Signal-to-Noise Ratio in Doppler Radar System for Heart and Respiratory Rate Measurements

• Published in: IEEE transactions on microwave theory and techniques Vol. 57; no. 10; pp. 2498 - 2507
• Main Authors: Droitcour, A.D., Boric-Lubecke, O., Kovacs, G.T.A.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2009; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Biomedical applications of electromagnetic radiation; biomedical monitoring; cardiovascular system; CMOS analog integrated circuits; CMOS digital integrated circuits; Confidence intervals; Doppler radar; Heart; Human subjects; Integrated circuit measurements; Mathematical analysis; Matlab; microwave integrated circuits; Motion measurement; Noise; Phase noise; Printed circuit boards; Radar; Radar signal processing; Respiration; respiratory system; Sensors; Signal processing; Signal to noise ratio; Transceivers
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2009.2029668

A CMOS Doppler radar sensor has been developed and used to measure motion due to heart and respiration. The quadrature direct-conversion radar transceiver has been fully integrated in 0.25-mum CMOS, the baseband analog signal conditioning has been developed on a printed circuit board, and digital signal processing has been performed in Matlab . The theoretical signal-to-noise ratio (SNR) is derived based on the radar equation, the direct-conversion receiver's properties, oscillator phase noise, range correlation, and receiver noise. Heart and respiration signatures and rates have been measured at ranges from 0.5 to 2.0 m on 22 human subjects wearing normal T-shirts. The theoretical SNR expression was validated with this study. The heart rates found with the radar sensor were compared with a three-lead electrocardiogram, and they were within 5 beats/min with 95% confidence for 16 of 22 subjects at a 0.5-m range and 11 of 22 subjects at a 1.0-m range. The respiration rates found with the radar sensor were compared with those found using a piezoelectric respiratory effort belt, and the respiration rates were within five respirations per minute for 18 of 22 subjects at a 0.5-m range, 17 of 22 subjects at a 1.0-m range, and 19 of 22 subjects at a 1.5-m range.