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Robust contactless sensor for real-time vital signs monitoring Open Access


Other title
Free-space material characterization
Wireless vital signs monitoring
Circularly polarized ultra-wideband radar
Type of item
Degree grantor
University of Alberta
Author or creator
Chan, Kevin K.M.
Supervisor and department
Karumudi, Rambabu (Electrical and Computer Engineering)
Examining committee member and department
Brett, Michael (Electrical and Computer Engineering)
Adatia, Ian (Pediatrics)
Van, Vien (Electrical and Computer Engineering)
Fear, Elise (University of Calgary)
Department of Electrical and Computer Engineering
Electromagnetics and Microwaves
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Wireless sensing find many biomedical applications due to the benefit and convenience of having no contact with the patients. Low power radio waves, that are biologically safe, can monitor the patient’s medical conditions such as the breathing and heart beat rate. Electro-magnetic (EM) waves extract the small movements of the chest and heart via field disturbance phenomena. The patient’s breathing and heart beat modulate the radio waves for the vital signs to be monitored in real-time. Ultra-wideband (UWB) radar is an EM scattering technology that has been proven to discriminate targets with less than 30mm range resolution, which is smaller than the average size of a human heart. The UWB radar emits 200ps pulses that occupy a bandwidth from 3 to 10GHz. For linearly polarized radiation, the radar cross-section (RCS) of a moving target having complex shapes such as the thorax section of a human body causes regular fading. The scattering from a complex target rotates the radio wave vector to result in non-optimal signal reception due to polarization losses. The research focuses on the design of a circularly polarized (CP) UWB radar system for contactless vital signs monitoring of a patient. Circular polarization is introduced to address the fading RCS problem thus achieving a more robust system. The same CP UWB radar system with radio waves that penetrate through dielectric objects can be used for time-critical rescue operations in locating survivors buried under collapsed structures or in buildings engulfed in flames where visibility is hampered. Furthermore, by employing material characterization and microwave imaging techniques, it is possible to use the proposed system for other biomedical applications such as tumor localization and damaged tissue identification. The thesis is organized as follows. Firstly, the operation of UWB radar is presented and the research topic addressed. The pulse generator design suited for low pulse repetition rates is then introduced. The design of a decade bandwidth circularly polarized antenna array is described. The methodology and performance of the robust vital signs monitoring system is shown and compared with the linear polarized counterpart. A new method for material characterization using time domain RCS measurements is demonstrated. The future work is finally proposed.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
K.K.M. Chan, K. Rambabu, A.E.C. Tan, and M.Y.W. Chia, “Efficient Passive Low-Rate Pulse Generator for Ultra-Wideband Radar,” IET Microwaves, Antennas & Propagation, vol. 4, no. 12, pp. 2196–2199, Dec. 2010.K. Rambabu, A.E.C. Tan, K.K.M. Chan, and M.Y.W. Chia, “Estimation of Antenna Effect on Ultra-Wideband Pulse Shape in Transmission and Reception,” IEEE Trans. Electromagn. Compat., vol. 51, no. 3, pp. 604-610, Aug. 2009.K.K.M. Chan, A.E.C. Tan, and K. Rambabu, “Design and analysis of a Decade Bandwidth 180° Hybrid Coupler,” IET Microwaves, Antennas & Propagation, vol. 7, no. 1, pp. 71-77, Jan. 2013.K.K.M. Chan, A.E.C. Tan, and K. Rambabu, “Decade Bandwidth Circularly Polarized Antenna Array,” IEEE Trans. Antennas Propagat., vol. 61, no. 11, pp. 5435-5443, Nov. 2013.K.K.M. Chan, A.E.C. Tan, and K. Rambabu, “Circularly Polarized Ultra-Wideband Radar System for Vital Signs Monitoring,” IEEE Trans. Microw. Theory Tech., vol. 61, no. 5, pp. 2069-2075, May 2013.K. Rambabu, A.E.C. Tan, K.K.M. Chan, and M.Y.W. Chia, “Experimental Verification of Link Loss Analysis for Ultrawideband Systems,” IEEE Trans. Antennas Propag., vol. 59, no. 4, pp. 1428- 1432, Apr. 2011.

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