Capillary blood pressure (CBP) is the primary driving force for fluid exchange across microvessels. Subclinical systemic venous congestion prior to overt peripheral edema can directly result in elevated peripheral CBP. Therefore, CBP measurements can enable timely edema control in a variety of clinical cases including venous insufficiency, heart failure and so on. However, currently CBP measurements can be only done invasively and with a complicated experimental setup. In this work, we proposed an opto-mechanical system to achieve non-invasive and automatic CBP measurements through modifying the widely implemented oscillometric technique in home-use arterial blood pressure monitors. The proposed CBP system is featured with a blue light photoplethysmography sensor embedded in finger/toe cuffs to probe skin capillary pulsations. The experimental results demonstrated the proposed CBP system can track local CBP changes induced by different levels of venous congestion. Leveraging the decision tree technique, we demonstrate the use of a multi-site CBP measurement at fingertips and toes to classify four categories of subjects (total N = 40) including patients with peripheral arterial disease, varicose veins and heart failure. Our work demonstrates the promising non-invasive CBP measurement as well as its great potential in realizing point-of-care systems for the management of cardiovascular diseases.

This work details the non-invasive evaluation of a carotid arterial blood pressure (ABP) waveform during the Valsalva maneuver. Unfocused and wide acoustic beams are insonated on the carotid artery to achieve motion-tolerant measurements with a simple two-element ultrasound scanner. Arterial flow and distension waveforms are reliably estimated from spectral Doppler and M-mode ultrasound images whose qualities are consistently maintained in different phases of the maneuver despite possible displacements of the artery. A local pulse wave velocity is estimated using a flow-area method, and it is then combined with the distension waveform to produce the ABP waveform. Human subject validation on seven healthy subjects shows that the bias in pulse pressure estimates across subjects is 0.47 ± 13.1 mmHg. The average root mean square deviations of the ultrasonically measured waveform across subjects is 10.1 ± 2.43 mmHg, excluding the strain phase of the Valsalva maneuver, and 17.7 ± 6.30 mmHg in all phases. The mean correlation coefficient between the ultrasonically measured and reference waveform is calculated to be 0.92 ± 0.04 across subjects. Detailed morphological features and their changes across different phases are observed as reported. This uninterrupted central ABP waveform monitoring under hemodynamics changes supports the idea of a novel stress test to evaluate the health and dynamics of the cardiovascular system at a spot check in clinical settings.

OBJECTIVE: Accurate quantification of neurodegenerative disease progression is an ongoing challenge that complicates efforts to understand and treat these conditions. Clinical studies have shown that eye movement features may serve as objective biomarkers to support diagnosis and tracking of disease progression. Here, we demonstrate that saccade latency-an eye movement measure of reaction time-can be measured robustly outside of the clinical environment with a smartphone camera. METHODS: To enable tracking of saccade latency in large cohorts of patients and control subjects, we combined a deep convolutional neural network for gaze estimation with a model-based approach for saccade onset determination that provides automated signal-quality quantification and artifact rejection. RESULTS: Simultaneous recordings with a smartphone and a high-speed camera resulted in negligible differences in saccade latency distributions. Furthermore, we demonstrated that the constraint of chinrest support can be removed when recording healthy subjects. Repeat smartphone-based measurements of saccade latency in 11 self-reported healthy subjects resulted in an intraclass correlation coefficient of 0.76, showing our approach has good to excellent test-retest reliability. Additionally, we conducted more than 19 000 saccade latency measurements in 29 self-reported healthy subjects and observed significant intra- and inter-subject variability, which highlights the importance of individualized tracking. Lastly, we showed that with around 65 measurements we can estimate mean saccade latency to within less-than-10-ms precision, which takes within 4 min with our setup. CONCLUSION AND SIGNIFICANCE: By enabling repeat measurements of saccade latency and its distribution in individual subjects, our framework opens the possibility of quantifying patient state on a finer timescale in a broader population than previously possible.

The most commonly used oscillometric upper-arm (UA) blood pressure (BP) monitors are not convenient enough for ambulatory BP monitoring, given the large size of the arm cuff and the compression of UA during the measurement. Finger-worn oscillometric BP devices featuring miniaturized finger cuff have been developed and researched as an alternative solution to the UA-based measurement, yet the reliability of the finger-based measurement is still questioned. To investigate the feasibility of oscillometric BP measurements at the finger position, we performed model-based analysis and experimental validation to explore the underlying issues associated with extending the cuff-based oscillometric approach from UA to other alternative sites. The simulation results revealed that a larger bone-to-tissue volume ratio produced a lower pressure transmission efficiency, which can account for the inter-site measurement discrepancies of mean blood pressure (MBP). We also experimentally compared the oscillometric MBP measurements at UA, middle forearm, wrist, finger proximal phalanx, and finger distal phalanx (FD) of 20 young adults, and each position was matched with a cuff of appropriate size and kept at the same height with the heart. The experimental results demonstrated that FD could be a superior alternative position for oscillometric BP measurement, as it requires the smallest cuff size while providing the most consistent MBP with the UA. Our analysis also suggested that further study is demanded to identify the appropriate oscillometric algorithm for reliable systolic blood pressure and diastolic blood pressure measurements at FD.

Eye movements can be affected by a number of neurological, neuromuscular, and neurodegenerative disorders that are important to diagnose and track longitudinally. To enable unobtrusive tracking of disease progression, we tailored and evaluated a set of candidate eye-tracking algorithms to operate on video sequences obtained from an iPhone 6, for accurate and robust determination of the time between the presentation of a visual stimulus and the beginning of the eye movement toward the stimulus (saccade latency). Additionally, we proposed a model-based method to determine the onset of the eye movement and demonstrate that the associated residual normalized root-mean-squared error can be used to automatically flag saccade tracings that should not be included in further analysis. A variant of the iTracker algorithm performs most robustly and results in mean saccade latencies and associated standard deviations on iPhone recordings that are essentially the same as those obtained from simultaneous recordings using a high-end, high-speed camera. Our results suggest that accurate and robust saccade latency determination is feasible using consumer-grade cameras and therefore might enable unobtrusive tracking of neurodegenerative disease progression.

To enable long-term medical monitoring, power consumption of the sensor nodes must be minimized. Most sensors power budgets are dominated by storing acquired data to memory or transmitting the information off the node. Body area networks (BAN) can decrease the power used by the sensor node and can be formed using body coupled communication (BCC). This paper will propose and verify an electrical model of the human body for BCC. This body model gives greater insight into how BCC works and how receiver architecture affects channel gain. Utilizing this insight the channel gain was increased by almost 20 dB. The proposed model allows for implants and explains how implants are able to transmit information outside the body using BCC. As it is important to have electrically isolated equipment to measure the BCC channel, a battery-powered wireless transmitter and receiver were created to measure the channel gain. The design of the measurement equipment is also detailed.

A low-power, wearable electrocardiogram (ECG) monitor was developed for long-term data acquisition and analysis. It was designed to maximize both comfort and ECG signal quality, and minimize obtrusiveness. The monitor consists of a central PCB that contains one electrode and most of the electronics. Two additional satellite PCBs house the remaining electrodes and buffer circuits and complete the system. It consumes 7.3 mW and can record single lead ECG for over one week under a variety of activity levels. A clinical test was performed to validate the monitor. Participants (N = 6) wore both the experimental cardiac monitor and a commercially available monitor while engaging in physical activities such as walking, stepping, and running. QRS sensitivity and QRS positive predictability were determined for each ECG waveform. The monitor performed as well or better than the commercial monitor in all interventions. It performed well even under high activity levels such as running, and may be a viable alternative to commercially available monitors.

Since the first demonstration of a comparator-based switched-capacitor circuit, analog-to-digital (A/D) converters based on virtual ground detection have made steady and significant progress. Comparators have been replaced by zero-crossing detectors, leading to the development of zero-crossing based circuits for faster speed and lower power. All facets of performance including the sampling rate, effective number of bits, noise floor, and figure-of-merit have improved substantially. This paper focuses on recent implementations of zero-crossing based A/D converters and discusses the technical issues unique to these A/D converters as well as solutions that have been developed to improve their performance and practicality. A series of prototype designs whose performance ranges from 8 bit, 200 MS/s to 12 bit, 50 MS/s are described. The ultimate low power potentials of these A/D converters are compared with various different types of complementary metal-oxide-semiconductor A/D converters from a fundamental thermal noise standpoint.

There has been burgeoning interest in wireless technologies that can use wider frequency spectrum. Technology advances, such as 802.11n and ultra-wideband (UWB), are pushing toward wider frequency bands. The analog-to-digital TV transition has made 100-250 MHz of digital whitespace bandwidth available for unlicensed access. Also, recent work on WiFi networks has advocated discarding the notion of channelization and allowing all nodes to access the wide 802.11 spectrum in order to improve load balancing. This shift towards wider bands presents an opportunity to exploit frequency diversity. Specifically, frequencies that are far from each other in the spectrum have significantly different SNRs, and good frequencies differ across sender-receiver pairs.

Wideband technologies in the unlicensed spectrum can satisfy the ever-increasing demands for wireless bandwidth created by emerging rich media applications. The key challenge for such systems, however, is to allow narrowband technologies that share these bands (say, 802.11 a/b/g/n, Zigbee) to achieve their normal performance, without compromising the throughput or range of the wideband network.

Challenges in analog-to-digital (A/D) conversion for future scaled complementary metal-oxide-semiconductor (CMOS) technologies are investigated. The analysis of a figure of merit (FOM) that accounts for energy per conversion step indicates that op-amps are one of the most significant performance bottlenecks. New mixed-signal circuit architectures, which are more suitable for A/D conversion in scaled CMOS technologies and are more energy efficient than traditional architectures, are described. These circuits sense the crossing of virtual ground with comparators or zero-crossing detectors instead of forcing the virtual ground with op-amps. The FOM derivations for the comparator and zero-crossing based circuits indicate potentially a large improvement over traditional op-amp based circuits. The designs and experimental results of analog-to-digital converters based on a prototype comparator and zero-crossing are discussed in detail.

Millimeter-wave radiation and detection offers the possibility of detecting concealed weapons. Passive imaging measures the mm-wave radiation emitted from target objects. A passive mm-wave imager and the designs affecting the overall system performance are discussed. With low power receiver architecture and SiGe ICs, a focal plane based full staring array is feasible and can provide a high thermal resolution, ~-1.1K at >10Hz frame rate.

This panel discusses the following topics. With the ongoing trend towards more and more digitization in applications ranging from multimedia to telecommunications, there is a big debate about whether there will remain a need for analog circuits in scaled technologies. Analog circuits do not seem to take advantage of nanometer CMOS; rather they suffer from it. So if the question is asked "Will analog scale?", you get conflicting opinions. One camp argues for an almost-all-digital future: analog/RF content should be limited, because it's difficult, expensive, risky, and can be done with DSP. The opposing camp counters that some critical circuits simply do not want (or need) to scale, and analog is only "risky" when you let digital designers do it. So, what is the future role of analog circuits in scaled CMOS, and can analog EDA tools help in this .

This paper introduces a digital amplitude-to-phase conversion scheme to facilitate the outphase amplifying concept, enabling the use of high efficiency, non-linear power amplifiers in linear systems. The digital implementation enables a fast and accurate amplitude-to-phase conversion by exploiting the computational capability that can be easily incorporated in today’s integrated circuits (ICs). The proposed scheme minimizes amplitude variation of the outphase signals, which reduces the gain requirement of the power amplifiers that can be traded for higher efficiency. Our analysis demonstrates that outphase amplifying can be twice as efficient as the conventional class-A power amplifiers, and is suitable for wireless systems with large peak-to-average ratios.

Battery life-time is an important performance metric for many wireless networks and there is a growing need to improve the life-time of these networks. However, system analysis is complicated by the fact that the transceiver electronics energy cost is non-negligible and often has a major impact on the battery life. This paper develops a simple metric to evaluate the energy cost of both communication protocols and circuit electronics. This metric treats the electronics energy as an overhead cost on top of the Eb/No requirement. This enables the joint optimization of system and circuit parameters for energy limited wireless transceivers with arbitrary communication protocols.

Electronic energy disorder associated within amorphous and polycrystaline molecular organic thin film structures strongly affects the macroscopic observable behavior of organic field effect transistors (OFET) and poses practical challenges to implementing OFET circuits. It has been convenient to ignore the detailed physical processes associated with this disorder and model OFET behavior as equivalent to silicon FETs, but such simplifications limit our ability to develop integrated circuit technology as they fail to predict the true integrated OFET behavior. This talk will highlight the evolution of the organic electronic circuit technology and the challenges that lay ahead, emphasizing the need for physically accurate models of device behavior as the cornerstone of any future circuit advancements.

Once upon a time there was a wise and benevolent ruler whose Law multiplied his subjects' wealth and happiness--about 2X, every couple of years, but the kingdom was divided. Those in the happy hamlet of Digital got fatter (and faster), year after year. Not so the talented artisans in the town of Analog complained constantly about "voltage headroom", "variability", "noise", "matching", "kT/C limits", the rising costs of supporting their neighbors' insatiable addiction to shrinking transistors, and how the grass looked greener just over the border, in Silicon-Germania. So, what's a King to do? Will we see billion transistor chips with integrated RF made from transistors that are 25 atoms wide? Or will the peasants in the land of Analog really revolt.

The paper describes the modelling of short-range transceivers for microsensor applications. A simple energy model is derived and used to analyze the transceiver battery life. This model takes into account energy dissipation during the start-up, receive, and transmit modes. It shows that there is a significant fixed cost in the transceiver energy consumption and this fixed cost can be driven down by increasing the data rate of the transceiver.

Many tasks performed by intelligent transportation systems involve processing of natural scenes. Wide dynamic range visible spectrum image sensors are required to achieve optimal processing performance. Recently several approaches that rely on the multiple sampling technique to achieve wide dynamic range have been presented. The behavior of a novel predictive variant of these algorithms is analyzed together with its key assumptions and limits to its performance and flexibility.

Article Share on Energy efficient Modulation and MAC for Asymmetric RF Microsensor Systems Authors: Andrew Wang Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MAView Profile , SeongHwan Cho Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MAView Profile , Charles Sodini Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MAView Profile , Anantha Chandrakasan Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MAView Profile Authors Info & Claims ISLPED '01: Proceedings of the 2001 international symposium on Low power electronics and designAugust 2001 Pages 106–111https://doi.org/10.1145/383082.383105Online:06 August 2001Publication History 133citation1,499DownloadsMetricsTotal Citations133Total Downloads1,499Last 12 Months8Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

A differential oscillator topology with an integrated resonator is presented that allows for low supply voltages and RF/microwave frequencies.On-chip, pad-to-pad bond wire inductors and noise matching techniques are used to minimize phase noise.Operation in the 1.8GHz range with a phase noise spectral dens@ of -94dBc/Hz at a 1OOkHz offset is achieved with 5mA drawn from a IV supply, and oscillation is supported down to power supply levels of 3.3mW * .-

A system design for performing low-level image processing tasks in real time is presented. The design is based on large processor-per-pixel arrays implemented using integrated circuit technology. Two integrated circuit architectures are summarized: an associative parallel processor and a parallel processor employing DRAM cells. In both architectures, the layout pitch of one-bit-wide logic is matched to the pitch of memory cells to form high-density processing element arrays. The system design features an efficient control path implementation, providing high processing element array utilization without demanding complex controller hardware. Sequences of array instructions are generated by a host computer before processing begins, then stored in a simple controller. Once processing begins, the host computer initiates stored sequences to perform pixel-parallel operations. A programming framework implemented using the C++ programming language supports application development. A prototype system employs associative parallel processor devices, a controller, and the programming framework. Three sample applications, smoothing and segmentation, median filtering, and optical flow, establish the suitability of the system for real-time image processing.

The use of switched capacitor (SC) networks as an alternative to large resistor networks for performing computations in VLSI circuits for real-time machine vision and image processing systems is investigated. A mapping can be made from any resistor network to an equivalent SC network that has the same node voltage solution in steady state. However, it takes several switching cycles for a charge to be distributed in the SC network before steady state is reached. Results indicate that SC networks can be used in moderate resolution systems (250*250 pixels) operating at video rate. A chip that implemented several switched capacitor networks for spatial smoothing of images in one dimension was fabricated and tested. The amount of spatial smoothing can be adjusted when the clocking scheme applied to the network is varied.>