{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,9]],"date-time":"2026-05-09T17:33:32Z","timestamp":1778348012854,"version":"3.51.4"},"reference-count":42,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2019,2,15]],"date-time":"2019-02-15T00:00:00Z","timestamp":1550188800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61831001"],"award-info":[{"award-number":["61831001"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"High-Level Talent Introduction Project of Beihang University","award":["ZG216S1878"],"award-info":[{"award-number":["ZG216S1878"]}]},{"name":"Youth-Top-Talent Support Project of Beihang University","award":["ZG226S1821"],"award-info":[{"award-number":["ZG226S1821"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper describes a low-cost, small size, and high-sensitivity microwave sensor using a Complementary Circular Spiral Resonator (CCSR), which operates at around 2.4 GHz, for identifying liquid samples and determining their dielectric constants. The proposed sensor was fabricated and tested to effectively identify different liquids commonly used in daily life and determine the concentrations of various ethanol\u2013water mixtures at by measuring the resonant frequency of the CCSR. Using acrylic paint, a square channel was drawn at the most sensitive position of the microwave sensor to ensure accuracy of the experiment. To estimate the dielectric constants of the liquids under test, an approximate model was established using a High-Frequency Simulator Structure (HFSS). The results obtained agree very well with the existing data. Two parabolic equations were calculated and fitted to identify unknown liquids and determine the concentrations of ethanol\u2013water mixtures. Thus, our microwave sensor provides a method with high sensitivity and low consumption of material for liquid monitoring and determination, which proves the feasibility and broad prospect of this low-cost system in industrial application.<\/jats:p>","DOI":"10.3390\/s19040787","type":"journal-article","created":{"date-parts":[[2019,2,17]],"date-time":"2019-02-17T22:11:50Z","timestamp":1550441510000},"page":"787","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":105,"title":["High-Sensitivity Microwave Sensor for Liquid Characterization Using a Complementary Circular Spiral Resonator"],"prefix":"10.3390","volume":"19","author":[{"given":"Xingyun","family":"Zhang","sequence":"first","affiliation":[{"name":"School of Electronic and Information Engineering, Beihang University, Beijing 100191, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5248-9333","authenticated-orcid":false,"given":"Cunjun","family":"Ruan","sequence":"additional","affiliation":[{"name":"School of Electronic and Information Engineering, Beihang University, Beijing 100191, China"},{"name":"Beijing Key Laboratory for Microwave Sensing and Security Applications, Beihang University, Beijing 100191, China"}]},{"given":"Tanveer ul","family":"Haq","sequence":"additional","affiliation":[{"name":"School of Electronic and Information Engineering, Beihang University, Beijing 100191, China"}]},{"given":"Kanglong","family":"Chen","sequence":"additional","affiliation":[{"name":"School of Electronic and Information Engineering, Beihang University, Beijing 100191, China"}]}],"member":"1968","published-online":{"date-parts":[[2019,2,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1088","DOI":"10.1016\/j.scitotenv.2017.12.344","article-title":"Monitoring the degradation of atropine and scopolamine in soil after spiking with naturally contaminated organic millet","volume":"625","author":"Both","year":"2018","journal-title":"Sci. Total Environ."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1016\/j.foodchem.2017.06.086","article-title":"Experimental and theoretical determination of pesticide processing factors to model their behavior during virgin olive oil production","volume":"239","year":"2018","journal-title":"Food Chem."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"849","DOI":"10.1016\/j.scitotenv.2017.12.340","article-title":"Integrating ecosystem services trade-offs with paddy land-to-dry land decisions: A scenario approach in Erhai Lake Basin, southwest China","volume":"625","author":"Hu","year":"2018","journal-title":"Sci. Total Environ."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"357","DOI":"10.1016\/j.jclepro.2018.01.044","article-title":"Sustainable patterns of main agricultural products combining different footprint parameters","volume":"179","author":"Borsato","year":"2018","journal-title":"J. Cleaner Prod."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"999","DOI":"10.1016\/j.energy.2015.09.104","article-title":"Sustainability in the food-energy-water nexus: Evidence from BRICS (Brazil, the Russian Federation, India, China, and South Africa) countries","volume":"93","author":"Ozturk","year":"2015","journal-title":"Energy"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"2159","DOI":"10.1109\/22.884209","article-title":"Accurate microwave resonant method for complex permittivity measurements of liquids [biological]","volume":"48","author":"Yu","year":"2000","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"972","DOI":"10.1109\/TMTT.2012.2231877","article-title":"A microwave and microfluidic planar resonator for efficient and accurate complex permittivity characterization of aqueous solutions","volume":"61","author":"Chretiennot","year":"2012","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1016\/j.sna.2012.10.027","article-title":"Metamaterial-based microfluidic sensor for dielectric characterization","volume":"189","author":"Withayachumnankul","year":"2013","journal-title":"Sens. Actuators A: Phys."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"211","DOI":"10.1016\/j.sna.2012.12.011","article-title":"Novel method for vegetable oil type verification based on real-time microwave sensing","volume":"202","author":"Korostynska","year":"2013","journal-title":"Sens. Actuators A: Phys."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"810","DOI":"10.1002\/prep.201300068","article-title":"X-band microwave properties and ignition predictions of neat explosives","volume":"38","author":"Daily","year":"2013","journal-title":"Propellants Explos. Pyrotech."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1109\/MIM.2016.7384959","article-title":"Microwave sensing of quality attributes of agricultural and food products","volume":"19","author":"Trabelsi","year":"2016","journal-title":"IEEE Instrum. Meas. Mag."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.biosystemseng.2004.01.007","article-title":"An overview of microwave processing and dielectric properties of agri-food materials","volume":"88","author":"Venkatesh","year":"2004","journal-title":"Biosyst. Eng."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1016\/S0925-4005(03)00527-6","article-title":"A novel technique for the detection of added water to full fat milk using single frequency admittance measurements","volume":"96","author":"Mabrook","year":"2003","journal-title":"Sens. Actuators B"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"876","DOI":"10.1016\/j.snb.2016.06.168","article-title":"Microwave based sensors with phthalocyanine films for acetone, ethanol and methanol detection","volume":"237","author":"Rydosz","year":"2016","journal-title":"Sens. Actuators B"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Abduljabar, A.A., Porch, A., and Barrow, D.A. (2014). Real-time measurements of size, speed, and dielectric property of liquid segments using a microwave microfluidic sensor. IEEE MTT-S Int. Micro. Symp., 1\u20134.","DOI":"10.1109\/MWSYM.2014.6848387"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2611","DOI":"10.1109\/JSEN.2011.2149517","article-title":"Optimized microwave sensor for online concentration measurements of binary liquid mixtures","volume":"11","author":"Kapilevich","year":"2011","journal-title":"IEEE Sens. J."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1857","DOI":"10.1109\/JSEN.2013.2244035","article-title":"A microwave resonant sensor for concentration measurements of liquid solutions","volume":"13","author":"Gennarelli","year":"2013","journal-title":"IEEE Sens. J."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"248","DOI":"10.1109\/JSEN.2014.2345477","article-title":"Detection of volatile organic compounds using microwave sensors","volume":"15","author":"Zarifi","year":"2014","journal-title":"IEEE Sens. J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"4814","DOI":"10.1109\/JSEN.2017.2718659","article-title":"Portable six-port reflectometer for determining moisture content of biomass material","volume":"17","author":"Julrat","year":"2017","journal-title":"IEEE Sens. J."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"4700","DOI":"10.1109\/TMTT.2013.2285356","article-title":"Transmission lines loaded with bisymmetric resonators and their application to angular displacement and velocity sensors","volume":"61","author":"Naqui","year":"2013","journal-title":"IEEE Trans. Microwave Theory Tech."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"224","DOI":"10.1016\/j.sna.2015.06.031","article-title":"High resolution microwave microstrip resonator for sensing applications","volume":"233","author":"Zarifi","year":"2015","journal-title":"Sens. Actuators A: Phys"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"12868","DOI":"10.1063\/1.4907944","article-title":"Microbead-assisted high resolution microwave planar ring resonator for organic-vapor sensing","volume":"106","author":"Zarifi","year":"2015","journal-title":"Appl. Phys. Lett."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"7545","DOI":"10.3390\/s110807545","article-title":"Novel sensors based on the symmetry properties of split ring resonators (SRRs)","volume":"11","author":"Naqui","year":"2011","journal-title":"Sensors"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"11790","DOI":"10.3390\/s120911790","article-title":"Alignment and position sensors based on split ring resonators","volume":"12","author":"Naqui","year":"2012","journal-title":"Sensors"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1153","DOI":"10.1109\/JSEN.2012.2231065","article-title":"Displacement sensor based on diamond-shaped tapered split ring resonator","volume":"13","author":"Horestani","year":"2013","journal-title":"IEEE Sens. J."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1109\/MMM.2011.2181448","article-title":"Metamaterial inspired microwave sensors","volume":"13","author":"Schueler","year":"2012","journal-title":"IEEE Microw. Mag."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1665","DOI":"10.1109\/TIE.2017.2733423","article-title":"Low-cost microwave vector system for liquid properties monitoring","volume":"65","author":"Staszek","year":"2018","journal-title":"IEEE Trans. Ind. Electron."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"3778","DOI":"10.1109\/TIM.2009.2019717","article-title":"Bimodal method of determining fat and salt content in beef products by microwave techniques","volume":"58","author":"Ng","year":"2009","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"4073","DOI":"10.3390\/s110404073","article-title":"Determination of moisture content in oil palm fruits using a five-port reflectometer","volume":"11","author":"Yee","year":"2011","journal-title":"Sensors"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"632","DOI":"10.1016\/j.snb.2015.10.061","article-title":"Microwave ring resonator-based non-contact interface sensor for oil sands applications","volume":"224","author":"Zarifi","year":"2016","journal-title":"Sens. Actuators B"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1345","DOI":"10.1109\/JSEN.2013.2295312","article-title":"High-sensitivity metamaterial-inspired sensor for microfluidic dielectric characterization","volume":"14","author":"Ebrahimi","year":"2014","journal-title":"IEEE Sens. J."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"8151","DOI":"10.1109\/JSEN.2016.2604855","article-title":"Wireless communication in feedback-assisted active sensors","volume":"16","author":"Abdolrazzaghi","year":"2016","journal-title":"IEEE Sens. J."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"063912","DOI":"10.1063\/1.4791713","article-title":"Novel microwave near-field sensors for material characterization, biology, and nanotechnology","volume":"113","author":"Joffe","year":"2013","journal-title":"J. Appl. Phys."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2195","DOI":"10.1109\/TMTT.2013.2250516","article-title":"Microwave-based noninvasive concentration measurements for biomedical applications","volume":"61","author":"Hofmann","year":"2013","journal-title":"IEEE Trans. Microwave Theory Tech."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1451","DOI":"10.1109\/TMTT.2005.845211","article-title":"Equivalent circuit models for split ring resonators and complementary split ring resonators coupled to planar transmission lines","volume":"53","author":"Baena","year":"2005","journal-title":"IEEE Trans. Microwave Theory Tech."},{"key":"ref_36","unstructured":"Vargas, M.P. (2014). Planar Metamaterial Based Microwave Sensor Arrays for Biomedical Analysis and Treatment, Springer."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1843","DOI":"10.1109\/TMTT.2018.2791942","article-title":"Strongly enhanced sensitivity in planar microwave sensors based on metamaterial coupling","volume":"66","author":"Abdolrazzaghi","year":"2018","journal-title":"IEEE Trans. Microwave Theory Tech."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1109\/LMWC.2018.2883715","article-title":"3-D Printing Microfluidic Channels with Embedded Planar Microwave Resonators for RFID and Liquid Detection","volume":"29","author":"Wiltshire","year":"2019","journal-title":"IEEE Microwave Wireless Compon. Lett."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"343","DOI":"10.1016\/j.biosystemseng.2004.04.008","article-title":"Dielectric characteristics of grape juice and wine","volume":"88","author":"Garcia","year":"2004","journal-title":"Biosystems Eng."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"344","DOI":"10.1016\/j.jfoodeng.2010.03.015","article-title":"Effects of milk concentration and freshness on microwave dielectric properties","volume":"99","author":"Guo","year":"2010","journal-title":"J. Food Eng."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"539","DOI":"10.1109\/LMWC.2018.2833202","article-title":"Simultaneous Measurement of Thickness and Permittivity by Means of the Resonant Frequency Fitting of a Microstrip Line Ring Resonator","volume":"28","author":"Lim","year":"2018","journal-title":"IEEE Microwave Wireless Compon. Lett."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"4441","DOI":"10.1063\/1.471197","article-title":"Microwave dielectric characterization of binary mixtures of water, methanol, and ethanol","volume":"104","author":"Bao","year":"1996","journal-title":"J. Chem. Phys."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/4\/787\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:32:17Z","timestamp":1760185937000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/4\/787"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,2,15]]},"references-count":42,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2019,2]]}},"alternative-id":["s19040787"],"URL":"https:\/\/doi.org\/10.3390\/s19040787","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,2,15]]}}}