New Method for Generating Orbital Angular Momentum Vortex Beams in the Radio Frequency Domain

Transcription

1 Forum for Electromagnetic Research Methods and Application Technologies (FERMAT) New Method for Generating Orbital Angular Momentum Vortex Beams in the Radio Frequency Domain Shixing Yu and Long Li * School of Electronic Engineering, Xidian University No.2 South Taibai Road, Xi an , Shaanxi, China * lilong@mail.xidian.edu.cn Abstract: Orbital Angular Momentum (OAM) has drawn great attention of worldwide academia in the recent years. It has been intensively applied in the domains of optics. Recent studies imply that OAM vortex wave can be used in radio not only limited to optics. Then, the application of OAM in radio has gradually become a research hotspot, and developing effective antennas to produce OAM beams is one of the key issues. To date, there are several methods to generate OAM beams, such as spiral phase plate, holographic diffraction gratings, spiral reflectors, and antenna arrays. Among them, the first two methods come from the optics and mainly going to be used in high frequency like millimeter wave. The latter two types mainly targets the low frequency. However, the spiral reflectors in many cases, due to its specifically curved surface, is difficult to manufacture. On the other hand, the array antenna, when equipped with controllable phase shifters, can achieve different functionalities electronically, but generally becomes very expensive due to its complicated beam-former and many high-cost amplifier modules. Here, we present a new method for the generation of an electromagnetic vortex wave by reflective metasurface in radio frequency. It can easily avoided transmission loss, and has the flexibility in phase control. The proposed method paves a new way to generate the OAM vortex waves for radio and microwave wireless communication applications. Key words: Orbital Angular Momentum (OAM), reflective metasurfaces, vortex waves, radio and microwave wireless communications References: [1] Wang J, Yang J Y, Fazal I M, et al. Terabit free-space data transmission employing orbital angular momentum multiplexing. Nature Photonics, 2012, 6(7):

2 [2] Tamburini F, Mari E, Sponselli A, et al. Encoding many channels on the same frequency through radio vorticity: first experimental test. New Journal of Physics, 2012, 14(3): [3] Yan Y, Xie G, Lavery M P J, et al. High-capacity millimeter-wave communications with orbital angular momentum multiplexing. Nature communications, 2014, 5. [4] Mohammadi S M, Daldorff L K S, Bergman J E S, et al. Orbital angular momentum in radio-a system study. IEEE Transactions on Antennas and Propagation, 2010, 58(2): [5] Mohammadi S M, Daldorff L K S, Forozesh K, et al. Orbital angular momentum in radio: Measurement methods. Radio Science, 2010, 45(4). [6] Gibson G, Courtial J, Padgett M, et al. Free-space information transfer using light beams carrying orbital angular momentum. Optics Express, 2004, 12(22): [7] Allen L, Beijersbergen M W, Spreeuw R J C, et al. Orbital angular momentum of light and the transformation of Laguerre-Gaussian laser modes. Physical Review A, 1992, 45(11): [8] Thidé B, Then H, Sjöholm J, et al. Utilization of photon orbital angular momentum in the low-frequency radio domain. Physical review letters, 2007, 99(8): [9] Tamburini F, Mari E, Thidé B, et al. Experimental verification of photon angular momentum and vorticity with radio techniques. Applied Physics Letters, 2011, 99(20): [10] Tamagnone M, Craeye C, Perruisseau-Carrier J. Comment on 'Reply to Comment on "Encoding many channels on the same frequency through radio vorticity: first experimental test". New Journal of Physics, 2013, 15: [11] Edfors O, Johansson A J. Is orbital angular momentum (OAM) based radio communication an unexploited area?. IEEE Transactions on Antennas and Propagation, 2012, 60(2): [12] Tamburini F, Thidé B, Mari E, et al. Reply to Comment on 'Encoding many channels on the same frequency through radio vorticity: first experimental test'. New Journal of Physics, 2012, 14(11): [13] Turnbull G A, Robertson D A, Smith G M, et al. The generation of free-space

3 Laguerre-Gaussian modes at millimetre-wave frequencies by use of a spiral phase plate. Optics communications, 1996, 127(4): [14] Schemmel P, Maccalli S, Pisano G, et al. Three-dimensional measurements of a millimeter wave orbital angular momentum vortex. Optics letters, 2014, 39(3): [15] Gao X, Huang S, Song Y, et al. Generating the orbital angular momentum of radio frequency signals using optical-true-time-delay unit based on optical spectrum processor. Optics letters, 2014, 39(9): [16] X. L. Gao, S. G. Huang, Y. F. Wei, et al. An orbital angular momentum radio communication system optimized by intensity controlled masks effectively: Theoretical design and experimental verification. Applied Physics Letters, 2014, 105(24): [17] X. N. Hui, S. L. Zheng, Y. L. Chen, et al. Multiplexed millimeter wave communication with dual orbital angular momentum (OAM) mode antennas. Scientific Reports, 2015, 5: [18] L. Cheng, W. Hong, and Z. C. Hao. Generation of electromagnetic waves with arbitrary orbital angular momentum modes. Scientific Reports, 2014, 4:4814. [19] S. X. Yu, L. Li, G. M. Shi, et al. Design, fabrication, and measurement of reflective metasurface for orbital angular momentum vortex wave in radio frequency domain. Applied Physics Letters, 2016, 108: [20] S. X. Yu, L. Li, G. M. Shi, C. Zhu, et al. Generating multiple orbital angular momentum vortex beams using a metasurface in radio frequency domain. Applied Physics Letters, 2016, 108: Long Li was born in Guizhou province, China. He received the B. E. and Ph. D. degrees in electromagnetic fields and microwave technology from Xidian University, Xi an, China, in 1998 and 2005, respectively. He joined the School of Electronic Engineering, Xidian University in 2005 and was promoted to Associate Professor in He was a Senior Research Associate in the Wireless Communications Research Center, City University of Hong Kong in He received the Japan Society for Promotion of Science (JSPS) Postdoctoral Fellowship and visited Tohoku University, Sendai, Japan, as a JSPS Fellow from Nov to Nov He was a Senior Visiting Scholar in the

4 Pennsylvania State University, USA, from Dec to July He is currently a Professor in the School of Electronic Engineering, head of Department of Telecommunications Engineering, Xidian University. His research interests include metamaterials, computational electromagnetics, electromagnetic compatibility, novel antennas, wireless power transfer technology, and OAM vortex waves. Prof. Li received the Nomination Award of National Excellent Doctoral Dissertation of China in He won the Best Paper Award in the International Symposium on Antennas and Propagation in He received the Program for New Century Excellent Talents in University of the Ministry of Education of China in He received the First Prize of Awards for Scientific Research Results offered by Shaanxi Provincial Department of Education, China, in He received the IEEE APS Raj Mittra Travel Grant Senior Researcher Award in Prof. Li is a senior member of the Chinese Institute of Electronics (CIE) and IEEE. *This use of this work is restricted solely for academic purposes. The author of this work owns the copyright and no reproduction in any form is permitted without written permission by the author. *

5 New Method for Generating Orbital Angular Momentum Vortex Beams in Radio Frequency Domain Shixing Yu and Long Li* School of Electronic Engineering Xidian University Xi an, China *

6 Outline 1 Research Background 2 Generation of OAM Vortex Beams Using Planar Reflectarray (Metasurfaces) 3 Simulation and Measurement Results 4 Conclusions

7 1 Research Background In 1992, Allen et al. pointed out that light beams with the azimuthal phase dependence of exp(imφ) carrying orbital angular momentum (OAM). This OAM is completely different from the spin angular momentum (SAM). The electromagnetic fields carrying OAM will not propagate with plane wavefront, but with helical phase front. It has been widely used in optical regime, such as optical manipulation, quantum information process, and optical communication. Angular Momentum:

8 History of radio vortex 1 Research Background 1992, Allen et al. found that helically phased beams carried an OAM. 2004, Gibson et al. conducted an experiment for OAM optical communication.

9 1 Research Background 2007, the first radio OAM simulation was performed, which demonstrated that OAM modes are orthogonal among one another and can be allowed in principle to increase the transmission capacity. Radio OAM techniques hold promise for the development of novel information-rich radar and wireless communication concepts and methodologies.

10 1 Research Background 2009, Mohammdadi et al. proposed a comprehensive system simulation of OAM carried by radio beams generated by a circular antenna array.

11 1 Research Background 2010, Tamburini et al. verified that OAM-carrying beams can be readily generated and exploited by using radio techniques.

12 1 Research Background 2011, Tamburini and Thide verified that it is possible to use two independent radio channels to transmit signals at the same frequency but encoded in two different orbital angular momentum states.

13 1 Research Background 2011, Nature reported a news titled Adding a twist to radio technology spiralling radio waves could revolutionize telecommunications which has drawn wide attention.

14 1 Research Background The research in radio vortex has been a hotspot. One is how to improve communication capacity via OAM multiplexing, another is how to design high performance antennas or devices to generate OAM vortex beams. 2014, a planar-spiral phase plate was proposed to generate mixed OAM beams at 94GHz, based on the concept of transmit array antenna. (L. Chen, W. Hong, Z. C. Hao, Sci. Rep, 4, 4814, 2014.)

15 How to generate a radio vortex? 1 Research Background Spiral phase plate Helicoidal parabolic antenna In this work, we propose a new method to generate an OAM vortex wave in radio frequency domain by using a planar reflectarray (reflective metasurface). Antenna array

16 2 Generating OAM Vortex by Reflectarray Planar reflectarray design (x f, y f, z f ) M N c E (u) ˆ = F( r ) ( ˆ ) ( ˆ ˆ) { [ ˆ mn r f Ar mn u0 Au0 u exp jk0 r mn r f + r mn u] + jφmn} Advantages m= 1n= 1 Surface mountable with lower mass and volume Easily deployable Lower manufacturing cost Scannable beam Easy feeding Very large aperture array

17 2 Generating OAM Vortex by Reflectarray

18 2 Generating OAM Vortex by Reflectarray The phase-shift required at each reflective elements for an OAM vortex wave in the desired direction can be obtained c φ ˆ mn = lϕmn k 0 rmn rf rmn u + 0, l = 0, ± 1, ± 2,...

19 2 Generating OAM Vortex by Reflectarray OAM vortex wave in RF band (5.8GHz) x Floquet Port d y L γl Free space w s w m D Top view Substrate Element z ε r Air t T Air x O GND GND y Tri-dipole element of the reflectarray The reflection phase of the tri-dipole elemnent

20 2 Generating OAM Vortex by Reflectarray Figure: Numerical simulation results of OAM vortex wave with different mode numbers generated by the planar reflectarray. Wavefront phase characteristics on the observational reference plane z=3.0m with (a) l=1, (b) l=2, and (c) l=4 OAM beams and corresponding far-field radiation patterns with (d) l=1, (e) l=2, and (f) l=4.

21 3 Simulation and Measurement Results Simulation r f = 0.4m Experiment The fabricated prototype of the OAM generating reflectarray with feeding horn antenna in normal incidence. * S. X. Yu, L. Li, G. M. Shi, et al, Applied Physics Letters, 108, , 2016.

22 3 Simulation and Measurement Results B 2 =300cm (D1+D 2 =10m) B 1 =70cm B 1 =70cm D 2 =80cm 10m from the surface D 1 =40cm E-field 1.2m from the surface 3D far-field pattern

23 3 Simulation and Measurement Results

24 3 Simulation and Measurement Results

25 3 Simulation and Measurement Results

26 3 Simulation and Measurement Results

27 3 Simulation and Measurement Results (a) l=2 (b) l=1 l=1 l=1 (c) (d) l=2 l=1 l=1 l=1

28 3 Simulation and Measurement Results

29 3 Simulation and Measurement Results

30 3 Simulation and Measurement Results u y Probe Probe z 0 =3m x Turntable v Near-field scanning plane

31 3 Simulation and Measurement Results Simulation Experiment (a) (b) (a) (b) (c) (d) (c) (d) * S. X. Yu, L. Li, G. M. Shi, et al, Applied Physics Letters, 108, , 2016.

32 3 Simulation and Measurement Results Simulated 3D Far-field Pattern Comparison between simulation and experiment

33 * S. X. Yu, L. Li, Applied Physics Express, 9, , Simulation and Measurement Results

34 3 Simulation and Measurement Results lx=1 ly=2

35 3 Simulation and Measurement Results

36 3 Simulation and Measurement Results Measurement Simulation

37 4 Conclusions Planar reflectarrays or reflective metasurfaces can be used to effectively generate vortex beams with orbital angular momentum in RF domain. It is worth pointing out that the design method is also adapted to dual-linear polarization and circular polarization states when using different sub-wavelength reflective elements, which belongs to the spin angular momentum (SAM) regulation. By using the proposed configuration, it is much easier to produce the vortex radio waves with different mode numbers, which provides a simple way to generate the OAM vortex waves for radio and microwave wireless communication applications.

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