{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,9]],"date-time":"2026-05-09T14:31:06Z","timestamp":1778337066987,"version":"3.51.4"},"reference-count":39,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2024,4,15]],"date-time":"2024-04-15T00:00:00Z","timestamp":1713139200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"German Federal Ministry of Education and Research (BMBF)","award":["16KISK038"],"award-info":[{"award-number":["16KISK038"]}]},{"name":"University of Duisburg-Essen","award":["16KISK038"],"award-info":[{"award-number":["16KISK038"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper details the design and implementation of a harmonic frequency-modulated continuous-wave (FMCW) radar system, specialized in detecting harmonic tags and achieving precise range estimation. Operating within the 2.4\u20132.5 GHz frequency range for the forward channel and 4.8\u20135.0 GHz for the backward channel, this study delves into the various challenges faced during the system\u2019s realization. These challenges include selecting appropriate components, calibrating the system, processing signals, and integrating the system components. In addition, we introduce a single-layer passive harmonic tag, developed specifically for assessing the system, and provide an in-depth theoretical analysis and simulation results. Notably, the system is characterized by its low power consumption, making it particularly suitable for short-range applications. The system\u2019s efficacy is further validated through experimental evaluations in a real-world indoor environment across multiple tag positions. Our measurements underscore the system\u2019s robust ranging accuracy and its ability to mitigate self-interference, showcasing its significant potential for applications in harmonic tag detection and ranging.<\/jats:p>","DOI":"10.3390\/s24082541","type":"journal-article","created":{"date-parts":[[2024,4,16]],"date-time":"2024-04-16T04:21:59Z","timestamp":1713241319000},"page":"2541","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Harmonic FMCW Radar System: Passive Tag Detection and Precise Ranging Estimation"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7431-0226","authenticated-orcid":false,"given":"Ahmed","family":"El-Awamry","sequence":"first","affiliation":[{"name":"Institute of Digital Signal Processing, University of Duisburg-Essen, 47057 Duisburg, Germany"},{"name":"Benha Faculty of Engineering, Benha University, Benha 13512, Egypt"}]},{"given":"Feng","family":"Zheng","sequence":"additional","affiliation":[{"name":"Institute of Digital Signal Processing, University of Duisburg-Essen, 47057 Duisburg, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9679-5968","authenticated-orcid":false,"given":"Thomas","family":"Kaiser","sequence":"additional","affiliation":[{"name":"Institute of Digital Signal Processing, University of Duisburg-Essen, 47057 Duisburg, Germany"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1422-7244","authenticated-orcid":false,"given":"Maher","family":"Khaliel","sequence":"additional","affiliation":[{"name":"Institute of Digital Signal Processing, University of Duisburg-Essen, 47057 Duisburg, Germany"},{"name":"Benha Faculty of Engineering, Benha University, Benha 13512, Egypt"}]}],"member":"1968","published-online":{"date-parts":[[2024,4,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"906","DOI":"10.1109\/TMTT.2020.3026353","article-title":"A Compact Harmonic Radar System with Active Tags at 61\/122 GHz ISM Band in SiGe BiCMOS for Precise Localization","volume":"69","author":"Hansen","year":"2021","journal-title":"IEEE Trans. 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