Available online at www.sciencedirect.com
ScienceDirect Procedia Computer Science 86 (2016) 47 – 50
2016 International Electrical Engineering Congress, iEECON2016, 2-4 March 2016, Chiang Mai, Thailand
Investigation of Patch Phase Array Antenna Orientation at 28 GHz for 5G Applications Low Ching Yua and Muhammad Ramlee Kamarudinb* a,b
Wireless Communication Centre (WCC), Faculty of Electrical Engineering, Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor, Malaysia
Abstract In this paper, three different configurations of patch array antennas are designed to investigate their radiation patterns with different orientation and excitation phase at 28 GHz for 5G application. All antennas are fed by inset feed line. The excitation phases are changed to study the radiation pattern of each patch array antenna with different orientations. Simulated and measured S11, S12 and simulated radiation patterns are presented. The simulated result showed that the designed antennas are able to operate at 28GHz. Antenna 1 and 2 provide beam shifting covers the angles up to 66°, while for Antenna 3 is 94°. ©2016 2016The TheAuthors. Authors. Published by Elsevier © Published by Elsevier B.V.B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Organizing Committee of iEECON2016. Peer-review under responsibility of the Organizing Committee of iEECON2016 Keywords: 5G; millimeter wave; 28GHz; microstrip patch antenna; array antenna
1. Introduction Wireless communication technology has developed so fast to meet the demand of high traffic capacity in electronic devices. The 5G technology uses higher frequency bands to provide large data capabilities for supporting multi-Gbps data rates, and to gather infinite data broadcast within newest mobile technology [1]. Many researches have been done at 28 GHz as Local Multipoint Distribution Service (LMDS) which operate at 28GHz to 30GHz provide fixed wireless, broadband and point-to-multipoint technology [2]. Millimeter-wave communication systems using narrow beams at the transmitter and receiver, which suppress the interference of neighboring beams. However, narrow transmitter and receiver beams cause the multipath components of millimeter waves to be limited. Therefore,
* Corresponding author. Tel.: 07-5535350; fax: 07-5535252. E-mail address:
[email protected]
1877-0509 © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Organizing Committee of iEECON2016 doi:10.1016/j.procs.2016.05.012
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by having the beam shifting, beam-forming weights can be adjusted to point toward the base station effectively [2]. Modern wireless communication systems require a low profile, lightweight, high gain and simple structure antennas to ensure reliability, mobility, and high efficiency [3]. Therefore, the microstrip patch antenna is preferred due to its low profile, easy to fabricate and feed, and even easy to use in the array or incorporate with other microstrip circuit elements [4]. Furthermore, patch antennas are used as simple and highly preferred in many applications such as circular polarizations, dual characteristics, dual frequency operation, frequency agility, broad bandwidth, feed line flexibility and beam scanning can be easily obtained from these patch antennas as described in [5]. In this paper, three different configurations of patch array antennas are designed to perform at 28 GHz. This is to study how the orientation of patch array antenna can affect the beam forming and which orientations give a maximum performance on the beam forming and beam steering. 2. Microstrip Patch Antenna with Inset Feed line Fig. 1 shows the geometry of the rectangular microstrip patch antenna with inset feed line. The patch can be notched to provide an inset feed point (y0). Table 1 shows the optimized parameters for a single patch design. Table 1 Optimize parameters for a single patch design
Parameter
Value (mm)
W
4.24
L
3.27
ݕ
0.77
Wh
0.40
Wf
0.79
Fig. 1 Dimensions of single patch design
The calculations [4] on the dimensions of a single element of the rectangular patch antenna in Fig. 1 are shown below by equations (1) and (2).
c
W
f
2
H r 1 r
(1)
2
Where c is the velocity of light, while ݂ is the operating frequency, and Hr is the dielectric constant of the substrate. In the formula (2), the actual length of the patch ( )ܮcan be determined after obtaining the values of the effective length of the patch (ܮ ) and the length extension (ο)ܮ.
L
L
eff
2'L
(2)
3. Microstrip Patch Array Antenna Configurations Fig. 2 (a) (b) and (c) show the proposed antennas with three different configurations. Each antenna consists of three layers. The lower layer is a fully ground plane with copper. The middle substrate is Rogers 5880 with dielectric constant, Hr =2. 2 and dielectric loss tangent, tan δ=0.0009, and a height of substrate, h=0. 254mm. The
Low Ching Yu and Muhammad Ramlee Kamarudin / Procedia Computer Science 86 (2016) 47 – 50
thickness of the copper used is 0.017mm. The upper layer is a patch with dimension of W=4.24mm and L=3.27mm. Distance between two patches is λ/2 or equivalent to 5.36mm. The patch is fed by a microstrip line with 50Ω input impedance. All three antennas of different configurations are designed based on the above standards. a
b
c
Fig. 2 Three different configurations of patch array antennas designed. (a) Antenna 1; (b) Antenna 2; (c) Antenna 3
Fig. 3 Measured and simulated return loss ȁܵଵଵ ȁ for designed Antenna 1,2 and 3
Fig. 4 Measured and simulated mutual coupling ȁܵଵଶ ȁ of the Antenna 3
4. Result and Discussion The patch array antennas operate at 28 GHz is designed and optimized using software CST Microwave Studio. Simulated results for the S-parameter antennas are compared with those measured by the performance network analyzer. Simulated far-field radiation patterns at different of excitation phase are shown as well. Reflection coefficient |S11| and transmission coefficient |S12| are shown below. Fig. 3 presents measured and simulated reflection coefficient results |S11| of the fabricated antennas. Three different configurations of antennas designed have the same |S11| due to the similar shape of the patch. Because of the antenna’s structure is symmetry, |S22| is same as |S11| as expected. It is seen that the fabricated antennas can operate over a bandwidth of about 1.4GHz, which is double then that is simulated result. This is due to the losses in dielectric constant of the substrate as it is drilled with a hole in order to fit in the connector. The existence of the air gap in substrate reduces the dielectric constant which eventually causes an increase in bandwidth [6]. The difference in the measured and simulated results is mainly caused by the shift in the resonant frequencies [7]. This frequency shift may due to fabrication tolerance on the insertion loss of Cu microstrip which is manufactured by etching and gravure [8] as well as the dielectric constant of the substrate. Fig. 4 shows measured and simulated mutual coupling results between two feeding ports on the configuration of Antenna 3. It can be seen that the isolation between the ports at 28 GHz is more than 20 dB. A good isolation performance over a wide frequency range is achieved. This is because the size of the patches is too small to give an impact on mutual coupling [9]. The radiation pattern of all three designed antennas have been shown. Fig. 5 shows the simulated far-field and radiation patterns when two ports are excited at phase difference 0°. Antenna 1 gives a directed beam with maximum gain of 8.64 dB. Antenna 2 and 3 has a gain of 7.47 dB and 7.46 dB respectively. This is because
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a
b
c
a
b
c
Fig. 5 Simulated far-field and radiation patterns when the excitation phase difference is 0°/360˚ (a) Antenna 1; (b) Antenna 2; (c) Antenna 3
a
a
b
c
b
c
Fig. 6 Simulated far-field and radiation patterns when the excitation phase difference is 180° (a) Antenna 1; (b) Antenna 2; (c) Antenna 3
Antenna 1 has a same side feeding structure which gives a constructive interference on radiation patterns during 0° and 360° phase difference. Meanwhile, Antenna 2 and 3 are opposite feeding structures whereby radiation patterns interfere destructively. However, opposite patch structure reacts more completely compare to that of side patch structure. The main lobe of the Antenna 2 and 3 is tilted by -33° and 47° respectively. Fig. 6 shows the simulated far-field and radiation patterns when two ports are excited at phase difference 180°. During this case, radiation field of Antenna 1 interferes destructively while for Antenna 2 and 3 interfere constructively. Antenna 1, 2 and 3 has a gain of 6.30 dB, 7.87 dB, and 8.45 dB respectively. The main lobe of the Antenna 1 is tilted by -33°. The simulated results showed that the beam of the linear antenna array can be steered only in one plane by proving Antenna 1 and 2 provide scan range from -33°to 33° in the H-plane, while Antenna 3 has a scan range -47°to 47° in the E-plane.
Acknowledgements The authors would like to thank the Ministry of Education Malaysia and Universiti Teknologi Malaysia for supporting this work under FRGS grant (4F283) and RUG grants (Vote 11H59 and 03G33).
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