A Noncontact FMCW Radar Sensor for Displacement Measurement in Structural Health Monitoring

Abstract

This paper investigates the Frequency Modulation Continuous Wave (FMCW) radar sensor for multi-target displacement measurement in Structural Health Monitoring (SHM). The principle of three-dimensional (3-D) displacement measurement of civil infrastructures is analyzed. The requirements of high-accuracy displacement and multi-target identification for the measuring sensors are discussed. The fundamental measuring principle of FMCW radar is presented with rigorous mathematical formulas, and further the multiple-target displacement measurement is analyzed and simulated. In addition, a FMCW radar prototype is designed and fabricated based on an off-the-shelf radar frontend and data acquisition (DAQ) card, and the displacement error induced by phase asynchronism is analyzed. The conducted outdoor experiments verify the feasibility of this sensing method applied to multi-target displacement measurement, and experimental results show that three targets located at different distances can be distinguished simultaneously with millimeter level accuracy.

Improved FMCW Radar System for Multi-Target Detection of Human Respiration Vital Sign

“…The phase changes that occur can then be used to extract movement from the target. The LPF output from the FMCW system is written as (8). Where τ is the phase shift caused by the target's position.…”

“…There are some requirements to be a large frequency to identify different targets whose distance between objects is 1 mm. Refer to (8) we can determine the minimum bandwidth for differentiating the targets with 1 m distance difference. The resolution that needed, can be achieved with a minimum bandwidth of 150 MHz.…”

“…The resolution of the FMCW radar depends on the bandwidth of the chirp signal used as the modulating signal. A number of methods have also been developed to increase resolution on radar [8]- [9]. However, the results still cannot meet the resolution needs for detecting small shifts such as those of human vital signs.…”

“…Phase processing in a radar system has been studied as a method for detecting targets with high accuracy results. But with phase repetition to detect larger displacement, the measurement limit needs to be established [6], [8]- [9]. In this paper, the elaboration of the concept of phase detection in the FMCW system is explored to detect small shifts in human respiratory rate detection.…”

Time and Frequency Domain Feature Extraction Method of Doppler Radar for Hand Gesture Based Human to Machine Interface

“…Development of non-contacting sensors based on radar systems has been done in several fields such as in medical field for detecting a human vital signs (respiration, heartbeat [14][15][16], structure health monitoring [17], and landslide monitoring [18]. Doppler radar is a radar system that detects the Doppler effect that occur on a target.…”