\r\nusage of contact electrodes or any type of in-body sensors, has

\r\nseveral applications such as sleeping monitoring and continuous

\r\nmonitoring of vital signals in bedridden patients. This system has

\r\nalso applications in the vehicular environment to monitor the driver,

\r\nin order to avoid any possible accident in case of cardiac failure.

\r\nThus, the bio-radar system proposed in this paper, can measure vital

\r\nsignals accurately by using the Doppler effect principle that relates

\r\nthe received signal properties with the distance change between the

\r\nradar antennas and the person’s chest-wall. Once the bio-radar aim

\r\nis to monitor subjects in real-time and during long periods of time,

\r\nit is impossible to guarantee the patient immobilization, hence their

\r\nrandom motion will interfere in the acquired signals. In this paper,

\r\na mathematical model of the bio-radar is presented, as well as its

\r\nsimulation in MATLAB. The used algorithm for breath rate extraction

\r\nis explained and a method for DC offsets removal based in a motion

\r\ndetection system is proposed. Furthermore, experimental tests were

\r\nconducted with a view to prove that the unavoidable random motion

\r\ncan be used to estimate the DC offsets accurately and thus remove

\r\nthem successfully.","references":"[1] C. Li, V. Lubecke, O. Boric-Lubecke, and J. Lin, \u201dA Review on\r\nRecent Advances in Doppler Radar Sensors for Noncontact Healthcare\r\nMonitoring,\u201d IEEE Transactions on Microwave Theory and Techniques,\r\n61, 5, 2013, pp. 2046-2060.\r\n[2] D. Malafaia, et. al., \u201dCognitive Bio-Radar: The Natural Evolution of\r\nBio-Signals Measurement,\u201d Journal of Medical Systems, 40, 10, 2016,\r\np. 219.\r\n[3] O. Boric-Lubecke, V. Lubecke, A. Droitcour, B. Park, and A. Singh,\r\nDoppler Radar Physiological Sensing, John Wiley & Sons, 2015.\r\n[4] J. C. Lin, Non-Invasive Microwave Measurement of Respiration,\r\nProceedings of the IEEE, 63, 10, 1975, p. 1530.\r\n[5] J. C. Lin, E. Dawe and J. Majcherek, A Non-Invasive Microwave Apnea\r\nDetector, Proceedings of the San Diego Biomedical Symposium, 16,\r\n1977, p. 441.\r\n[6] J. C. Lin, J. Kiernicki, M. Kiernicki and P. B. Wollschlaeger,\r\nMicrowave Apexcardiography, IEEE Transactions on Microwave Theory\r\nand Techniques, 27, 6, 1979, pp. 618-620.\r\n[7] K. H. Chan, J. C. Lin, Microprocessor-based Cardiopulmonary Rate\r\nMonitor, Medical and Biological Engineering and Computing, Springer,\r\n25, 1, 1987, pp. 41-44.\r\n[8] C. Li, X. Yu, C. M. Lee, D. Li, L. Ran, and J. Lin, \u201dHigh Sensitivity\r\nSoftware Configurable 5.8 GHz Radar Sensor Receiver Chip in 0.13 \u03bcm\r\nCMOS for Non-Contact Vital Sign Detection,\u201d IEEE Transactions on\r\nMicrowave Theory and Techniques, 58, 5, 2010, pp. 1410-1419.\r\n[9] D. Malafaia, J. Vieira and A. Tom\u00b4e, \u201dImproving Performance of\r\nBio-Radars for Remote Heartbeat and Breathing Detection by using\r\nCyclostationary Features,\u201d Proceedings of the International Joint\r\nConference on Biomedical Engineering Systems and Technologies, 4, pp.\r\n344-349.\r\n[10] M. Zakrzewski, H. Raittinen, and J. Vanhala, \u201dComparison of Center\r\nEstimation Algorithms for Heart and Respiration Monitoring with\r\nMicrowave Doppler Radar,\u201d IEEE Sensors Journal, 12, 3, 2012, pp.\r\n627-634.\r\n[11] Q.Lv, Y. Dong, Y. Sun, C. Li and L. Ran, \u201dDetection of bio-signals\r\nfrom body movement based on high-dynamic-range Doppler radar\r\nsensor\u201d, RF and Wireless Technologies for Biomedical and Healthcare\r\nApplications (IMWS-BIO), 2015 IEEE MTT-S, 2015 International\r\nMicrowave Workshop Series, 2015, pp. 88-89.\r\n[12] , A. Vergara, N. Petrochilos, O. Boric-Lubecke, A. Host-Madsen and V.\r\nLubecke, \u201dBlind source separation of human body motion using direct\r\nconversion Doppler radar\u201d, Microwave Symposium Digest, 2008 IEEE\r\nMTT-S International, 2008, pp. 1321-1324.\r\n[13] B. Park, V. Lubecke, O. Boric-Lubecke, and A. H\u00f8st-Madsen,\r\n\u201dCenter Tracking Quadrature Demodulation for a Doppler Radar Motion\r\nDetector,\u201d Microwave Symposium IEEE\/MTT-S International, 2007, pp.\r\n1323-1326.\r\n[14] O. Gal, \u201dEllipse Fit using Least Squares criterion\u201d,\r\nhttp:\/\/it.mathworks.com\/matlabcentral\/fileexchange\/3215-fit-ellipse,\r\naccessed: 2018","publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 140, 2018"}