Chest-worn health monitor based on a bistatic self-injection-locked radar

• Published in: IEEE MTT-S International Microwave Symposium digest pp. 1 - 4
• Main Authors: Fu-Kang Wang, You-Rung Chou, Yen-Chen Chiu, Mu-Cyun Tang, Tzyy-Sheng Horng
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.05.2015
• Subjects: Biomedical imaging; cardiopulmonary sensor; Doppler continuous-wave radar; Frequency modulation; Health monitor; Indexes; Mixers; pedometer; Performance evaluation; Prototypes; Radar; time-frequency spectrogram; wearable device; wireless transmission
• ISSN: 0149-645X
• DOI: 10.1109/MWSYM.2015.7167083

This paper presents a chest-worn health monitor based on continuous-wave Doppler radar technology. To achieve low complexity, low power consumption and simultaneous wireless transmission of Doppler information, the radar architecture is bistaic with a self-injection-locked oscillator (SILO) tag and an injection-locked oscillator (ILO) based frequency demodulator. In the experiments with a prototype operated in the 2.36-2.4 GHz Medical Body Area Networks (MBAN) band, the SILO tag is attached to the chest of a subject to transform the movement of the chest due to cardiopulmonary activities and body exercises into a transmitted frequency-modulated wave. The ILO-based frequency demodulator that is located 30 cm away from the subject receives and demodulates the wave to provide a waveform associated with the chest movement. This waveform is further analyzed using short-time Fourier transform (STFT) and ultimately displayed as time-frequency spectrograms. Promisingly, the experimental results as presented in this paper reveal that the proposed monitor is capable of tracking cardiopulmonary activity of a subject during exercise.