IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 10, 2011 817

Octaband Internal Antenna for 4G Mobile HandsetChan-Woo Yang, Young-Bae Jung, Member, IEEE, and Chang Won Jung, Member, IEEE

Abstract—A compact internal antenna that is composedof a coupled loop with two branch lines is presented. Theproposed antenna operates at two wide frequency bands(698 960 MHz/1710 2690 MHz) to cover octabands LTE700/GSM 850/GSM 900/DCS 1800/PCS 1900/WCDMA 2100/LTE2300/LTE 2500 for the 4G mobile handset. The proposed antennais designed and fabricated on a support (polyester; )with a limited volume, i.e., mm . The design methodsand the measured results of the proposed antenna are presentedin detail.

Index Terms—4G, internal antenna, Long-Term Evolution(LTE), mobile handset, octaband.

I. INTRODUCTION

I N THESE days, mobile communication requires a mobilephone to be operated in various communication services

with multifunctions. This has led to a great demand for de-signing multiband antennas. A variety of small-sized mobilephone antennas for covering multibands have been reported inthe published articles [1]–[5]. Now, the communication envi-ronment is evolving to the fourth generation, and Long-TermEvolution (LTE) is a strong technical candidate of the next-gen-eration services with high qualities surpassing existing servicessuch as GSM, DCS, PCS, and WCDMA. Thus many serviceproviders require multiband internal antennas operated in bothLTE and existing services for the latest mobile phones. Ac-cording to this technical issue, several methods have been re-searched to satisfy these multiple bands. However, these aredifficult to apply for various mobile devices due to impedancematching issues of multiple bands and size reduction issues ofthe internal antenna [6], [7].In this letter, we present a novel internal antenna consisting

of a coupled loop with two branch lines to cover the octa-bands including the LTE bands. Fig. 1 shows the concept ofthe proposed antenna for frequency operation. Basically, theoctabands can be divided into two bands: “Low band” for LTE700 (698 787 MHz)/GSM 850 (824 894 MHz)/GSM 900(880 960 MHz) service bands and “High band” for DCS 1800(1710 1880 MHz)/PCS 1900 (1850 1990 MHz)/WCDMA2100 (1920 2170 MHz)/LTE 2300 (2305 2400 MHz)/LTE2500 (2500 2690 MHz) service bands. The proposed antenna

Manuscript received May 24, 2011; revised July 14, 2011; accepted August01, 2011. Date of publication August 08, 2011; date of current version August25, 2011. This work was supported by the National Research Foundation ofKorea under Grant 2011-0005692 funded by the Korea government.C.-W. Yang and C. W. Jung are with Graduate School of NID Fusion Tech-

nology, Seoul National University of Science and Technology, Seoul 139-743,Korea (e-mail: changwoj@snut.ac.kr).Y.-B. Jung is with the Division of Electrics, Electronics and Control Engi-

neering, Hanbat National University, Daejeon 305-719, Korea.Color versions of one or more of the figures in this letter are available online

at http://ieeexplore.ieee.org.Digital Object Identifier 10.1109/LAWP.2011.2164049

Fig. 1. Concept of frequency operation for the proposed antenna.

is designed to cover the high band with a monopole and branchline 1 and the low band with a coupled loop and a branch line 2.This design method satisfies broad bandwidth and multibandoperation without impedance matching circuits. The pro-posed antenna is designed and fabricated for mobile handsetapplications such as the recent smartphones.

II. ANTENNA CONFIGURATION AND DESIGN

Fig. 2(a) shows a development figure of the proposed an-tenna, and Fig. 2(b) shows side view of the proposed antenna.The development figure shows the designed antenna on thesupport with three faces (Face 1, Face 2, and Face 3) in aplane. The overall size of a printed circuit board (PCB) (FR-4;

) is 122 46 mm , and the thickness is 1 mm.The volume of the antenna support (polyester; ) is

mm , which usually fitsfor the smallest mobile phones. Fig. 2(c) shows an equivalentdiagram of the proposed antenna. The proposed antenna iscomposed of a coupled loop and two branch lines (branch1 and branch 2). Basically, the antenna is designed with thecoupled loop antenna, which is composed with a monopoleantenna and a coupled shorting line. The monopole antenna isan inverted-L shape, and the electrical length of the monopoleis a quarter-wavelength at 2300 2500 MHz for LTE 2300and LTE 2500 service bands. The dimension of the monopoleantenna is 23 monopole width (MW) mm . In addition,the monopole antenna with the coupled shorting line config-ures the coupled loop antenna for the low band operation of824 960MHz to cover GSM 850 and GSM 900 service bands.The optimized length of the coupled shorting line is 52 mm.The overlapped area between the monopole and the coupledshorting line is 20 mm. However, only the coupled loop antennais not enough to cover the desired octabands. To enhance thebandwidth, we used an additional two branch lines (branch 1and branch 2), which are connected in the coupled shortingline. The branch line 1 is designed for the additional high

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818 IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 10, 2011

Fig. 2. Geometry of the proposed antenna (unit: millimeters): (a) developmentfigure of the proposed antenna; (b) side view of the proposed antenna; (c) equiv-alent circuit diagram.

Fig. 3. Simulated reflection coefficients by varying MW.

band operation of 1710 2170 MHz to cover DCS 1800/PCS1900/WCDMA 2100 service bands, and its optimized length is

Fig. 4. Photograph of the fabricated antenna.

Fig. 5. Simulated and measured reflection coefficient of the proposed antenna.

21 mm. Also, the branch line 2 with the longest line length isdesigned for the lowest band operation of 698 MHz to coverLTE 700 service band, and its optimized length is 62 mm.Therefore, the coupled loop with two branch lines is able tocover whole octabands configuring two wide frequency bands,(low band: 698 960 MHz; high band: 1710 2690 MHz).Moreover, the control of the MW is required to improve theimpedance matching. Simulation results of reflection coeffi-cient by varying MW from 4 to 12 mm are shown in Fig. 3. Thereflection coefficient of the proposed antenna is improved, andbandwidth is increased as MW increases. However, MW cannotbe increased more due to the limitation of the antenna size, andMW is optimized to 12 mm. Fig. 4 shows a photograph of thefabricated antenna on a bare PCB.

III. MEASUREMENT RESULTS AND DISCUSSION

Fig. 5 shows the simulated and measured reflection coeffi-cient of the proposed antenna. The measured result matchedwell with the simulation result, and two wide operating bands(low band, high band) cover the octabands. The bandwidth(VSWR 3:1) of the low band is 502 MHz (698 1200 MHz;53%), and the high band is 1090 MHz (1710 2800 MHz;48%). Fig. 6 shows the radiation patterns in and planesat the edge and center frequencies of each low and high band,698, 829, 960, 1710, 2200, and 2690 MHz, respectively. The

YANG et al.: OCTABAND INTERNAL ANTENNA FOR 4G MOBILE HANDSET 819

Fig. 6. Measured radiation patterns at 698, 829, 960, 1710, 2200, and2690 MHz: (a) plane; (b) plane.

measured radiation patterns are a donut-shaped pattern in thelow band (698, 829, 960 MHz) operations and are slightlydirective to the -axis of the ground plane in the high band(1710, 2200, 2690 MHz) operations since a quarter-wavelengthof the high band is relatively smaller than the length of theground plane [6], [7]. The measured peak gains and radiationefficiencies are summarized and plotted in Fig. 7. The measuredpeak gains of the low band are 1.1 2.2 dBi, and of the highband are 0.55 4.95 dBi. The measured radiation efficienciesof the low band are 55.3 71.3 %, and of the high band are32.5 98.1%. Both the peak gains and the radiation efficien-

Fig. 7. Measured peak gains and radiation efficiencies of the proposed antenna.

cies are degraded in each band edge as we expected and aresatisfying the gain requirements of the current mobile phones.

IV. CONCLUSION

An octaband internal antenna is designed and fabricated in avolume with, i.e., mm for small mobile handset ap-plications. The design method of the proposed antenna provesthat the single antenna element can cover octabands by twowideband (low/high band) operations. The measured antennagains and radiation efficiencies over the octabands are satisfiedwith the requirements of the current mobile phones. The pro-posed antenna can be easily fabricated and modified to variousmobile phones as a compact internal antenna.

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