International Conference on Emerging Trends in Electrical, Electronics and Sustainable Energy Systems (ICETEESES–16)
Multiband Millimeter Wave Antenna Array for 5G Communication Prithu Roy1, R.K. Vishwakarma2, Akshay Jain3 and Rashmi Singh4 Abstract—This paper presents a simulated design of millimeter wave square patch antenna 1X6 array on silicon and Roger RO4003 substrate for prominent multiple bands i.e. 58GHz-60GHz, 65GHz-68GHz, 72GHz-77GHz.Designed antenna can serve 5G cellular network as well as advance device-to-device (D2D) network which is special feature of 5G communication system to reduce end-to-end latency and to implement Mission Critical Push-To-Talk Communication (MCPTT) and Vehicle-to-Anything (V2X) Communication. Designed antenna has peakgain of 9 dB and very high efficiency. Return loss for given bands at their resonant frequencies are as low as -35dB and total bandwidth of 9.57 GHz. Silicon is used under feeding network to enhance the bandwidth and reduce the size of feeding network and low dielectric material under patch to reduce dielectric loss thus maintaining the efficiency. Symmetrical parallel feeding network is used to enhance gain. Inset fed with quarter wave transformers are used for feeding and matching, along with maintaining the conformity. A novel design is used to kill the spurious radiation due to feed network, thus shaping the radiation pattern for cellular application. Overall size of antenna is 6.7mmX30mmX1.2mm compatible with miniaturized devices and is printable.1 Keywords: 5G, Millimeter Wave Antenna, Array, Device-to-device Network, Antenna on Silicon, LOS (Line of Sight), Milimeter Waves (mmWaves), High Gain
I.
INTRODUCTION
5G wireless network marks a beginning of new era of digital world with the advent of these technology new features like Internet of Things (IoT), Advance D2D network will be introduced which will revolutionize how we do things. The unprecedented latencies offered by 5G Networks will enable users to indulge in gigabit speed immersive services regardless of geographical and time dependent factors. [1] By the year 2020, Nokia and Samsung forecast a 10,000x growth in traffic on wireless networks with virtually no latency for content access. [2] Requirement of large bandwidth is the key problem of 5G wireless network which can be fulfilled by huge bandwidth inmm wave band 30GHz to 300GHz. [3] Advance D2D network is new feature of 5G communication system that leads to direct connection between devices without intermediate service provider link. It requires large bandwidth for Line of Sight 1,2,3,4Electronics
& Communication Dept., Jaypee University of Engineering & Technology, GUNA, Madhya Pradesh, India E-mail:
[email protected]
communication which is available in millimeter wave band but lower frequency of this band sufferssevere attenuation due to atmospheric oxygen. Antenna arrays are promising especially for non-line-of-sight channels where significant gain is necessary to satisfy link budgets without sacrificing spectral efficiency. [1]
Fig. 1: Atmospheric Attenuation in dB/km across mm Wave Band. Green Area Marks the Region with Low Attenuation to Oxygen, i.e. Comparable to Free Space [3]
The blue circle in Fig.1 is 60GHz band which is assigned for IEEE 802.11ad is better when is used for device-to-device close range networks as these specific high attenuation mm Wave bands will be suited for local or personal area networks like “whisper radios” with coverage distances constrained to few meters [4]– [6]. Whereas green circle is 73GHz band which shows great promise for cellular communication networks owing to lower attenuation due to atmospheric oxygen shown by experiments in [7].Some advance antenna for 5Ghas been discussed in [8] focusing on multi antenna transmission only for cellular communication.60GHz integrated antenna has been designed in [9] with circular polarization and in [10] for Wi-Gig application. 79 GHz integrated antenna has been designed in [11] with low gain of 1.31dB. The design process of antenna has certain challenges in this band like inaccurate measure of dielectric constant, noise due to connectors and fabrication errors. [12] Our design focuses firstly on 60 GHz band antenna array for D2D networks as path loss at this frequency is very high and does not fit for cellular communication. Implementing this unlicensed spectrum for short range, peer-to-peer and LOS networks is more suitable. Secondly 978-1-5090-2118-5/16/$31.00 ©2016 IEEE
Multiband Millimeter Wave Antenna Array for 5G Communication 103
by slotting the antenna for inset feed multiple resonances are generated, since slots also resonates. This method has been used to produce multiple bands in E-band (73GHz) for 5G cellular communication. Thirdly a superstrate technique has been used to constraint spurious radiation.
TABLE 2
W 1.37
W1 0.435
Patch Dimension (mm) W2 Wf Lf 0.435 0.42 0.855
Wt 0.302
Lt 1.25
II. ANTENNA CONFIGURATION The configuration of antenna illustrated in Fig. 1.
Fig. 3: Patch Geometry
Fig. 2: Model of Simulated Antenna Array
Dimension of patch is calculated from [13] L= ∗ ( ∗ )
C. Feeding Technique (1)
‘μeff’is effective permeability which is assumed unity in this case. ‘ϵeff’ is effective permittivity calculated from 2. ‘fr’ is resonant frequency and ‘c’ speed of light. ( ) ( ) ϵeff = + (2)W=6h +2L (2) ‘ϵr’ is dielectric constant of substrate, ‘h’ is height of substrate and W is width of ground plane, but value lower than ‘W’ can be taken to minimize the size. A. Substrate TABLE 1 Substrate Roger RO4003 Silicon
Substrate Parameters Dielectric constant Dimension (LXBXH) in mm 3.55 3.5 X 30 X 1.1 11.9 3.2 X 30 X 1.1
Patch has been designed on Roger RO4003 substrate. Array feed network has been designed on silicon substrate to reduce the size of quarter wave transformer strip and enhance the bandwidth. Antennaon silicon uses silicon as dielectric material but performance degrades i.e. lower efficiency and gain [14], [15] so lower dielectric medium for patch is used. Optimum dielectric for good performance is 2.43 [12], but using slightly higher value does not degrade performance much. B. Patch Patch has been designed on rectangular 6.7 X 30 (in mm) ground plane of height 0.1mm. All the patch parameters are calculated for 60GHz resonant frequency. Patch has been considered as sheet with perfect electrical boundaries for simulation in HFSS. 978-1-5090-2118-5/16/$31.00 ©2016 IEEE
Microstrip lineinset-feeding technique has been used to make antenna conformal and printable. Impedance point on patch of 120Ω has been calculated from [16].Feed pointY0comes out to be 0.542mm. Lf length strip (impedance=120Ω) has been protruded out from patch to Lt (impedance=77.5Ω) the quarter wave transformer, so that entire patch remains on lower dielectric substrate whereas transformer along with 50Ω feed-line remain on higher dielectric substrate i.e. silicon. Lf and Ltis calculated from [13] for given dielectric and impedance.50Ω feed line of width 0.9753mm and length 30mm has been used to feed each antenna simultaneously and symmetrically. The source has been connected at the center of the line through another square patch of side 0.9753mm. This new type of feeding techniques gives good performances and impedance matching for large range of frequencies with comparatively lesser area then corporate and series array feed network. III. SIMULATION RESULTS The designed antenna shows multiple radiation bands due to slots made for inset feed. Out of many bands six major bands are enlisted that can be used for D2D network, Internet of Things and cellular uplink as well as downlink of 5G communication system. Fig.4 shows the six major bands, bands A, B, C i.e. 58-68.8 GHz shows total of 4.84 GHz bandwidth that can be used for Wi-Gig [17] or D2D network. Band D, E, F i.e. 72-77GHz band is used to implement wireless and backhaul network [18]. Return loss parameter and resonant frequency for each of these bands is specified in Table 3 High gain is striking feature of this antenna design 60 GHz and 67GHz band show peak gain of 9 dB whereas
104 International Conference on Emerging Trends in Electrical, Electronics and Sustainable Energy Systems (ICETEESES–16)
other bands have gain>0dB, which is far better than design in [10],[11]. Antenna for band A, B, C shows high gain, desired for D2D network since antenna need to be directive in this band whereas band D, E, F are having low gain value as they are meant for cellular communication with Omni-directional radiation pattern i.e. not being biased to any specific direction
Fig. 7: Gain (dB) vs. Frequency (GHz)
IV. COMPARISON
Fig. 4: Return Loss (dB) vs. Frequency (GHz) TABLE 3 Resonant Frequency (fr) (GHz) 59.63 65.8 67.6 72.08 75.78 77
Bandwidth (GHz)
Return loss (in dB)
Band (GHz)
2.14 0.5 2.2 1.19 2.59 0.95
-34.65 -22.43 -13.19 -15.39 -34 -21.42
58.04-60.15 65.5-66 66.60-68.80 71.9-73.09 73.64-76.23 76.35-77.30
For array Microstrip line feed network has been used but it suffers spurious radiation, i.e. feed lines radiate and distort the radiation pattern as encircled in fig.8 but on covering the feed network with high dielectric material this spurious radiation can be inhibited. Fig.9 shows by covering the feed network with a 1mm high silicon superstrate, radiation pattern approaches Omni-directional pattern as number of nulls are reduced without degrading the gain performance. Omnidirectional pattern is desirable for cellular communication which can be generated by Superstrate technique
Spurious radiation
Fig. 8: Electric Field Vector on Patch
Fig. 5: VSWR vs. Frequency (GHz)
Fig. 9: E Field Pattern (θ=90) at 73 GHz of (A) Normal Design (B) Feed Network Covered by Silicon
Fig. 6: Radiation Pattern
Increasing the height of superstrate or the dielectric constant will further constrain the field over feed-line inside the dielectric eradicating the spurious radiation but will come at the cost of increased height.
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Multiband Millimeter Wave Antenna Array for 5G Communication 105
V. CONCLUSION This paper presents first ever work on antenna array for 5G targeting both the D2D network as well as cellular communication with very high gain for multiple bands. Continuous spectrum of more than 1GHz in each band and multiple separated bands provides spectrum for high speed downlink and uplink. Omni-directional radiation pattern has also been achieved by coating the feed-line with 1mm silicon which constrained the undesirable spurious radiation. Thedesigned antenna fulfills all the requirement of 5G system, lesser fabrication steps, compact size and conformal design makes it promising candidate for large scale production. Use of silicon substrate reduces the cost drastically so it also appeals for low cost features. Challenges in this area are attenuation due to rain, oxygen and shadowing.mm wave has adversary effect on humaneyes prolong period of exposure causes itching and burning sensation as reported in many experimental studies. Lot of work is going on to mitigate these problems in 73GHz and 60GHz band which is the future of mmWave communication.
[7]
[8] [9] [10] [11]
[12]
[13] [14]
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