Doppler Radar Respiratory Displacement Assessment Method Based on Phase Offset Between Thorax and Abdomen

Doppler radar is an effective tool for measurements of human respiration. Accurate respiratory patterns and depth recovery are important for a variety of applications, including tumor tracking during radiotherapy, sleep studies, and the detection of respiratory diseases. Involvement of the thorax and abdomen in respiratory effort creates a multi-point scattering of the incident radar signal. The phase delay between these two components affects the accuracy of the Doppler radar measurements. In this paper, the effect of the phase offset between the thorax and abdomen on the accuracy of the Doppler radar measurement of respiratory displacement is investigated. Simulation and experimental results demonstrated that high accuracy can be achieved for low-phase offsets, while measurements in the presence of high-phase offsets are not reliable. The proposed method of selecting data segments with low phase offsets ensures accurate respiratory pattern and depth assessment.