Vital-Signs Detector Based on Frequency-Shift Keying Radar

2021

Self Cite

A detrending technique is proposed for continuous-wave (CW) radar to remove the effects of direct current (DC) offset, including DC drift, which is a very slow noise that appears near DC. DC drift is mainly caused by unwanted vibrations (generated by the radar itself, target objects, or surroundings) or characteristic changes in components in the radar owing to internal heating. It reduces the accuracy of the circle fitting method required for I/Q imbalance calibration and DC offset removal. The proposed technique effectively removes DC drift from the time-domain waveform of the baseband signals obtained for a certain time using polynomial fitting. The accuracy improvement in the circle fitting by the proposed technique using a 5.8 GHz CW radar decreases the error in the displacement measurement and increases the signal-to-noise ratio (SNR) in vital signal detection. The measurement results using a 5.8 GHz radar show that the proposed technique using a fifth-order polynomial fitting decreased the displacement error from 1.34 mm to 0.62 mm on average when the target was at a distance of 1 m. For a subject at a distance of 0.8 m, the measured SNR improved by 7.2 dB for respiration and 6.6 dB for heartbeat.

where i DC ( t ) and q DC ( t ) are the time-variant DC offset voltages, and I DC and Q DC are the static DC offset voltages in the I/Q baseband signals.…”

Section: Detrending Techniquementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Detrending Technique for Denoising in CW Radar

Lee

Park

2021

Self Cite

“…The extraction of respiration and heartbeat signals from the variations in transceiving signal characteristics is a promising remote vital signal detection technology because it can escape the physical restraint of a contact sensor and be used in various applications [1][2][3]. A continuous wave (CW) Doppler radar, which monitors the Doppler frequency change in the CW signal caused by the thoracic movement from respiration and the heart's periodic movement, can acquire remote vital signals using a simple hardware configuration [4,5].…”

Section: Introductionmentioning

confidence: 99%

Vital Signal Detection Using Multi-Radar for Reductions in Body Movement Effects

Jang

Lee

2021

Self Cite

Vital signal detection using multiple radars is proposed to reduce the signal degradation from a subject’s body movement. The phase variation in the transceiving signals of continuous-wave radar due to respiration and heartbeat is generated by the body surface movement of the organs monitored in the line-of-sight (LOS) of the radar. The body movement signals obtained by two adjacent radars can be assumed to be the same over a certain distance. However, the vital signals are different in each radar, and each radar has a different LOS because of the asymmetric movement of lungs and heart. The proposed method uses two adjacent radars with different LOS to obtain correlated signals that reinforce the difference in the asymmetrical movement of the organs. The correlated signals can improve the signal-to-noise ratio in vital signal detection because of a reduction in the body movement effect. Two radars at different frequencies in the 5.8 GHz band are implemented to reduce direct signal coupling. Measurement results using the radars arranged at angles of 30°, 45°, and 60° showed that the proposed method can detect the vital signals with a mean accuracy of 97.8% for the subject moving at a maximum velocity of 53.4 mm/s.

“…In addition, high integration and low power consumption of the VCO-based readout circuit are advantageous for implementing a large-scale sensor array [ 6 , 7 ]. Radar sensors that monitor the change of electromagnetic-wave between the transmitted and received signals generated from the VCO remotely measure the distance, velocity, and vital-signs in real time [ 8 , 9 , 10 ]. Various sensors using VCOs require low phase noise characteristics in VCOs [ 11 , 12 , 13 ].…”

Section: Introductionmentioning

confidence: 99%

Switched-Biasing Techniques for CMOS Voltage-Controlled Oscillator

Kang

Moon

2021

Self Cite

A voltage-controlled oscillator (VCO) is a key component to generate high-speed clock of mixed-mode circuits and local oscillation signals of the frequency conversion in wired and wireless application systems. In particular, the recent evolution of new high-speed wireless systems in the millimeter-wave frequency band calls for the implementation of the VCO with high oscillation frequency and low close-in phase noise. The effect of the flicker noise on the phase noise of the VCO should be minimized because the flicker noise dramatically increases as the deep-submicron complementary metal-oxide-semiconductor (CMOS) process is scaled down, and the flicker corner frequency also increases, up to several MHz, in the up-to-date CMOS process. The flicker noise induced by the current source is a major factor affecting the phase noise of the VCO. Switched-biasing techniques have been proposed to minimize the effect of the flicker noise at the output of the VCO with biasing AC-coupled signals at the current source of the VCO. Reviewing the advantages and disadvantages reported in the previous studies, it is analyzed which topology to implement the switched-biasing technique is advantageous for improving the performance of the CMOS VCOs.