{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T02:35:41Z","timestamp":1760236541937,"version":"build-2065373602"},"reference-count":31,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2021,12,2]],"date-time":"2021-12-02T00:00:00Z","timestamp":1638403200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper proposes a method for optimizing and designing a wireless power transfer system operating at 13.56\u00a0MHz. It can be used as guidelines for designing coils for the new-trending technology that enables NFC devices to not only to communicate but also to charge. Since NFC wireless charging is an emerging technology, it is of interest to propose optimizations and a dedicated circuit design for such systems. This work proposes an optimization procedure to calculate the dimensions of a transmitter and receiver pair that assures the highest efficiency while considering all possible positions of a receiver that is placed on a desired surface. This procedure seeks to facilitate and automate the design of rectangular-shaped coils, whereas the literature proposes mainly square-shaped coils. Afterwards, a circuit analysis was conducted, and the series-parallel compensation network is proposed as the most promising topology of the receiver to assure a low efficiency sensibility to load variations for 13.56\u00a0MHz wireless power transfer systems. A pair of optimized transmitter and receiver coils is prototyped, and the experimental results are tested against the theory. The transmitter of 7\u00a0cm\u00d711.4\u00a0cm and receiver of 4\u00a0cm\u00a0\u00d74\u00a0cm are separated by 10\u00a0mm. The receiver can move on a surface of 8\u00a0cm\u00a0\u00d712\u00a0cm and the load can vary from 36\u00a0\u03a9 to 300\u00a0\u03a9 while assuring a minimum and maximum efficiency of 80% and 88.3%, respectively.<\/jats:p>","DOI":"10.3390\/s21238074","type":"journal-article","created":{"date-parts":[[2021,12,6]],"date-time":"2021-12-06T03:10:38Z","timestamp":1638760238000},"page":"8074","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Optimized NFC Circuit and Coil Design for Wireless Power Transfer with 2D Free-Positioning and Low Load Sensibility"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5838-5626","authenticated-orcid":false,"given":"Guilherme Germano","family":"Buchmeier","sequence":"first","affiliation":[{"name":"Continental Automotive France, 31100 Toulouse, France"},{"name":"Laboratory for Analysis and Architecture of Systems (LAAS-CNRS), University of Toulouse, CNRS, 31400 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alexandru","family":"Takacs","sequence":"additional","affiliation":[{"name":"Laboratory for Analysis and Architecture of Systems (LAAS-CNRS), University of Toulouse, CNRS, 31400 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8589-6093","authenticated-orcid":false,"given":"Daniela","family":"Dragomirescu","sequence":"additional","affiliation":[{"name":"Laboratory for Analysis and Architecture of Systems (LAAS-CNRS), University of Toulouse, CNRS, 31400 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Juvenal","family":"Alarcon Ramos","sequence":"additional","affiliation":[{"name":"Continental Automotive France, 31100 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Amaia","family":"Fortes Montilla","sequence":"additional","affiliation":[{"name":"Continental Automotive France, 31100 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,12,2]]},"reference":[{"key":"ref_1","unstructured":"(2021, September 29). 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