Design of Dual-Band Millimeter-Wave Antenna Array for 5G Communication System

Shengjie Wu, Anping Zhao, and Zhouyou Ren

Advanced Technology Team Shenzhen Sunway Communication Co., Ltd.

Shenzhen 518057, China

Abstract – In this paper, a dual-band millimeter-wave antenna array is proposed. The dual-band antenna consists of a monopole branch and a patch that are printed on a cavity-backed ceramic block. The first resonance is generated by the coupling between the monopole and the patch, and the second resonance is generated by the monopole. The antenna can be mounted on the PCB. Simulated antenna return loss indicates that the proposed antenna can meet the requirements of the two potential Chinese fifth generation(5G) millimeter-wave bands (26GHz and 40GHz). And the beam scanning performance of an eight-element antenna linear array is presented for the above two bands.

Index Terms — 5G, millimeter-wave, dual-band, phased array antenna.

1. Introduction

In the 5G communication system, in order to improve the performance of communication in the transmission rate and the maximum number of access, the simple and effective way is to increase the bandwidth of the communication system. Therefore, the millimeter-wave(mm-wave) which has enough spectrum resources has become one of the working bands of 5G communication system. It was announced by Chinese Ministry of Industry and Information Technology (MIIT) that the following two mm-wave bands will be potentially used in Chinese 5G communication system: the 26GHz band (24.75GHz-27.5GHz), and the 40GHz band (37GHz-42.5GHz).

Unlike traditional 2/3/4G antennas, mm-wave antennas need to be used as antenna array because the propagation loss of mm-wave is very large. Recently, more and more attentions have been paid to mm-wave antenna designs, but most of them were just focused on single band, such as [1-2]. Although a dual-band mm-wave antenna was proposed in [3], it can only cover the 40GHz band of Chinese 5G mm-wave spectrum. A dual-band slotted patch antenna was proposed in [4], but its performance in terms of antenna radiation pattern is not suitable for forming an array. Therefore, how to design an antenna array that can operate simultaneously at both the 26GHz and 40GHz bands has become a research topic or direction.

In this paper, a dual-band mm-wave antenna linear array that can cover both the 26GHz and 40GHz bands is proposed. The performance of the antenna array in terms of antenna return loss and beam scanning property is presented. All the results are obtained with CST software.

2. Single Antenna Element

Fig. 1 shows the configuration of the proposed single antenna element, which consists of a monopole branch, a patch, a cavity-backed ceramic block and a PCB. The cavity-backed ceramic block (with εr = 8, tanδ = 0.002) is mounted on the PCB, which is made of the Rogers RO3003 with εr = 3, tanδ = 0.001, and thickness = 0.127mm. The dimensions of the ceramic block are fixed at Ws = Ls = 2.5mm, Hs = 1.8mm, Wc = Lc = 2mm, and Hc = 1.55mm. The monopole branch and the patch are printed on the front and top surfaces of the ceramic block, respectively, and they are located in the center of each surface. The height and width of the monopole branch are Hm = 1.15mm, Wm = 0.3mm, respectively; and the length and width of the patch are described by Lp = Wp =1.98mm. The ceramic block is mounted on the PCB by a U-shaped pad, which is printed on the bottom of the ceramic block. The U-shaped pad is connected to the PCB ground by vias. Finally, the antenna is fed by 50Ω microstrip line which is connected to the monopole branch. The proposed antenna does not need any clearance on the PCB. And, the use of the cavity-backed of the ceramic block is to improve the performance of the antenna array, including the gain and the impedance bandwidth.

Fig. 1. Configuration of the antenna: (a) the perspective view,

(b) without ceramic block and substrate, (c) the front view, and (d) the right side view of the antenna.

3. 1×8 Array Design and Simulated Results

Fig.2 shows the 1×8 linear array consists of eight antenna elements, which is located at the edge of the PCB of a

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

[ThP-73]

807

mobile handset, where the size of the PCB of the mobile handset is 140mm×70mm. The simulated S-parameters of the proposed antenna array in the mobile handset are shown in Fig. 3. One can see from Fig. 3 that the return loss of the antenna element is better than -9.8dB within both the 26GHz and 40GHz bands; and the isolation between antenna elements is smaller than -12dB. The working principle of the dual-band antenna system can be analyzed by parametric study. And it is found that the first resonance(26GHz) is generated by the coupling between the monopole and the patch, and the second resonance(40GHz) is generated by the monopole. By tuning the size of the patch and the monopole, one can easily get the needed resonant frequency.

Fig. 2. Array located at the PCB of a mobile handset.

Fig. 3. Simulated S-parameters of the proposed antenna array.

It is well known that, the beam forming and scanning properties, which are used to realize the point-to-point communication between the base station and mobile devices, are a very important function in the 5G communication system. In general antenna array designs, if the distance between two adjacent antenna elements is too close to each other, then the isolation of the antenna elements and the gain of the array will get worse. On the other hand, if the distance between the two adjacent antenna elements is too far away from each other, then the side lobe and back lobe of the pattern of the array will deteriorate, especially when the scanning angle is large. So, in this work, in order to get a balanced performance for the array between the 26GHz and 40GHz bands, the distance of two adjacent antenna elements is set to 4.2mm, which is about half-wavelength of frequency at the center frequency of the two operating bands.

Fig. 4 shows the 3D radiation patterns of the proposed antenna array at 26 GHz and 40 GHz, while the scanning angle is 0 degree, and 30 degrees. Furthermore, in order to facilitate the analysis, the simulated realized gains (in the x-z plane) of the proposed antenna array at 26GHz and 40GHz with different scanning angles are illustrated in Fig. 5. The simulated results show that, when the scanning angle is from

0 degree to 60 degrees, quite good beam scanning characteristics can be achieved at both 26GHz and 40GHz.

Fig. 4. 3D radiation patterns of the proposed antenna array at

26 GHz and 40GHz.

Fig. 5. Simulated realized gain of the proposed antenna array

at 26GHz and 40GHz with different scanning angles.

4. Conclusion

A dual-band mm-wave antenna array which can cover both the 26GHz and 40GHz bands of Chinese 5G candidate frequency is presented. The beam forming and scanning of the antenna array are realized by selecting a suitable distance between two adjacent antenna elements. The proposed antenna system has good performance and compact structure. In addition, it is quite easy to be integrated with the mm-wave RF front-end system.

Acknowledgment

The authors would like to thank the Shenzhen Science and Technology Innovation Committee, China for the financial support under Key Project 2017-0237.

References

[1] S. Verma, L. Mahajan, R. Kumar, H. S. Saini, and N. Kumar, “A small microstrip patch antenna for future 5G applications,” in International Conference on Reliability, INFOCOM Technologies and Optimization, 2016.

[2] W. El-Halwagy, J. Mezler, M. Hossain, and P. Mousavi, “A 28 GHz compact vertically-polarized dipole for 5G smartphone edge,” in IEEE International Symposium on Antennas and Propagation & Usnc/ursi National Radio Science Meeting, 2017, pp. 2573-2574.

[3] A. Zhao, F. Ai, “Dual-band 5G millimeter-wave MIMO antenna array for mobile phone application,” in Proc. European Conference on Antennas and Propagation (EuCAP), 2018, London, UK, pp. T01-13.2.

[4] M. K. M. Amin, M. F. Mansor, N. Misran, and M. T. Islam, “28/38GHz dual band slotted patch antenna with proximity-coupled feed for 5G communication,” in Proc. International Symposium on Antennas and Propagation (ISAP),2017, Phuket, Thailand, pp. 1-2.

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

808