Received: 24 February 2018

DOI: 10.1002/mop.31387

A wideband antenna usingmetasurface for the 2G/3G/LTE/5G communications

Botao Feng1 | Lei Li1 |

Qingsheng Zeng2 | Kwok L. Chung3

1College of Electronic Science and Technology, Shenzhen University,Shenzhen, China2College of Aeronautics, Nanjing University of Aeronautics andAstronautics, Nanjing, China3School of Communications and Electronic Engineering, QingdaoUniversity of Technology, Qingdao, China

CorrespondenceBotao Feng, College of Electronic Science and Technology, ShenzhenUniversity, Shenzhen 518 060, China.Email: fengbotao@szu.edu.cn

Funding informationFundamental Research Foundation of Shenzhen, Grant/Award Number: No.JCYJ20160308100236349; Key Project of Department of Education ofGuangdong Province, Grant/Award Number: No.2015KTSCX123; NaturalScience Foundation of Guangdong Province, China, Grant/Award Number:No.2016A030310056; Natural Science Foundation of SZU, Grant/AwardNumber: No.2016021

AbstractA wideband antenna using metasurface is proposed for thefuture 5G communications. By using the metasurface andthe multi-layer substrate with high relative permittivity, theheight of the proposed antenna can be reduced to 0.11 ?c inthe operating frequency band. The metasurface including40 unit cells are arranged on the second layer to improve thegain at the upper frequencies. Besides, by employing thedual arc-shaped defected ground structure, the impedancebandwidth can also be broaden and the gain can beimproved. The measured result shows that an impedancebandwidth of 77.2% (1.63-3.68 GHz) with a stable gain of5.1� 1.2 dBi can be obtained. Hence, the proposed antennais potentially suitable for the future 5G communications.

KEYWORDS

Metasurface antenna, wideband antenna, magneto-electric(ME) dipole,

stable beamwidth

1 | INTRODUCTION

WIDE bandwidth antennas with stable gain, which can satisfythe need of modern wireless communication system, have

attracted many researches attention because of its prominentmerits, such as much stabler data transmission rate and highercapacity.1 Since 2015, the frequency band ranging from 3.4 to3.6 GHz has been assigned to the future the fifth generation(5G) mobile communication by World Radio CommunicationConference 2015 (WRC-15).2 Therefore, the mobile commu-nication frequency bands for 2G/3G/LTE/5G communicationmay be expanded to 1.71-2.69 GHz and 3.4-3.6 GHz, respec-tively.3 Among the numerous antennas, the magneto-electric(ME) dipole antenna, which owns the outstanding advantagessuch as wide impedance bandwidth, stable gain, good front-to-back ratio (FBR) and low cross-polarization, and so on, isone of the most competitive candidates.4,5 However, one ofthe obvious drawbacks of the previous ME dipole antennas isthe bulky structure with high profile >0.25 λc6 (where λc isthe free-space wavelength at the center frequency). The tech-nology of antenna printed on the multi-layer substrate is oneof the most effective ways to obtain low profile feature.7

On the other hand, metasurface (MS) which owns theunique electromagnetic properties as the metamaterial hasbecome a hot research topic recently. Conventionally, the MSwhich consists of electrically small scatters is used to improvethe antenna performance. For example, by setting the MSnearby the radiated microstrip patches, the impedance band-width can be widen and the gain can also be increased. Inreference,8 by placing a MS above of the linear polarizationsource antenna, the signal can be converted between the linearand circular polarizations. However, due to the existence ofan air gap between the source antenna and the MS, the profileof the antenna is still high. On the other hand, frequencyreconfiguration can also be attained by mechanically rotatingthe MS around the center of the radiated antenna.9 In addition,the radar cross section can be reduced by using an asymmetriccross-shaped MS.10 Nevertheless, this kind of MS antennastill suffers from the narrow impedance bandwidth.

In this article, a low profile wideband antenna using MSis proposed for the future 5G mobile communication. Unlikethe traditional 3D ME dipole antenna, the ME antenna isprinted on the 5-layer integrated substrate to acquire thelow-profile property. By arranging the MS above the secondlayer, the antenna gain can be improved due to the MSinherent electromagnetic properties. Besides, the stair-shaped feeding structure cooperated with the arc-shapeddefected ground to achieve a good impedance matching. Asa result, an impedance bandwidth of 75% with a stable gainof 5.1 dBi and cross polarization <−30 dB can be obtainedover the entire operating frequency.

2 | ANTENNA GEOMETRY ANDWORKING MECHANISM

The geometry and detailed dimensions of the proposedantenna are shown in Figure 1 and Table 1, respectively. Theproposed substrate integrated ME dipole antenna is printed on

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Taconic RF-35 substrate with a dielectric constant of 3.5 anda loss tangent of 0.0018. The antenna consists of the top-layerradiated electric dipole patch with bow-tie slot, the MS whichconsists of 40 unit cells set on the second layer, the arc-shapeddefeated ground above the fifth-layer substrate, and the stair-shaped feeding structure which is located at the center of the5-layer substrate. The bow-tie slot etched on the radiatedpatch is used to achieve a wide impedance bandwidth due tothe increased effective electric length. The electric dipolepatch is connected with the ground plane by a pair of viaholes. The via holes and the ground between them form themagnetic dipole. The stair-shaped feeding structure helps toreduce the height and provides flexible impedance matching.The electric dipole together with the magnetic dipole consti-tute a ME dipole antenna. It can be excited by the stair-shapedfeeding structure to obtain the complementary radiation pat-tern. Due to the MS and the arc-shaped defected ground, thegain can be increased and the profile of the antenna can alsobe reduced. Noting that the third- and fourth-layer substratesare used to improve the via hole impedance matching at thecost of slightly increasing the height of the antenna.

3 | PARAMETRIC STUDY ANDRESULT DISCUSSION

In order to study how the structures and the dimensionsaffected the antenna performances, such as wide

impedance bandwidth, H-plane beamwidth, and gain, etc.,some critical parameters are investigated by ANSYS elec-tromagnetic simulation software High Frequency Struc-ture Simulation.11

To understand the antenna working mechanism, thecurrent distributions on the radiated electric dipolepatches in a period at 1.8 GHz are depicted in Figure 2.At the time t = 0, the currents on the radiated patchesattain the strongest intensity and are dominated in thepositive y-direction, whereas the currents on the mag-netic dipoles get minimum strength (Because the cur-rents on the surfaces of the magnetic dipoles are soweak that they cannot be seen in the pictures). Then att = T/4 (where T is a period of time), the currents onthe radiated electric dipole patches become weakestintensity and are still towards the positive y-direction,whereas the currents on the surfaces of the magneticdipoles get maximum strength and are dominated. Andat t = T/2, the currents on the radiated patches achievethe strongest intensity again and are dominated in theminus y-direction, whereas the currents on the surfacesof the magnetic dipoles get minimum strength. Finally,at t = 3 T/4, the currents on the radiated electric patchesbecome weakest intensity and still keep towards theminus y-direction, whereas the currents on the surfacesof the magnetic dipoles get maximum strength and aredominated. That is to say, the electric and magnetic

(A)

(B) (D)

(C)

FIGURE 1 The geometry of the proposed antenna [Color figure can be viewed at wileyonlinelibrary.com]

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dipoles are dominated to work in turn and hence thecomplementary unidirectional patterns can be obtainedin a period. As a result, the linearly polarized radiationpattern with a wide frequency bandwidth can beachieved.

In addition, Figure 3 shows the effect of the different-shape dipoles. Compared with the other 2 kinds ofdipoles, the proposed dipole antenna owns the much widerbandwidth (SWR ≤ 2) and the more stable gain in themeantime, especially at the high-frequency band. Becauseit is a combination of the other 2 kinds of dipoles whichcan either obtain the widest bandwidth or the highest gain.Figure 4 shows the effect of the MS. It can be easily seenthat with rhombic MS or without MS, the much widerbandwidth can be achieved at the high frequency; how-ever, the corresponding gains drop sharply in the high

TABLE 1 Dimensions for the proposed antenna

Parameters Ls Ws1 Ws2 Lp Wp1 Wp2 Ls1 Ls2

Values/mm 72 70 85 71.4 21.3 3.3 12 20.2

Parameters Ls3 Ws1 Ws2 Ws3 Lm1 Lm2 Wm1 Wm2

Values/mm 45.2 5.2 11.5 19.9 8 4 4.8 2.8

Parameters Wm3 Lf1 Lf2 Lf3 Lf4 Lf5 Wf1 Wf2

Values/mm 2.2 1.6 0.8 2.3 1.4 2 2 1

Parameters Wf3 Le We H1 H2 H3 H4 H5

Values/mm 1 11.8 15.1 3 3 3 1.5 1.5

Parameters H6 Rf1 Rf2 Rf3 Rp1 Rp2

Values/mm 1.5 0.5 0.35 0.9 0.45 1

FIGURE 2 Current distribution on the dipole over a period of time at 1.8 GHz [Color figure can be viewed at wileyonlinelibrary.com]

1.5 2.0 2.5 3.0 3.5 4.01

2

3

4

5

6

VS

WR

Frequency(GHz)

The proposed radiated dipole

Bow-ties hape radiated dipole

Bow-tie arc-shape radiated dipole

-2

0

2

4

6

8

Ga

in(d

Bi)

FIGURE 3 Simulated SWR and gain of different dipoles [Colorfigure can be viewed at wileyonlinelibrary.com]

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frequency band. To cover the 5G frequency band and keepthe gain stable, the proposed MS with rectangular cells ischosen. Conversely, as shown in Figure 5, with the tradi-tional η-shaped feeding structure or with the stair-shapedtransmission line feeding structure, the impedance mis-matching is obvious in the lower frequency band. Accord-ingly, there are major variations on the gain in the lowerfrequency band. On the other hand, the proposed stair-shaped coupling strip feeding structure can provide flexi-ble capacitive and inductive impedance matching. Hence,good impedance matching and stable gain can be obtainedin the entire operating frequency band. Furthermore,Figure 6 shows the effect of different shaped ground.Without notches etched on the ground, there is a largefluctuation in the SWR and the corresponding gain. Thereis the similar effect in the ground with rectangularnotches. Owing to the more effective electric length, theproposed ground with dual-arc-shaped notches which cansupply the good impedance matching and stable gain is

selected. Figure 7 shows the antenna radiation efficiency.As depicted, the average radiation efficiency is >75% inthe entire operating frequency band. As the frequencyincreases, the radiation efficiency is slightly enhanced and

1.5 2.0 2.5 3.0 3.5 4.0

2

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14V

SW

R

Frequency(GHz)

The proposed metasurface

Without metasurface

With rhombic metasurface

-8

-4

0

4

8

Gain

(dB

i)

FIGURE 4 Simulated SWR and gain with different MSs [Colorfigure can be viewed at wileyonlinelibrary.com]

1.5 2.0 2.5 3.0 3.5 4.0

2

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WR

Frequency(GHz)

The proposed feeding structure

Stair-shaped trans mission line

feeding structure

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0

4

8

Gain

(dB

i)

FIGURE 5 Simulated SWR and gain with different feedingstructures [Color figure can be viewed at wileyonlinelibrary.com]

1.5 2.0 2.5 3.0 3.5 4.0

2

4

6

8

10

VSW

R

Frequency(GHz)

The proposed groundGround without notchesGround with rectangular notches

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0

2

4

6

8G

ain(dBi)

FIGURE 6 Simulated SWR and gain with different groundstructures [Color figure can be viewed at wileyonlinelibrary.com]

1.5 2.0 2.5 3.0 3.5 4.0

20

40

60

80

100

Measured

Rad

iatio

n ef

ficie

ncy(

%)

Frequency(GHz)

FIGURE 7 The measured radiation efficiency of the proposedantenna

1.5 2.0 2.5 3.0 3.5 4.0

1

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VS

WR

Frequency(GHz)

Simulated

Measured

-8

-6

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0

2

4

6

8

Ga

in(d

Bi)

FIGURE 8 The SWR and gain of the proposed antenna [Colorfigure can be viewed at wileyonlinelibrary.com]

FENG ET AL. 2485

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(F) 3.5GHz (measured)

Co-pol-Sim(H-plane:YOZ plane) Crsso-pol-Sim(H-plane:YOZ plane)

Co-pol-Sim(E-plane:XOZ plane) Cross-pol-Sim(E-plane:XOZ plane)

Co-pol-Mea(H-plane:YOZ plane) Crsso-pol-Mea(H-plane:YOZ plane

Co-pol-Mea(E-plane:XOZ plane) Cross-pol-Mea(E-plane:XOZ plane

FIGURE 9 Radiation patterns of the proposed antenna at 1.8, 2.7, and 3.5 GHz [Color figure can be viewed at wileyonlinelibrary.com]

TABLE 2 Summary of the measured radiation patterns at different frequencies

ParametersE-plane H-plane

Frequency (GHz) Co-pol(HPBW) (deg) Cross-pol (deg) FBR (dB) Co-pol(HPBW) (deg) Cross-pol (deg) FBR (dB)

1.8 89.1 −31.5 10.6 81.6 −34.3 10.7

2.7 100.5 −32.9 13.9 107.3 −32.1 11.7

3.5 91.8 −31.6 16.7 101.2 −30.9 13.9

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can be up to 85%. In other words, the power conversionefficiency is high. Figure 8 shows the SWR and the gainof the proposed antenna. The simulated bandwidth rangesfrom 1.62 to 3.69 GHz with a stable gain of 5.1 � 1.1 dBi,while measured bandwidth ranges from 1.63 to 3.68 GHzwith a stable gain of 5.1 � 1.2 dBi. They show the goodagreement. Figure 9 shows the radiation patterns at differ-ent frequencies. A short summary of them can bedescribed in Table 2. It can be seen that nearly the sym-metrical E- and H-plane radiation patterns can beobtained. In addition, the cross-polarizations of bothplanes are <−30 dB and the FBR is >10.6 dB over theentire bandwidth. Furthermore, the beamwidth in the H-plane is more than 89� over the entire operating frequencyband. In particular, it can be up to 107� in the 5G high fre-quency band. Table shows the comparison of the pro-posed antenna with the other referenced antennas. Exceptthe lower gain, the proposed antenna is better in theaspects of wide bandwidth, wide beamwidth in H-plane,low profile.

4 | CONCLUSION

A wideband antenna using MS is proposed for the future 5Gcommunications. By combining the inherent properties ofME dipole and MS, the antenna can achieve an impedancebandwidth of 77.2% (1.63-3.68 GHz) with a stable gain of5.1 � 1.2 dBi and a low-profile of 0.11 λc. In addition, byintroducing the arc-shaped defeated ground planes, theimpedance matching and the gain are improved. With theabove-mentioned features, the antenna can be suitable forthe future 5G applications.

ACKNOWLEDGMENTS

The research was supported by the Natural ScienceFoundation of Guangdong Province, China (No.2016A030310056), the Key Project of Department ofEducation of Guangdong Province (No.2015KTSCX123),the Fundamental Research Foundation of Shenzhen (No.JCYJ20160308100236349) and the Natural Science Foun-dation of SZU (No.2016021).

ORCID

Botao Feng http://orcid.org/0000-0003-3662-0183

Kwok L. Chung http://orcid.org/0000-0002-5381-7327

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How to cite this article: Feng B, Li L, Zeng Q,Chung KL. A wideband antenna using metasurfacefor the 2G/3G/LTE/5G communications. Microw OptTechnol Lett. 2018;60:2482–2487. https://doi.org/10.1002/mop.31387

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