Switched Parasitic Dielectric Resonator Antenna Array Using Capacitor Loading for 5G Applications.

Transcription

1 Switche Parasitic Dielectric Resonator Antenna Arra Using Capacitor Loaing for 5G Applications. N. H. Shahaan 1,2, M. R. Kamaruin 2, M. H. Jamaluin 2, M. Khalil 3 an M. Jusoh 4 1 Department of Poltechnic, Ministr of Eucation Malasia, Presint 4, 621 W.P. Putrajaa, Malasia. aumaui2@gmail.com 2 Wireless Communication Centre (WCC), Universiti Teknologi Malasia, UTM Johor, Johor 8131, Malasia. ramlee@fke.utm.m 3 Institute for Communication Sstems (ICS), Home of the 5G Innovation Centre, Department of Electronic Engineering, Universit of Surre, Guilfor GU2 7XH, Unite Kingom. m.khalil@surre.ac.uk 4 School of Computer an Communication Engineering, Universiti Malasia Perlis. muammil@unimap.eu.m Abstract This paper presents a brief account of the finings on a switche parasitic ielectric resonator antenna (DRA) arra ecite in a higher-orer moe. The scanning phase can be change b using switching technique an capacitor loaing at the parasitic element. The riven DR an parasitic DRs have a ielectric constant of 1 an were fe b a microstrip slot aperture. The impact of mutual coupling on the reflection coefficient was eamine through a numerical calculation which combines both ANSYS HFSS an MATLAB. This phase arra was shown to be able to steer the antenna beam from -26 egrees to +26 egrees at 15 GH, which is consiere suitable for 5G applications. The impeance matching was maintaine at all beam steering angles an a banwith of 2.6 GH has been achieve. Ine Terms Dielectric resonator antenna, higher-orer moe, phase arra, parasitic element, 5G. I. INTRODUCTION Telecommunication technolog has evolve rapil from the first generation (1G) to the fifth generation (5G) ue to the increasing eman for unlimite access to information an sharing of ata. 5G technolog [1] nees a high gain an steerable beam irectional antenna an wie banwith to meet all the requirements of a long istance communication [2]. In [3], the spectrum bans up to 6 GH are consiere ieal for 5G applications. Due to that, this work has propose 15 GH as the antenna operating frequenc. Phase arra esign allows for more irectional antennas which are electricall steerable. However, the phase shifters are costl an require complicate feeing networks which will result in large losses at higher frequencies [4]. Therefore, there is a nee to evelop low cost phase arras using ifferent approaches. Some efforts have been taken [5]-[7] to evelop steerable antenna without the nee of phase shifters, namel electronicall steerable passive arra raiator (ESPAR). The ESPAR antenna is ecite b one of the elements in the arra (riven element) while other elements are fe through the mutual coupling between them. The phase shifts require for beam steering can be ajuste b changing the reactance of the capacitor loaing on the parasitic elements. Previousl, ESPAR investigations have focuse on wire [5] an patch elements [7]. Nevertheless, microstrip ESPAR suffers from limite scan range aroun the boresight. The beam steering angle onl achieve the range of ±15 in [8] an ±2 in [4]. Besies that, the impeance banwith of the microstrip ESPAR is narrow an it is also ifficult to maintain the impeance matching uring the beam scanning [9]. Recentl, ielectric resonator antenna (DRA) ESPAR irectl ecite b microstrip line has been reporte in [1], in which as usual the DRAs were ecite in their funamental moe. There is no much ifference on impeance banwith between DRA ESPAR in [1] an microstrip ESPAR in [8]. Taking the avantages of higher-orer moe DRA to enhance the impeance banwith [11] an gain [12] at lower frequencies, the author investigate it at 15 GH. In this paper, the ESPAR esign which consists of a riven DRA an two parasitic DRAs with controlling switches is presente. All DRAs were ecite using a higher-orer moe. This paper is organie as follows. In Section II, the single element DRA esigne using a funamental moe (TE 1 δ1 ) an a higher-orer moe (TE 1 δ3 ), respectivel were iscusse. In section III, the numerical calculations to get the effective range of capacitance from the DRA ESPAR esign were iscusse. The ieal switches were then ae to the ESPAR DRA esign to control the beam scanning. The paper is conclue in Section V. II. SINGLE ELEMENT DESIGN OF DIELECTRIC RESONATOR ANTENNA The DRA of TE m δn with a ielectric constant, ε r =1 at 15 GH can be preicte from the ielectric waveguie moel [13]. When the groun plane is present, the moes of the DRA cannot be ecite if n is an even number. It is because these moes require the E-fiel to be maimum at =, which

2 is contraictor to the bounar conition that the tangential E-fiel shoul vanish on the groun plane [14]. Therefore, the ine n must be an o number. The single element DRA has been create, an then simulate using ANSYS High Frequenc Structural Simulator (HFSS) software to obtain optimum parameter value. Duroi 588 ielectric substrate with a thickness of.254 mm, a permittivit of 2.2 an a loss tangent of.1 was use in the esign. Microstrip slot aperture was chosen as the feeing technique because it will give a high irectivit an antenna gain to fulfil the 5G requirements [15]. A. Antenna Configuration The configuration of the single element DRA is shown in Fig. 1. Through the simulation an optimiation of the esign parameters, the optimum parameters are shown in Table I. ecite using ifferent moes. Obviousl, this will affect the antenna banwith, raiation pattern an also gain. 2) Reflection Coefficient: The simulate reflection coefficients of the DRA ecite in a funamental moe (TE 1 δ1 ) an higher-orer moe (TE 1 δ3 ) are presente in Fig. 3. With reference to the figures, both esigns have a goo S 11 at 15 GH. The 1-B impeance banwith has achieve 2.7 GH (13.4 GH 16.1 GH) for DRA ecite in the TE 1 δ3 moe but onl 2 GH (14.1 GH 16.1 GH) was observe for DRA ecite in TE 1 δ1 moe. Groun plane h w Rectangular DRA Substrate Microstrip fee line (bottom) s Ls Ws Fig. 2. Magnetic fiels insie the single element DRA TE 1 δ 1 TE 1 δ 3 Fig. 1. Configuration of the single element DRA 3D view Top view TABLE I. W DESIGN PARAMETERS OF THE SINGLE ELEMENT DRA Parameter w h L s W s S W Value (mm) for TE 1 δ 1 Value (mm) for TE 1 δ B. Comparison of the Simulate Results for Single Element DRA Using Different Ecitation Moes. 1) Magnetic Fiel Distribution: Fig. 2 epicts the simulate H -fiel insie the DRA which was ecite in TE 1 δ1 an TE 1 δ3 moe. The H component of the magnetic fiel is ominant along the center of the DRA. As it is shown in Fig. 2, the ifferent H-fiel istributions insie the DRA were S11 (B) Frequenc (GH) Fig. 3. Simulate reflection coefficients of the single element DRA 3) Raiation Characteristics an Gain: The raiation pattern for E-plane an H-plane are compare in Fig. 4. As it can be seen, both esigns have a broasie raiation. Nevertheless, the DRA ecite in TE 1 δ3 moe has more than one equivalent magnetic ipole along the height [14]. The separation between the equivalent magnetic ipoles is etermine b the DRA imensions. Therefore, a narrower

3 beamwith can be achieve with a DRA ecite in TE 1 δ3 moe, in comparison with the DRA ecite in TE 1 δ1 moe. Besies that, the gain for the single DRA ecite in TE 1 δ3 moe has achieve 9.9 Bi in comparison to 5.6 Bi when it was ecite in TE 1 δ1 moe. 1 5 Parasitic DR 1 Driven DR Parasitic DR 2 3 mm 2 mm Gain (B) Port 2 Port 3 C A C B Theta (eg) Port 1 Fig. 5. Configuration of DRA with parasitic elements an capacitor loaing B using (1), the ratio between the current on the two parasitic DRs an the current on the riven DR was obtaine, as shown in (2). Gain (B) -1 (2) Theta (eg) Fig. 4. Simulate raiation patterns of the single element DRA E-plane ( plane) H-plane ( plane) III. DRA WITH PARASITIC ELEMENTS AND CAPACITOR LOADING The comparison of simulate results in Section II shows the avantages of using a higher-orer moe (TE 1 δ3 ) in 5G applications. DRA with parasitic elements an capacitor loaing was then eamine b using TE 1 δ3 moe. Besies that, numerical calculations were also evelope in this section to stu the capacitance range that will affect the steering angle. A. Theor an Design The esign in Fig. 5 consists of three elements of ielectric resonator. The riven DR at port 1 was fe b an RF source an the parasitic DR at port 2 an 3 were ecite b the riven DR through the mutual coupling. The mutual coupling was etermine b the istance between the ielectric resonator elements an the phase shifts between the elements, which have been ajuste b changing the reactance of C A an C B. The best istance, between the elements is.4λ. This arra can be anale with three-port network theor in [4], with the help of Z matri in (1): (1) The raiation pattern of the phase arra was calculate b multipling the arra factor b the raiation pattern of a single DRA. The arra factor of the three DRA was foun to be: where k is the wavenumber an is the center to center istance between the DRAs. B. Effective Capacitance Range As state, the capacitances C A an C B are the ke controls for the raiation pattern. B ajusting their values, the input impeance of the parasitic DRs can be controlle an this in turn will allow the controlling of the current istributions on them. First, the preicte value for effective range of capacitances C A an C B for the esign in Fig. 5 was obtaine b etermining the reflection coefficient, Γ in (4). where Z C =1/jωC is the reactance provie b either capacitor C A or C B an the input impeance, Z in can be calculate as in (5): The values for all Z parameters involve in these numerical calculations were obtaine from ANSYS HFSS. Then, b (3) (4) (5)

4 using MATLAB, the reflection coefficient, Γ was calculate for parasitic DR at port 2 b varing capacitance C A. Fig. 6 shows the magnitue an phase of Γ versus C A in which no change was note in Γ an Γ ϕ when the capacitance ecees 1. The same thing happens when C B is varie. Since Γ is high when C A <.1 an nearl flat when C A > 1, the range of.1 1 was consiere as the effective capacitances that woul affect the raiation pattern of the propose antenna. 1 Parasitic DR 1 Driven DR Parasitic DR 2 SW 1 3 mm SW 2 SW 3 SW 4 SW 5 SW 6 2 mm Reflection Coefficient, Γ C 1 C 2 C 2 C 1 C 3 C 3 Shorting pin Fig. 7. Configuration of switche parasitic DRA with capacitor loaing TABLE II. SWITCH CONFIGURATION FOR ANTENNA BEAM STEERING Reflection Coefficient, Γ ϕ (º) Capacitor, C A () Capacitor, C A () Fig. 6. Variation of Γ with capacitance C A magnitue of Γ phase of Γ IV. A. Propose Design SWITCHED PARASITIC DRA WITH CAPACITOR LOADING A irectional beam was forme b an appropriate choice of the parasitic element termination, an the beam was steere b switching the termination on the parasitic elements. Fig. 7 shows the top view laout of the propose switche parasitic DRA to perform five ifferent steering angles. The switching configuration for antenna beam steering is shown in Table II. The ON an OFF states refer to the short-circuit an opencircuit between the corresponing capacitor an the parasitic element, respectivel. The shorting pin was use to connect the groun plane. C 1=.1 Parasitic DR1 C 3=1 C 2=.1 C 2=.1 Parasitic DR2 C 3=1 C 1=.1 SW1 SW2 SW3 SW4 SW5 SW6 Case I OFF ON OFF OFF OFF ON Case II OFF OFF ON OFF OFF ON Case III ON OFF OFF OFF OFF ON Case IV ON OFF OFF ON OFF OFF Case V ON OFF OFF OFF ON OFF B. Simulate Result 1) Reflection Coefficient, S 11 (B): The simulate reflection coefficient is shown in Fig. 8. These results inicate an insignificant variation of impeance matching in ifferent cases which oes not affect the normal operation of the antenna as epecte. The -1 B impeance banwith has achieve 2.6 GH in the range of 13.7 GH 16.3 GH for all cases. S 11 (B) Case I Case II Case III Case IV Case V Frequenc (GH) Fig. 8. Simulate reflection coefficients for ifferent cases as mentione in Table II

5 2) H-plane Raiation Pattern an Gain: The beam steering angle (relative to the boresight) for five ifferent cases is illustrate in Fig. 9. It was observe that when SW2 was terminate with C 3 =1 an SW6 was terminate with C 1 =.1, the beam has reache its maimum coverage at When the capacitance values were alternate, in which SW1 was terminate with C 1 =.1 while SW5 with C 3 =1, the steering angle was foun to shift back to 26. The maimum coverage of beam was recore at when both SW1 an SW6 were terminate with C 1 =.1. The simulate peak gain an scan angle for ifferent cases are shown in Table III. The gain was foun to ecrease when the scan angle was increase ue to the emergence of sie lobe Case I Case II Case III Case IV Case V Fig. 9. Simulate raiation patterns for ifferent cases as mentione in Table II. TABLE III. 18 SIMULATED PEAK GAIN AND SCAN ANGLE FOR DIFFERENT CASES Case I Case II Case III Case IV Case V Peak gain (Bi) Scan angle (eg) V. CONCLUSION A new switche parasitic DRA ecite in a higher-orer moe has been emonstrate using switching technique at capacitor loaing. It shoul be note that impeance matching was maintaine at all beam steering angles an a gain of more than 7.7 Bi has been achieve. Using a higher-orer moe DRA allows for a wier banwith an a higher gain. With this esign, it is possible to achieve ±26 scanning capabilities without using phase shifter. It is believe that this new phase arra approach is the enabling technique for 5G low cost phase arras. Further eploration into how a higher gain an a larger steering angle can be achieve is being carrie out b the authors ACKNOWLEDGMENT The authors woul like to thank the Ministr of Eucation (MOE) for sponsoring the PhD stu at Universiti Teknologi Malasia (UTM). Also, special thanks go to MOE an UTM for sponsoring this work uner FRGS (Vot 4F733 an 4F283), UTM GUP (Vot 5H62&11H59) an MG (M69). REFERENCES [1] F. Boccari, R. W. Heath, A. Loano, T. L. Maretta an P. Popovski, Five Disruptive Technolog Directions for 5G, IEEE Commmunication Magaine, 214 [2] J. Rorigue, Funamentals of 5G Mobile Network. Unite Kingom: Wile, 215, pp.242 [3] Spectrum above 6 GH for future mobile communications.[online].available: binaries/consultations/above- 6gh/summar/spectrum_above_6_GH_CFI.pf. [4] Y. Yusuf an X. Gong, A low-cost patch antenna phase arra with analog beam steering using mutual coupling an reactive loaing, IEEE Antennas Wireless Propag, Lett., vol. 7, pp , 28. [5] H. Kawakami an T. Ohira, Electronicall steerable passive arra raiator (ESPAR) antennas, IEEE Antennas Propag. Mag., vol. 47, pp. 43, 25. [6] M. R. Islam an M. Ali, Elevation plane beam scanning of a novel parasitic arra raiator antenna for 19 MH mobile hanhel terminals, IEEE Trans. Antennas Propag., vol. 58, pp , 21. [7] D. T. Nguen, R. Siragusa an S. Tejini, Beam steering patch antenna using reactive loaing an agi-antenna concept, Microwave an Optical Technolog Letters., vol. 57, pp , 215. [8] J. J. Luther, S. Ebai an X. Gong, A microstrip patch electronicall steerable parasitic arra raiator (ESPAR) antenna with reactance-tune coupling an maintaine resonance, IEEE Trans. Antennas Propag., vol. 6, pp , 212. [9] M. R. Islam an M. Ali, A 9 MH beam steering parasitic antenna arra for wearable wireless application, IEEE Trans. Antennas Propag., vol. 61, pp , 213. [1] M. R. Nikkah, J. Rashe-Mohassel, an A. A. Kishk, Compact lowcost phase arra of ielectric resonator antenna using parasitic elements an capacitor loaing, IEEE Trans. Antennas Propag., vol. 61, pp , 213. [11] G. B. Babik, C. D. Nallo, an A. Faraone, Multimoe ielectric resonator antenna of ver high permittivit, IEEE Antennas Propagation Smposium, vol. 2, pp , 24. [12] A. Petosa, S. Thirakoune, an A. Ittipiboon, Higher-orer moes in rectangular DRAs for gain enhancement, 13 th International Smposium on Antenna Technolog an Applie Electromagnetics, 29. [13] R. K. Mongia, an A. Ittipiboon, Theoretical an eperimental investigation on rectangular ielectric resonator antenna, IEEE Trans. Antennas Propag., vol. 45, pp , [14] K. M. Luk an K. W. Leung, Dielectric Resonator Antenna, Englan: Research Stuies Press, 22. [15] N. H. Shahaan, M. R. Kamaruin, N. A. Zainal, J. Nasir, M. Khalil, an M. H. Jamaluin, "Investigation on Feeing Techniques for Rectangular Dielectric Resonator Antenna in Higher-Orer Moe for 5G Applications, Applie Mechanics an Materials, vol. 781, pp , August 215.