 1 Xujun Yang1 Zheng Dong1 Dengguo Zhang 1 and Xierong Zeng2

1College of Electronic Science and Technology Shenzhen University Shenzhen China2College of Material Science and Engineering Shenzhen University Shenzhen China

Correspondence should be addressed to Lei Ge leigeszueducn

Received 19 January 2018 Accepted 25 March 2018 Published 15 May 2018

Academic Editor Luca De Nardis

Copyright copy 2018 Lei Ge et al This is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Magneto-electric (ME) dipole antennas with the function of changing the antenna characteristics such as frequency polarizationor radiation patterns are reviewed in this paper The reconfigurability is achieved by electrically altering the states of diodes orvaractors to change the surface currents distributions or reflector size of the antenna The purpose of the designs is to obtain agileantenna characteristics togetherwith gooddirective radiation performances such as low cross-polarization level high front-to-backratio and stable gain By reconfiguring the antenna capability to support more than one wireless frequency standard switchablepolarizations or cover tunable areas the reconfigurableME dipole antennas are able to switch functionality as themission changesTherefore it can help increase the communication efficiency and reduce the construction cost This shows very attractive featuresin base station antennas of modern wireless communication applications

1 Introduction

Owing to the tremendous evolution of wireless communica-tions the electromagnetic frequency spectrum is more andmore crowded and the communication environment is moreand more complex To improve the communication qualitythe fifth-generation (5G) mobile communications were pro-posed several years ago and will be commercially available inearly 2020 In 5G mobile communications higher transmis-sion speed higher reliability and lower delay are required

There are three ways to increase the communicationcapacity as shown in Figure 1 (1) using new frequencybands with wider bandwidth (2) improving the spectrumefficiency (3) using more radio frequency (RF) cells withsmaller size Because of this in 5G mobile communicationsmillimeter-wave bands will be used to increase the frequencybandwidth multi-input multi-output (MIMO) antennas willbe applied to increase the network density In the past severalyears reconfiguration technique applied in RF systems toeffectively increase the spectrum efficiency has been demon-strated Accordingly reconfiguration technique with the abil-ity to improve the frequency spectrumutilization has aroused

great research interest in both industrial and academic areasAs the front end antennas play a very important role inany wireless communication system Antennas with recon-figurable characteristics can effectively enhance the systemperformance because they are able to adjust the antenna char-acteristics automatically and make them suitable to complexscenarios Antennas with the function to dynamically changetheir operating frequency polarization or radiation patternsare needed to improve the channel capacity in communica-tion systems According to Friis transmission equation

119875119877119875119879 = (1 minus 1003816100381610038161003816Γ11987910038161003816100381610038162) (1 minus 1003816100381610038161003816Γ11987710038161003816100381610038162)119866119879119866119877 1003816100381610038161003816120588119879 sdot 12058811987710038161003816100381610038162 ( 120582

4120587119903)2

(1)

The transmission efficiency between the transmitter andreceiver mainly depends on three factors impedancematching (Γ119879 Γ119877) antenna gain (119866119879 119866119877) and polarizationmatching (120588119879 120588119877) Therefore reconfigurable antennas can bebasically categorized into three types (1) frequency reconfig-urable antennas [1ndash5] (2) polarization reconfigurable anten-nas [6ndash11] (3) pattern reconfigurable antennas [5 12ndash18]

HindawiWireless Communications and Mobile ComputingVolume 2018 Article ID 2408923 8 pageshttpsdoiorg10115520182408923

2 Wireless Communications and Mobile Computing

Required capacity

Currentcapacity

Spec

trum

effici

ency

Frequency bandwidthNetw

ork density

Figure 1 Methods for increasing the capacity

Although many reconfigurable antennas have been pro-posed they are usually designed based on microstrip struc-tures [1 3ndash5 9ndash13 15 16] Due to the narrow bandwidththey are not appropriate to be applied in base stations Onthe other hand along with the development of wirelesscommunications antennas with wider bandwidth and gooddirection radiation patterns are required Therefore theconventional directional antenna candidates cannot satisfythe need of reconfigurable base station antennas

In 2006 Prof Luk invented a new antenna type specifiedas the magneto-electric (ME) dipole antenna [19] whichconsists of a magnetic dipole and an electric dipole Byexciting the complementary dipoles with suitable amplitudesand phases simultaneously the antenna is able to producegood radiation characteristics over a wide frequency bandTaking advantages of the ME dipole antennas they are veryappreciated for the extensive applications of mobile cellularnetworks When combining the ME dipole with reconfigura-tion technique consequent reconfigurable ME dipole anten-nas can be developed for base stations in modern wirelesssystems In this paper three different kinds of reconfigurableME dipole antennas are reviewed namely frequency recon-figurable ME dipole polarization reconfigurable ME dipoleand beamwidth reconfigurable ME dipoles In Section 2 afrequency reconfigurable ME dipole antenna is reviewed InSection 3 several polarization switchableMEdipole antennasare reviewed In Section 4 three beamwidth reconfigurableME dipole antennas are reviewedThese designs show attrac-tive features for modern wireless communication systems

2 Frequency Reconfigurable MEDipole Antenna

In this section we depict a frequency reconfigurable MEdipole antenna [2] Figure 2 gives the configuration of theantenna The wide-narrowband antenna reconfiguration isdemonstrated by systematically incorporating a broadbandME dipole antenna and a frequency reconfigurable narrow-band dipole antenna The ME dipole as a part of the overallantenna structure plays a crucial role in providing widebandoperation On the other hand a length-switchable directed

dipole antenna is designed to feature reconfigurable narrow-band operation A vertically oriented balun is used to feed thedipole By using a box-shaped cavity the dipole can generategood unidirectional radiation performance By dynamicallyswitching the states of PIN diodes embedded in the thindipole a changeable effective length is achieved Besides thesurface current flowed on the thin dipole and the ME dipolecan be changed by five groups of switches Therefore theantenna can be switched between four narrowband modesand a wideband mode Notably when the thin dipole isswitched OFF the ME dipole radiates with a wide band thatcan cover the operating frequency of the four narrow bands

Themeasured reflection coefficients are presented in Fig-ure 3 As observed from the figure the fractional impedancebandwidth of the wideband mode is 89 and four differentnarrow bands appear at 095 135 17 and 2GHz respectivelyIn addition the main beam of the radiation patterns isalways fixed in the broadside direction with front-to-backratios of above 20 dB and cross-polarization levels of belowminus22 dB Therefore the design can work in one widebandmode for sensing and four reconfigurable narrowbandmodesfor communications which is attractive for base stations incognitive radio

3 Polarization Reconfigurable MEDipole Antenna

In this section we present three polarization reconfigurableME dipole antennas All the three designs [6ndash8] are basedon similar four-sectional ME dipole geometry while thepolarization reconfiguration is realized by different feedstructures and switching methods The based ME dipolestructure is based on the designs in [20 21]

In [6] a feeding structure of an end-curving crossdipole for excitation of the polarization diversity antenna isproposed as shown in Figure 4(a) PIN diodes are embeddedinto the arms of the cross dipole Diodes can be switchedON or OFF in real time therefore the RF signals can becoupled from the coaxial cable to theME dipole Accordinglya polarization diversity betweenhorizontal and vertical polar-ization modes can be produced An overlapped impedancebandwidth ranging from 186 to 235GHz is achieved atboth orthogonally polarized states Furthermore the antennapresents a good radiation performance with an 8 dBi gainover the whole band

In [7] another ME dipole antenna with the diversityof polarization is presented which can operate betweenone linear polarization (LP) and two orthogonal circularpolarizations (CP) In this design four PIN diodes areembedded into the thin line printed on the diagonal positionof four horizontal metal plates for controlling connection ordisconnection When all diodes are in OFF LP operationis achieved which means no thin lines are connected Torealize CP radiation one single thin line is connected at thediagonal parts perturbation is therefore introduced and thencorresponding left-handed circularly polarization (LHCP)or right-handed circularly polarization (RHCP) can emergeThe proposed design possesses admirable features such asgain stability and good directional radiation patterns

Wireless Communications and Mobile Computing 3

xy

z

240240

Horizontal DC lines

48

Rectangular cavityFolded bowtie dipole

SubstrateThin dipole

(a) (b)

Figure 2 Geometry of the frequency reconfigurable ME dipole antenna [2] (a) 3D view of the design (b) fabricated prototype

Measured results

Wide bandNB1NB2

NB3NB4

minus25

minus20

minus15

minus10

minus5

0

|S11|

(dB)

10 12 14 16 18 20 2208Frequency (GHz)

Figure 3 Measured |11987811| of the frequency reconfigurableME dipoleantenna

In [8] the antenna is composed of an ME dipole asubstrate-integrate waveguide (SIW) cavity and some DClines as given in Figure 5 The design is comprised of foursquare metallic patches four vertically oriented metal postsand a strip In this design two sets of PIN diodes (SW1and SW2) are used to help connecting or disconnecting thediagonalmetal patcheswith the strip By controlling the statesof the two pairs of switches one LP and two CP modes canbe switched as depicted in Figure 6 When all diodes areON LP radiation can emerge To excite CP modes one ofthe two diode groups is ON while another is OFF Hencethree polarization states can be realized by controlling thestates of the switches The effective overlapped bandwidth is16 covering 507ndash595GHz for applications of 5GWiFiThemeasured antenna gain maintains stability at approximately82 dBi across the band of interest for all operation states

4 Beamwidth Reconfigurable MEDipole Antenna

As discussed frequency reconfigurable and polarizationreconfigurable antennas can be designed on the basis of theME dipole In this section we will discuss radiation pattern

reconfiguration based on the ME dipole structure Conven-tionally pattern reconfigurable antennas are mainly designedto switch the radiating direction of the antenna Furthermorean antenna with the ability of electronically controllingits radiation beamwidth can enhance the communicationquality of wireless systems Thus beamwidth reconfigurableantennas are demanded for modern base stations In thissection three different methods are introduced to implementbeamwidth reconfiguration of ME dipole antennas

First a three-element linear ME dipole array is used toachieve tunable beamwidth [17] As shown in Figure 7 thelinear array is composed of three ME dipoles and a feedingnetwork The feeding network is able to reset the phasedistribution with a power distribution ratio of 1 2 1 for threeantenna elements The phase difference between Antennas1 and 3 and Antenna 2 is 120573 = 0∘50∘108∘ The operationprinciple of the antenna can be explained by a simplifiedthree-element linear array As illustrated in Figure 8 thethree elements are located along the 119910-axis and the spacebetween them is 119889 In this condition it is assumed that thethree antenna elements are all the same andwell-isolatedTheradiation field in the yoz-plane can be expressed as

119865 (120579)119879= [1198861119890minus119895(1198961199031+1205951) + 1198862119890minus119895(1198961199032+1205952) + 1198863119890minus119895(1198961199033+1205953)] 119891 (120579) (2)

where the amplitudes and phases of excitations are an and120595119899(119899 = 1 2 3) and 119891(120579) is the radiation pattern of a singleantenna element In order to achieve symmetrical radiationpattern in the 119867-plane the amplitudes and phases of Ant 1and 3 are set to be the same Assuming 1198862 = 1198721198861 = 11987211988631205952 = 1205951 + 120573 = 1205953 + 120573 and the factor of the antenna array isdecreased to

119860119865 = 1198861 [2 cos (119896119889 sin 120579) + 119872 cos120573 minus 119895119872 sin120573] (3)

For different 120573 the array factor in the yoz-plane is givenin Figure 9 with 119889 = 051205820 and 119872 = radic2 Especially byutilizing the variation of the beam of the array factor andthen multiplying the array factor with the pattern of a singleelement the reconfiguration of the beamwidth is able to berealized


(a) (b)

Figure 4 Geometry of the polarization reconfigurable ME dipole antennas (a) the antenna in [6] (b) the antenna in [7]

zy

x

DC linesStrip Patch

Substrate 1

Substrate 2

ViaPost

Feed

Slot

(a)

x

y

Feed

D S

L

L P

Capacitors

SW1

SW1

SW2

SW2

G2

G1

G1

G2

LS

S1

S1 WS

S2

(b)

Figure 5 Geometry of the polarization reconfigurable ME dipole antenna [8] (a) 3D view (b) top view

(a) (b) (c)

Figure 6 Switching states of the polarization reconfigurable ME dipole antenna [8] (a) LP state (b) RHCP state (c) LHCP state


x

yz

Ant 3

Ant 2

Ant 1Ground plane

d

W

Copper plateΓ-shaped probe

GL

GW

Figure 7 Geometry of the three-element linear ME dipole arraywith beamwidth reconfiguration

z

yd d

r1

r2r3

Ant 1 Ant 2 Ant 3(a11) (a22) (a33)

Figure 8 Three-element array model

Secondly LP and DP ME dipole antennas with the prop-erty of a dynamic 119867-plane beamwidth control are achievedas shown in Figure 10 [14] Two tunable parasitic dipoles areput on the sides of a driven ME dipole along its 119867-planeVaractor diodes are loaded on the parasitic thin dipoles tochange the strength of the mutual coupling When changingthe state of the varactor diode the overall radiation pattern ofthe antenna could be tuned Different from the first methodthis design uses the magnitude distribution instead of thephase distribution in the first method to obtain beamwidthreconfiguration Figure 11 describes the simplified equivalentcircuit of the designThemutual coupling between the drivenand parasitic dipoles is represented by a transformer Sincethe varactor diodes are inserted in the parasitic dipoles theimpedance of the parasitic element is able to be varied bymeans of changing the capacitance of the varactor diodesTherefore themagnitude and phase distribution of the drivenand parasitic dipoles are decided by the varactor diodesConsequently the entire antenna works similarly to a three-element array where the center element is an ME dipoleand the left and right elements are dipoles with an identicalmagnitude and phase distribution The capacitance values ofthe varactor diodes determine the coupling strength and inturn the magnitude distribution Hence the entire radiationpattern of the antenna could be varied by tuning the powerdistribution of the dipoles The simulated radiation patternsin the 119867-plane is presented in Figure 12 with different 119862 (thecapacitance value of varactor diodes) We can see that alongwith 119862 which reduces from 4 to 08 pF the 3 dB beamwidthof the proposed antenna rises from 80∘ to 160∘

270

300

330

0

30

60

90

0 dB

minus10

minus20

= 0∘

= 45∘

= 90∘

= 135∘

= 180∘

Figure 9 Array factor for different 120573 with 119889 = 051205820 and 119872 = radic2

Finally an LP design with beamwidth reconfigurationis realized in [18] As shown in Figure 13 the antenna iscomposed of a Γ-probe-fed ME dipole Along its 119867-planethere are three pairs of tunable strip gratings Each strip iscut into 16 short portions and 15 PIN diodes are inserted intothe gaps When forward biased the PIN diodes are ON andthe strips serve as reflectors When unbiased the PIN diodesareOFF and the strips can be seen as transparent for radiatingwave Furthermore because the PINdiodes ondifferent stripsare commanded by separated DC signals by changing theamplitude of the DC signals the size of the reflector can bevaried as indicated in Figure 14 Therefore the beamwidthof the proposed antenna could be changed It should beemphasized that this method for beamwidth reconfigurationis different from the aforementioned The first two methodsare implemented by tuning the amplitude and phase distri-butions of the parasitic elements while this design is realizedby reconfiguring the size of the reflector The characteristicsof this simple antenna are highly attractive for applications incellular systems It has an impedance bandwidth as wide as40 The 119867-plane beamwidth can be tuned from 153∘ to 81∘

5 Conclusion

In this paper some reconfigurable ME dipole antennashave been reviewed A frequency reconfigurable design hasbeen first reviewed showing a wideband mode for sensingand reconfigurable narrowband modes for communicationswhich is attractive for base stations in cognitive radioSecondly polarization reconfigurable designs which are ableto switch between the LP RHCP and LHCP states havebeen reviewed The designs own the ability of degradingmultipath-fading effects and enhancing the system stabilityand are useful for indoor wireless communication systemsand can also be used as antenna elements for the outdoor basestations Finally three different beamwidth reconfigurabledesigns have been reviewed with dynamic control overtheir radiation beamwidth according to the environmentrequirement These designs are attractive for outdoor basestations in future wireless communication systems

Compared with other reconfigurable directional antennacandidates the ME dipole owns some very attractive advan-tages as indicated in Table 1 The ME dipole can obtain wide


x

yz

180180

DC line

Ground

Wide dipole

Substrate

Parasitic thin dipole

Metal plates

2

29

49

7

30

6

To SMA

feedΓ-shaped

(a)

x

yz 240240

DC line

Ground

Square patch

Substrate


Metal post

To SMA

Γ-shaped feed 1

Fl

Fd

Fw

Fℎ

(b)

Figure 10 Geometry of the linearly polarized and dual-polarized beamwidth reconfigurable ME dipole antennas [14] (a) LP antenna (b)DP antenna

Mutualcoupling

C

C

ZD

ZP

ZPD

ZPD

Figure 11 Equivalent circuit of the LP antenna 119885119863 119885119875 119885119875119863represent the impedances of the wide planer dipole shorted quarter-wavelength patch antenna and the parasitic dipoles respectively

C = 4 pFC = 16 pFC = 12 pF

C = 1 pFC = 08 pF

300 60 90minus60 minus30minus90 (degree)

minus10

minus8

minus6

minus4

minus2

0

Mag

nitu

de (d

B)

Figure 12 Simulated radiation patterns in the 119867-plane at 2GHzwith different 119862

bandwidth and excellent unidirectional radiation patternswhen designed for reconfigurable antennasThis is attributedto the advantages of the ME dipole Besides since the DCbiasing lines can be hidden in the metal posts (magneticdipole) the DC biasing lines can cause ignorable effects on

DC lines

Rectangular reflector

Horizontal substrate

ME dipole

Tunable strips

PositiveDC voltages

PIN diodes

Strip 1Strip 2

Strip 3d

ddH

Vertical substrate

25

28

49

39

11

To SMA

x

yz

feedΓ-shaped

0V DC voltage

Figure 13 Geometry of the beamwidth reconfigurable ME dipoleantenna using tunable strip grating

Table 1 Comparison between ME dipole with other reconfigurabledirectional antenna candidates

Reconfigurabledirectionalantennacandidates

Bandwidth

Unidirectionalradiationpatterns

(front-to-backratio

cross-pol)

Difficulty levelto be

integrated withtuning

mechanisms

Patch antenna[1] Narrow Poor Easy

Cavity-backedslot antenna[12]

Fair Fair Easy

Yagi-Udaantenna[13]

Fair Fair Difficult

Dipole[2] Wide Good Difficult

ME dipole Wide Excellent Fair

the antenna performance Therefore the ME dipole is easyto be integrated with tuning mechanisms especially with


(a) (b)

(c) (d)

Figure 14 Equivalent structures of the antenna in different beamwidth states (a) State 1 (b) State 2 (c) State 3 (d) State 4

the electronically controlled switches As discussed abovethe ME dipole shows very attractive features over otherdirectional antenna candidates in reconfigurable base stationantenna designThese designs may be useful for base stationsin wireless communication systems

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The work is supported by the National Natural ScienceFoundation of China (no 61601303) Fundamental ResearchFoundation of Shenzhen (no JCYJ20160308095149392)Fundamental Research Foundation of Shenzhen (noJCYJ20170817095519575) and SZU RD Fund (no 2016022)

References

[1] M R Hamid P Gardner P S Hall and F Ghanem ldquoSwitched-band Vivaldi antennardquo IEEE Transactions on Antennas andPropagation vol 59 no 5 pp 1472ndash1480 2011

[2] L Ge and K-M Luk ldquoA band-reconfigurable antenna based ondirected dipolerdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 1 pp 64ndash71 2014

[3] A T Kolsrud M-Y Li and K Chang ldquoDual-frequency elec-tronically tunable CPW-fed CPS dipole antennardquo IEEE Elec-tronics Letters vol 34 no 7 pp 609ndash611 1998

[4] B Avser and G M Rebeiz ldquoTunable dual-band antennasfor 07ndash11-GHz and 17ndash23-GHz carrier aggregation systemsrdquoInstitute of Electrical and Electronics Engineers Transactions onAntennas and Propagation vol 63 no 4 part 2 pp 1498ndash15042015

[5] K Chung Y Nam T Yun and J Choi ldquoReconfigurable micro-strip-patch antenna with frequency and polarization-diversityfunctionsrdquo Microwave and Optical Technology Letters vol 47no 6 pp 605ndash607 2005

[6] F Wu and K-M Luk ldquoA Reconfigurable Magneto-ElectricDipole Antenna Using Bent Cross-Dipole Feed for PolarizationDiversityrdquo IEEE Antennas andWireless Propagation Letters vol16 pp 412ndash415 2017

[7] F Wu and K M Luk ldquoWideband tri-polarization reconfig-urable magneto-electric dipole antennardquo Institute of Electricaland Electronics Engineers Transactions on Antennas and Propa-gation vol 65 no 4 pp 1633ndash1641 2017

[8] L Ge X Yang D Zhang M Li and H Wong ldquoPolarization-ReconfigurableMagnetoelectric Dipole Antenna for 5GWi-FirdquoIEEE Antennas and Wireless Propagation Letters vol 16 pp1504ndash1507 2017

[9] W Lin and H Wong ldquoPolarization reconfigurable wheel-shaped antenna with conical-beam radiation patternrdquo IEEETransactions on Antennas and Propagation vol 63 no 2 pp491ndash499 2015

[10] Y J Sung T U Jang and Y-S Kim ldquoA reconfigurable micro-strip antenna for switchable polarizationrdquo IEEE Microwave andWireless Components Letters vol 14 no 11 pp 534ndash536 2004


[11] U L Bombale and S Gupta ldquoBroadband planer array withswitchable polarizationsrdquo Microwave and Optical TechnologyLetters vol 49 no 10 pp 2415ndash2419 2007

[12] J-S Row andM-J Hou ldquoDesign of polarization diversity patchantenna based on a compact reconfigurable feeding networkrdquoIEEE Transactions on Antennas and Propagation vol 62 no 10pp 5349ndash5352 2014

[13] P FWahidMAAli andB CDeLoach ldquoA reconfigurable Yagiantenna for wireless communicationsrdquo Microwave and OpticalTechnology Letters vol 38 no 2 pp 140-141 2003

[14] L Ge and K-M Luk ldquoLinearly polarized and dual-polarizedmagneto-electric dipole antennas with reconfigurable beam-width in the H-planerdquo Institute of Electrical and ElectronicsEngineers Transactions on Antennas and Propagation vol 64no 2 pp 423ndash431 2016

[15] P-Y Qin Y J Guo A R Weily and C-H Liang ldquoA patternreconfigurable U-slot antenna and its applications in MIMOsystemsrdquo IEEE Transactions on Antennas and Propagation vol60 no 2 pp 516ndash528 2012

[16] G Monti L Corchia and L Tarricone ldquoA microstrip antennawith a reconfigurable pattern for RFID applicationsrdquo Progress inElectromagnetics Research B no 45 pp 101ndash116 2012

[17] L Ge and K M Luk ldquoA three-element linear magneto-electricdipole array with beamwidth reconfigurationrdquo IEEE Antennasand Wireless Propagation Letters vol 14 pp 28ndash31 2015

[18] L Ge and K M Luk ldquoBeamwidth Reconfigurable Magneto-Electric Dipole Antenna Based onTunable StripGrating Reflec-torrdquo IEEE Access vol 4 pp 7039ndash7045 2016

[19] K M Luk and H Wong ldquoA new wideband unidirectionalantenna elementrdquo International Journal of Microwave and Opti-cal Technology vol 1 no 1 pp 35ndash44 2006

[20] Y Li and K M Luk ldquo60-GHz Dual-Polarized Two-Dimen-sional Switch-Beam Wideband Antenna Array of Aperture-Coupled Magneto-Electric Dipolesrdquo IEEE Transactions onAntennas and Propagation vol 64 no 2 pp 554ndash563 2016

[21] Y Li and K-M Luk ldquoA 60-GHz wideband circularly polar-ized aperture-coupled magneto-electric dipole antenna arrayrdquoInstitute of Electrical and Electronics Engineers Transactions onAntennas and Propagation vol 64 no 4 pp 1325ndash1333 2016

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Advances in

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Submit your manuscripts atwwwhindawicom


Required capacity

Currentcapacity

Spec

trum

effici

ency

Frequency bandwidthNetw

ork density

Figure 1 Methods for increasing the capacity

Although many reconfigurable antennas have been pro-posed they are usually designed based on microstrip struc-tures [1 3ndash5 9ndash13 15 16] Due to the narrow bandwidththey are not appropriate to be applied in base stations Onthe other hand along with the development of wirelesscommunications antennas with wider bandwidth and gooddirection radiation patterns are required Therefore theconventional directional antenna candidates cannot satisfythe need of reconfigurable base station antennas

In 2006 Prof Luk invented a new antenna type specifiedas the magneto-electric (ME) dipole antenna [19] whichconsists of a magnetic dipole and an electric dipole Byexciting the complementary dipoles with suitable amplitudesand phases simultaneously the antenna is able to producegood radiation characteristics over a wide frequency bandTaking advantages of the ME dipole antennas they are veryappreciated for the extensive applications of mobile cellularnetworks When combining the ME dipole with reconfigura-tion technique consequent reconfigurable ME dipole anten-nas can be developed for base stations in modern wirelesssystems In this paper three different kinds of reconfigurableME dipole antennas are reviewed namely frequency recon-figurable ME dipole polarization reconfigurable ME dipoleand beamwidth reconfigurable ME dipoles In Section 2 afrequency reconfigurable ME dipole antenna is reviewed InSection 3 several polarization switchableMEdipole antennasare reviewed In Section 4 three beamwidth reconfigurableME dipole antennas are reviewedThese designs show attrac-tive features for modern wireless communication systems

2 Frequency Reconfigurable MEDipole Antenna

In this section we depict a frequency reconfigurable MEdipole antenna [2] Figure 2 gives the configuration of theantenna The wide-narrowband antenna reconfiguration isdemonstrated by systematically incorporating a broadbandME dipole antenna and a frequency reconfigurable narrow-band dipole antenna The ME dipole as a part of the overallantenna structure plays a crucial role in providing widebandoperation On the other hand a length-switchable directed

dipole antenna is designed to feature reconfigurable narrow-band operation A vertically oriented balun is used to feed thedipole By using a box-shaped cavity the dipole can generategood unidirectional radiation performance By dynamicallyswitching the states of PIN diodes embedded in the thindipole a changeable effective length is achieved Besides thesurface current flowed on the thin dipole and the ME dipolecan be changed by five groups of switches Therefore theantenna can be switched between four narrowband modesand a wideband mode Notably when the thin dipole isswitched OFF the ME dipole radiates with a wide band thatcan cover the operating frequency of the four narrow bands

Themeasured reflection coefficients are presented in Fig-ure 3 As observed from the figure the fractional impedancebandwidth of the wideband mode is 89 and four differentnarrow bands appear at 095 135 17 and 2GHz respectivelyIn addition the main beam of the radiation patterns isalways fixed in the broadside direction with front-to-backratios of above 20 dB and cross-polarization levels of belowminus22 dB Therefore the design can work in one widebandmode for sensing and four reconfigurable narrowbandmodesfor communications which is attractive for base stations incognitive radio

3 Polarization Reconfigurable MEDipole Antenna

In this section we present three polarization reconfigurableME dipole antennas All the three designs [6ndash8] are basedon similar four-sectional ME dipole geometry while thepolarization reconfiguration is realized by different feedstructures and switching methods The based ME dipolestructure is based on the designs in [20 21]

In [6] a feeding structure of an end-curving crossdipole for excitation of the polarization diversity antenna isproposed as shown in Figure 4(a) PIN diodes are embeddedinto the arms of the cross dipole Diodes can be switchedON or OFF in real time therefore the RF signals can becoupled from the coaxial cable to theME dipole Accordinglya polarization diversity betweenhorizontal and vertical polar-ization modes can be produced An overlapped impedancebandwidth ranging from 186 to 235GHz is achieved atboth orthogonally polarized states Furthermore the antennapresents a good radiation performance with an 8 dBi gainover the whole band

In [7] another ME dipole antenna with the diversityof polarization is presented which can operate betweenone linear polarization (LP) and two orthogonal circularpolarizations (CP) In this design four PIN diodes areembedded into the thin line printed on the diagonal positionof four horizontal metal plates for controlling connection ordisconnection When all diodes are in OFF LP operationis achieved which means no thin lines are connected Torealize CP radiation one single thin line is connected at thediagonal parts perturbation is therefore introduced and thencorresponding left-handed circularly polarization (LHCP)or right-handed circularly polarization (RHCP) can emergeThe proposed design possesses admirable features such asgain stability and good directional radiation patterns


xy

z

240240

Horizontal DC lines

48



(a) (b)


Measured results

Wide bandNB1NB2

NB3NB4

minus25

minus20

minus15

minus10

minus5

0

|S11|

(dB)

10 12 14 16 18 20 2208Frequency (GHz)












(a) (b)


zy

x

DC linesStrip Patch

Substrate 1

Substrate 2

ViaPost

Feed

Slot

(a)

x

y

Feed

D S

L

L P

Capacitors

SW1

SW1

SW2

SW2

G2

G1

G1

G2

LS

S1

S1 WS

S2

(b)


(a) (b) (c)



x

yz

Ant 3

Ant 2

Ant 1Ground plane

d

W


GL

GW


z

yd d

r1

r2r3

Ant 1 Ant 2 Ant 3(a11) (a22) (a33)



270

300

330

0

30

60

90

0 dB

minus10

minus20

= 0∘

= 45∘

= 90∘

= 135∘

= 180∘



5 Conclusion




x

yz

180180

DC line

Ground

Wide dipole

Substrate


Metal plates

2

29

49

7

30

6

To SMA

feedΓ-shaped

(a)

x

yz 240240

DC line

Ground

Square patch

Substrate


Metal post

To SMA

Γ-shaped feed 1

Fl

Fd

Fw

Fℎ

(b)


Mutualcoupling

C

C

ZD

ZP

ZPD

ZPD


C = 4 pFC = 16 pFC = 12 pF

C = 1 pFC = 08 pF


minus10

minus8

minus6

minus4

minus2

0

Mag

nitu

de (d

B)



DC lines



ME dipole

Tunable strips

PositiveDC voltages

PIN diodes

Strip 1Strip 2

Strip 3d

ddH

Vertical substrate

25

28

49

39

11

To SMA

x

yz

feedΓ-shaped

0V DC voltage




Bandwidth


(front-to-backratio

cross-pol)



mechanisms



Fair Fair Easy

Yagi-Udaantenna[13]

Fair Fair Difficult





(a) (b)

(c) (d)





Acknowledgments


References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



xy

z

240240

Horizontal DC lines

48



(a) (b)


Measured results

Wide bandNB1NB2

NB3NB4

minus25

minus20

minus15

minus10

minus5

0

|S11|

(dB)

10 12 14 16 18 20 2208Frequency (GHz)












(a) (b)


zy

x

DC linesStrip Patch

Substrate 1

Substrate 2

ViaPost

Feed

Slot

(a)

x

y

Feed

D S

L

L P

Capacitors

SW1

SW1

SW2

SW2

G2

G1

G1

G2

LS

S1

S1 WS

S2

(b)


(a) (b) (c)



x

yz

Ant 3

Ant 2

Ant 1Ground plane

d

W


GL

GW


z

yd d

r1

r2r3

Ant 1 Ant 2 Ant 3(a11) (a22) (a33)



270

300

330

0

30

60

90

0 dB

minus10

minus20

= 0∘

= 45∘

= 90∘

= 135∘

= 180∘



5 Conclusion




x

yz

180180

DC line

Ground

Wide dipole

Substrate


Metal plates

2

29

49

7

30

6

To SMA

feedΓ-shaped

(a)

x

yz 240240

DC line

Ground

Square patch

Substrate


Metal post

To SMA

Γ-shaped feed 1

Fl

Fd

Fw

Fℎ

(b)


Mutualcoupling

C

C

ZD

ZP

ZPD

ZPD


C = 4 pFC = 16 pFC = 12 pF

C = 1 pFC = 08 pF


minus10

minus8

minus6

minus4

minus2

0

Mag

nitu

de (d

B)



DC lines



ME dipole

Tunable strips

PositiveDC voltages

PIN diodes

Strip 1Strip 2

Strip 3d

ddH

Vertical substrate

25

28

49

39

11

To SMA

x

yz

feedΓ-shaped

0V DC voltage




Bandwidth


(front-to-backratio

cross-pol)



mechanisms



Fair Fair Easy

Yagi-Udaantenna[13]

Fair Fair Difficult





(a) (b)

(c) (d)





Acknowledgments


References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



(a) (b)


zy

x

DC linesStrip Patch

Substrate 1

Substrate 2

ViaPost

Feed

Slot

(a)

x

y

Feed

D S

L

L P

Capacitors

SW1

SW1

SW2

SW2

G2

G1

G1

G2

LS

S1

S1 WS

S2

(b)


(a) (b) (c)



x

yz

Ant 3

Ant 2

Ant 1Ground plane

d

W


GL

GW


z

yd d

r1

r2r3

Ant 1 Ant 2 Ant 3(a11) (a22) (a33)



270

300

330

0

30

60

90

0 dB

minus10

minus20

= 0∘

= 45∘

= 90∘

= 135∘

= 180∘



5 Conclusion




x

yz

180180

DC line

Ground

Wide dipole

Substrate


Metal plates

2

29

49

7

30

6

To SMA

feedΓ-shaped

(a)

x

yz 240240

DC line

Ground

Square patch

Substrate


Metal post

To SMA

Γ-shaped feed 1

Fl

Fd

Fw

Fℎ

(b)


Mutualcoupling

C

C

ZD

ZP

ZPD

ZPD


C = 4 pFC = 16 pFC = 12 pF

C = 1 pFC = 08 pF


minus10

minus8

minus6

minus4

minus2

0

Mag

nitu

de (d

B)



DC lines



ME dipole

Tunable strips

PositiveDC voltages

PIN diodes

Strip 1Strip 2

Strip 3d

ddH

Vertical substrate

25

28

49

39

11

To SMA

x

yz

feedΓ-shaped

0V DC voltage




Bandwidth


(front-to-backratio

cross-pol)



mechanisms



Fair Fair Easy

Yagi-Udaantenna[13]

Fair Fair Difficult





(a) (b)

(c) (d)





Acknowledgments


References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



x

yz

Ant 3

Ant 2

Ant 1Ground plane

d

W


GL

GW


z

yd d

r1

r2r3

Ant 1 Ant 2 Ant 3(a11) (a22) (a33)



270

300

330

0

30

60

90

0 dB

minus10

minus20

= 0∘

= 45∘

= 90∘

= 135∘

= 180∘



5 Conclusion




x

yz

180180

DC line

Ground

Wide dipole

Substrate


Metal plates

2

29

49

7

30

6

To SMA

feedΓ-shaped

(a)

x

yz 240240

DC line

Ground

Square patch

Substrate


Metal post

To SMA

Γ-shaped feed 1

Fl

Fd

Fw

Fℎ

(b)


Mutualcoupling

C

C

ZD

ZP

ZPD

ZPD


C = 4 pFC = 16 pFC = 12 pF

C = 1 pFC = 08 pF


minus10

minus8

minus6

minus4

minus2

0

Mag

nitu

de (d

B)



DC lines



ME dipole

Tunable strips

PositiveDC voltages

PIN diodes

Strip 1Strip 2

Strip 3d

ddH

Vertical substrate

25

28

49

39

11

To SMA

x

yz

feedΓ-shaped

0V DC voltage




Bandwidth


(front-to-backratio

cross-pol)



mechanisms



Fair Fair Easy

Yagi-Udaantenna[13]

Fair Fair Difficult





(a) (b)

(c) (d)





Acknowledgments


References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



x

yz

180180

DC line

Ground

Wide dipole

Substrate


Metal plates

2

29

49

7

30

6

To SMA

feedΓ-shaped

(a)

x

yz 240240

DC line

Ground

Square patch

Substrate


Metal post

To SMA

Γ-shaped feed 1

Fl

Fd

Fw

Fℎ

(b)


Mutualcoupling

C

C

ZD

ZP

ZPD

ZPD


C = 4 pFC = 16 pFC = 12 pF

C = 1 pFC = 08 pF


minus10

minus8

minus6

minus4

minus2

0

Mag

nitu

de (d

B)



DC lines



ME dipole

Tunable strips

PositiveDC voltages

PIN diodes

Strip 1Strip 2

Strip 3d

ddH

Vertical substrate

25

28

49

39

11

To SMA

x

yz

feedΓ-shaped

0V DC voltage




Bandwidth


(front-to-backratio

cross-pol)



mechanisms



Fair Fair Easy

Yagi-Udaantenna[13]

Fair Fair Difficult





(a) (b)

(c) (d)





Acknowledgments


References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



(a) (b)

(c) (d)





Acknowledgments


References

























RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia
















RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


Documents

Reconfigurable Magneto-Electric Dipole Antennas for Base …downloads.hindawi.com/journals/wcmc/2018/2408923.pdf · Reconfigurable Magneto-Electric Dipole Antennas for Base Stations