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A Smartwatch Dipole Antenna for LTE/GPS/WWAN Applications Jui-Han Lu, Jing-Hui Zhuang and Jia-Wen Hsu Department of Electronic Communication Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan Abstract A novel dipole antenna is proposed for LTE/GPS/WWAN system by embedding an arc-shaped slit into the circular surface of a smartwatch housing. The impedance bandwidths across LTE / WWAN bands can meet the bandwidth specification. The measured peak gains and antenna efficiencies are approximately 2.4 / 4.5 / 4.6 dBi and 55 / 66 / 96 % across the LTE/WWAN bands, respectively. Index Terms —LTE, WWAN, Smartwatch. 1. Introduction Due to the significantly higher data rate than that of 3G wireless wide area network (WWAN) operations for mobile broadband services, the long term evolution (LTE) system with three operating bands in the LTE700 (698 ~ 787 MHz), LTE2300 (2300 ~ 2400 MHz) and LTE2500 (2500 ~ 2690 MHz) has integrated into 3G WWAN technology to support dual wideband operations in the mobile devices for the 4G communication system. And, smart wearable devices have gained more attentions to access with the mobile devices from industries and publics, thus antennas become a necessary component [1-7]. However, due to the limited space within the wearable device, most of smart wearable devices today only have either a Bluetooth or a Wi-Fi antenna [1-5]. In order to increase the accessibility to mobile cellular network, some monopole antennas are introduced to cove 2G/3G/4G cellular bands by conforming it on the watch belt. However, for the forthcoming 5G (sub-6GHz) communication system, the above antenna designs can’t provide 3.5 GHz operating band. Then, this work proposes a smartwatch dipole antenna to meet the bandwidth specification of LTE/GPS/WWAN systems. An arc-shaped slit is introduced into the circular surface of the smartwatch housing. To comply with the SAR requirement, this work also analyzes the simulated body SAR results of the proposed dipole antenna. Details of the proposed antenna design are described in this study, and the related results for the obtained performance operated across LTE/GPS/WWAN bands are presented and discussed. 2. Antenna design and experimental results Fig. 1 illustrates the geometry of the proposed dipole antenna for a LTE/GPS/WWAN smartwatch. An arc-shaped slit is introduced and embedded into the circular surface of the watch housing. Then, a pair of metal strap with half- wavelength of 700 MHz band is presented to be conformed on the watch belt. To obtain B4G 3.5 GHz band, an arc-strip with the length of 27 mm (about 0.31λ) is introduced to be on the slit and connected with the upper-arm belt. (a) Front view (b) Back view (c) Fig. 1. Geometry of the proposed smartwatch dipole antenna for LTE/GPS/WWAN applications. To demonstrate the above deduction and guarantee the correctness of simulated results, the electromagnetic simulator HFSS based on the finite element method [8] has been applied for the proposed dipole design. Fig. 2(a) shows the related simulated and experimental return loss for the proposed smartwatch dipole antenna. From the experimental results, the measured impedance bandwidths (RL 6 dB) can meet the band specification of LTE / GPS / WWAN operating bands, respectively. The related results across LTE3500 MHz band is shown in the Fig. 2(b). It is shown that the operating bandwidth can fully meet the bandwidth specification of LTE3500 MHz band. The 3D radiation 2018 International Symposium on Antennas and Propagation (ISAP 2018) October 23~26, 2018 / Paradise Hotel Busan, Busan, Korea [FrD1-1] 361

A Smartwatch Dipole Antenna for LTE/GPS/WWAN Applications · 2018-10-19 · LTE/GPS/WWAN Applications Jui-Han Lu, ... the long term evolution (LTE) system with three operating bands

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Page 1: A Smartwatch Dipole Antenna for LTE/GPS/WWAN Applications · 2018-10-19 · LTE/GPS/WWAN Applications Jui-Han Lu, ... the long term evolution (LTE) system with three operating bands

A Smartwatch Dipole Antenna for LTE/GPS/WWAN Applications

Jui-Han Lu, Jing-Hui Zhuang and Jia-Wen Hsu

Department of Electronic Communication Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan

Abstract – A novel dipole antenna is proposed for LTE/GPS/WWAN system by embedding an arc-shaped slit into the circular surface of a smartwatch housing. The impedance bandwidths across LTE / WWAN bands can meet the bandwidth specification. The measured peak gains and antenna efficiencies are approximately 2.4 / 4.5 / 4.6 dBi and 55 / 66 / 96 % across the LTE/WWAN bands, respectively.

Index Terms —LTE, WWAN, Smartwatch.

1. Introduction

Due to the significantly higher data rate than that of 3G wireless wide area network (WWAN) operations for mobile broadband services, the long term evolution (LTE) system with three operating bands in the LTE700 (698 ~ 787 MHz), LTE2300 (2300 ~ 2400 MHz) and LTE2500 (2500 ~ 2690 MHz) has integrated into 3G WWAN technology to support dual wideband operations in the mobile devices for the 4G communication system. And, smart wearable devices have gained more attentions to access with the mobile devices from industries and publics, thus antennas become a necessary component [1-7]. However, due to the limited space within the wearable device, most of smart wearable devices today only have either a Bluetooth or a Wi-Fi antenna [1-5]. In order to increase the accessibility to mobile cellular network, some monopole antennas are introduced to cove 2G/3G/4G cellular bands by conforming it on the watch belt. However, for the forthcoming 5G (sub-6GHz) communication system, the above antenna designs can’t provide 3.5 GHz operating band. Then, this work proposes a smartwatch dipole antenna to meet the bandwidth specification of LTE/GPS/WWAN systems. An arc-shaped slit is introduced into the circular surface of the smartwatch housing. To comply with the SAR requirement, this work also analyzes the simulated body SAR results of the proposed dipole antenna. Details of the proposed antenna design are described in this study, and the related results for the obtained performance operated across LTE/GPS/WWAN bands are presented and discussed.

2. Antenna design and experimental results

Fig. 1 illustrates the geometry of the proposed dipole antenna for a LTE/GPS/WWAN smartwatch. An arc-shaped slit is introduced and embedded into the circular surface of the watch housing. Then, a pair of metal strap with half-wavelength of 700 MHz band is presented to be conformed on the watch belt. To obtain B4G 3.5 GHz band, an arc-strip

with the length of 27 mm (about 0.31λ) is introduced to be on the slit and connected with the upper-arm belt.

(a) Front view (b) Back view

(c)

Fig. 1. Geometry of the proposed smartwatch dipole antenna for LTE/GPS/WWAN applications.

To demonstrate the above deduction and guarantee the

correctness of simulated results, the electromagnetic simulator HFSS based on the finite element method [8] has been applied for the proposed dipole design. Fig. 2(a) shows the related simulated and experimental return loss for the proposed smartwatch dipole antenna. From the experimental results, the measured impedance bandwidths (RL ≥ 6 dB) can meet the band specification of LTE / GPS / WWAN operating bands, respectively. The related results across LTE3500 MHz band is shown in the Fig. 2(b). It is shown that the operating bandwidth can fully meet the bandwidth specification of LTE3500 MHz band. The 3D radiation

2018 International Symposium on Antennas and Propagation (ISAP 2018)October 23~26, 2018 / Paradise Hotel Busan, Busan, Korea

[FrD1-1]

361

Page 2: A Smartwatch Dipole Antenna for LTE/GPS/WWAN Applications · 2018-10-19 · LTE/GPS/WWAN Applications Jui-Han Lu, ... the long term evolution (LTE) system with three operating bands

patterns of the proposed smartwatch dipole antenna are measured in anechoic chamber by using NSI-800F system with Agilent PNA N5230A. Fig. 3 shows the measured peak gains and efficiencies of the proposed dipole antenna mounted on the plastic and leather belts. For the plastic belt under bending case, the maximum measured peak antenna gains and efficiencies are 2.4 / 4.5 / 4.6 dBi and 55 / 66 / 96 % across LTE/WWAN bands, respectively.

(a)

(b)

Fig. 2 Simulated and measured results against frequency for the proposed smartchwatch antenna.

(a)

(b)

Fig. 3. Simulated and measured peak gains and efficiencies across the operating bands for the proposed smartwatch antenna.

3. Conclusions

A novel dipole antenna for a LTE/GPS/WLAN smartwatch has been proposed and investigated. It provides enough impedance bandwidth for LTE/WWAN operating bands. Also, the proposed antenna provides maximum peak antenna gains and efficiencies of 2.4 / 4.5 / 4.6 dBi and 55 / 66 / 96 % across LTE/WWAN bands, respectively.

References

[1] C. H. Wu, K. L. Wong, Y. C. Lin and S. W. Su, “Internal shorted monopole antenna for the watch-type wireless communication device for bluetooth operation”,

[2] S. W. Su and Y. T. Hsieh, ‘‘Integrated Metal-Frame Antenna for Smartwatch Wearable Device’’, IEEE Trans. Antennas Propag., vol. 63, pp. 3301-3305, July. 2015.

[3] D. Wu, S. W. Cheung, Q. L. Li, and T. I. Yuk, “Slot antenna for all-metal smartwatch applications,” 2016 10th European Conf. (EuCAP), pp. 1144–1147.

[4] S. W. Su and C. T. Lee, ‘‘Metal-Frame GPS Antenna for Smartwatch Applications’’, Progress in Electromagnetics Research Letter, vol. 62, pp. 41-47, Sept. 2016.

[5] S. Sayah1 and R. Sarkis, “Design and analysis of conformal antennas for smart watch”, 2017 Progress in Electromagnetics Research Symposium, pp. 1889-1894.

[6] K. Zhao, Z. Ying and S. He, “Antenna designs of smart watch for cellular communications by using metal belt,” 2015 9th European Conference on Antennas and Propagation (EuCAP).

[7] Y. Tasaka and H. Iwasaki, “Small size dual band monopole antenna of smart watch for cellular communications,” 2016 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC).

[8] http://www.ansoft.com/products/hf/hfss, Ansoft Corporation HFSS.

2018 International Symposium on Antennas and Propagation (ISAP 2018)October 23~26, 2018 / Paradise Hotel Busan, Busan, Korea

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