| With the advancement of science and technology,people have begun to pay more and more attention to the protection and monitoring of life safety.Real-time and effective monitoring and collection of various vital signs data of the human body can be timely aware of potential dangers and automatically take measures when emergencies occur.Such as monitoring the physical condition of athletes during training,monitoring the health of the elderly in long-term care facilities,monitoring sudden infant death syndrome or adult sleep apnea.At present,wearable and portable testing equipment includes oximeter,chest strap,wearable ECG acquisition device,etc.However,they inevitably need to have a physical connection with the main body,which are bound by cables.Consequently,they are limited in many occasions and are not suitable for daily life.Therefore,in many scientific and engineering applications,it is of great significance to realize the detection of vital signs without physical contact with the human body.Although many studies have used Doppler radar to achieve non-contact monitoring of a single target's vital signs,single-frequency continuous wave systems lack instantaneous bandwidth.Ordinary linear frequency modulated continuous wave radars are limited by range resolution,making it difficult to distinguish between very large distances.Nearly two goals vital signs.Hence,multitarget vital sign detection still facing major challenges when multiple targets are close to each other in the same beam,such as real-time monitoring of vital signs of drivers and passengers in a car,home-based sleep monitoring research,and vital signs monitoring of indoor complex environments,etc.This paper proposes a novel time-division multi-target vital signs detection radar system based on filter tags.The solution is based on the time-division method of beat signals.The system uses tags to reflect signals of different frequency bands to distinguish different targets.So that we can realize the vital signs detection and separation of two close targets in the same beam.The vital sign of multiple targets can be obtained by deriving precise phase-based range histories due to the coherence feature of the radar systems.Main tasks as follows:1)A time-division multi-target vital signs detection radar method is proposed,which solves the problem of vital signs detection and separation of two close targets in the same beam.Detailed theoretical derivation,feasibility analysis and system signal simulation of the proposed scheme are carried out.The simulation results show that the multi-target vital signs can be distinguished by the time division scheme of filtering tags.2)A novel filter tag is proposed.By using the tunable band-pass filter,the cavity-backed rectangular patch antenna and the substrate integrated waveguide transmission line,a planar passive tunable narrowband tag with polarization rotation characteristics is realized.The polarization rotation characteristics can be achieved by using two different configurations of radiating elements,and the center frequency adjustable characteristics can be achieved by using a mechanically adjustable SIW filter.The tag achieves a tuning range from 22.22 GHz to23.72 GHz,and the stopband rejection is greater than 20 d B.3)A time-division multi-target vital signs monitoring radar system based on filter tags is realized.First,the label's polarization rotation characteristics are verified through the experiment of single target wearing tag,and then the multi-target vital sign detection experiment realizes that when the distance between two targets under the same beam is less than 0.1m,the vital signs detection of the two targets is mainly Monitoring of respiratory rate.Experimental results show that the accuracy rate of the respiratory rate measured by the proposed system is about 97%compared with the respiratory rate monitored by the respiratory chest strap,which verifies the feasibility of the scheme. |
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