  This study proposes a data fusion method for multiradar systems to enable
measurement of the respiration of multiple people located at arbitrary
positions. Using the proposed method, the individual respiration rates of
multiple people can be measured, even when echoes from some of these people
cannot be received by one of the radar systems because of shadowing. In
addition, the proposed method does not require information about the positions
and orientations of the radar systems used because the method can estimate the
layout of these radar systems by identifying multiple human targets that can be
measured from different angles using multiple radar systems. When a single
target person can be measured using multiple radar systems simultaneously, the
proposed method selects an accurate signal from among the multiple signals
based on the spectral characteristics. To verify the effectiveness of the
proposed method, we performed experiments based on two scenarios with different
layouts that involved seven participants and two radar systems. Through these
experiments, the proposed method was demonstrated to be capable of measuring
the respiration of all seven people by overcoming the shadowing issue. In the
two scenarios, the average errors of the proposed method in estimating the
respiration rates were 0.33 and 1.24 respirations per minute (rpm),
respectively, thus demonstrating accurate and simultaneous respiratory
measurements of multiple people using the multiradar system.
