Simulation research on vital sign detection radar system

The non-invasive vital sign detection (NIVSD) system works on the principle of change in phase of electromagnetic waves due to partial reflection from separation of two mediums and invasion all the way through the medium. Radio frequency (RF) system based non-invasive measurement methods neither confines nor cause distress as conventional vital sign measurement methods to the human being. This aspect of non-invasive detection becomes predominantly significantfor long-term continuous monitoring of vital signs of human being. The paper reports a reconfigurable multiband NIVSD RF system for effective use of available frequency bands without increasing the size, cost and power consumption level of the system. The proposed system simultaneously operates in entire WLAN band. Experimentally, it has been observed that 2.48-/5.15-GHz frequency band is found better in terms of low radiation power; while 2.48-/5.35-GHz band is better in terms of receivingpower at the antenna.

Vital signs such as heart rate (HR) and respiration rate (RR) are essential physiological parameters that are routinely used to monitor human health and bodily functions. They can be continuously monitored through contact or contactless measurements performed in the home or a hospital. In this study, a contactless Doppler radar W‐band sensing system was used for short‐range, contactless vital sign estimation. Frequency‐modulated continuous wave (FMCW) measurements were performed to reduce the influence of a patient's micromotion. Sensing software was developed that can process the received chirps to filter and extract heartbeat and breathing rhythm signals. The proposed contactless sensing system eliminates the need for the contact electrodes, electric patches, photoelectric sensors, and conductive wires used in typical physiological sensing methods. The system operates at 76–81 GHz in FMCW mode and can detect objects on the basis of changes in frequency and phase. The obtained signals are used to precisely monitor a patient's HR and RR with minimal noise interference. In a laboratory setting, the heartbeats and breathing rhythm signals of healthy young participants were measured, and their HR and RR were estimated through frequency‐ and time‐domain analyses. The experimental results confirmed the feasibility of the proposed W‐band mm‐wave radar for contactless and short‐range continuous detection of human vital signs.

A Multi-phase continuous-wave (CW) Doppler Radar is proposed for measuring small periodic displacement. Multi-phase local oscillator (LO) signals are incident to quadrature mixers to simultaneously generate multiple arcs on the complex plane. Multiple arcs obtained from synchronized data at the same time can be provided in the circle fitting method to compensate for DC offset voltages on the radar. A 5.8 GHz CW Doppler radar with four-phased LO signals, which are generated by a passive balun and two hybrid couplers, is implemented on an FR4 PCB for measuring the periodic displacement at the distance of 0.5 m. Compared to the conventional CW Doppler radar based on a single arc, measurement results show a lower root mean square error (RMSE) and that the RMSE is effectively reduced by more than three times at displacements less than 2 mm.

본 논문에서는 기상 제약이 많은 CCTV 보완을 위해 CW 도플러 레이더를 사용하는 감시 시스템에서 두 개 이상의 물체 접근 또는 이탈 정보를 감지하기 위한 모니터링 프로그램을 개발하였으며, 물체의 접근 또는 이탈 정보를 효율적으로 감지하기 위한 알고리즘을 제안하였다. 제안하는 알고리즘은 CW 도플러 레이더에서 수신한 신호를 FFT 처리하여 실수부와 허수부로 분리 후 각 동일 주파수 마다 진폭을 합산하여 이들의 위치를 통해 접근 또는 이탈을 판단하는 방식이다. 이를 시뮬레이션 및 실험을 통해 검증하였으며, 두 개 물체의 접근 또는 이탈을 감지한 결과 정상적으로 감지하는 것을 확인할 수 있었다. The CCTV is limited by weather conditions. To overcome this limitation, we develop a monitoring program that can sense the approach or recede of two or more objects within a surveillance system that uses a continuous-wave (CW) Doppler radar, and we proposed an algorithm to efficiently detect the approach or recede information of the object. The proposed algorithm separates the signal received by the CW Doppler radar into the real and imaginary parts using Fast Fourier Transform (FFT), and sums the amplitudes for each frequency to determine whether the objects are approaching or receding, using their locations. The algorithm is verified by simulations and experiments, which confirms that it successfully detects the approach or recede of two objects.

This paper presents a Doppler radar sensor system with camera-aided random body movement cancellation (RBMC) techniques for noncontact vital sign detection. The camera measures the subject's random body motion that is provided for the radar system to perform RBMC and extract the uniform vital sign signals of respiration and heartbeat. Three RBMC strategies are proposed: 1) phase compensation at radar RF front-end, 2) phase compensation for baseband complex signals, and 3) movement cancellation for demodulated signals. Both theoretical analysis and radar simulation have been carried out to validate the proposed RBMC techniques. An experiment was carried out to measure a subject person who was breathing normally but randomly moving his body back and forth. The experimental result reveals that the proposed radar system is effective for RBMC.

<div class="htmlview paragraph">An anticipatory crash sensor for actuation of deployable passive restraint systems has been developed. The system consists of a 10 GH<sub>z</sub> continuous wave (CW) doppler radar. In operation, position discrimination is achieved through use of separate receiving and transmitting antennas, located on opposite sides of the front of the vehicle. An object is detected only when within the region of overlap of the two antenna patterns. Velocity discrimination has been achieved very simply in both digital and linear realizations. A threshold circuit permits adjustment of the minimum target size to which the sensor will respond.</div> <div class="htmlview paragraph">A variety of circuit and antenna configurations has been examined and constructed to obtain optimal system performance. These include hybrid systems which make use of mechanical confirmation of impact in an intermediate speed range, and more elaborate antenna configurations. Characteristics of typical targets have been determined experimentally. In addition, studies are being carried out to permit preliminary estimates of cost and reliability for production sensors, and-using available accident data-to indicate the probable effectiveness of such systems.</div>

Occupancy estimation and occupant entry/exit detection can play a significant role in designing energy-efficient heating, ventilation, and air conditioning (HVAC) systems. Radar-based occupancy estimation is gaining attention as it is unobtrusive and does not give rise to privacy issues associated with video imaging. Most research is focused on estimating the number of occupants by employing frequency-modulated continuous wave (FMCW) radar using a micro-Doppler signature. Continuous wave (CW) radar has a simple architecture and fewer signal processing steps than FMCW radar and is mostly employed for sensing micro-Doppler signatures produced by human cardiopulmonary motion. This paper investigates the feasibility of using wavelet analysis to extract occupant entry and exit information from data produced by a single antenna 2.4 GHz CW radar occupancy sensor. Preliminary experimental results on a short scale demonstrated that maximum wavelet coefficient frequency (MWCF) and wavelet coefficient energy (WCE) vary significantly during the entry and exit event of occupants, and can provide a reliable indicator to estimate the number of occupants.

Using a continuous wave (CW) Doppler radar at 60 GHz, the radar cross sections of long metallic rods were measured. The results show linear increase with growing distance between radar and rods. A new expression for the radar cross section, which was also derived, demonstrates good agreement with the measured data.

Continuous-wave (CW) Doppler radar with a quadrature direct-conversion receiver (DCR) has critical issues about Direct-current (DC) offset to manage and measure it when remotely monitoring vital signs which are closely resemble DC values. The characterization process using Radio frequency (RF) single tone has been carried out to measure DC offset, but there is no known method for supporting multiple CW. This paper categorizes DC offset as one of a system DC offset and an environment DC offset, and proposes 1 to 5 experiments of a DC offset characterization process supporting multiple CW. The result experimentally shows that DC offsets have the tendency to follow experiment 4 of characterization when the RF-to-local oscillator (LO) isolation is achieved by using the absorber in front of the antenna.

A novel low-power transceiver topology for noncontact vital sign detection including the power management technique

The non-contact vital sign detection of an individual in indoor environments using a radar sensor has been widely researched by recent advances in the IoT industry. Most of these studies have been conducted by analyzing the spectrum of extracted phase variations in the echo signal of a motionless individual that has only micro-motion (that is, vital signs) caused by both the lung and the heart. However, in the case of a walking individual, the performance of the vital sign detection using conventional methods may be rapidly degraded owing to extreme phase fluctuations caused by the relatively large movement of the individual compared to the vital sign motions. To address this problem, we propose a new motion compensation method for the vital sign detection of a walking individual. First, we conduct a modeling of the echo signal for a walking individual using a radar and discuss problems in vital sign detection. Next, a new algorithm for real-time motion compensation is suggested based on a moving averaging filter and mode in statistics. In the experiments using an IR-UWB (Impulse-radio ultra-wideband) radar, we observed that the proposed method performed a successful real-time vital sign detection of a walking individual.

The integration of sensing and communication functions in one platform has become a pivotal use case in future communication systems. This research investigated the optimal integrated sensing and communication (ISAC) waveforms for the purpose of vital signs detection. In order to incorporate both functions in the system and make it favorable for sensing the micro-doppler effect associated with vital signs, orthogonal frequency division multiplexing (OFDM) and phase-coded frequency modulated continuous wave (PC-FMCW) signals were adopted and compared, and the performances were evaluated against the system based on the classic frequency modulated continuous wave (FMCW). Several phase coded FMCW signals have been investigated and the simulated results indicated that the Frank-coded PC-FMCW waveform exhibited an optimal performance for vital signs detection in a line-of-sight setting. The work is beneficial for search and rescue applications where high-performance sensing such as vital signs detection and limited communication capability is required.

In this paper, a miniaturized circularly polarized (CP) continuous wave Doppler radar system operating at 2.4 GHz is presented. The radar front end consists of one left-handed CP (LHCP) antenna and one right-handed CP (RHCP) antenna, which share a single patch antenna aperture. Orthogonal polarization is achieved through a modified ring-shaped quadrature hybrid coupler (QHC), and the resulting isolation between the two CP antennas is better than 30 dB. With 0 dBm input power to the transmitting antenna, the proposed radar system can accurately detect heartbeat and respiration movements of human test subjects under 1 m and over a wide angular range. The single dual CP antenna achieves 280% size reduction compared to a traditional two linear polarization patch antenna array with the same isolation level.

Microwave Doppler radar has potential to provide a practical tool for noncontact detecting cardiopulmonary movement. In this paper, a noncontact sensor of vital signs was realized based on continuous wave Doppler radar, in addition, real-time signal processing was studied for single target noncontact cardiopulmonary monitoring, including short-time Fourier transform, Sinc interpolation and peak searching. These methods can improve the accuracy, response speed and shorten the latency of cardiopulmonary Doppler radar signal processing considerably, with relatively small amount of calculation.

The Doppler radar-based technique for noncontact vital sign detection has drawn increasing interest in recent years. In this paper, the signal model of human micro-motion is established and the Complex Continuous Basis Pursuit (CCBP)based vital sign detection algorithm for extracting the frequencies of human respiration and heartbeat signal is proposed. By exploiting the sparsity property of the established signal model, the proposed CCBP algorithm can extract the vital signal information by using the polar interpolation and the convex optimization problem solving technique. Simulation experiment results have verified the effectiveness and correctness of the proposed algorithm in the vital sign detection.