Abstract

Ultra-wideband (UWB) radar has become a critical remote-sensing tool for non-contact vital sign detection such as emergency rescues, securities, and biomedicines. Theoretically, the magnitude of the received reflected signal is dependent on the central frequency of mono-pulse waveform used as the transmitted signal. The research is based on the hypothesis that the stronger the received reflected signals, the greater the detectability of life signals. In this paper, we derive a new formula to compute the optimal central frequency to obtain as maximum received reflect signal as possible over the frequency up to the lower range of Ka-band. The proposed formula can be applicable in the optimization of hardware for UWB life detection and non-contact monitoring of vital signs. Furthermore, the vital sign detection results obtained by the UWB radar over a range of central frequency have been compared to those of the former continuous (CW) radar to provide additional information regarding the advantages and disadvantages of each radar.

Highlights

  • Nowadays, radars are used to detect long-ranged targets such as military airplanes, and they are used for short-range detections, especially in the monitoring of human activities, monitoring sleeping infants or adults, etc

  • The detection of vital signs using radar system is essentially based on interpreting the echo signals scattered from human micromovements

  • Monocycle UWB radar is popularly used as a non-contact monitor since it could free the person from wearable sensors and imposes no infringement on personal privacy

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Summary

Introduction

Radars are used to detect long-ranged targets such as military airplanes, and they are used for short-range detections, especially in the monitoring of human activities, monitoring sleeping infants or adults, etc In such biomedical applications, radars can be widely categorized into types, namely continuous wave (CW) radar and ultra-wideband (UWB) radar. For UWB radars, the strengths of the heartbeat and breathing signals can be improved by adjusting the central frequency of the mono-pulse transmitted waveform. We do not have the luxury of unlimited bandwidth for which sensing hardware (like antennas, PA, LNA), once set up, can operate at best on a few gigahertz of we can sweep across the entire range frequencies. Regarding the advantages and disadvantages of non-contact vital sign detection

Transmitted Signal Model
Received Signal Model
Detection Block Diagram
Spectral
J 1 Bessel Function
Respiratory Model
Heartbeat Model
Avoiding the Central Frequency for the Peak R3 harmonic and the Null Point H1
Vital Sign Spectrum Model of Monocycle UWB
Simulation parameters
Analysis ofInOptimal
Detected
Comparison of Heartbeat Strength with R3 Harmonic
The relative strength versusversus the central with the small–large r from
Discussion on the Optimal Central Frequency
Experimentation
Experimentation for Optimal Central Frequency of Respiration
Conclusions

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