Multi-person vital sign monitoring with the mmWBat. (a) Photograph of experiment scenario. (b), Measured result of the chest wall displacement signal corresponding to the individual on the left. The inset shows the obvious heart beat component. (c) RR and HR tracking results of the individual on the left with comparison of the references. Two dotted lines on both sides of the reference are the defined deviation boundaries of ±3 Beats/Min (i.e., confidence intervals). (d) Vital sign monitoring accuracy of all three individuals. The accuracy is calculated as the percentage of the time when the measured rate falls into the confidence interval, which contains the success rates that the RR and HR are different from the corresponding references of 1 b.p.m., 2 b.p.m., and 3 b.p.m., respectively.