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Journal of Sensors
Volume 2015, Article ID 548136, 13 pages
Research Article

Noncontact Detection and Analysis of Respiratory Function Using Microwave Doppler Radar

1School of Engineering, Faculty of Science, Engineering and Built Environment, Deakin University, Geelong, VIC 3216, Australia
2Department of Electrical and Electronic Engineering, Melbourne University, Parkville, VIC 3010, Australia
3University Hospital Geelong, Geelong, VIC 3220, Australia

Received 28 October 2014; Accepted 9 January 2015

Academic Editor: Yu Chen Tsai

Copyright © 2015 Yee Siong Lee et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Real-time respiratory measurement with Doppler Radar has an important advantage in the monitoring of certain conditions such as sleep apnoea, sudden infant death syndrome (SIDS), and many other general clinical uses requiring fast nonwearable and non-contact measurement of the respiratory function. In this paper, we demonstrate the feasibility of using Doppler Radar in measuring the basic respiratory frequencies (via fast Fourier transform) for four different types of breathing scenarios: normal breathing, rapid breathing, slow inhalation-fast exhalation, and fast inhalation-slow exhalation conducted in a laboratory environment. A high correlation factor was achieved between the Doppler Radar-based measurements and the conventional measurement device, a respiration strap. We also extended this work from basic signal acquisition to extracting detailed features of breathing function (I : E ratio). This facilitated additional insights into breathing activity and is likely to trigger a number of new applications in respiratory medicine.