366 research outputs found
A Twin Spiral Planar Antenna for UWB Medical Radars
A planar-spiral antenna to be used in an ultrawideband (UWB) radar system for heart activity monitoring is presented. The antenna, named “twin,” is constituted by two spiral dipoles in a compact structure. The reflection coefficient at the feed point of the dipoles is lower than −8 dB over the 3–12 GHz band, while the two-dipoles coupling is about −20 dB. The radiated beam is perpendicular to the plane of the spiral, so the antenna is wearable and it may be an optimal radiator for a medical UWB radar for heart rate detection. The designed antenna has been also used to check some hypotheses about the UWB radar heart activity detection mechanism. The radiation impedance variation, caused by the thorax vibrations associated with heart activity, seems to be the most likely explanation of the UWB radar operation
Noncontact monitoring of heartbeat and movements during sleep using a pair of millimeter-wave ultra-wideband radar systems
We experimentally evaluate the performance of a noncontact system that measures the heartbeat of a sleeping person. The proposed system comprises a pair of radar systems installed at two different positions. We use millimeter-wave ultra-wideband multiple-input multiple-output array radar systems and evaluate the performance attained in measuring the heart inter-beat interval and body movement. The importance of using two radar systems instead of one is demonstrated in this paper. We conduct three types of experiments; the first and second experiments are radar measurements of three participants lying on a bed with and without body movement, while the third experiment is the radar measurement of a participant actually sleeping overnight. The experiments demonstrate that the performance of the radar-based vital measurement strongly depends on the orientation of the person under test. They also show that the proposed system detects 70% of rolling-over movements made overnight
Investigation of an ultra wideband noise sensor for health monitoring
Quick on-scene assessment and early intervention is the key to reduce the mortality of stroke and trauma patients, and it is highly desirable to develop ambulance-based diagnostic and monitoring devices in order to provide additional support to the medical personnel. We developed a compact and low cost ultra wideband noise sensor for medical diagnostics and vital sign monitoring in pre-hospital settings. In this work, we demonstrated the functionality of the sensor for respiration and heartbeat monitoring. In the test, metronome was used to manipulate the breathing pattern and the heartbeat rate reference was obtained with a commercial electrocardiogram (ECG) device. With seventeen tests performed for respiration rate detection, sixteen of them were successfully detected. The results also show that it is possible to detect the heartbeat rate accurately with the developed sensor
Feasibility Study and Design of a Wearable System-on-a-Chip Pulse Radar for Contactless Cardiopulmonary Monitoring
A new system-on-a-chip radar sensor for next-generation wearable wireless interface applied to the human health care and safeguard is presented. The system overview is provided and the feasibility study of the radar sensor is presented. In detail, the overall system consists of a radar sensor for detecting the heart and breath rates and a low-power IEEE 802.15.4 ZigBee radio interface, which provides a wireless data link with remote data acquisition and control units. In particular, the pulse radar exploits 3.1–10.6 GHz ultra-wideband signals which allow a significant reduction of the transceiver complexity and then of its power consumption. The operating principle of the radar for the cardiopulmonary monitoring is highlighted and the results of the system analysis are reported. Moreover, the results obtained from the building-blocks design, the channel measurement, and the ultra-wideband antenna realization are reported
Bio-Radar Applications for Remote Vital Signs Monitoring
Nowadays, most vital signs monitoring techniques used in a medical context and/or daily
life routines require direct contact with skin, which can become uncomfortable or even
impractical to be used regularly. Radar technology has been appointed as one of the most
promising contactless tools to overcome these hurdles. However, there is a lack of studies
that cover a comprehensive assessment of this technology when applied in real-world
environments. This dissertation aims to study radar technology for remote vital signs
monitoring, more specifically, in respiratory and heartbeat sensing.
Two off-the-shelf radars, based on impulse radio ultra-wideband and frequency modu lated continuous wave technology, were customized to be used in a small proof of concept
experiment with 10 healthy participants. Each subject was monitored with both radars
at three different distances for two distinct conditions: breathing and voluntary apnea.
Signals processing algorithms were developed to detect and estimate respiratory and
heartbeat parameters, assessed using qualitative and quantitative methods.
Concerning respiration, a minimum error of 1.6% was found when radar respiratory
peaks signals were directly compared with their reference, whereas a minimum mean
absolute error of 0.3 RPM was obtained for the respiration rate. Concerning heartbeats,
their expression in radar signals was not as clear as the respiration ones, however a
minimum mean absolute error of 1.8 BPM for heartbeat was achieved after applying a
novel selective algorithm developed to validate if heart rate value was estimated with
reliability.
The results proved the potential for radars to be used in respiratory and heartbeat
contactless sensing, showing that the employed methods can be already used in some mo tionless situations. Notwithstanding, further work is required to improve the developed
algorithms in order to obtain more robust and accurate systems.Atualmente, a maioria das técnicas usadas para a monitorização de sinais vitais em
contexto médicos e/ou diário requer contacto direto com a pele, o que poderá tornar-se
incómodo ou até mesmo inviável em certas situações. A tecnologia radar tem vindo a ser
apontada como uma das mais promissoras ferramentas para medição de sinais vitais à
distância e sem contacto. Todavia, são necessários mais estudos que permitam avaliar esta
tecnologia quando aplicada a situações mais reais. Esta dissertação tem como objetivo o
estudo da tecnologia radar aplicada no contexto de medição remota de sinais vitais, mais
concretamente, na medição de atividade respiratória e cardíaca.
Dois aparelhos radar, baseados em tecnologia banda ultra larga por rádio de impulso
e em tecnologia de onda continua modulada por frequência, foram configurados e usados
numa prova de conceito com 10 participantes. Cada sujeito foi monitorizado com cada
um dos radar em duas situações distintas: respirando e em apneia voluntária. Algorit mos de processamento de sinal foram desenvolvidos para detetar e estimar parâmetros
respiratórios e cardíacos, avaliados através de métodos qualitativos e quantitativos.
Em relação à respiração, o menor erro obtido foi de 1,6% quando os sinais de radar
respiratórios foram comparados diretamente com os sinais de referência, enquanto que,
um erro médio absoluto mínimo de 0,3 RPM foi obtido para a estimação da frequência
respiratória via radar. A expressão cardíaca nos sinais radar não se revelou tão evidente
como a respiratória, no entanto, um erro médio absoluto mínimo de 1,8 BPM foi obtido
para a estimação da frequência cardíaca após a aplicação de um novo algoritmo seletivo,
desenvolvido para validar a confiança dos valores obtidos.
Os resultados obtidos provaram o potencial do uso de radares na medição de atividade
respiratória e cardíaca sem contacto, sendo esta tecnologia viável de ser implementada em
situações onde não existe muito movimento. Não obstante, os algoritmos desenvolvidos
devem ser aperfeiçoados no futuro de forma a obter sistemas mais robustos e precisos
Theoretical limits for estimation of periodic movements in pulse-based UWB systems
Cataloged from PDF version of article.In this paper, Cramer-Rao lower bounds (CRLBs) for
estimation of signal parameters related to periodically moving objects
in pulse-based ultra-wideband (UWB) systems are presented.
The results also apply to estimation of vital parameters, such as
respiration rate, using UWB signals. In addition to obtaining the
CRLBs, suboptimal estimation algorithms are also presented.
First, a single-path channel with additive white Gaussian noise
is considered, and closed-form CRLB expressions are obtained
for sinusoidal object movements. Also, a two-step suboptimal
algorithm is proposed, which is based on time delay estimation
via matched filtering followed by least-squares estimation, and its
asymptotic optimality property is shown in the limit of certain
system parameters. Then, a multipath environment is considered,
and exact and approximate CRLB expressions are derived. Moreover,
suboptimal schemes for parameter estimation are studied.
Simulation studies are performed for the estimation of respiration
rates in order to evaluate the lower bounds and performance of
the suboptimal algorithms for realistic system parameters
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