{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T09:56:56Z","timestamp":1785405416373,"version":"3.56.0"},"reference-count":52,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2026,6,22]],"date-time":"2026-06-22T00:00:00Z","timestamp":1782086400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Science and Technology Council","award":["NSTC 114-2221-E-167-006"],"award-info":[{"award-number":["NSTC 114-2221-E-167-006"]}]},{"award":["NSTC 114-2221-E-167-006"],"award-info":[{"award-number":["NSTC 114-2221-E-167-006"]}],"id":[{"id":"https:\/\/ror.org\/02kv4zf79","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Parkinson\u2019s disease (PD) is a neurodegenerative disorder with an increasing incidence rate that significantly affects patients\u2019 motor functions and quality of life. Involuntary upper limb tremors (ULTs) commonly manifest unilaterally, affecting either the left or right upper limb. Clinically, ULT frequencies can be categorized into three distinct classes: low-frequency (&lt;4.0 Hz), mid-frequency (4.0\u20137.0 Hz), and high-frequency (&gt;7.0 Hz) tremors. These tremor motions are characterized by oscillatory or rotational (angular displacement) movements, commonly referred to as the micro-Doppler effect (mDE). This study aims to develop a short-range (&lt;1.0 m) and contactless sensing method for ULT detection based on Doppler millimeter-wave (mm-Wave) radar. The reflected electromagnetic waves indicate time-varying frequency characteristics, which can be analyzed by using time\u2013frequency transform (TFT) methods, such as the Wigner\u2013Ville distribution (WVD) and smoothed pseudo WVD (SPWVD). These TFT methods are employed to extract mDE features, which are subsequently visualized as color-coded spectrograms for ULT classification. Then, a two-dimensional (2D) convolutional neural network (CNN) is employed to automatically recognize the visual feature patterns for ULTs classification based on frequency and amplitude information. In the experimental setup, the W-band (76\u201381 GHz) Doppler mm-Wave biosensor is implemented for sensing and extracting feature patterns. The proposed classifiers based on \u201cWVD + 2D CNN\u201d and \u201cSPWVD + 2D CNN\u201d are trained and validated by using the collected datasets, with 60% randomly selected for training datasets and 40% for testing datasets in each fold validation. A 10-fold cross-validation method is applied to evaluate the classifier\u2019s performances, achieving an average precision of 95.92 \u00b1 0.60%, average recall of 95.89 \u00b1 0.62%, average F1-score of 0.9588 \u00b1 0.0060, and average accuracy of 95.89 \u00b1 0.62%, respectively. The experimental results demonstrate the feasibility of the proposed classifier for real-time ULTs classification in PD patients using short-range (&lt;1.0 m) and contactless sensing.<\/jats:p>","DOI":"10.3390\/s26123955","type":"journal-article","created":{"date-parts":[[2026,6,24]],"date-time":"2026-06-24T01:03:23Z","timestamp":1782263003000},"page":"3955","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Upper Limb Tremors Classification for Parkinson\u2019s Disease Using W-Band (76\u201381 GHz) Doppler Millimeter-Wave Sensing and Deep-Learning-Based Classifier"],"prefix":"10.3390","volume":"26","author":[{"given":"Pi-Yun","family":"Chen","sequence":"first","affiliation":[{"name":"Department of Electrical Engineering, National Chin-Yi University of Technology, Taichung City 41170, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chun-Yu","family":"Lin","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, National Chin-Yi University of Technology, Taichung City 41170, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Neng-Sheng","family":"Pai","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, National Chin-Yi University of Technology, Taichung City 41170, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1645-8986","authenticated-orcid":false,"given":"Ping-Tzan","family":"Huang","sequence":"additional","affiliation":[{"name":"Department of Biomechatronics Engineering, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4989-3618","authenticated-orcid":false,"given":"Chao-Lin","family":"Kuo","sequence":"additional","affiliation":[{"name":"Department of Maritime Information and Technology, National Kaohsiung University of Science and Technology, Kaohsiung City 80543, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chien-Ming","family":"Li","sequence":"additional","affiliation":[{"name":"Infectious Disease Division of Internal Medicine Department, The Tainan Municipal Hospital, Tainan City 701, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0150-8001","authenticated-orcid":false,"given":"Chia-Hung","family":"Lin","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, National Chin-Yi University of Technology, Taichung City 41170, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,22]]},"reference":[{"key":"ref_1","first-page":"1102","article-title":"Cardiopulmonary resuscitation in a super-aging society\u2014Is there an age limit for cardiopulmonary resuscitation?","volume":"80","author":"Tahara","year":"2016","journal-title":"Circ. 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