LTE/5G C-band MIMO antennas for laptop computers

Wen-Shan Chen1, Ming-Han Liang2

1-2Department of Electronic Engineering, Southern Taiwan University of Science and Technology, Taiwan

Abstract - The paper presents a design of MIMO antennas for laptop computers operating at LTE (long term evolution) band and 5th generation wireless systems (5G) C-band. The antenna is designed with a parasitic open slot and a PIFA located at the top edge of the display ground. The antenna can cover the LTE 700 (698-787 MHz), LTE 2300 (2305-2400 MHz), LTE 2500 (2500-2690 MHz) and 5G C-band (3400-3600 MHz). The antenna size is 12 × 75 × 4 mm3 printed on a FR-4 substrate with a thickness of 0.8mm and adding a cooper sheet above the bending line. The size of the system ground made of copper sheet with a thickness of 0.1mm is 200 × 310 mm2. More design concepts and results will be discussed in detail in this paper.

Index Terms —antenna of laptop computer, open slot, MIMO antennas, LTE band, 5G C-band.

1. Introduction

The products with LTE services are widely all over the world. The 5G wireless systems and its standards are developed very fast in recently. It is need that the product with the LTE and 5G applications. The antennas inside the laptop must have a broadband coverage for the LTE 700 (698-787 MHz) LTE 2300 (2305-2400 MHz) LTE 2500 (2500-2690 MHz) and 5G C-band (3400-3600 MHz). For improving data speed, MIMO technology should be adopted too. For MIMO antenna design, some methods of MIMO antennas for LTE or 5G C-band [1]-[4] have been reported, and most of them are designed in a coupled architecture. Some antennas are designed with a parasitic open slot [5], or planar inverted-F antenna (PIFA) [6]. But these designs are not applied to LTE or 5G applications.

In the paper, a design uses a parasitic open slot and a PIFA to achieve the desired goal. And, the design is extended to the design of MIMO antennas. The design of MIMO antennas with multi-frequency bands covers the LTE 700/2300/2500 and 5G C-band. The LTE 700 band of the design is obtained by combing the two modes produced by the parasitic open slot and the longest path of the antenna. The LTE 2300/2500 and 5G C-bands are excited by the higher mode of the longest path and the higher mode of the parasitic open slot.

2. Antenna Design Details

The geometry of the design of MIMO antennas with LTE/5G C-bands is shown in Fig. 1. The antenna size 12 × 75 mm2 printed on a FR-4 substrate with a thickness of 0.8-mm, and a 4-mm metal plate is used for three-dimensional

bending. Fig. 1(b) the sheet of copper of 200 x 310 x 0.2 mm3 is used to simulate the system ground of the laptop computer. The antennas are located in the upper left corner and upper right corner of the copper sheet. The distance from the left edge of the system ground of the laptop computer is about 20 mm, and spacing between the antennas is 120mm apart. The antennas are fed by 50-Ω coaxial cables. Combining two mode produced by the parasitic open slot and the longest path of the antenna, the LTE700 band can be obtained. The bands excited by the higher mode of the longest path and the higher mode of the parasitic open slot are achieving the LTE 2300/2500 and 5G C-bands. The detail antenna dimensions of the MIMO antennas are also listed in table I.

Fig. 1 (a) Antenna geometry (b) Full view of the design

TABLE I Antenna dimensions of the proposed design

Parameters L1 L2 L3 L4 Unit (mm) 3.5 4 4 7 Parameters L5 H1 W1 W2 Unit (mm) 2 4 12 15 Parameters W3 W4 W5 W6 Unit (mm) 28 70.5 44.5 16.5 Parameters W7 W8 W9 Unit (mm) 14.5 12.5 66

3. Results And Discussion

Fig. 2 shows the comparison of simulated and measured S11 and S22. These are in good in agreement. The S11 and S22 of the LTE 700/2300/2500 and 5G C-bands are less than -6dB for the operating frequency bands. Fig. 3 shows the

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

[FrD1-4]

367

comparison of the simulated and measured S21 of the proposed design. It can be seen that the measured S21 is below -15 dB for all operating bands, which means that the two antennas have less interference with each other. From the above results, the antenna can covers the bands of LTE 700 (698-787 MHz), LTE 2300 (2305-2400 MHz), LTE 2500 (2500-2690 MHz) and 5G C-band (3400-3600 MHz). The simulated S11, S22, and S21 and radiation characteristics are performed by using the High Frequency Structure Simulator (HFSS) electromagnetic simulation software.

Fig. 2 S-parameters of Simulated and measured (S11, S22)

Fig. 3 S-parameters of Simulated and measured (S21)

Fig. 4 shows the simulated antenna gain and radiation efficiency of Ant1. In the band of 698 MHz-787 MHz, the antenna gain is above 0.9dBi and the radiation efficiency is above 40%. In the band of 2305 MHz-2690 MHz, the antenna gain is above 2.8dBi and the radiation efficiency is above 75%. In the band of 3400 MHz-3600 MHz, the antenna gain is above 3dBi and the radiation efficiency is above 80%. The simulated result of the antenna gain and radiation efficiency of the ANT2 is very similar to that of the ANT1. For brevity, the results of ANT2 are not shown in the paper.

Fig. 4 Simulated radiation efficiency and antenna Gain of Antenna 1 (Ant1). (a) 698-787 MHz (b) 2305-2690 MHz and 3400-3600 MHz

4. Conclusion

A design of MIMO antenna for laptop computer has been proposed and investigated in the paper. The design is with simple structure, good impedance matching for the LTE 700/2300/2500 and 5G C-bands, and good radiation performances. It is suitable for practical applications in laptop computers and operating LTE700/2300/2500 and 5G C-bands.

References

[1] P. W. Lin, T. J. Wu, and K. L. Wong, “Small-size LTE 700/2300/2500 antenna and high-isolation antenna array using the same for the laptop computer,” IEEE International Symposium Antennas and Propagation Society (IEEE APSURSI 2013), pp. 514-515, July 2013.

[2] S. C. Chen, and J. Y. Sze, “Isolation-improved LTE MIMO antenna for laptop-computer applications,” IEEE Transactions on Antennas and Propagation, pp. 425-426, Dec. 2014.

[3] A. Ahmad, and F. A. Tahir, “Multiband MIMO antenna on variable-sized tablet PCs,” Asia Pacific Microwave Conference (APMC 2017), pp. 612-615, Nov. 2017.

[4] Y. C. Lu, Y. C. Chan, H. J. Li, Y. C. Lin, S. C. Lo, G. C.-H. Chuang, “Design and system performances of a dual-band 4-port MIMO antenna for LTE applications,” IEEE International Symposium Antennas and Propagation Society (IEEE APSURSI 2011), pp. 2227-2230, July 2011.

[5] K. L. Wong, W. J. Chen, L. C. Chou, M. R. Hsu, “Bandwidth enhancement of the small-size Internal laptop computer antenna using a parasitic open slot for penta-band WWAN operation,” IEEE Transactions on Antennas and Propagation, vol. 58, pp. 3431-3435, Oct. 2010.

[6] L. Pazin, and Y. Leviatan, “Inverted-F laptop antenna with enhanced bandwidth for Wi-Fi/WiMAX applications,” IEEE Transactions on Antennas and Propagation, vol. 59, pp. 1065-1068, Dec. 2010.

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

368