A review on recent progress of portable short-range noncontact microwave radar systems. An X-band microwave life-detection system. Noninvasive microwave measurement of respiration. Ultrasound contrast imaging: current and new potential methods. Heart sound segmentation algorithm based on heart sound envelogram. Acoustical performance of the stethoscope: a comparative analysis. A flexible and highly sensitive strain-gauge sensor using reversible interlocking of nanofibres. A wearable and highly sensitive pressure sensor with ultrathin gold nanowires. Wearable photoplethysmographic sensors-past and present. Photoplethysmography and its application in clinical physiological measurement. Pulse transit time measured from the ECG: an unreliable marker of beat-to-beat blood pressure. Our system is capable of monitoring multiple people simultaneously and could lead to the cost-effective automation of vital sign monitoring in care facilities. To maximize reading range and immunity to multipath interference caused by indoor occupant motion, active tags could be placed in the front pocket and in the wrist cuff to measure the antenna reflection due to near-field coherent sensing and then the vital signals sampled and transmitted entirely in digital format.
To minimize deployment and maintenance cost, passive tags can be integrated into garments at the chest and wrist areas, where the two multiplexed far-field backscattering waveforms are collected at the reader to retrieve the heart rate, blood pressure, respiration rate and breath effort.
The approach, which does not require direct skin contact, offers two possible implementations: passive and active radiofrequency identification tags. Here we show that the external and internal mechanical motion of a person can be directly modulated onto multiplexed radiofrequency signals integrated with unique digital identification using near-field coherent sensing. The measurement process can also be uncomfortable due to the need for direct skin contact, which can disrupt the circadian rhythm and restrict the motion of the patient. Monitoring the heart rate, blood pressure, respiration rate and breath effort of a patient is critical to managing their care, but current approaches are limited in terms of sensing capabilities and sampling rates.