# Detection of Quasi-Static Trapped Human Being Using Mono-Static UWB Life-Detection Radar
## 4 Discussion  
In this article, we presented an effective detection strategy, including stationary operating mode and scanning operating mode, dealing with general and practical cases when there exist quasi-static trapped human beings.  
Figure 19: Measurement results for multistorey building. (**a,b**) The output range-frequency images using the normal FFT-based respiration detection methods using the echoes from a single radar. (**c**) The output 2D slice (range \(\times\) range) image for the specific respiration frequency.  
Figure 18: The experimental setup for a multistorey building. (**a**) The deployment of two Golay-coded radars. (**b**)The tested human object.  
Based on the experimental results for stationary operating mode, the proposed radar system with the \"stationary operating mode\" shows excellent VSF detection performance for non-periodic but non-weak micro-motion targets.  
Based on the type-I experiment, the conclusions can be summarized as follows:  
1. When the distance between the beacon and the Golay-coded radar is within 35 m, compared to the \"FFT-based respiration detection method\", the \"scanning operating mode\" always gives the results with higher accuracy.
2. When the distance between the beacon and the Golay-coded radar ranges from 37 to 39 m, the No. 2 radar fails to locate the target using the \"FFT-based respiration detection method\". Notably, the \"scanning operating mode\" can avoid the misjudment to give the correct result.
3. The most attractive case: When the distance between the beacon and the Golay-coded radar is longer than 41 m, the \"FFT-based respiration detection method\" fails to provide the correct location of the target due to the two failure observation points, while the \"scanning operating mode\" can still work.  
Based on the type- II experiment, for the target located 22 m behind the wall, using a single radar to detect the vital signs is prone to failures and false alarms. In contrast, using the \"scanning operating mode\" proposed in the paper can provide accurate positioning results.  
Based on the two practical experiments, the proposed radar system with the \"scanning operating mode\" showed excellent VSF detection performance in practical complex rescue environments.  
In addition, for the scanning operating mode, based on the wireless control, the novel deployed UWB radar system for rescuing trapped persons can take advantage of the distributed radar configuration, where several Golay-coded radars are deployed on a 2D observation aperture and controlled in the network to capture information from all possible wave incident and scattering angles. Specifically, for the mono-static UWB radar at one observation point, the transmitter illuminates the target area, and the receiver collects the scattered field depending on the position of the observation point and the current posture of the trapped person. On the one hand, the SNR of vital sign is improved compared to that of the traditional case. On the other hand, different from the traditional 1D range information obtained from the observation point, the 2D azimuth locations of the trapped persons can also be obtained from the echoes received at different observation points, which can improve the rescue efficiency remarkably.  
The choice of the two modes introduced in this article depends on the actual application scenario. In practical applications, the environment is completely unknown for the operators. The traditional detection strategy using the single-station quasi-static mode or the FFT method are firstly selected to detect the area of interest. If the target cannot be detected, the new detection strategy described in this paper is worth trying. The scanning mode combining multiple radars and multiple observation echoes is selected to detect the potential targets in the measured area. If the target has not been detected, it may be indicated that there is no target, or the vital signal is too weak to be extracted.