A Broadband MFCW Agile Radar Concept for Vital-Sign Detection Under Various Thoracic Movements

• Published in: IEEE transactions on microwave theory and techniques Vol. 70; no. 8; pp. 4056 - 4070
• Main Authors: Lin, Yi-Hsien, Cheng, Jen-Hao, Chang, Li-Chi, Lin, Wen-Jie, Tsai, Jeng-Han, Huang, Tian-Wei
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Broadband; Carrier frequencies; Circuit boards; CMOS; Continuous radiation; Cross correlation; Doppler radar; Dual band; dual-band transceiver; Empirical analysis; ensemble empirical mode decomposition (EEMD); Experiments; frequency agility; Heart beat; Heart rate; Intermodulation; multiple-frequency continuous-wave (MFCW) radar; Phase frequency detectors; principal component analysis (PCA); Principal components analysis; Printed circuits; Radar; Radar detection; Radar equipment; resolution; Signal processing; Transceivers; vital-sign detection
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2022.3186014

A multiple-frequency continuous-wave (MFCW) agile radar system has the ability to cope with various physiological conditions of a human subject. Following the mathematic model, a favorable carrier frequency for detection is pursued by analyzing the amplitude and composition of the baseband signal. In Experiment-1, a CMOS dual-band transceiver prototype emulate searching a subject from a distance. The frequencies of the dual-band system are 4.26-4.95 GHz and 17.06-19.79 GHz. During the experiment, the respiratory signal could be detected up to 12 m, and the heartbeat signal up to 6 m. Even with a wooden or a brick barrier in the path, the vital-sign detection remained satisfactory. Later, a concurrent MFCW detection is performed in Experiment-2 for more precise analyses. From the concurrent results, the breathing status can be inferred, and by cross-correlating the results after the ensemble empirical mode decomposition (EEMD) and principal component analysis (PCA), the nonlinear effects of respiratory harmonics or intermodulation tones are reduced, resulting in an accurate heart rate extraction. The receiver front-end and the signal source are manufactured using a 180-nm CMOS process, both packaged on an RO4003C printed-circuit board (PCB).