The paper describes the designs of a frequency-reconfigurable, polarization reconfigurable and pattern reconfigurable antennas using metasurfaces (MS). The frequency-reconfigurable and polarization reconfigurable antennas are composed of a simple circular patch antenna or slot antenna as the source antenna and a circular MS with the same diameter, with both source antenna and MS implemented using planar technology. The pattern reconfigurable antenna is composed of a circular patch antenna as the source antenna and a semicircular MS with the same diameter. In all these reconfigurable antennas, the MS is placed directly atop of the source antenna, making the antenna very compact and low profile with a thickness of only 0.05λ0. By rotating the MS around the center with respect to the source antenna, the frequency, polarization or pattern of the reconfigurable antenna can be reconfigured.published_or_final_versionThe 2014 Progress In Electromagnetics Research Symposium (PIERS 2014), Guangzhou, China, 25-28 August 2014. In PIERS Proceedings, 2014, p. 2400-240

Cheung, WSW

Yuk, TI

Zhu, H

HKU Scholars Hub

Title Antenna reconfiguration using metasurfacesAuthor(s) Zhu, H; Cheung, WSW; Yuk, TICitationThe 2014 Progress In Electromagnetics Research Symposium(PIERS 2014), Guangzhou, China, 25-28 August 2014. In PIERSProceedings, 2014, p. 2400-2404Issued Date 2014URL http://hdl.handle.net/10722/204116Rights Creative Commons: Attribution 3.0 Hong Kong License2400 PIERS Proceedings, Guangzhou, China, August 25–28, 2014Antenna Reconfiguration Using MetasurfacesHailiang Zhu, S. W. Cheung, and T. I. YukDepartment of Electrical and Electronic EngineeringThe University of Hong Kong, Hong KongAbstract— The paper describes the designs of a frequency-reconfigurable, polarization reconfig-urable and pattern reconfigurable antennas using metasurfaces (MS). The frequency-reconfigurableand polarization reconfigurable antennas are composed of a simple circular patch antenna or slotantenna as the source antenna and a circular MS with the same diameter, with both sourceantenna and MS implemented using planar technology. The pattern reconfigurable antenna iscomposed of a circular patch antenna as the source antenna and a semicircular MS with thesame diameter. In all these reconfigurable antennas, the MS is placed directly atop of the sourceantenna, making the antenna very compact and low profile with a thickness of only 0.05λ0. Byrotating the MS around the center with respect to the source antenna, the frequency, polarizationor pattern of the reconfigurable antenna can be reconfigured.1. INTRODUCTIONIn general, operating frequency, polarization and radiation pattern are the three major character-istics in the design of antennas. As the growing demand for integrating multiple wireless standardsinto a single wireless platform, it is highly desirable if one or more of the above mentioned perfor-mance characteristics in an antenna can be reconfigured. Thus substantial research work has beencarried out to reconfigure these characteristics for antennas.The mechanism used to reconfigure the operating frequency, polarization and radiation patternof an antenna can be mechanical or electrical. Electrically reconfigurable antennas are far morepopular and can be achieved by using PIN-diode switches or varactor diodes. In the design of theseantennas, direct-current (DC) source and biasing circuits are needed to bias the PIN or varactordiodes. These electronic components and circuits may have adverse effects on the antennas perfor-mances such as efficiencies and radiation pattern. Moreover, the antenna performance depends onthe reliability of the electronic components and the DC sources [1]. Mechanically reconfigurableantennas usually require adjusting some movable parts to achieve reconfiguration [2]. The maindrawback is that the actuator used to produce the mechanical movements is very complicatedand usually occupies much space, making it bulky and expensive. In fact, change of size and/orshape is the common problem for most mechanically reconfigurable antennas. To overcome theseshortcomings, we propose to use metasurfaces to design reconfigurable antennas.Metasurface (MS) is a two-dimensional equivalent of metamaterial and essentially a surfacedistribution of electrically small scatterers [3]. Due to its succinct planar structure and low cost,MS provides a good option for the movable part of mechanically reconfigurable antennas and canbe easily integrated with printed planar antennas.In this paper, we describe the use of MS to design three different types of reconfigurable antennas,namely, frequency-reconfigurable, polarization-reconfigurable and pattern-reconfigurable antennas.The frequency-reconfigurable and polarization reconfigurable antennas have been introduced in ourprevious papers [6, 7] in details and the idea of pattern reconfigurable antenna using MS is firsttime presented.2. ANTENNAS DESIGN2.1. Frequency-reconfigurable AntennaThe frequency-reconfigurable metasurfaced (FRMS) antenna described here, as shown in Fig. 1,consists of a patch antenna (as the source antenna) and a MS which uses a rectangular loop as theunit cell [6]. The patch antenna and MS are designed to have a circular shape with same diameter.The patch antenna is designed on a double-sided substrate using planar technology as shown inFig. 1(a), while the MS is designed on a single-sided substrate, as shown in Figs. 1(b) and (c). Thefrequency reconfigurability of the antenna is achieved by rotating the MS around the center relativeto the patch antenna. The rotation angle θR is measured from the y-axis as shown in Fig. 1(b).Due to the horizontal and vertical symmetries of the MS, θR = −θR and the maximum rotationangle without repeating is 90◦. In assembling the FRMS antenna, the non-copper side of the MS isProgress In Electromagnetics Research Symposium Proceedings,Guangzhou,China,Aug. 25–28, 2014 2401(a) (b) (c)Figure 1: Geometries of (a) patch antenna, (b) MSand (c) unit cell.Figure 2: Assembly schematic of FRMS antenna.Table 1: Dimensions of FRMS antenna (Unit: mm).Pa Pb a b w Lp Wp Wf Pf Pe D12.4 5.4 10 3 1 16 12 2 11 2 40placed in direct contact with the radiator of the patch antenna as shown in Fig. 2, leading to a verycompact and low profile structure. The antenna is designed on the Rogers substrates RO4350B,having a thickness of 1.524mm and a relative permittivity of εr = 3.48. The optimized dimensionsare listed in Table 1.2.2. Polarization Reconfigurable AntennaThe polarization-reconfigurable metasurfaced (PRMS) antenna, as shown in Fig. 3, consists of aslot antenna (as the source antenna) and a metasurface (MS) [7]. The MS is composed of corner-truncated square unit cells as shown in Fig. 3(a) on a single-sided substrate. The polarizationreconfigurablity of the antenna is accomplished by rotating the MS around the center relative tothe slot antenna. The rotation angle θR is measured from the y-axis as shown in Fig. 3(a). Studieshave shown that with θR = 0◦ and 90◦, the operation of the antenna is left-hand circular polarization(LHCP) and right-hand circular polarization (RHCP), respectively. With θR = 45◦ and 135◦, theantenna is linearly polarized (LP) along the y-axis, same as that of the source antenna (the slotantenna). In assembling the PRMS antenna, the non-copper side of the MS is placed atop the slotantenna and is in direct contact with the feed-line (top side) of it as shown in Fig. 4. This leadsto a very compact and low profile structure. An SMA connector is used to feed to the feed-linethrough the ground plane and the substrate material of the slot antenna. The dimensions of thefinal design are listed in Table 2.2.3. Radiation Pattern Reconfigurable AntennaThe pattern reconfigurable metasurfaced antenna (PaRMS) is composed of a simple circular patchantenna and a semicircular MS with the same diameter, as shown in Figs. 5 and 6. The MS consistsof small square patches used as the unit cells. Due to the semicircular structure of the MS, the(a) (b)Figure 3: Geometries of (a) MS and (b) slot antenna. Figure 4: Assembly schematic of PRMS antenna.2402 PIERS Proceedings, Guangzhou, China, August 25–28, 2014integrated antenna will generate a tilted beam, making an angle of 30◦ with the boresight direction.By rotating the MS around the center of the antenna, the tilted beam can be steered to differentdirections. As the source antenna is circular and fed by a SMA connector at the center, the S11of the PaRMS antenna is unchanged in rotation, thus simplifying the optimization work of theantenna significantly. The dimensions of the final design are listed in Table 3.Table 2: Dimensions of PRMS antenna (Unit: mm).a b c sw sl fw fl fy p T18.5 5.3 1 3 20 2.5 24.5 2 2 78Table 3: Dimensions of PaRMS antenna (Unit:mm).a G Pr T6 0.3 18 70(a) (b) (c)Figure 5: Geometries of (a) patch antenna, (b) MSand (c) unit cell.Figure 6: Assembly schematic of PaRMS antenna.3. SIMULATION AND MEASUREMENT RESULTS3.1. Frequency Reconfigurable AntennaThe frequency reconfigurability of the FRMS antenna is studied using reflection coefficient S11. Thesimulated and measured S11 of the antenna with different rotation angles θR are shown in Fig. 7.The resonant frequency is proportional to the rotation angle. As the rotation angle increases from10◦ to 25◦, 35◦, 55◦ and 80◦, the resonant frequency shifts up from 4.77GHz to 4.9, 5.07, 5.31and 5.51GHz, respectively, with a fractional tuning range of 14.6%. The simulated and measuredefficiencies are shown in Fig. 8. It can be seen that the simulated and measured efficiencies areabove 80% at the resonant frequencies.Figure 7: Simulated and measured S11 of FRMSantenna with different rotation angles.Figure 8: Simulated and measured efficiencies ofFRMS antenna.3.2. Polarization Reconfigurable AntennaThe simulated and measured S11 of the PRMS antenna with different rotation angles θR are shownin Fig. 9. The impedance bandwidth (for S11 < −10 dB) in LHCP (θR = 90◦) and RHCP (θR = 90◦)are more than from 3–4GHz as shown in Figs. 9(a) and (c), respectively. In LP, i.e., θR = 45◦,Fig. 9(b) shows that the simulated and measured frequency bands shift down slightly to 2.82–3.7GHz and 2.8–3.7GHz, respectively. However, at θR = 135◦, Fig. 9(d) shows that the simulatedand measured frequency bands shift up slightly to 3.28–4.08GHz and 3.3–4.05GHz, respectively.Progress In Electromagnetics Research Symposium Proceedings,Guangzhou,China,Aug. 25–28, 2014 2403(a) (b) (c) (d)Figure 9: Simulated and measured S11 of PRMS antenna for (a) θR = 0◦, (b) θR = 45◦, (c) θR = 90◦ and(b) θR = 135◦.(a) (b) (c) (d)Figure 10: Simulated and measured ARs for different rotation angles.The simulated and measured axial ratios (ARs) in the boresight of the PRMS antennas (alongthe +z axis as shown in Fig. 3) are shown in Fig. 10. The simulated and measured ARs are lessthan 3 dB from 3.3–3.7GHz for both LHCP and RHCP, with an axial ration bandwidth (ARBW)of 400MHz (or a fractional bandwidth of 11.4%) as shown in Figs. 10(a) and (c), respectively.With θR = 45◦ and 135◦ when the antenna is operated in LP, Figs. 10(b) and (d) show that thesimulated ARs are larger than 40 dB from 3–4GHz, indicating very high linear polarization purity.Since the antenna measurement equipment, Satimo Starlab System, can measure the AR of CPantennas only up to 20 dB, the measured result is therefore a horizontal straight line at 20 dB inFigs. 10(b) and (d).3.3. Radiation Pattern Reconfigurable AntennaThe simulated S11 of the PaRMS antenna is shown as the red line in Fig. 11. Due to the symmetricalantenna structure and the unchanged feeding position, the S11 does not vary with the rotationangle. The peak directivity and realized gain are shown in the same figure by the blue lines for theconvenience of viewing the operating bandwidth. It can be seen that in the operating bandwidthfrom 5.48–5.7GHz (4%), the peak realized gain is above 7 dBi with a peak of 7.7 dBi at 5.6GHz,where the directivity can reach up to 8.2 dBi. The radiation pattern of the antenna at 5.6GHz isFigure 11: Final operating band-width.Figure 12: 2D radiation pattern. Figure 13: 3D radiation pattern.2404 PIERS Proceedings, Guangzhou, China, August 25–28, 2014shown in Fig. 12. It can be seen that the main beam makes an angle of 32◦ with the boresightdirection. The 3D radiation pattern is plotted in Fig. 13. It can be seen that the main beam istilted towards to the opposite side of the MS. Thus, the main beam can be steered continuously byrotating the MS around the center of the antenna.4. CONCLUSIONSThree different types of reconfigurable antennas, namely, frequency, polarization and pattern config-urations, designed using matesurfaces have been presented. The source antennas of these reconfig-urable antennas have circular shapes. Results have shown that, by using different MSs underneaththe source antennas, the operating frequency, polarization and radiation pattern of the sourceantennas can be reconfigured by simply rotating the MS around the center of the source antenna.REFERENCES1. Sun, X. L., S. W. Cheung, and T. I. Yuk, “Dual-band monopole antenna with frequency-tunable feature for WiMAX applications,” IEEE Antennas and Wireless Propagation Letters,Vol. 12, 100–103, 2013.2. Bernhard, J. T., E. Kiely, and G. Washington, “A smart mechanically actuated two-layer elec-tromagnetically coupled microstrip antenna with variable frequency, bandwidth, and antennagain,” IEEE Transactions on Antennas and Propagation, Vol. 49, 597–601, 2001.3. Holloway, C. L., E. F. Kuester, J. A. Gordon, J. O’Hara, J. Booth, and D. R. Smith, “Anoverview of the theory and applications of metasurfaces: The two-dimensional equivalents ofmetamaterials,” IEEE Antennas and Propagation Magazine, Vol. 54, 10–35, 2012.4. Zhu, H. L., S. W. Cheung, K. L. Chung, and T. I. Yuk, “Linear-to-circular polarization conver-sion using metasurface,” IEEE Transactions on Antennas and Propagation, Vol. 61, 4615–4623,2013.5. Zhu, H. L., K. L. Chung, X. L. Sun, S. W. Cheung, and T. I. Yuk, “CP metasurfaced an-tennas excited by LP sources,” 2012 IEEE Antennas and Propagation Society InternationalSymposium (APSURSI), 1–2, 2012.6. Zhu, H., S. Cheung, X. Liu, and T. Yuk, “Design of polarization reconfigurable antenna usingmetasurface,” IEEE Transactions on Antennas and Propagation, Vol. PP, No. 99, 1 (pages),2014.7. Zhu, H. L., X. H. Liu, S. W. Cheung, and T. I. Yuk, “Frequency-reconfigurable antenna usingmetasurface,” IEEE Transactions on Antennas and Propagation, Vol. 62, 80–85, 2014.

Antenna reconfiguration using metasurfaces

http://hub.hku.hk/bitstream/10722/204116/1/Content.pdf

Antenna reconfiguration using metasurfaces

Abstract

Similar works

Full text

Available Versions

HKU Scholars Hub