Comparative Performance Assessment of Circular and Linear Polarized Antennas Used for Doppler Radar Measurement of Respiratory Motion

The quality of human respiratory motion measurements made with Doppler radar depends on the amount of reflected signal received and the overall signal to noise ratio (SNR) of the measurement. The non-uniform characteristics of the human torso and its motion impact both the amount of signal returned toward the radar and its polarization. This study used a 2.4 GHz continuous wave Doppler radar system to compare the respiratory motion measurement performance for circular polarized antennas and linear polarized antennas, using mechanical respiratory phantom measurements at a nominal distance of one meter. While the different surfaces examined produced varied levels of signal at the original and other polarizations, the measurements using circular polarized antennas consistently provided less overall received signal and no significant improvement of SNR.