{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,25]],"date-time":"2026-01-25T06:16:12Z","timestamp":1769321772648,"version":"3.49.0"},"reference-count":81,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2021,4,14]],"date-time":"2021-04-14T00:00:00Z","timestamp":1618358400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010664","name":"H2020 Future and Emerging Technologies","doi-asserted-by":"publisher","award":["FETOPEN-73687"],"award-info":[{"award-number":["FETOPEN-73687"]}],"id":[{"id":"10.13039\/100010664","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003741","name":"Instituci\u00f3 Catalana de Recerca i Estudis Avan\u00e7ats","doi-asserted-by":"publisher","award":["ICREA"],"award-info":[{"award-number":["ICREA"]}],"id":[{"id":"10.13039\/501100003741","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>As the current standardization for the 5G networks nears completion, work towards understanding the potential technologies for the 6G wireless networks is already underway. One of these potential technologies for the 6G networks is reconfigurable intelligent surfaces. They offer unprecedented degrees of freedom towards engineering the wireless channel, i.e., the ability to modify the characteristics of the channel whenever and however required. Nevertheless, such properties demand that the response of the associated metasurface is well understood under all possible operational conditions. While an understanding of the radiation pattern characteristics can be obtained through either analytical models or full-wave simulations, they suffer from inaccuracy and extremely high computational complexity, respectively. Hence, in this paper, we propose a neural network-based approach that enables a fast and accurate characterization of the metasurface response. We analyze multiple scenarios and demonstrate the capabilities and utility of the proposed methodology. Concretely, we show that this method can learn and predict the parameters governing the reflected wave radiation pattern with an accuracy of a full-wave simulation (98.8\u201399.8%) and the time and computational complexity of an analytical model. The aforementioned result and methodology will be of specific importance for the design, fault tolerance, and maintenance of the thousands of reconfigurable intelligent surfaces that will be deployed in the 6G network environment.<\/jats:p>","DOI":"10.3390\/s21082765","type":"journal-article","created":{"date-parts":[[2021,4,14]],"date-time":"2021-04-14T15:30:39Z","timestamp":1618414239000},"page":"2765","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":24,"title":["Radiation Pattern Prediction for Metasurfaces: A Neural Network-Based Approach"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8732-6086","authenticated-orcid":false,"given":"Hamidreza","family":"Taghvaee","sequence":"first","affiliation":[{"name":"NaNoNetworking Center in Catalonia (N3Cat), Universitat Polit\u00e8cnica de Catalunya, 08034 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6986-2720","authenticated-orcid":false,"given":"Akshay","family":"Jain","sequence":"additional","affiliation":[{"name":"NaNoNetworking Center in Catalonia (N3Cat), Universitat Polit\u00e8cnica de Catalunya, 08034 Barcelona, Spain"}]},{"given":"Xavier","family":"Timoneda","sequence":"additional","affiliation":[{"name":"NaNoNetworking Center in Catalonia (N3Cat), Universitat Polit\u00e8cnica de Catalunya, 08034 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4521-7353","authenticated-orcid":false,"given":"Christos","family":"Liaskos","sequence":"additional","affiliation":[{"name":"Foundation for Research and Technology Hellas, 71110 Heraklion, Greece"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0941-0260","authenticated-orcid":false,"given":"Sergi","family":"Abadal","sequence":"additional","affiliation":[{"name":"NaNoNetworking Center in Catalonia (N3Cat), Universitat Polit\u00e8cnica de Catalunya, 08034 Barcelona, Spain"}]},{"given":"Eduard","family":"Alarc\u00f3n","sequence":"additional","affiliation":[{"name":"NaNoNetworking Center in Catalonia (N3Cat), Universitat Polit\u00e8cnica de Catalunya, 08034 Barcelona, Spain"}]},{"given":"Albert","family":"Cabellos-Aparicio","sequence":"additional","affiliation":[{"name":"NaNoNetworking Center in Catalonia (N3Cat), Universitat Polit\u00e8cnica de Catalunya, 08034 Barcelona, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2021,4,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1109\/MVT.2019.2921208","article-title":"6G Wireless Networks: Vision, Requirements, Architecture, and Key Technologies","volume":"14","author":"Zhang","year":"2019","journal-title":"IEEE Veh. Technol. Mag."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"134","DOI":"10.1109\/MNET.001.1900287","article-title":"A Vision of 6G Wireless Systems: Applications, Trends, Technologies, and Open Research Problems","volume":"34","author":"Saad","year":"2020","journal-title":"IEEE Netw."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1109\/MVT.2019.2921162","article-title":"6G: The Next Frontier: From Holographic Messaging to Artificial Intelligence Using Subterahertz and Visible Light Communication","volume":"14","author":"Barbarossa","year":"2019","journal-title":"IEEE Veh. Technol. Mag."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1533","DOI":"10.1109\/JLT.2015.2510021","article-title":"What is LiFi?","volume":"34","author":"Haas","year":"2016","journal-title":"J. Light. Technol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"116753","DOI":"10.1109\/ACCESS.2019.2935192","article-title":"Wireless communications through reconfigurable intelligent surfaces","volume":"7","author":"Basar","year":"2019","journal-title":"IEEE Access"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Renzo, M.D., Debbah, M., Phan-Huy, D.T., Zappone, A., Alouini, M.S., Yuen, C., Sciancalepore, V., Alexandropoulos, G.C., Hoydis, J., and Gacanin, H. (2019). Smart radio environments empowered by reconfigurable AI meta-surfaces: An idea whose time has come. Eurasip J. Wirel. Commun. Netw., 129.","DOI":"10.1186\/s13638-019-1438-9"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Di Renzo, M., Habibi Danufane, F., Xi, X., de Rosny, J., and Tretyakov, S. (2020, January 26\u201329). Analytical Modeling of the Path-Loss for Reconfigurable Intelligent Surfaces\u2014Anomalous Mirror or Scatterer?. Proceedings of the 2020 IEEE 21st International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Atlanta, GA, USA.","DOI":"10.1109\/SPAWC48557.2020.9154326"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"3523","DOI":"10.1109\/TVT.2020.2970018","article-title":"Performance Analysis of Cell-Free Massive MIMO Systems: A Stochastic Geometry Approach","volume":"69","author":"Papazafeiropoulos","year":"2020","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"162","DOI":"10.1109\/MCOM.2018.1700659","article-title":"A New Wireless Communication Paradigm through Software-Controlled Metasurfaces","volume":"56","author":"Liaskos","year":"2018","journal-title":"IEEE Commun. Mag."},{"key":"ref_10","unstructured":"Elmeadawy, S., and Shubair, R.M. (2020). Enabling Technologies For 6g Future Wireless Communications: Opportunities And Challenges. arXiv."},{"key":"ref_11","unstructured":"Rajatheva, N., Atzeni, I., Bjornson, E., Bourdoux, A., Buzzi, S., Dor\u00e9, J., Erkucuk, S., Fuentes, M., Guan, K., and Hu, Y. (2020). White Paper on Broadband Connectivity in 6G. arXiv."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2055","DOI":"10.1137\/120903610","article-title":"Enhancement of Near Cloaking for the Full Maxwell Equations","volume":"73","author":"Ammari","year":"2013","journal-title":"Siam J. Appl. Math."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1016\/S1369-7021(09)70072-0","article-title":"Electromagnetic cloaking with metamaterials","volume":"12","author":"Alitalo","year":"2009","journal-title":"Mater. Today"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2713","DOI":"10.1109\/TAP.2003.817558","article-title":"Two-dimensional beam steering using an electrically tunable impedance surface","volume":"51","author":"Sievenpiper","year":"2003","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"6261","DOI":"10.1021\/acs.nanolett.5b02926","article-title":"High-Efficiency All-Dielectric Metasurfaces for Ultracompact Beam Manipulation in Transmission Mode","volume":"15","author":"Shalaev","year":"2015","journal-title":"Nano Lett."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1038\/s41928-018-0190-1","article-title":"Optimally diverse communication channels in disordered environments with tuned randomness","volume":"2","author":"Fink","year":"2019","journal-title":"Nat. Electron."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2683","DOI":"10.1109\/JSAC.2020.3007055","article-title":"MIMO Transmission Through Reconfigurable Intelligent Surface: System Design, Analysis, and Implementation","volume":"38","author":"Tang","year":"2020","journal-title":"IEEE J. Sel. Areas Commun."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Zhao, H., Shuang, Y., Wei, M., Cui, T.J., Hougne, P.d., and Li, L. (2020). Metasurface-Assisted Passive Wireless Communication with Commodity Wi-Fi Signals. Sci. Rep., 11.","DOI":"10.1038\/s41467-020-17808-y"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1109\/MVT.2020.3023682","article-title":"Radio Localization and Mapping With Reconfigurable Intelligent Surfaces: Challenges, Opportunities, and Research Directions","volume":"15","author":"Wymeersch","year":"2020","journal-title":"IEEE Veh. Technol. Mag."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Del Hougne, P., Imani, M.F., Fink, M., Smith, D.R., and Lerosey, G. (2018). Precise localization of multiple noncooperative objects in a disordered cavity by wave front shaping. Phys. Rev. Lett., 121.","DOI":"10.1103\/PhysRevLett.121.063901"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"043224","DOI":"10.1103\/PhysRevResearch.2.043224","article-title":"Robust position sensing with wave fingerprints in dynamic complex propagation environments","volume":"2","year":"2020","journal-title":"Phys. Rev. Res."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"100006","DOI":"10.1016\/j.patter.2020.100006","article-title":"Intelligent Electromagnetic Sensing with Learnable Data Acquisition and Processing","volume":"1","author":"Li","year":"2020","journal-title":"Patterns"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"255104","DOI":"10.1088\/1361-6463\/aa7194","article-title":"Terahertz Kerr nonlinearity analysis of a microribbon graphene array using the harmonic balance method","volume":"50","author":"Taghvaee","year":"2017","journal-title":"J. Phys. Appl. Phys."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1901913","DOI":"10.1002\/advs.201901913","article-title":"Learned Integrated Sensing Pipeline: Reconfigurable Metasurface Transceivers as Trainable Physical Layer in an Artificial Neural Network","volume":"7","author":"Imani","year":"2020","journal-title":"Adv. Sci."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Qian, C., Zheng, B., Shen, Y., Jing, L., Li, E., Shen, L., and Chen, H. (2020). Deep-learning-enabled self-adaptive microwave cloak without human intervention. Nat. Photonics, 14.","DOI":"10.1038\/s41566-020-0604-2"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Lalbakhsh, A., and Esselle, K.P. (2016, January 10\u201313). Directivity improvement of a Fabry-Perot cavity antenna by enhancing near field characteristic. Proceedings of the 2016 17th International Symposium on Antenna Technology and Applied Electromagnetics (ANTEM), Montreal, QC, Canada.","DOI":"10.1109\/ANTEM.2016.7550182"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1080\/09205071.2019.1688693","article-title":"Single-layer polarization-insensitive frequency selective surface for beam reconfigurability of monopole antennas","volume":"34","author":"Das","year":"2020","journal-title":"J. Electromagn. Waves Appl."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"153630","DOI":"10.1016\/j.aeue.2021.153630","article-title":"Single-layer ultra-wide stop-band frequency selective surface using interconnected square rings","volume":"132","author":"Paul","year":"2021","journal-title":"Aeu Int. J. Electron. Commun."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1400","DOI":"10.1109\/LAWP.2019.2917767","article-title":"3-D-Printed Phase-Rectifying Transparent Superstrate for Resonant-Cavity Antenna","volume":"18","author":"Hayat","year":"2019","journal-title":"IEEE Antennas Wirel. Propag. Lett."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"3328","DOI":"10.1109\/TAP.2020.2969888","article-title":"Low-Cost Nonuniform Metallic Lattice for Rectifying Aperture Near-Field of Electromagnetic Bandgap Resonator Antennas","volume":"68","author":"Lalbakhsh","year":"2020","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Liu, F., Pitilakis, A., Mirmoosa, M.S., Tsilipakos, O., Wang, X., Tasolamprou, A.C., Abadal, S., Cabellos-Aparicio, A., Alarc\u00f3n, E., and Liaskos, C. (2018, January 27\u201330). Programmable Metasurfaces: State of the Art and Prospects. Proceedings of the 2018 IEEE International Symposium on Circuits and Systems (ISCAS), Florence, Italy.","DOI":"10.1109\/ISCAS.2018.8351817"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Liaskos, C., Nie, S., Tsioliaridou, A., Pitsillides, A., Ioannidis, S., and Akyildiz, I. (2018, January 12\u201315). Realizing Wireless Communication Through Software-Defined HyperSurface Environments. Proceedings of the 2018 IEEE 19th International Symposium on \u201cA World of Wireless, Mobile and Multimedia Networks\u201d (WoWMoM), Chania, Greece.","DOI":"10.1109\/WoWMoM.2018.8449754"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"105320","DOI":"10.1109\/ACCESS.2020.3000424","article-title":"Scalability Analysis of Programmable Metasurfaces for Beam Steering","volume":"8","author":"Taghvaee","year":"2020","journal-title":"IEEE Access"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2868","DOI":"10.1038\/s41598-019-39266-3","article-title":"Reprogrammable Graphene-based Metasurface Mirror with Adaptive Focal Point for THz Imaging","volume":"9","author":"Hosseininejad","year":"2019","journal-title":"Sci. Rep."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"987","DOI":"10.1109\/72.712178","article-title":"Artificial neural networks for solving ordinary and partial differential equations","volume":"9","author":"Lagaris","year":"1998","journal-title":"IEEE Trans. Neural Netw."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"734","DOI":"10.1109\/TNANO.2019.2923727","article-title":"Digital Metasurface Based on Graphene: An Application to Beam Steering in Terahertz Plasmonic Antennas","volume":"18","author":"Hosseininejad","year":"2019","journal-title":"IEEE Trans. Nanotechnol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1819","DOI":"10.1021\/acs.nanolett.6b05137","article-title":"Achromatic Metalens over 60 nm Bandwidth in the Visible and Metalens with Reverse Chromatic Dispersion","volume":"17","author":"Khorasaninejad","year":"2017","journal-title":"Nano Lett."},{"key":"ref_38","unstructured":"Valasoulis, K., Fotiadis, D.L., Lagaris, I.E., and Likas, A. (2002, January 1\u20133). Solving differential equations with neural networks: Implementation on a DSP platform. Proceedings of the 2002 14th International Conference on Digital Signal Processing, DSP 2002 (Cat. No.02TH8628), Santorini, Greece."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"2385","DOI":"10.1016\/j.neucom.2008.12.004","article-title":"Solving differential equations with constructed neural networks","volume":"72","author":"Tsoulos","year":"2009","journal-title":"Neurocomputing"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"241102","DOI":"10.1063\/1.5033327","article-title":"Neural network based design of metagratings","volume":"112","author":"Inampudi","year":"2018","journal-title":"Appl. Phys. Lett."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"1900128","DOI":"10.1002\/advs.201900128","article-title":"Deep Learning: A Rapid and Efficient Route to Automatic Metasurface Design","volume":"6","author":"Qiu","year":"2019","journal-title":"Adv. Sci."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"62","DOI":"10.1109\/JETCAS.2020.2970077","article-title":"Error Analysis of Programmable Metasurfaces for Beam Steering","volume":"10","author":"Taghvaee","year":"2020","journal-title":"IEEE J. Emerg. Sel. Top. Circuits Syst."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"584","DOI":"10.1016\/j.jsv.2015.11.008","article-title":"Machine learning algorithms for damage detection: Kernel-based approaches","volume":"363","author":"Santos","year":"2016","journal-title":"J. Sound Vib."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"321","DOI":"10.1038\/nrg3920","article-title":"Machine learning applications in genetics and genomics","volume":"16","author":"Libbrecht","year":"2015","journal-title":"Nat. Rev. Genet."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1257\/jep.31.2.87","article-title":"Machine learning: An applied econometric approach","volume":"31","author":"Mullainathan","year":"2017","journal-title":"J. Econ. Perspect."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"6570","DOI":"10.1021\/acs.nanolett.8b03171","article-title":"Generative Model for the Inverse Design of Metasurfaces","volume":"18","author":"Liu","year":"2018","journal-title":"Nano Lett."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"8872","DOI":"10.1021\/acsnano.9b02371","article-title":"Free-Form Diffractive Metagrating Design Based on Generative Adversarial Networks","volume":"13","author":"Jiang","year":"2019","journal-title":"Acs Nano"},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Hodge, J.A., Mishra, K.V., and Zaghloul, A.I. (2019, January 13\u201316). Joint Multi-Layer GAN-Based Design of Tensorial RF Metasurfaces. Proceedings of the 2019 IEEE 29th International Workshop on Machine Learning for Signal Processing (MLSP), Pittsburgh, PA, USA.","DOI":"10.1109\/MLSP.2019.8918860"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"2001433","DOI":"10.1002\/adom.202001433","article-title":"Multifunctional Metasurface Design with a Generative Adversarial Network","volume":"9","author":"An","year":"2021","journal-title":"Adv. Opt. Mater."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"1800132","DOI":"10.1002\/adts.201800132","article-title":"Machine-Learning Designs of Anisotropic Digital Coding Metasurfaces","volume":"2","author":"Zhang","year":"2019","journal-title":"Adv. Theory Simulat."},{"key":"ref_51","unstructured":"An, S., Fowler, C., Shalaginov, M.Y., Zhang, Y., Su, P., Kang, M., Zheng, B., Tang, H., Li, H., and Agarwal, A.M. (2019, January 14\u201319). Modeling of All-Dielectric Metasurfaces Using Deep Neural Networks. Proceedings of the 2019 International Applied Computational Electromagnetics Society Symposium (ACES), Miami, FL, USA."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"912","DOI":"10.1109\/LAWP.2016.2614498","article-title":"Multiobjective Particle Swarm Optimization to Design a Time-Delay Equalizer Metasurface for an Electromagnetic Band-Gap Resonator Antenna","volume":"16","author":"Lalbakhsh","year":"2017","journal-title":"IEEE Antennas Wirel. Propag. Lett."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"329","DOI":"10.1021\/acs.nanolett.9b03971","article-title":"Deep Learning Meets Nanophotonics: A Generalized Accurate Predictor for Near Fields and Far Fields of Arbitrary 3D Nanostructures","volume":"20","author":"Wiecha","year":"2020","journal-title":"Nano Lett."},{"key":"ref_54","doi-asserted-by":"crossref","unstructured":"Taghvaee, H., Abadal, S., Georgiou, J., Cabellos-Aparicio, A., and Alarc\u00f3n, E. (2019, January 26\u201329). Fault Tolerance in Programmable Metasurfaces: The Beam Steering Case. Proceedings of the 2019 IEEE International Symposium on Circuits and Systems (ISCAS), Sapporo, Japan.","DOI":"10.1109\/ISCAS.2019.8702080"},{"key":"ref_55","doi-asserted-by":"crossref","unstructured":"Saeed, T., Abadal, S., Liaskos, C., Pitsillides, A., Taghvaee, H., Cabellos-Aparicio, A., Lestas, M., and Alarc\u00f3n, E. (2019, January 25\u201327). Workload Characterization of Programmable Metasurfaces. Proceedings of the Sixth Annual ACM International Conference on Nanoscale Computing and Communication, Association for Computing Machinery, New York, NY, USA.","DOI":"10.1145\/3345312.3345470"},{"key":"ref_56","doi-asserted-by":"crossref","unstructured":"Ashraf, N., Lestas, M., Saeed, T., Taghvaee, H., Abadal, S., Pitsillides, A., and Liaskos, C. (2020, January 7\u201311). Extremum Seeking Control for Beam Steering using Hypersurfaces. Proceedings of the 2020 IEEE International Conference on Communications Workshops (ICC Workshops), Dublin, Ireland.","DOI":"10.1109\/ICCWorkshops49005.2020.9145206"},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"044024","DOI":"10.1103\/PhysRevApplied.11.044024","article-title":"Intelligent Metasurfaces with Continuously Tunable Local Surface Impedance for Multiple Reconfigurable Functions","volume":"11","author":"Liu","year":"2019","journal-title":"Phys. Rev. Appl."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"2397","DOI":"10.1109\/TAP.2017.2677951","article-title":"Analysis of Metasurfaces at Oblique Incidence","volume":"65","author":"Yazdi","year":"2017","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"174101","DOI":"10.1063\/1.5023324","article-title":"A thin wideband high-spatial-resolution focusing metasurface for near-field passive millimeter-wave imaging","volume":"112","author":"Chu","year":"2018","journal-title":"Appl. Phys. Lett."},{"key":"ref_60","doi-asserted-by":"crossref","unstructured":"HShah, S.M.Q.A., Shoaib, N., Ahmed, F., Alomainy, A., Quddious, A., Nikolaou, S., Imran, M.A., and Abbasi, Q.H. (2021). A multiband circular polarization selective metasurface for microwave applications. Sci. Rep., 11.","DOI":"10.1038\/s41598-021-81435-w"},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"e2188","DOI":"10.1002\/jnm.2188","article-title":"Metamaterial characterization by applying different boundary conditions on triangular split ring resonator type metamaterials","volume":"30","author":"Karaaslan","year":"2017","journal-title":"Int. J. Numer. Model. Electron. Netw. Devices Fields"},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"244504","DOI":"10.1063\/1.4954224","article-title":"Magnetically tunable metamaterial perfect absorber","volume":"119","author":"Lei","year":"2016","journal-title":"J. Appl. Phys."},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"4113","DOI":"10.1364\/AO.55.004113","article-title":"Frequency-tunable metamaterial absorber using a varactor-loaded fishnet-like resonator","volume":"55","author":"Kim","year":"2016","journal-title":"Appl. Opt."},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"051906","DOI":"10.1063\/1.3477960","article-title":"Switchable metamaterial reflector\/absorber for different polarized electromagnetic waves","volume":"97","author":"Zhu","year":"2010","journal-title":"Appl. Phys. Lett."},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"121901","DOI":"10.1063\/1.4979033","article-title":"Reconfigurable conversions of reflection, transmission, and polarization states using active metasurface","volume":"110","author":"Tao","year":"2017","journal-title":"Appl. Phys. Lett."},{"key":"ref_66","doi-asserted-by":"crossref","unstructured":"Najafi, M., and Schober, R. (2019, January 9\u201313). Intelligent Reflecting Surfaces for Free Space Optical Communications. Proceedings of the 2019 IEEE Global Communications Conference (GLOBECOM), Waikoloa, HI, USA.","DOI":"10.1109\/GLOBECOM38437.2019.9013840"},{"key":"ref_67","doi-asserted-by":"crossref","first-page":"1781","DOI":"10.1109\/OJCOMS.2020.3036839","article-title":"Reconfigurable Intelligent Surfaces for Smart Cities: Research Challenges and Opportunities","volume":"1","author":"Kisseleff","year":"2020","journal-title":"IEEE Open J. Commun. Soc."},{"key":"ref_68","doi-asserted-by":"crossref","first-page":"798","DOI":"10.1109\/OJCOMS.2020.3002955","article-title":"Reconfigurable Intelligent Surfaces vs. Relaying: Differences, Similarities, and Performance Comparison","volume":"1","author":"Ntontin","year":"2020","journal-title":"IEEE Open J. Commun. Soc."},{"key":"ref_69","doi-asserted-by":"crossref","first-page":"2450","DOI":"10.1109\/JSAC.2020.3007211","article-title":"Smart Radio Environments Empowered by Reconfigurable Intelligent Surfaces: How It Works, State of Research, and The Road Ahead","volume":"38","author":"Zappone","year":"2020","journal-title":"IEEE J. Sel. Areas Commun."},{"key":"ref_70","doi-asserted-by":"crossref","unstructured":"Masini, B.M., Silva, C.M., and Balador, A. (2020). The Use of Meta-Surfaces in Vehicular Networks. J. Sens. Actuator Netw., 9.","DOI":"10.3390\/jsan9010015"},{"key":"ref_71","doi-asserted-by":"crossref","first-page":"10385","DOI":"10.1109\/TVT.2020.3004598","article-title":"On the Performance of RIS-Assisted Dual-Hop UAV Communication Systems","volume":"69","author":"Yang","year":"2020","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_72","doi-asserted-by":"crossref","unstructured":"Liu, J. (2013). Radial Basis Function (RBF) Neural Network Control for Mechanical Systems: Design, Analysis and Matlab Simulation, Springer Science & Business Media.","DOI":"10.1007\/978-3-642-34816-7"},{"key":"ref_73","first-page":"394","article-title":"Radial basis function artificial neural network: Spread selection","volume":"2","author":"Kasiviswanathan","year":"2012","journal-title":"Int. J. Adv. Comput. Sci."},{"key":"ref_74","doi-asserted-by":"crossref","first-page":"525","DOI":"10.1016\/S0893-6080(05)80056-5","article-title":"A scaled conjugate gradient algorithm for fast supervised learning","volume":"6","year":"1993","journal-title":"Elsevier Neural Netw."},{"key":"ref_75","doi-asserted-by":"crossref","first-page":"e16172","DOI":"10.1038\/lsa.2016.172","article-title":"Information entropy of coding metasurface","volume":"5","author":"Cui","year":"2016","journal-title":"Light Sci. Appl."},{"key":"ref_76","doi-asserted-by":"crossref","first-page":"235402","DOI":"10.1103\/PhysRevB.96.235402","article-title":"Polarizability extraction of complementary metamaterial elements in waveguides for aperture modeling","volume":"96","author":"Bowen","year":"2017","journal-title":"Phys. Rev. B"},{"key":"ref_77","doi-asserted-by":"crossref","first-page":"2950","DOI":"10.1109\/TAP.2019.2952671","article-title":"Analytic Model of Coax-Fed Printed Metasurfaces and Analysis of Antenna Parameters","volume":"68","author":"Yoo","year":"2020","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_78","doi-asserted-by":"crossref","first-page":"333","DOI":"10.1126\/science.1210713","article-title":"Light Propagation with Phase Discontinuities: Generalized Laws of Reflection and Refraction","volume":"334","author":"Yu","year":"2011","journal-title":"Science"},{"key":"ref_79","doi-asserted-by":"crossref","first-page":"1800633","DOI":"10.1002\/adom.201800633","article-title":"Pairing Toroidal and Magnetic Dipole Resonances in Elliptic Dielectric Rod Metasurfaces for Reconfigurable Wavefront Manipulation in Reflection","volume":"6","author":"Tsilipakos","year":"2018","journal-title":"Adv. Opt. Mater."},{"key":"ref_80","first-page":"1","article-title":"A programmable metasurface with dynamic polarization, scattering and focusing control","volume":"6","author":"Yang","year":"2016","journal-title":"Sci. Rep."},{"key":"ref_81","unstructured":"(2020, October 02). CS231n Convolutional Neural Networks for Visual Recognition. Available online: https:\/\/cs231n.github.io\/convolutional-networks\/."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/8\/2765\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:47:57Z","timestamp":1760161677000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/8\/2765"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,4,14]]},"references-count":81,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2021,4]]}},"alternative-id":["s21082765"],"URL":"https:\/\/doi.org\/10.3390\/s21082765","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,4,14]]}}}