Sensitive transmit receive architecture for body wearable RF plethysmography sensor
01 Dec 2016-pp 1-4
TL;DR: Clear detection of three modulations indicate that the RF plethysmography signals can be used for diagnosing different health conditions and perform better than the commercially available PPG sensor.
Abstract: A new wearable RF plethysmography (RPG) sensor is developed to monitor wrist pulse rate and variability System design, numerical simulations, fabrication and measurements were carried out to demonstrate the performance of the plethysmography sensor The RF sensor detects not only pulse rate but also modulations within each pulse Clear detection of three modulations indicate that the RF plethysmography signals can be used for diagnosing different health conditions A cavity based H-slot antenna is designed as a near field sensor Two transmit and receive architectures based on conventional coupler/power combiner and innovative differential LNA approaches are designed in order to improve sensitivity of pulse detection Both these architectures are based on the principle of isolation of the reflected signal from the transmitted signal It is observed that the present RPG sensors perform better than the commercially available PPG sensor
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TL;DR: A proof-of-concept of a fully integrated, high frequency (bandwidth 40 MHz), electromagnetic sensing device for monitoring limb hemodynamics and morphology associated with blood flow and its RF attributes such as resonant frequency shift and magnitude variation of reflection coefficient due to fluid volume displacement can be successfully detected through the proposed hardware architecture.
Abstract: Non-intrusive monitoring of blood flow parameters is vital for obtaining physiological and pathophysiological information pertaining to dynamic cardiovascular events and is feasible to achieve via non-invasive, conformal, wearable technologies. Here, we present a proof-of-concept of a fully integrated, high frequency (bandwidth 40 MHz), electromagnetic sensing device for monitoring limb hemodynamics and morphology associated with blood flow. The sensing architecture integrates a novel radio frequency (RF) skin patch resonator embedded with a coplanar outer loop antenna and a scalable, standalone wireless readout hardware based on standing wave ratio (SWR) bridge. The resonator itself is a copper-based open circuit planar Archimedean spiral with a rectangular cross-sectional area, chemically etched on a flexible polyimide substrate. The readout hardware is developed exploiting off-the-shelf components, fabricated on the top of a rigid FR4 substrate. The proposed readout circuit can measure resonant frequency of an RLC network. When energized by the external oscillating RF field via loop antenna, the resonator produces an electromagnetic field response which can be perturbed by dielectric variation inside its field boundary. Through leveraging this principle, the in-vitro experimental results from the benchtop models suggest that the resonator's RF attributes such as resonant frequency shift and magnitude variation of reflection coefficient due to fluid volume displacement can be successfully detected through the proposed hardware architecture. Hence, the system could be an alternative to the conventional, multimodal, non-invasive wearable sensing with an unprecedented capability of ubiquitous fluid phenomena detection from multiple sites of the human body.
17 citations
Cites background from "Sensitive transmit receive architec..."
...blood flow, respectively, using enhanced sensitivity schemes [16], [17], [19], [21], [23]–[25], [30], [33]....
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...Hence, an impedance matching transformer, or directional coupler, in the detection circuit is recommended to potentially solve this problem [21], [31]....
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...The skin patch sensor detects fluid shifts based on resonant frequency shift and reflection coefficient modulation, more specifically, a change in S11 amplitude due to nearfield dielectric perturbation of the RF resonator [16], [17], [20], [21], [24], [43]....
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...respiration rate [16]–[21], [23]–[26], [30]–[32]....
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TL;DR: In this paper, a microwave planar resonant sensor is designed and developed for simultaneous detection of permittivity and permeability of an unknown sample using a nondestructive technique.
Abstract: In this paper, a novel microwave planar resonant sensor is designed and developed for simultaneous detection of permittivity and permeability of an unknown sample using a nondestructive technique. It takes advantage of two-pole filter topology where the interdigitated capacitor (IDC) and spiral inductor are used for placement of a sample with significant relative permittivity and permeability values. The developed sensor model has the potential for differentiating permittivity and permeability based on the odd mode and even mode resonant frequencies. It operates in the ISM (industrial, scientific and medical) frequency band of 2.2–2.8 GHz. The sensor is designed using the full wave electromagnetic solver, HFSS 13.0, and an empirical model is developed for the accurate calculation of complex permittivity and permeability of an unknown sample in terms of shifts in the resonant frequencies and transmission coefficients (S21) under loaded condition. The designed resonant sensor of size 44×24 mm2 is fabricated on a 1.6 mm FR4 substrate and tested, and corresponding numerical model is experimentally verified for various samples (e.g., magnetite, soft cobalt steel (SAE 1018), ferrite core, rubber, plastic and wood). Experimentally, it is found that complex permeability and permittivity measurement is possible with an average error of 2%.
8 citations
Cites methods from "Sensitive transmit receive architec..."
...Among the resonant methods, the sensing and characterization of a sample can be performed either using rectangular waveguide cavity resonator [8], H-slot cavity resonator [9] or with the help of planar resonant sensors [10]....
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01 Jan 2021
TL;DR: A comprehensive review of the latest progress concerning smart wearable sensors is presented with a focus on biosensor and the telemetry link in this article, where several issues related to the device reliability, safety of human health has also been addressed.
Abstract: Advancement in digital health-care system has enthused to develop wearable and smart sensor with high-performance index. Mobile health-care technologies induce great potential for reducing health-care cost and provide assurance in continuous health monitoring of a critical patient from a remote location. The major demand in this domain is to establish a secure, harmless, and reliable medical device for accurately monitoring important signs of the human organ or the environment inside/outside of the human body through flexible sensors. Nevertheless, it is expected that the wearable or implantable medical devices do not possess additional health risks and allow the patient for daily activities; thus, biocompatibility of the sensor is the other essential consideration. In this chapter, a comprehensive review of the latest progress concerning these smart wearable sensors is presented with a focus on biosensor and the telemetry link. In addition to these several issues related to the device reliability, safety of human health has also been addressed.
3 citations
01 Nov 2019
TL;DR: An intelligent safety supervision system is developed for substation inspection and maintenance that can comprehensively analyze the data collected by smart wearable devices and other intelligent equipment to realize personnel certification, smart warning, risk analysis and all-around protection for maintenance personnel.
Abstract: The workload of inspection and maintenance continues increasing as the power grid expands, which has necessitated the development of intelligent supervision methodologies employing advanced information technology that is superior to the traditional ones in terms of efficiency, timeliness, cost and so forth. Therefore, in this paper, an intelligent safety supervision system is developed for substation inspection and maintenance. Based on big data and artificial intelligence technology, the proposed system can comprehensively analyze the data collected by smart wearable devices and other intelligent equipment to realize personnel certification, smart warning, risk analysis and all-around protection for maintenance personnel. In particular, the functions including on-line guidance, approach-electric alarm and healthy analysis can be achieved by virtue of the customized wearable devices.
2 citations
Cites background from "Sensitive transmit receive architec..."
...Thereby, the safety of all levels can be guaranteed, the function of identity authentication and defense against malicious attacks can be realized as well [12]....
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TL;DR: In this article , a wearable RF biosensor that detects multisite hemodynamic events due to pulsatile blood flow through noninvasive tissue-electromagnetic (EM) field interaction is presented.
Abstract: Modern wearable devices show promising results in terms of detecting vital bodily signs from the wrist. However, there remains a considerable need for a device that can conform to the human body’s variable geometry to accurately detect those vital signs and to understand health better. Flexible radio frequency (RF) resonators are well poised to address this need by providing conformable bio-interfaces suitable for different anatomical locations. In this work, we develop a compact wearable RF biosensor that detects multisite hemodynamic events due to pulsatile blood flow through noninvasive tissue–electromagnetic (EM) field interaction. The sensor consists of a skin patch spiral resonator and a wearable transceiver. During resonance, the resonator establishes a strong capacitive coupling with layered dielectric tissues due to impedance matching. Therefore, any variation in the dielectric properties within the near-field of the coupled system will result in field perturbation. This perturbation also results in RF carrier modulation, transduced via a demodulator in the transceiver unit. The main elements of the transceiver consist of a direct digital synthesizer for RF carrier generation and a demodulator unit comprised of a resistive bridge coupled with an envelope detector, a filter, and an amplifier. In this work, we build and study the sensor at the radial artery, thorax, carotid artery, and supraorbital locations of a healthy human subject, which hold clinical significance in evaluating cardiovascular health. The carrier frequency is tuned at the resonance of the spiral resonator, which is 34.5 ± 1.5 MHz. The resulting transient waveforms from the demodulator indicate the presence of hemodynamic events, i.e., systolic upstroke, systolic peak, dicrotic notch, and diastolic downstroke. The preliminary results also confirm the sensor’s ability to detect multisite blood flow events noninvasively on a single wearable platform.
1 citations
References
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TL;DR: The design and implementation of the first in-band full duplex WiFi radios that can simultaneously transmit and receive on the same channel using standard WiFi 802.11ac PHYs are presented and achieves close to the theoretical doubling of throughput in all practical deployment scenarios.
Abstract: This paper presents the design and implementation of the first in-band full duplex WiFi radios that can simultaneously transmit and receive on the same channel using standard WiFi 802.11ac PHYs and achieves close to the theoretical doubling of throughput in all practical deployment scenarios. Our design uses a single antenna for simultaneous TX/RX (i.e., the same resources as a standard half duplex system). We also propose novel analog and digital cancellation techniques that cancel the self interference to the receiver noise floor, and therefore ensure that there is no degradation to the received signal. We prototype our design by building our own analog circuit boards and integrating them with a fully WiFi-PHY compatible software radio implementation. We show experimentally that our design works robustly in noisy indoor environments, and provides close to the expected theoretical doubling of throughput in practice.
2,084 citations
"Sensitive transmit receive architec..." refers methods in this paper
...This interference cancelation technique allows to obtain a clean signal with the information of the pulse rate and variability [4, 6, 8]....
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TL;DR: This paper explores the use of dry/noncontact electrodes for clinical use by first explaining the electrical models for dry, insulated and noncontact electrodes and show the performance limits, along with measured data and an extensive review of the latest dry electrode developments in the literature.
Abstract: Recent demand and interest in wireless, mobile-based healthcare has driven significant interest towards developing alternative biopotential electrodes for patient physiological monitoring. The conventional wet adhesive Ag/AgCl electrodes used almost universally in clinical applications today provide an excellent signal but are cumbersome and irritating for mobile use. While electrodes that operate without gels, adhesives and even skin contact have been known for many decades, they have yet to achieve any acceptance for medical use. In addition, detailed knowledge and comparisons between different electrodes are not well known in the literature. In this paper, we explore the use of dry/noncontact electrodes for clinical use by first explaining the electrical models for dry, insulated and noncontact electrodes and show the performance limits, along with measured data. The theory and data show that the common practice of minimizing electrode resistance may not always be necessary and actually lead to increased noise depending on coupling capacitance. Theoretical analysis is followed by an extensive review of the latest dry electrode developments in the literature. The paper concludes with highlighting some of the novel systems that dry electrode technology has enabled for cardiac and neural monitoring followed by a discussion of the current challenges and a roadmap going forward.
879 citations
"Sensitive transmit receive architec..." refers background in this paper
...With the advancement of body wearable physiologic sensors and information technology, physicians and health professionals are able to monitor the health of patients, diagnose and identify critical health problems [2]....
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TL;DR: Aortic pulse wave velocity (PWV) and augmentation index are independent predictors of adverse cardiovascular events, including mortality as discussed by the authors, which can be obtained from both central (aortic) and peripheral (radial artery) pressure waveforms, but absolute values of wave reflection amplitude and wasted left ventricular (LV) pressure energy can only be extracted from the central arterial pressure waveform.
878 citations
"Sensitive transmit receive architec..." refers background or methods in this paper
...In this case, the H-slot is placed on the wrist in a way that the length of the slot is perpendicular to the three arteries (radial and ulnar) [7]....
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...In real conditions, as the blood flows through the wrist, it varies the diameter of the radial and ulnar arteries [7] and the effective permittivity in the region changes....
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TL;DR: This paper reviews recent advances in biomedical and healthcare applications of Doppler radar that remotely detects heartbeat and respiration of a human subject and reviews different architectures, baseband signal processing, and system implementations.
Abstract: This paper reviews recent advances in biomedical and healthcare applications of Doppler radar that remotely detects heartbeat and respiration of a human subject. In the last decade, new front-end architectures, baseband signal processing methods, and system-level integrations have been proposed by many researchers in this field to improve the detection accuracy and robustness. The advantages of noncontact detection have drawn interests in various applications, such as energy smart home, baby monitor, cardiopulmonary activity assessment, and tumor tracking. While many of the reported systems were bench-top prototypes for concept verification, several portable systems and integrated radar chips have been demonstrated. This paper reviews different architectures, baseband signal processing, and system implementations. Validations of this technology in a clinical environment will also be discussed.
625 citations
"Sensitive transmit receive architec..." refers background in this paper
...Miniaturized bio-medical sensors along with advanced signal processing techniques are becoming less expensive, reliable and accurate [1]....
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TL;DR: It is confirmed that PPG provides accurate interpulse intervals from which HRV measures can be accurately derived in healthy subjects under ideal conditions, suggesting this technique may prove a practical alternative to ECG for HRV analysis.
Abstract: Measures of heart rate variability (HRV) are widely used to assess autonomic nervous system (ANS) function. The signal from which they are derived requires accurate determination of the interval between successive heartbeats; it can be recorded via electrocardiography (ECG), which is both non-invasive and widely available. However, methodological problems inherent in the recording and analysis of ECG traces have motivated a search for alternatives. Photoplethysmography (PPG) constitutes another means of determining the timing of cardiac cycles via continuous monitoring of changes in blood volume in a portion of the peripheral microvasculature. This technique measures pulse waveforms, which in some instances may prove a practical basis for HRV analysis. We investigated the feasibility of using earlobe PPG to analyse HRV by applying the same analytic process to PPG and ECG recordings made simultaneously. Comparison of 5-minute recordings demonstrated a very high degree of correlation in the temporal and frequency domains and in nonlinear dynamic analyses between HRV measures derived from PPG and ECG. Our results confirm that PPG provides accurate interpulse intervals from which HRV measures can be accurately derived in healthy subjects under ideal conditions, suggesting this technique may prove a practical alternative to ECG for HRV analysis. This finding is of particular relevance to the care of patients suffering from peripheral hyperkinesia or tremor, which make fingertip PPG recording impractical, and following clinical interventions known to introduce electrical artefacts into the electrocardiogram.
250 citations
"Sensitive transmit receive architec..." refers methods in this paper
...In [3], it has been shown that PPG recordings provide accurate interpulse intervals and hence can be used to estimate heart rate...
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