Sensor Front-end Research Articles

An FPGA-Based High-Speed Error Resilient Data Aggregation and Control for High Energy Physics Experiment

Due to the dramatic increase of data volume in modern high energy physics (HEP) experiments, a robust high-speed data acquisition (DAQ) system is very much needed to gather the data generated during different nuclear interactions. As the DAQ works under harsh radiation environment, there is a fair chance of data corruption due to various energetic particles like alpha, beta, or neutron. Hence, a major challenge in the development of DAQ in the HEP experiment is to establish an error resilient communication system between front-end sensors or detectors and back-end data processing computing nodes. Here, we have implemented the DAQ using field-programmable gate array (FPGA) due to some of its inherent advantages over the application-specific integrated circuit. A novel orthogonal concatenated code and cyclic redundancy check (CRC) have been used to mitigate the effects of data corruption in the user data. Scrubbing with a 32-b CRC has been used against error in the configuration memory of FPGA. Data from front-end sensors will reach to the back-end processing nodes through multiple stages that may add an uncertain amount of delay to the different data packets. We have also proposed a novel memory management algorithm that helps to process the data at the back-end computing nodes removing the added path delays. To the best of our knowledge, the proposed FPGA-based DAQ utilizing optical link with channel coding and efficient memory management modules can be considered as first of its kind. Performance estimation of the implemented DAQ system is done based on resource utilization, bit error rate, efficiency, and robustness to radiation.

An Energy-Efficient Miniaturized Intracranial Pressure Monitoring System

A miniaturized pressure-sensing microsystem targeting intracranial pressure monitoring is presented. The system takes full advantage of Invensense MEMS-CMOS process to heterogeneously integrate the sensor and interface. This integration type requires no fabrication postprocessing and results in sub-pF sensor-interface parasitic interconnection capacitance C, which is an order of magnitude smaller than previously reported C,s. Since energy efficiency is of main concern, the minimum energy consumption for maintaining a certain signal-to-noise ratio (SNR) is analytically calculated and compared for two energy-efficient sensor front ends, namely, the switched-capacitor (SC) capacitance-to-voltage converter (CVC) and the successive approximation register (SAR) capacitance-to-digital converter (CDC). The comparison reveals for small values of C, and for low-to-moderate SNR, the SAR CDC outperforms the SC CVC in terms of power consumption. Heterogeneous integration of sensor and CMOS electronics results in only 720 fF of C, which enables direct SAR capacitance-to-digital conversion. Correlated double sampling is also integrated into the proposed SAR switching scheme to combat 1/f noise and the input-referred offset voltage of the comparator. The entire pressure-sensing system measures 2.2 × 2.6 × 0.4 mm 3 in size, consumes 130 nW at 60-Hz sampling rate, and obtains 57-dB SNR with 0.2% sensor-electronics combined linearity over 520-mmHg pressure range.

A Mobile-Based High Sensitivity On-Field Organophosphorus Compounds Detecting System for IoT-Based Food Safety Tracking

A mobile-based high sensitivity absorptiometer is presented to detect organophosphorus (OP) compounds for Internet-of-Things based food safety tracking. This instrument consists of a customized sensor front-end chip, LED-based light source, low power wireless link, and coin battery, along with a sample holder packaged in a recycled format. The sensor front-end integrates optical sensor, capacitive transimpedance amplifier, and a folded-reference pulse width modulator in a single chip fabricated in a 0.18 μm 1-poly 5-metal CMOS process and has input optical power dynamic range of 71 dB, sensitivity of 3.6 nW/cm2 (0.77 pA), and power consumption of 14.5 μW. Enabled by this high sensitivity sensor front-end chip, the proposed absorptiometer has a small size of 96 cm3, with features including on-field detection and wireless communication with a mobile. OP compound detection experiments of the handheld system demonstrate a limit of detection (LOD) of 0.4 μmol/L, comparable to that of a commercial spectrophotometer. Meanwhile, an android-based application (APP) is presented which makes the absorptiometer access to the Internet-of-Things (IoT).

Advanced Wireless Sensor Nodes - MSFC

IMAPS Device Packaging Conference 2017 Engineered Micro Systems & Devices Track Advanced Wireless Sensor Nodes - MSFC Abstract Kosta Varnavas NASA / Marshall Space Flight Center NASA field center Marshall Space Flight Center (Huntsville, AL), has invested in advanced wireless sensor technology development. Developments for a wireless microcontroller back-end were primarily focused on the commercial Synapse Wireless family of devices. These devices have many useful features for NASA applications, good characteristics and the ability to be programmed Over-The-Air (OTA). The effort has focused on two widely used sensor types, mechanical strain gauges and thermal sensors. Mechanical strain gauges are used extensively in NASA structural testing and even on vehicle instrumentation systems. Additionally, thermal monitoring with many types of sensors is extensively used. These thermal sensors include thermocouples of all types, resistive temperature devices (RTDs), diodes and other thermal sensor types. The wireless thermal board will accommodate all of these types of sensor inputs to an analog front end. The analog front end on each of the sensors interfaces to the Synapse wireless microcontroller, based on the Atmel Atmega128 device. Once the analog sensor output data is digitized by the onboard analog to digital converter (A/D), the data is available for analysis, computation or transmission. Various hardware features allow custom embedded software to manage battery power to enhance battery life. This technology development fits nicely into using numerous additional sensor front ends, including some of the low-cost printed circuit board capacitive moisture content sensors currently being developed at Auburn University.

A 7 μW Offset- and Temperature-Compensated pH-to-Digital Converter

This paper demonstrates a micropower offset- and temperature-compensated smart pH sensor, intended for use in battery-powered RFID systems that monitor the quality of perishable products. Low operation power is essential in such systems to enable autonomous logging of environmental parameters, such as the pH level, over extended periods of time using only a small, low-cost battery. The pH-sensing element in this work is an ion-sensitive extended-gate field-effect transistor (EGFET), which is incorporated in a low-power sensor front-end. The front-end outputs a pH-dependent voltage, which is then digitized by means of a co-integrated incremental delta-sigma ADC. To compensate for the offset and temperature cross-sensitivity of the EGFET, a compensation scheme using a calibration process and a temperature sensor has been devised. A prototype chip has been realized in a 0.16 μm CMOS process. It occupies 0.35 × 3.9 mm2 of die area and draws only 4 μA from a 1.8 V supply. Two different types of custom packaging have been used for measurement purposes. The pH sensor achieves a linearity of better than ±0.1 for pH values ranging from 4 to 10. The calibration and compensation scheme reduces errors due to temperature cross-sensitivity to less than ±0.1 in the temperature range of 6°C to 25°C.

Implementation of Cloud BIM-based Platform Towards High-performance Building Services

In this research effort, we aim to develop an advanced integrated platform between FM, BIM, BMS, and front-end sensor data visualization. We first assessed of the status quo, conceptual design of the platform components and configuration, and identified the LoD. Subsequently, the BMS and environmental sensing information were incorporated into the BIM-based platform. Such information categories include the building geometry, indoor air quality, energy generation and consumption. This integrated BIM-based platform is exemplified in one existing low-rise zero energy office building in Tropics as a demonstration and pilot study. In this research effort, the platform to link different types of building information system and the visualization of front-end data in the phase of building operation and maintenance was developed. Also, the implementation process of this BIM-based platform together with a user-friendly dashboard for ease of O&M was demonstrated. The research results are expected to serve as the solid basis towards larger scale and comprehensive platform development.

A 0.5 V 55 $\mu \text{W}$ 64 $\times $ 2 Channel Binaural Silicon Cochlea for Event-Driven Stereo-Audio Sensing

This paper presents a $64 \times 2$ channel stereo-audio sensing front end with parallel asynchronous event output inspired by the biological cochlea. Each binaural channel performs feature extraction by analog bandpass filtering, and the filtered signal is encoded into events via asynchronous delta modulation (ADM). The channel central frequencies $f_{0}$ are geometrically scaled across the human hearing range. Two design techniques are highlighted to achieve the high system power efficiency: source-follower-based bandpass filters (BPFs) and asynchronous delta modulation (ADM) with adaptive self-oscillating comparison. The chip was fabricated in 0.18 $\mu \text{m}$ 1P6M CMOS, and occupies an area of $10.5 \times 4.8$ mm2. The core cochlea system operating under a 0.5 V power supply consumes 55 $\mu \text{W}$ at an output rate of 100k event/s. The measured range of $f_{0}$ is from 8 Hz to 20 kHz, and the BPF quality factor ${Q}$ can be tuned from 1 to almost 40. The 1 $\sigma $ mismatch of $f_{0}$ and ${Q}$ between two ears is 3.3% and 15%, respectively, across all channels at ${Q}\approx $ 10. Reconstruction of speech input from the event output of the chip is performed to validate the information integrity in event-domain representation, and vowel discrimination is demonstrated as a simple application using histograms of the output events. This type of silicon cochlea front end targets integration with embedded event-driven processors for low-power smart audio sensing with classification capabilities, such as voice activity detection and speaker identification.

Electric Hum Signal Readout Circuit for Touch Screen Panel Applications

This paper presents a new touch sensing mechanism that detects different signals on a touch panel generated by an electric field formed from household power. Without requiring complicated transmitter and receiver circuits, a 16-channel front-end sensor and shared readout circuits are proposed to realize the new touch-sensing mechanism. This touch-sensing technique can be applied on the appliance control panel to detect the operation control. The signal readout circuit is implemented in a 0.18-µm CMOS process, which occupied an area of 2.64 mm2. The proposed sensing technique achieves 46.5-dB signal-to-noise ratios with finger touch. With battery power supply of 1.8 V and 2.5 V, total power consumption of the proposed readout circuit is measured as just 2 mW.

A DNA hybridization detection sensor based on photo biased ZnO thin film FET devices

Purpose The purpose of this paper is to present a DNA hybridization detection sensor. An inexpensive fabrication procedure was used so that the sensors can be disposed economically after the measurement is completed. Design/methodology/approach Field effect transistor (FET) devices are used in the proposed structure. The FET device acts as a charge detection element and produces an amplified output current based on surface charge variations. As amplification is performed directly at the sensor frontend, noise sources have less effect on the detected signal, and thus, acceptably low DNA concentrations can be detected with simple external electronics. ZnO nano layers are used as the FET active semiconductor channel. Furthermore, a photobiasing approach is used to adjust the operating point of the proposed FET without the need for an additional gate terminal. Findings The proposed sensor is evaluated by applying matched and unmatched target DNA fragments on the fabricated sensors with capture probes assembled either directly on the ZnO surface or on a nano-platinum linker layer. It is observed that the presented approach can successfully detect DNA hybridization at the nano mole range with no need for complex laboratory measurement devices. Originality/value The presented photobiasing approach is effective in the adjustment of the sensor sensitivity and decreases the fabrication complexity of the achieved sensor compared with previous works.

Silicon Carbide Fully Differential Amplifier Characterized Up to 500 °C

This paper presents a monolithic fully differential amplifier implemented in a low-voltage 4H-silicon carbide bipolar junction transistor technology. The circuit has been designed, considering the variation of device parameters over a large temperature range. A base-current compensation technique has been applied to overcome the low input resistance of the amplifier. The bare chip of the amplifier has been measured from 27 °C to 500 °C using a hot-chuck probe station. Its open-loop gain is 58 dB at 27 °C, and monotonically decreases to 37 dB at 500 °C. Its closed-loop gain reduction is $\sim 5$ dB over the investigated temperature range. The gain-bandwidth product drops from 2.8 MHz at 27 °C to 1.3 MHz at 500 °C with 470 pF off-chip compensation capacitors. A low total-harmonic-distortion of −58.4 dB at 27 °C and −46.9 dB at 500 °C is achieved due to the fully differential implementation. A low input offset voltage of 0.5 mV at 27 °C and 6.9 mV at 500 °C is achieved without calibration. The relative high linearity and the low offset demonstrate the potential of this technology to be further investigated for the front-end sensor circuits in high-temperature applications.

An Auditory Nerve Stimulation Chip with Integrated AFE, Sound Processing, and Power Management for Fully Implantable Cochlear Implants.

This paper presents a system on chip for a fully implantable cochlear implant. It includes acoustic sensor front-end, 4-channel digital sound processing and auditory nerve stimulation circuitry. It also features a digital, switched mode, single inductor dual output power supply that generates two regulated voltages; 0.4 V used to supply on-chip digital blocks and 0.9 V to supply analog blocks and charge the battery when an external RF source is detected. All passives are integrated on-chip including the inductor. The system was implemented in 14nm CMOS and validated with post layout simulations.

A Wearable EEG-HEG-HRV Multimodal System With Simultaneous Monitoring of tES for Mental Health Management.

A multimodal mental management system in the shape of the wearable headband and earplugs is proposed to monitor electroencephalography (EEG), hemoencephalography (HEG) and heart rate variability (HRV) for accurate mental health monitoring. It enables simultaneous transcranial electrical stimulation (tES) together with real-time monitoring. The total weight of the proposed system is less than 200 g. The multi-loop low-noise amplifier (MLLNA) achieves over 130 dB CMRR for EEG sensing and the capacitive correlated-double sampling transimpedance amplifier (CCTIA) has low-noise characteristics for HEG and HRV sensing. Measured three-physiology domains such as neural, vascular and autonomic domain signals are combined with canonical correlation analysis (CCA) and temporal kernel canonical correlation analysis (tkCCA) algorithm to find the neural-vascular-autonomic coupling. It supports highly accurate classification with the 19% maximum improvement with multimodal monitoring. For the multi-channel stimulation functionality, after-effects maximization monitoring and sympathetic nerve disorder monitoring, the stimulator is designed as reconfigurable. The 3.37 × 2.25 mm(2) chip has 2-channel EEG sensor front-end, 2-channel NIRS sensor front-end, NIRS current driver to drive dual-wavelength VCSEL and 6-b DAC current source for tES mode. It dissipates 24 mW with 2 mA stimulation current and 5 mA NIRS driver current.

A Fully-Integrated CMOS LDO Regulator for Battery-Operated On-Chip Measurement Systems

This paper presents a fully-integrated 0.18 μm CMOS low drop-out (LDO) regulator designed to drive on-chip low power front-end sensor nodes. The proposed LDO is based on a simple telescopic amplifier stage with internal cascode compensation driving a PMOS pass-device, providing a high precision 1.8 V output voltage for input voltages from 3.6 V to 1.92 V up to a 50 mA load current with only 22 μA quiescent current. Line and load regulation are respectively better than 0.017 mV/V and 0.003 mV/mA, while recovery times are below 4 μs over a (-40 °C, 120 °C) temperature span.

Development of intelligent instruments with embedded HTTP servers for control and data acquisition in a cryogenic setup--The hardware, firmware, and software implementation.

The power of Ethernet for control and automation technology is being largely understood by the automation industry in recent times. Ethernet with HTTP (Hypertext Transfer Protocol) is one of the most widely accepted communication standards today. Ethernet is best known for being able to control through internet from anywhere in the globe. The Ethernet interface with built-in on-chip embedded servers ensures global connections for crate-less model of control and data acquisition systems which have several advantages over traditional crate-based control architectures for slow applications. This architecture will completely eliminate the use of any extra PLC (Programmable Logic Controller) or similar control hardware in any automation network as the control functions are firmware coded inside intelligent meters itself. Here, we describe the indigenously built project of a cryogenic control system built for linear accelerator at Inter University Accelerator Centre, known as "CADS," which stands for "Complete Automation of Distribution System." CADS deals with complete hardware, firmware, and software implementation of the automated linac cryogenic distribution system using many Ethernet based embedded cryogenic instruments developed in-house. Each instrument works as an intelligent meter called device-server which has the control functions and control loops built inside the firmware itself. Dedicated meters with built-in servers were designed out of ARM (Acorn RISC (Reduced Instruction Set Computer) Machine) and ATMEL processors and COTS (Commercially Off-the-Shelf) SMD (Surface Mount Devices) components, with analog sensor front-end and a digital back-end web server implementing remote procedure call over HTTP for digital control and readout functions. At present, 24 instruments which run 58 embedded servers inside, each specific to a particular type of sensor-actuator combination for closed loop operations, are now deployed and distributed across control LAN (Local Area Network). A group of six categories of such instruments have been identified for all cryogenic applications required for linac operation which were designed to build this medium-scale cryogenic automation setup. These devices have special features like remote rebooters, daughter boards for PIDs (Proportional Integral Derivative), etc., to operate them remotely in radiation areas and also have emergency switches by which each device can be taken to emergency mode temporarily. Finally, all the data are monitored, logged, controlled, and analyzed online at a central control room which has a user-friendly control interface developed using LabVIEW(®). This paper discusses the overall hardware, firmware, software design, and implementation for the cryogenics setup.

Concept Design for a 1-Lead Wearable/Implantable ECG Front-End: Power Management.

Power supply quality and stability are critical for wearable and implantable biomedical applications. For this reason we have designed a reconfigurable switched-capacitor DC-DC converter that, aside from having an extremely small footprint (with an active on-chip area of only 0.04 mm), uses a novel output voltage control method based upon a combination of adaptive gain and discrete frequency scaling control schemes. This novel DC-DC converter achieves a measured output voltage range of 1.0 to 2.2 V with power delivery up to 7.5 mW with 75% efficiency. In this paper, we present the use of this converter as a power supply for a concept design of a wearable (15 mm × 15 mm) 1-lead ECG front-end sensor device that simultaneously harvests power and communicates with external receivers when exposed to a suitable RF field. Due to voltage range limitations of the fabrication process of the current prototype chip, we focus our analysis solely on the power supply of the ECG front-end whose design is also detailed in this paper. Measurement results show not just that the power supplied is regulated, clean and does not infringe upon the ECG bandwidth, but that there is negligible difference between signals acquired using standard linear power-supplies and when the power is regulated by our power management chip.

Compact and Supply-Voltage-Scalable Temperature Sensors for Dense On-Chip Thermal Monitoring

This paper presents compact and voltage-scalable temperature sensor circuits for implementing dynamic thermal management (DTM) in high-performance microprocessors and Systems-on-Chips (SoC). The proposed sensor front ends require only 6 to 8 NMOS transistors, resulting in more than one order of magnitude smaller area than the previous state of the art. The sensor supply voltage can be scaled down to 0.6 V, so it can be integrated with digital circuits employing a dynamic-voltage-scaling technique without additional power distribution and regulation. Sensor front ends with three different sizes (115, 279, and $400\;\upmu {\text{m}^2}$ ) and their back ends have been prototyped in a 65 nm CMOS technology. The measurement results of the $279\;\upmu {{\rm m}^{2}}$ front end at 0.6 V show a worst-case error of 7.0° C across 64 instances 0° C to 100° C after a low-cost one-temperature-point calibration. With the same conditions, the measurements of the $400\;\upmu {{\rm m}^{2}}$ front end show a worst-case error of 5.4° C across 64 instances. The compact sensor designs make it possible to integrate an order of magnitude more sensors on a chip with little additional overhead and thereby enable very dense thermal monitoring in digital VLSI systems.

Grounding and Isolation of Sensitive Measurement Equipment for Arc Flash Testing at High-Power Laboratory

It is often necessary to place sensitive measurement equipment in high-power laboratories when conducting tests for arc flash research. However, direct contact or induced voltage from an arcing test can have serious consequences for testing equipment, particularly for sensitive measurement equipment, and therefore, thorough consideration of grounding or isolation schemes is required to ensure accuracy of the measurement and survivability of the equipment. Traditionally, grounding and isolation systems at high-power laboratories are designed to prevent ground loops and remove mutual interference during signal transfer. However, for arc flash testing, front-end sensors such as copper slug-type calorimeters constantly experience exposure to high-voltage contacts throughout the test. Without a proper grounding and isolation scheme, kilovolt-level common-mode voltage surges inject into the data collection and control end, potentially destroying sensitive electronic devices and ruining measurement results. Essential to avoiding such scenarios is the adoption of adequate grounding/isolation schemes for data acquisition (DAQ) systems. This paper discusses the implementation of a robust grounding and isolation topology for the whole DAQ system. A high channel separation differential input signal conditioning circuit is applied on the transducer end to avoid common-mode surge signals from the high-voltage source; a common isolated ground power supply provides single-point reference for the whole DAQ system; a high-channel-separation analog-to-digital converter avoids crosstalk among measurement signals; and optical fiber communication between DAQ and personal computer (PC) avoids electromagnetic interference/radio frequency interference and provides an additional layer of protection to the PC and the personnel. The proposed grounding and isolation scheme has been verified in high-power-rating arc flash testing and can be also applied to DAQ systems in industrial and commercial power systems with similar environments.

Integrated electronic system for implantable sensory NFC tag.

We have designed the complete electronic system for an implanted sensory NFC-A tag (type 1) that monitors a physiological parameter, e.g. blood glucose, dehydration, bladder pressure, to name some of the target applications that we pursue. The tag is meant to be implanted under the skin and is powered by an NFC reader held close to it, such as a smart phone or a smart watch. The electronic system consists of a sensor front-end, ADC, NFC-A transceiver and NFC power harvester. In its present status, the physical layer of the communication and the power harvester have been implemented on one ASIC, and the sensor front-end and ADC on another, while the digital circuits realizing the higher level NFC protocol have been implemented on an FPGA. Simulations and a few preliminary test results are presented in this paper. The ultimate goal after thorough testing of this first prototype is to integrate all of these modules on a single ASIC.

Development of Data Acquisition Management System for ITER DC Testing Platform

To acquire multi-channel signals with 10 kHz sampling rate from various front-end sensors, a Data Acquisition Management System (DAMS) based on MDSplus was designed for the International Thermonuclear Experimental Reactor (ITER) Direct Current (DC) testing platform. Due to a large number of experimental data generated from long-pulse operation, it is very important to view and analyze experimental data online during operation. To meet the requirement of online data processing, slice storage and thumbnail technology were applied in DAMS. The long pulse data is gradually written in MDSplus database. The DAMS has been verified in the ITER DC power supply testing platform.

Trace Detection of 2, 4, 6-Trinitrotoluene Using Electrochemical Gas Sensor

In this paper, selective and sensitive detection of trace amounts of 2, 4, 6-trinitrotoluene is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensors as the detector. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors with integrated heaters were used to capture the signature of the explosive. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (down to 250 ng). The sensitivity was found to depend on the flow rate and sensor orientation. The sensitivity was found to increase with increasing flow rate. This detection technique has the potential to become an orthogonal technique to the existing explosive screening technologies for reducing the number of false positives/false negatives in a cost-effective manner.