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Breath Activity Monitoring With Wearable UWB Radars: Measurement and Analysis of the Pulses Reflected by the Human Body

Objective: Measurements of ultrawideband (UWB) pulses reflected by the human body are conducted to evidence the differences in the received signal time behaviors due to respiration phases, and to experimentally verify previously obtained numerical results on the body's organs responsible for pulse reflection. Methods: Two experimental setups are used. The first one is based on a commercially available impulse radar system integrated on a single chip, while the second one implements an indirect time-domain reflectometry technique using a vector network analyzer controlled by a LabVIEW virtual instrument running on a laptop. Results: When the UWB source is placed close to the human body, a small reflection due to the lung boundaries is present in the received pulse well distanced in time from the reflection due to the air-skin interface; this reflection proved to be linked to the different respiration phases. Conclusions: The changes in the reflected pulse could be used to detect, through wearable radar systems, lung movements associated with the breath activity. Significance: The development of a wearable radar system is of great importance because it allows the breath activity sensing without interfering with the subject daily activities.