{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,9]],"date-time":"2026-06-09T07:15:47Z","timestamp":1780989347359,"version":"3.54.1"},"reference-count":31,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2018,9,13]],"date-time":"2018-09-13T00:00:00Z","timestamp":1536796800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["NRF - 2017M1A7A1A03064220"],"award-info":[{"award-number":["NRF - 2017M1A7A1A03064220"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Ministry of Education","award":["21A20131600011"],"award-info":[{"award-number":["21A20131600011"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A design method of large-sized square-loop and circular-loop frequency selective surface (FSS) filters for protection of mm-wave imagining receivers is presented. Due to fine cell structure requirements, the performance of the FSS structures at mm-wave frequencies can be significantly affected by fabrication tolerances, especially involved with large-size panel fabrication. Through a comprehensive parametric variation study on the performance of square-loop and circular-loop FSS structures, it is found that the circular-loop FSS structure performs much less sensitively to the fabrication tolerances, thereby producing better and consistent performances with given design values. As a design example, square-loop and circular-loop notch filters resonating at 105 GHz were designed and the performances were evaluated with multiple prototypes. The resonant frequencies of the implemented circular-loop FSS filters deviated by only about 0.5 GHz from the accurate designed value, which can be easily adjusted in the design process. The implemented square-loop and circular loop FSS filters provided low-loss in the pass-band and high rejection of 23 dB at the resonant frequency with good oblique angle performance.<\/jats:p>","DOI":"10.3390\/s18093079","type":"journal-article","created":{"date-parts":[[2018,9,13]],"date-time":"2018-09-13T11:46:04Z","timestamp":1536839164000},"page":"3079","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":15,"title":["Comparative Study of Square and Circular Loop Frequency Selective Surfaces for Millimeter-Wave Imaging Diagnostics Systems"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7514-2463","authenticated-orcid":false,"given":"Wahab","family":"Mohyuddin","sequence":"first","affiliation":[{"name":"School of Electronics Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dong Hwi","family":"Kim","sequence":"additional","affiliation":[{"name":"School of Electronics Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hyun Chul","family":"Choi","sequence":"additional","affiliation":[{"name":"School of Electronics Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kang Wook","family":"Kim","sequence":"additional","affiliation":[{"name":"School of Electronics Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2018,9,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Munk, B.A. (2000). Frequency Selective Surfaces: Theory and Design, John Wiley & Sons.","DOI":"10.1002\/0471723770"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1725","DOI":"10.1002\/j.1538-7305.1975.tb03551.x","article-title":"On the theory of self-resonant grids","volume":"54","author":"Anderson","year":"1975","journal-title":"Bell Syst. Tech. J."},{"key":"ref_3","unstructured":"Marcuvitz, N. (1951). Waveguide Handbook, McGraw-Hill."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1109\/MAP.2006.277152","article-title":"A Frequency-selective wall for interference reduction in wireless indoor environments","volume":"48","author":"Sung","year":"2006","journal-title":"IEEE Antennas Propag. Mag."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1239","DOI":"10.1109\/TAP.2007.895567","article-title":"A frequency selective surface with miniaturized elements","volume":"55","author":"Sarabandi","year":"2007","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"034704","DOI":"10.1063\/1.5023406","article-title":"A practical double-sided frequency selective surface for millimeter-wave applications","volume":"89","author":"Mohyuddin","year":"2018","journal-title":"Rev. Sci. Instrum."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"466","DOI":"10.1109\/TAP.1979.1142119","article-title":"Design of a dichroic cassegrain subreflector","volume":"27","author":"Agrawal","year":"1979","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1659","DOI":"10.1109\/8.362804","article-title":"Four-band frequency selective surface with double-square-loop patch elements","volume":"42","author":"Wu","year":"1994","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2740","DOI":"10.1109\/TAP.2012.2194640","article-title":"A frequency selective radome with wideband absorbing properties","volume":"60","author":"Costa","year":"2012","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"273","DOI":"10.1109\/LMWC.2011.2122303","article-title":"Waveguide dielectric permittivity measurement technique based on resonant FSS filters","volume":"21","author":"Costa","year":"2011","journal-title":"Microw. Wirel. Compon. Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1109\/MAP.2013.6529314","article-title":"Research and development on phase-shifting surfaces (PSSs)","volume":"55","author":"Gagnon","year":"2013","journal-title":"IEEE Antennas Propag. Mag."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"41505","DOI":"10.1038\/srep41505","article-title":"A circular polarizer with beamforming feature based on frequency selective surfaces","volume":"7","author":"Yin","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2457","DOI":"10.1109\/TAP.2010.2048874","article-title":"325 GHz single layer sub-millimeter wave FSS based split slot ring linear to circular polarization convertor","volume":"58","author":"Euler","year":"2010","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"5281","DOI":"10.1109\/TAP.2016.2620484","article-title":"A reconfigurable polarization converter using active metasurface and its application in horn antenna","volume":"64","author":"Li","year":"2016","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"3012","DOI":"10.1364\/OL.34.003012","article-title":"Wavelength-tunable microbolometers with metamaterial absorbers","volume":"34","author":"Maier","year":"2009","journal-title":"Opt. Lett."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Kim, H.K., Lee, D., and Lim, S. (2016). A fluidically tunable metasurface absorber for flexible large-scale wireless ethanol sensor applications. Sensors, 16.","DOI":"10.3390\/s16081246"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Lee, Y., Kim, S.-J., Park, H., and Lee, B. (2017). Metamaterials and metasurfaces for sensor applications. Sensors, 17.","DOI":"10.3390\/s17081726"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"79","DOI":"10.1109\/LMWC.2009.2038517","article-title":"Miniaturized FSS and patch antenna array coupling for angle-independent, high-order spatial filtering","volume":"20","author":"Bayatpur","year":"2010","journal-title":"Microw. Wirel. Compon. Lett."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Zhang, B., Zhang, Y., Duan, J., Zhang, W., and Wang, W. (2016). An omnidirectional polarization detector based on a metamaterial absorber. Sensors, 16.","DOI":"10.3390\/s16081153"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"023501","DOI":"10.1063\/1.3607474","article-title":"Bolometric THz-to-IR converter for terahertz imaging","volume":"99","author":"Kuznetsov","year":"2011","journal-title":"Appl. Phys. Lett."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"148","DOI":"10.1038\/nphoton.2009.3","article-title":"A metamaterial solid state terahertz phase modulator","volume":"3","author":"Chen","year":"2009","journal-title":"Nat. Photonics"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"2861","DOI":"10.1063\/1.1149808","article-title":"Application of band-stop filters for the 30-200 GHz range in oversized microwave systems","volume":"70","author":"Meiden","year":"1999","journal-title":"Rev. Sci. Instrum."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"S1030","DOI":"10.1585\/pfr.2.S1030","article-title":"Protection filters in ecei systems for plasma diagnostics","volume":"2","author":"Shen","year":"2017","journal-title":"Plasma Fusion Res."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Hu, X., Domier, C.W., and Luhman, N.C. (2015, January 23\u201328). Frequency selective surface applications in millimeter wave imaging diagnostics for fusion plasmas. Proceedings of the 40th International Conference on Infrared, Millimeter, and Terahertz waves (IRMMW-THz), Hong Kong, China.","DOI":"10.1109\/IRMMW-THz.2015.7327789"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"034704","DOI":"10.1063\/1.4977935","article-title":"Design of a 75\u2013140 GHz high-pass printed circuit board dichroic filter","volume":"88","author":"Kim","year":"2017","journal-title":"Rev. Sci. Instrum."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"11D820","DOI":"10.1063\/1.4890401","article-title":"Quasi 3D ECE imaging system for study of MHD instabilities in KSTAR","volume":"85","author":"Yun","year":"2014","journal-title":"Rev. Sci. Instrum."},{"key":"ref_27","unstructured":"Oh, J., Cho, S., Lee, C., Kim, J., and Choi, B. (2008, January 7\u201316). The fabrication of film-type frequency selective surface (FSS) attachable to window glass using inkjet printing technique. Proceedings of the 2008 URSI General Assembly and Scientific Symposium, Chicago, IL, USA."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"761","DOI":"10.1109\/TTHZ.2015.2452813","article-title":"Second-order terahertz bandpass frequency selective surface with miniaturized elements","volume":"5","author":"Ebrahimi","year":"2015","journal-title":"IEEE Trans. Terahertz Sci. Technol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1672","DOI":"10.1109\/TAP.2016.2537378","article-title":"Varactor-tunable second-order bandpass frequency-selective surface with embedded bias network","volume":"64","author":"Ebrahimi","year":"2016","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"166","DOI":"10.1109\/8.277210","article-title":"Tri-band frequency selective surface with circular ring elements","volume":"42","author":"Huang","year":"1994","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"027107","DOI":"10.1063\/1.4907929","article-title":"Optically transparent frequency selective surfaces on flexible thin plastic substrates","volume":"5","author":"Dewani","year":"2015","journal-title":"AIP Adv."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/18\/9\/3079\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:20:21Z","timestamp":1760196021000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/18\/9\/3079"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,9,13]]},"references-count":31,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2018,9]]}},"alternative-id":["s18093079"],"URL":"https:\/\/doi.org\/10.3390\/s18093079","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,9,13]]}}}