This paper presents the development of a non-contact, nonintrusive wrist pulse sensor based on the near-field variation of an array resonator. A compact resonator and its array were designed and fabricated on flexible substrate. The reflection coefficient of the resonator can vary as a function of the distance between the resonator and the walls of the major arteries, and the corresponding variation is utilized to obtain heart rate information at the wrist. To detect very weak pulse signals from the main arteries, a sensitivity enhancement technique was devised using a radio frequency (RF) array resonator. The sensor system was implemented with an RF switch to combine or select appropriate signals from the resonator element and was tested using the 2.4 GHz ISM band. The results demonstrated the sensor system's excellent performance in both sequential and simultaneous detection schemes. The measurement results showed that a heartbeat pulse can be detected from both radial and ulnar arteries via the array resonators. Considering the high sensitivity and characteristics, the proposed detection system can be utilized as a wearable, long-term health monitoring device.

No abstract

Novel nonintrusive technologies for wrist pulse detection have been developed and proposed as systems for sleep monitoring using three types of radio frequency (RF) sensors. The three types of RF sensors for heart rate measurement on wrist are a flexible RF single resonator, array resonators, and an injection-locked PLL resonator sensor. To verify the performance of the new RF systems, we compared heart rates between presleep time and postsleep onset time. Heart rates of ten subjects were measured using the RF systems during sleep. All three RF devices detected heart rates at 0.2 to 1 mm distance from the skin of the wrist over clothes made of cotton fabric. The wrist pulse signals of a flexible RF single resonator were consistent with the signals obtained by a portable piezoelectric transducer as a reference. Then, we confirmed that the heart rate after sleep onset time significantly decreased compared to before sleep. In conclusion, the RF system can be utilized as a noncontact nonintrusive method for measuring heart rates during sleep.

No abstract

This paper presents a vital sign detection sensor based on reflection coefficient variance from an antenna used in wireless communication devices. The near-field effect is estimated by performing 3D full-wave simulations using a dipole antenna and the magnitude variation of the reflection coefficient induced by human thorax movement due to heart and lungs is observed. The results support the possibility of vital sign detection based on the magnitude variation of the reflection coefficient from an antenna, which can be explained as a narrowband modulation scheme. In particular, a sensitivity enhancement method is proposed and analyzed, and experiments are carried out for heartbeat detection using a dipole antenna with the proposed system. Experimental results are compared between the direct detection and sensitivity enhancement detection schemes. FM signal is also applied to confirm that the proposed sensor works properly in conjunction with an existing communication system. The proposed cardiopulmonary detection sensor is implemented with off-the-shelf components at 2.4 GHz and excellent performance is obtained.

This paper presents a non-contact measurement method of vital signal by the use of multiple-input multiple-output (MIMO) bio-radar system, configured with two antennas that are separated by a certain distance. The direction of arrival (DOA) estimation algorithm for coherent sources was applied to detect vital signals coming from different spatial angles. The proposed MIMO bio-radar system was composed of two identical transceivers sharing single VCO with a PLL. In order to verify the performance of the system, the DOA estimation experiment was completed with respect to the human target at angles varying between -50° and 50° where the bio-radar system was placed at distances (corresponding to 50 cm and 95 cm) in front of a human target. The proposed MIMO bio-radar system can successfully find the direction of a human target. Ⅰ. IntroductionRecently, remote sensing techniques have been actively studied as a means of measuring vital signs. Among these techniques, the Doppler radar sensing of vital signs has received substantial attention due to its simple system architecture and non-contact detection capability [1,2]. Various Doppler radar architectures for sensing human vital signs have consequently been developed: a Doppler radar system based on board-level and chip-level design [3], a dual-antenna Doppler radar system compensated for background motion [4], a barrier penetration consisted of ultra-wide band (UWB), and a CW Doppler radar [5] are some examples. MIMO signal processing methods, such as blind source separation (BSS) and analytical constant modulus algorithm (ACMA), have attracted a great deal of interest for non-contact vital sign detection [6,7]. Until recently, however, the existing MIMO techniques for vital sign detection have been mainly investigated to separate vital signs from multiple sources.The use of MIMO radar technique for vital signal sensing has a number of potential advantages. For a given system design choice, some of these advantages are enhancement of the target detection performance, improvement of the angle estimation accuracy, and a decrease in the minimum detection velocity [8]. A MIMO bio-radar system can also be combined with well-known direction of arrival (DOA) estimation algorithms to provide solutions for direction finding of human subjects. In the present paper, a new approach is presented to find the direction of human vital signals with two identical transceiver architectures sharing a single VCO with a PLL. The MIMO Doppler radar system can be effectively applied to find a human target with respect to azimuth angle, making it a good candidate for applications in home health care systems, military surveillance, as well as security services. To the best of authors' knowledge, this is the first successfully implemented direction finding system for human targets based on a MIMO radar concept. Ⅱ. MIMO Bio-Radar System ConfigurationThe configuration of the proposed integrated MIMO bioradar system is shown in Fig. 1. This monostatic MIMO radar consists of two antennas...

This work presents heartbeat and respiration detection sensor to be applied for mobile communication devices. To estimate the near field effect, simulations are proceed to observe the magnitude variation of antenna reflection coefficient induced by human thorax movement of heart and lung. Experiments are carried out for heartbeat detection using dipole antenna with coupler and a method to improve the sensitivity of the system is proposed. Proposed cardiopulmonary detection system is implemented with off-the-shelf components at 2.4 GHz and excellent performance is obtained.Index Terms -Vital sign, antenna impedance mismatch, heart and respiration rates, handheld device, near field.

This paper presents a single-pole eight-throw switch, based on an eight-way power divider, using substrate integrate waveguide(SIW) technology. Eight sectorial-lines are formed by inserting radial slot-lines on the top plate of SIW power divider. Each sectorial-line can be controlled independently with high level of isolation. The switching is accomplished by altering the capacitance of the varactor on the line, which causes different input impedances to be seen at a central probe to each sectorial line. The proposed structure works as a switching circuit and an eight-way power divider depending on the bias condition. The change in resonant frequency and input impedance are estimated by adapting a tapered transmission line model. The detailed design, fabrication, and measurement are discussed.