{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,6]],"date-time":"2026-04-06T21:33:01Z","timestamp":1775511181880,"version":"3.50.1"},"reference-count":44,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2021,2,18]],"date-time":"2021-02-18T00:00:00Z","timestamp":1613606400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100014188","name":"Ministry of Science and ICT, South Korea","doi-asserted-by":"publisher","award":["2020R1H1A2011124"],"award-info":[{"award-number":["2020R1H1A2011124"]}],"id":[{"id":"10.13039\/501100014188","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>An ultralow-power ultrawideband (UWB) transmitter with an energy-efficient injection-locked radio frequency (RF) clock harvester that generates a carrier from an RF signal is proposed for RF energy-harvesting Internet-of-Things (IoT) sensor applications. The energy-efficient RF clock harvester based on the injection-locked ring oscillator (ILRO) is proposed to achieve optimal locking range and minimum input sensitivity to obtain an injection-locked 450 MHz clock in ultralow-power operation. A current-starved inverter-based delay stage is adopted that allows delay adjustment by bias voltage to minimize dynamic current consumption while maintaining a constant delay regardless of changes in process, supply voltage, and temperature (PVT). To minimize static current consumption, a UWB transmitter based on a digital-based UWB pulse generator and a pulse-driven switching drive amplifier is proposed. The proposed injection-locked RF clock harvester achieves the best RF input sensitivity of \u221234 dBm at a power consumption of 2.03 \u03bcW, enabling energy-efficient clock harvesting from low RF input power. In ultralow-power operation, a 23.8% locking range is achieved at the RF injection power of \u221215 dBm to cope with frequency changes due to PVT variations. The proposed UWB transmitter with RF clock harvester achieves the lowest energy consumption per pulse with an average power consumption of 97.03 \u03bcW and an energy consumption of 19.41 pJ\/pulse, enabling operation with the energy available in RF energy-harvesting applications.<\/jats:p>","DOI":"10.3390\/s21041426","type":"journal-article","created":{"date-parts":[[2021,2,18]],"date-time":"2021-02-18T21:59:58Z","timestamp":1613685598000},"page":"1426","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["An Energy-Efficient UWB Transmitter with Wireless Injection Locking for RF Energy-Harvesting Sensors"],"prefix":"10.3390","volume":"21","author":[{"given":"Jun-Tae","family":"Kim","sequence":"first","affiliation":[{"name":"Department of Electrical and Computer Engineering, College of Information Technology, Ajou University, Suwon 16499, Korea"}]},{"given":"Bo-Ram","family":"Heo","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, College of Information Technology, Ajou University, Suwon 16499, Korea"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2595-4965","authenticated-orcid":false,"given":"Ickjin","family":"Kwon","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, College of Information Technology, Ajou University, Suwon 16499, Korea"}]}],"member":"1968","published-online":{"date-parts":[[2021,2,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2199","DOI":"10.1109\/JSSC.2012.2197239","article-title":"Platform Architecture for Solar, Thermal, and Vibration Energy Combining with MPPT and Single Inductor","volume":"47","author":"Saurav","year":"2012","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_2","unstructured":"Shuo, L., Abhishek, R., and Benton, H.C. (2019, January 9\u201314). A Piezoelectric Energy-Harvesting System with Parallel-SSHI Rectifier and Integrated MPPT Achieving 417% Energy-Extraction Improvement and 97% Tracking Efficiency. Proceedings of the 2019 Symposium on VLSI Circuits, Kyoto, Japan."},{"key":"ref_3","unstructured":"Akshay, P., Mayur, J., Shreyas, J., Elton, B., and Apurva, V. (November, January 30). Energy Harvesting using Piezoelectricity. Proceedings of the 2015 IEEE International Conference Energy Systems and Applications, Pune, India."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Park, I., Maeng, J., Shim, M., Jeong, J., and Kim, C. (2019, January 9\u201314). A Bidirectional High-Voltage Dual-Input Buck Converter for Triboelectric Energy-Harvesting Interface Achieving 70.72% End-to-End Efficiency. Proceedings of the 2019 Symposium on VLSI Circuits IEEE, Kyoto, Japan.","DOI":"10.23919\/VLSIC.2019.8778018"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1109\/MCAS.2015.2510198","article-title":"RF Energy Harvesting for Embedded Systems: A Survey of Tradeoffs and Methodology","volume":"16","author":"Tolga","year":"2016","journal-title":"Circ. Sys. Mag."},{"key":"ref_6","unstructured":"Muhammad, P.K.P., Mohammad, S.A., and Achmad, M. (2018, January 4\u20135). Circular Waveguide Array for Radio Frequency Energy Harvesting. Proceedings of the 2018 12th International Conference on Telecommunication Systems, Services, and Applications (TSSA), Yogyakarta, Indonesia."},{"key":"ref_7","unstructured":"Sumit, B., and Suresh, B. (2018, January 24\u201326). Green Energy Harvesting Using Piezoelectric Materials from Bridge Vibrations. Proceedings of the 2018 2nd International Conference on Green Energy and Applications (ICGEA), Singapore, Singapore."},{"key":"ref_8","unstructured":"Zakariya, M.D. (2016, January 4\u20138). Energy Harvesting using Thermoelectric Generators. Proceedings of the 2016 IEEE International Energy Conference (ENERGYCON), Leuven, Belgium."},{"key":"ref_9","first-page":"1","article-title":"Electric-Field Energy Harvesting from Lighting Elements for Battery-Less Internet of Things","volume":"5","author":"Oktay","year":"2017","journal-title":"IEEE Access"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1624","DOI":"10.1109\/JSAC.2015.2391690","article-title":"Movers and shakers: Kinetic energy harvesting for the Internet of things","volume":"33","author":"Maria","year":"2015","journal-title":"J. Sel. Areas Commun."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"62717","DOI":"10.1109\/ACCESS.2018.2874134","article-title":"Resource management for cognitive IoT systems with RF energy harvesting in smart cities","volume":"6","author":"Bander","year":"2018","journal-title":"IEEE Access"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1680","DOI":"10.1109\/TMC.2017.2740378","article-title":"RF energy harvesting and transfer for spectrum sharing cellular IoT communications in 5G systems","volume":"17","author":"Ercan","year":"2018","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_13","unstructured":"Ken, M., Tsutomu, N., Yoshinobu, K., Hidenori, M., Hiroshi, S., Takashi, I., Yasunobu, A., Keiichi, M., Hideaki, Y., and Takashi, I. (2019, January 9\u201314). A 65nm Silicon-on-Thin-Box (SOTB) Embedded 2T-MONOS Flash Achieving 0.22 pJ\/bit Read Energy with 64 MHz Access for IoT Applications. Proceedings of the 2019 Symposium on VLSI Circuits, Kyoto, Japan."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"229","DOI":"10.1109\/JSSC.2012.2221233","article-title":"IEEE A modular 1 mm3 die-stacked sensing platform with low power I2C inter-die communication and multi-modal energy harvesting","volume":"48","author":"Lee","year":"2013","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_15","unstructured":"Hrishikesh, J., Lee, K., Lee, W.S., Arnab, R., Kim, Y., and Vijay, R. (2014, January 11\u201313). Powering the internet of things. Proceedings of the 2014 international Symposium Low Power Electronics and Design (ISLPED), La Jolla, CA, USA."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"314","DOI":"10.1109\/TCSII.2014.2312801","article-title":"A Subgigahertz UWB Transmitter with Wireless Clock Harvesting for RF Powered Applications","volume":"61","author":"Mao","year":"2014","journal-title":"IEEE Trans. Circuits Syst."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"3061","DOI":"10.1109\/JSSC.2011.2166432","article-title":"A low-power GSM\/EDGE\/WCDMA polar transmitter in 65-nm CMOS","volume":"46","author":"Michael","year":"2011","journal-title":"Ieee J. Solid-State Circuits"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1415","DOI":"10.1109\/JSSC.2004.831608","article-title":"A study of injection locking and pulling in oscillator","volume":"39","author":"Behzad","year":"2004","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_19","first-page":"1297","article-title":"Analysis of oscillator injection locking through phase domain impulse-response","volume":"55","author":"Paolo","year":"2015","journal-title":"IEEE Trans. Circuits Syst. I Regul. Pap."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2823","DOI":"10.1109\/TCSI.2013.2252654","article-title":"Modeling oscillator injection locking using the phase domain response","volume":"60","author":"Dustin","year":"2013","journal-title":"IEEE Trans. Circuits Syst. I Regul. Pap."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1686","DOI":"10.1109\/TMTT.2010.2049680","article-title":"An integrated divide-by-two direct injection locking frequency divider for bands S through Ku","volume":"58","author":"Stefano","year":"2010","journal-title":"Ieee Trans. Microw. Theory Tech."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"559","DOI":"10.1109\/LMWC.2011.2165277","article-title":"Design of ring-oscillator-based injection-locked frequency dividers with single phase inputs","volume":"21","author":"Yi","year":"2011","journal-title":"IEEE Microw. Wirel. Compon. Lett."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1161","DOI":"10.1109\/TMTT.2013.2244224","article-title":"Progressive mixing technique to widen the locking range of high division-ratio injec-tion-locked frequency dividers","volume":"61","author":"Ahmed","year":"2013","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_24","unstructured":"Abderrahmane, H., Remy, V., Nicolas, D., and Jean, G. (2017, January 25\u201328). A Fully Digital Ultra-wide Band Sub-GHz Pulse Generator. Proceedings of the 2017 15th IEEE International New Circuits and Systems Conference (NEWCAS), Strasbourg, France."},{"key":"ref_25","first-page":"1184","article-title":"A 200-Mb\/s Data Rate 3.1\u20134.8-GHz IR-UWB All-Digital Pulse Generator With DB-BPSK Modulation","volume":"62","author":"Na","year":"2015","journal-title":"IEEE Trans. Circuits Syst. II Express Briefs"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"865","DOI":"10.1002\/mop.28976","article-title":"A tunable ultrawideband digital impulse generator in 0.18 \u03bcm CMOS","volume":"57","author":"Yoo","year":"2015","journal-title":"Microw. Opt. Technol. Lett."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1049\/iet-cds.2015.0229","article-title":"CMOS impulse radio ultra-wideband Gaussian pulse generator with variable channel and bandwidth","volume":"10","author":"Choi","year":"2016","journal-title":"IET Circuits Devices Syst."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"20130204","DOI":"10.1587\/elex.10.20130204","article-title":"CMOS pulse generator based on spectral efficiently gated oscillator for UWB impulse radio","volume":"10","author":"Kim","year":"2013","journal-title":"IEICE Electron. Express"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"272","DOI":"10.1049\/iet-cds.2013.0331","article-title":"3\u201310 GHz ultra wideband front-end transceiver in 0.13 \u03bcm complementary metal oxide semi-conductor for low-power biomedical radar","volume":"8","author":"Wang","year":"2014","journal-title":"IET Circuits Devices Syst."},{"key":"ref_30","first-page":"701","article-title":"An Ultra Low-Power Dual-Band IR-UWB Transmitter in 130-nm CMOS","volume":"59","author":"Batur","year":"2012","journal-title":"IEEE Trans. Circuits Syst. II Express Briefs"},{"key":"ref_31","first-page":"1013","article-title":"An efficient method to analyze lock range in ring oscillators with multiple injections","volume":"62","author":"Aidin","year":"2015","journal-title":"IEEE Trans. Circuits Syst. II Express Briefs"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"620","DOI":"10.1109\/TMTT.2008.916868","article-title":"A 0.8-mW 55-GHz dual-injection-locked CMOS frequency divider","volume":"56","author":"Tang","year":"2008","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"656","DOI":"10.1109\/JSSC.2007.916602","article-title":"Multi-phase injection widens lock range of ring-oscillator-based fre-quency dividers","volume":"43","author":"Ahmad","year":"2008","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1712","DOI":"10.1109\/TCSI.2012.2230591","article-title":"Analysis and design of superharmonic injection-locked multipath ring oscillators","volume":"60","author":"Amr","year":"2013","journal-title":"IEEE Trans. Circuits Syst. I Regul. Pap."},{"key":"ref_35","first-page":"1336","article-title":"Strong injection locking and pulling in LC multiphase oscillator with multiple injection signal","volume":"66","author":"Aidin","year":"2019","journal-title":"IEEE Trans. Circuits Syst. II Express Briefs"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1109\/LMWC.2015.2409792","article-title":"Ring oscillator based injection locked frequency divider using dual injection paths","volume":"25","author":"Liu","year":"2015","journal-title":"IEEE Microw. Wirel. Compon. Lett."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"223","DOI":"10.1109\/TCSI.2017.2726100","article-title":"Generalized analytical equations for injected ring oscillator with RC-load","volume":"65","author":"Ali","year":"2018","journal-title":"IEEE Trans. Circuits Syst. I Regul. Pap."},{"key":"ref_38","first-page":"327","article-title":"A Wide-Locking Range Dual Injection-Locked Frequency Divider with An Automatic Frequency Calibration Loop in 65-nm CMOS","volume":"62","author":"Lee","year":"2015","journal-title":"IEEE Trans. Circuits Syst. II Express Briefs"},{"key":"ref_39","unstructured":"Mingze, L., Ralph, D.M., and Nahla, T.A.E.K. (2017, January 13\u201316). A fully synthesized injection locked ring oscillator based on a pulse injection locking technique. Proceedings of the IEEE Asia Pacific Microwave Conference (APMC), Kuala Lumpar, Malaysia."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1109\/TMTT.2017.2750666","article-title":"Design and analysis of W-band injection-locked frequency divider using split transformer coupled oscillator technique","volume":"66","author":"Lin","year":"2018","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"671","DOI":"10.1109\/JSSC.2005.843609","article-title":"A 44-\u03bcW 4.3-GHz Injection-Locked Frequency Divider with 2.3-GHz Locking Range","volume":"40","author":"Ken","year":"2005","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"2586","DOI":"10.1109\/TCSI.2014.2312491","article-title":"Tunable CMOS Delay Gate with Improved Matching Properties","volume":"61","author":"Prezemyslaw","year":"2014","journal-title":"IEEE Trans. Circuits Syst. I Regul. Pap."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"2227","DOI":"10.1109\/JSSC.2018.2825455","article-title":"A Wirelessly Powered UWB RFID Sensor Tag with Time-Domain Analog-to-Information Interface","volume":"53","author":"Bao","year":"2018","journal-title":"IEEE J. Solid-State Circuits"},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Chen, F., Li, Y., Liu, D., Rhee, W., Kim, J., Kim, D., and Wang, Z. (2014, January 9\u201313). 9.3 A 1 mW 1Mb\/s 7.75-to-8.25GHz chirp-UWB transceiver with low peak-power transmission and fast synchronization capability. Proceedings of the 2014 IEEE International Solid-State Circuits Conference Digest of Technical Papers (ISSCC), San Francisco, CA, USA.","DOI":"10.1109\/ISSCC.2014.6757382"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/4\/1426\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:25:45Z","timestamp":1760160345000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/4\/1426"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,2,18]]},"references-count":44,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2021,2]]}},"alternative-id":["s21041426"],"URL":"https:\/\/doi.org\/10.3390\/s21041426","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,2,18]]}}}