uwb pulse propagation into human tissues

In this paper the propagation of a UWB pulse into a layered model of the human body is studied to characterize absorption and reflection of the UWB signal due to the different body tissues. Several time behaviours for the incident UWB pulse are considered and compared with reference to the feasibility of breath and heartbeat activity monitoring. Results show that if the UWB source is placed far from the human body, the reflection coming from the interface between air and skin can be used to detect the respiratory activity. On the contrary, if the UWB source is placed close to the human body, a small reflection due to the interface between the posterior lung wall and the bone, which is well distanced in time from the reflections due to the first layers of the body model, can be used to detect lung and heart changes associated with the cardio-respiratory activity

Radar monitoring of heartbeats and respiration

This thesis addresses the use of radar for heartbeat and respiration monitoring. Medical radar can be used for detecting vital signs at distances up to several meters. A medical radar works by transmitting electromagnetic waves towards a person, and receiving echoes reflected off the person. Vital signs appear as modulations in the radar data in period with the heartbeats and respiration. We have measured and analyzed these modulations. The ability to detect human heartbeats from a distance can be used for monitoring patients’ heartbeats without the need of attaching the measurement equipment to the patient. A radar system can be placed over a bed, integrated in a mattress or chair or used for non-intrusive home monitoring. It could also be used as an alternative to the diagnostic monitoring tools of today. In this thesis, the understanding of radar heartbeat detection is explored. Although heartbeats and respiration monitoring using radar have been reported many times before, the optimal frequencies, waveforms and aspect angle of detection were not known. We have described the vital signs modulations as functions of frequency and aspect angle, and found both narrowband and ultra wideband radar to be suited for the task. In addition to quantizing the modulations, an experimental approach to understanding why heartbeat and respiration detection with radar is possible was made. We found that small body surface movements are the cause of the observed heartbeat modulations in radar data, discarding the theory that reflections from internal body organs are seen. On-body radar have been used as well, and a closer connection between the actual movements of the heart and the radar recordings were found than what is achievable using remote radar. With on-body radar and the processing presented in this thesis, details of the heart mechanics can be identified using radar. It is also possible to see changes in the measured waveform when the pulse and blood pressure of the person changes