Wireless Sensing for the Respiratory Activity of Human Beings: Measurements and Wide-band Numerical Analysis

Abstract

An electromagnetic sensing system for the measurement of the respiratory activity is presented. The aims are to demonstrate the feasibility of the proposed approach and in particular to evaluate the effect on the measured signal of the distance between the subject and the sensing apparatus. Moreover, an electromagnetic model of the system, including the monitored subject, is proposed as a tool to solve the problem of selecting working parameters for system design. The sensing system is based on the measurement of the phase variation of the reflection coefficient caused by the respiratory activity. The phase signal compared with the thorax displacement measured by a reference instrument shows a high correlation () for different subject postures (sitting, standing, and lying) and a reduction of the signal amplitude with the distance dB/cm is reported. The numerical simulations performed on a wide-band highlight the frequencies where the method exhibits the highest sensitivity to thorax movements. The sensitivity can be further improved by reducing the antenna beamwidth. Despite the signal amplitude reduction, the proposed system makes it possible to correctly operate at distances up to 2.5 m.

Substrate‐integrated waveguide based antenna in remote respiratory sensing

“…• EM sensing makes it possible to measure through clothes or fabric (bed sheets and blankets) without signal disturbances A number of examples for EM remote respiratory sensing are found in the literature such as [5], [6], [7], [8] and [9]. Table 1.2 summarizes the antenna type, number of antennas and operating frequency used by these EM systems.…”

“…Table 1.2 summarizes the antenna type, number of antennas and operating frequency used by these EM systems. [5] Horn antenna 1 for Tx/Rx 6 GHz Massagram [6] Patch antenna 2 (1 for Tx, 1 for Rx) 2.4 GHz Baltag [7] Horn antenna 1 for Tx/Rx 8-10 GHz Lubecke [8] Patch antenna 2 pairs (1 for Tx, 1 for Rx) 10 GHz Pieraccini [9] 4-element patch array 2 (1 for Tx, 1 for Rx) 2.42 GHz…”

“…Another example of an EM sensing system for respiratory activity is developed in [5]. The working principle of this system is based on the measurement of the EM signal back scattered by the monitored subject.…”

“…The experimental setup of [5] uses a vector network analyzer (VNA) to generate an output signal at 6 GHz to feed the antenna. The VNA is also used to measure the reflection coefficient of the antenna (S 11 ) which depends on both the antenna itself and on the reflected signal back scattered from the body.…”

Cardiorespiratory Frequency Monitoring Using the Principal Component Analysis Technique on UWB Radar Signal

“…The first radar system applied for the monitoring of respiratory activity was the Doppler radar, which uses a continuous wave signal in the microwave range [7][8][9]. The UWB radar is a valuable alternative due to its better performances compared with the Doppler one.…”