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In pulsed radars, repetitive pulses are transmitted to obtain Doppler information of a target. Radars used for the tracking of humans’ vital signs can be classified into pulsed radars and continuous wave (CW) or non-pulsed radars.
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The comparison is between the radar type, centre frequency, operating bandwidth (BW), and the detected vital signs. Table 1 shows a survey of some of the radar types in the literature for vital signs monitoring applications.
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Another challenge is the distortion of the vital signs signal caused by the presence of multiple targets in the environment or due to random body movement. Eliminating the DC offset is essential if amplifiers are required in further stages. Measuring such a low-frequency is challenging, especially if AC coupling is utilised in the radar system to eliminate the DC offset. The typical heart rate (HR) and respiration rate (RR) for a normal adult at rest are 60–100 beats per minute (1–1.67 Hz) and 12–20 breaths per minute (0.2–0.33 Hz), respectively. For example, the vital signs signals due to the heart and respiration rates have very-low-frequency components. Using radar sensors to monitor vital signs is challenging for many reasons. In addition, recent advances in radar technologies provide a high degree of miniaturisation and high performance. One of the main advantages of using radar sensors compared to camera sensors is their ability to monitor the vital signs through clothes and in the absence of light. A major drawback of this technique is that a light source is required to retrieve vital signs information.Īmong the remote vital signs monitoring devices, radars show good performance compared to other devices.
#Dc doppler radar skin
The principle of PPG is to monitor the changes in the skin colour that are produced by the changes in the volume of the tissues due to the blood's movement through the vessels. Camera-based devices have been used for remotely monitoring the vital signs based on photoplethysmography (PPG). However, sensors need to be attached to the patients during the vital signs recording, which might not be feasible to cope with the spread of the disease. Respiration measurements along with body temperature measurements are examples of preliminary diagnostic tests.Ĭontact vital signs monitoring devices such as electrocardiogram are widely used for tracking the vital signs. Besides showing fever symptoms, COVID-19 shows respiratory symptoms such as cough or difficulty in breathing. Fast and accurate diagnostic tests at the early stages of the disease are essential to cope with the spread of the pandemic. Worldwide infection diseases such as the corona virus disease (COVID-19) need special attention to cope with their spread. In addition, vital signs information is preserved at higher frequencies away from the high-pass filter in AC-coupled systems. The radar is capable of isolating the Doppler frequencies of the vital signs from the surrounding noise. In addition, they experimentally evaluated the proposed radar in measuring the vital signs of a human in a noisy environment. The authors compare the performance of the proposed radar system to a frequency modulated continuous wave radar in measuring the Doppler frequencies of two loudspeakers located at different ranges. In addition, an offset signal using Delta–Sigma modulation is generated to cope with the suppression of low-Doppler frequencies, very close to DC, in AC-coupled systems. The distance selectivity feature is achieved by the use of PRN modulation to focus on the desired target at a certain distance and suppress the Doppler frequencies of other targets at different distances. The radar is capable of measuring the vital signs of a human in a noisy environment with high precision.