146 research outputs found
An Efficient Probabilistic Algorithm to Detect Periodic Patterns in Spatio-Temporal Datasets
No full textAuthor Contributions: Conceptualization, C.G.-S.; methodology, C.G.-S.; software, C.G.-S.; validation, C.G.-S., P.G. and M.A.P.; formal analysis, C.G.-S.; investigation, C.G.-S., P.G. and M.A.P.; data curation, C.G.-S.; writing—original draft preparation, C.G.-S., P.G. and M.A.P.; writing—review and editing, M.A.P.; funding acquisition, C.G.-S. and M.A.P. All authors have read and agreed to the published version of the manuscript.Peer reviewe
An Algorithmic Readout Approach for Thermal Conductivity Based CO2 Sensors
No full textThis thesis presents a new approach to reading out thermal-conductivity-based gas sensors. This method is intended for the readout of a CMOS compatible resistive thermal-conductivity transducer for indoor CO2 sensing applications, without requiring precision off-chip components. Instead of accurately regulating the power dissipated in the transducer and measuring its temperature, the temperature and power dissipation are both measured using an algorithmic approach. A high-resolution ADC digitizes the voltage drop across the transducer and the current through it, measured using an on-chip reference resistor. Moreover, by digitizing several base-emitter voltages of an on-chip bipolar transistor, a precision bandgap voltage reference is constructed in the digital domain, and accurate information about the ambient temperature is obtained, which is used to temperature compensate the voltage reference and the reference resistor. Thus, all necessary ingredients are obtained to calculate the power dissipation and temperature of the transducer, from which the thermal conductivity of the surrounding air, and hence CO2 concentration, can be obtained. A prototype integrated circuit implementing this readout approach has been realized in 0.16um CMOS. It has been tested in a climate chamber in combination with a platinum resistor mimicking the transducer. The digitally-constructed voltage reference has a temperature coefficient of 9ppm/°C, while ambient temperature is sensed with accuracy of ±0.2°C, with a resolution of 0.15°C. The resistance readings have an inaccuracy ranging between -1mOhms to 4mOhms on a nominal resistance of about 100Ohms (-10ppm - 40ppm) with a resolution of around 2mOhms in the temperature range from 10°C to 40°C; for the power measurements, the circuit achieved an accuracy between -0.03% and 0.06%, with an 800nW of resolution (in the same temperature range) which is one order of magnitude better than results presented in previous work. Although no CO2 measurements have been performed, an estimated thermal resistance accuracy of around 2862ppm with a resolution of 155.64[K/W] should be possible, which would enable detection of the CO2 levels in the air with an accuracy of around 0.72% and a resolution of 7705ppm.Electronic InstrumentationMicroelectronicsElectrical Engineering, Mathematics and Computer Scienc
Multi-sensor Read-out Circuit with Temperature, Capacitance and Voltage Sensing Functionalities
No full textElectrical Engineering, Mathematics and Computer ScienceMicroelectronic
Capacitive Sensor Interface Using an Inverter-Based Period Modulator
No full textThis thesis discusses the basic principles, circuit implementation and measurements of an inverter-based capacitive-sensor interface based on period modulation. The interface employs an inverter-based OTA and comparator to increase the current efficiency. Moreover, it applies new circuit techniques to reduce the die size and to reduce noise. A prototype interface has been implemented in a 0.16 ?m CMOS process to prove these concepts. The measurement results show that it can achieve more than 10 bit resolution consuming 14 ?A from a 1 V supply. The die size and energy efficiency have improved by more than an order-of-magnitude compared to previous interfaces based on period modulation.MicroElectronicsMicro-electronics and Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Energy-Efficient Capacitive-Sensor Interfaces
No full textThis thesis describes the theory, design and realization of energy-efficient capacitive-sensor interfaces that are dedicated to energy-constrained applications. The goal of this work is to explore energy-efficient capacitive-sensor interface design techniques both at the system and the circuit level.Department of Micro-electronics and Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Energy-efficient readout of resonant sensors
No full textThis thesis discusses the theory, architecture and circuit design and measurements of an ultra-low-energy prototype interface circuit for a resonant gas sensor in standard 0.35-?m CMOS technology. A transient measurement method is used here. The resonant sensor is driven at a frequency close to its resonance frequency by an excitation source that can be intermittently disconnected causing the sensor oscillation amplitude to decay exponentially. From the ring-down signal, the frequency of the freely oscillating sensor and the quality factor are obtained. Test chips are fabricated to measure the resonance frequency and quality factor of the resonant sensor using ring-down measurement approach. The obtained results(resonance frequency and quality factor) show good consistency compared with what we obtained using an alternative approach (impedance analysis). The circuit consumes an energy of 237nJ per measurement.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Integrated Readout Circuit for Cross-Correlation Based Ultrasonic Ranging
No full textDistance measurement using ultrasonic waves is employed in a wide range of industrial applications. In this thesis our main goal is to investigate the possibility of processing ultrasonic signals with a ??-modulator and to process its bitstream output signal with the cross-correlation technique, while being independent of the transducer that is used. A compact chip has been designed in a 0.5 ?m CMOS process for the readout of the transducer. We present simulation results that show that the system is able to accurately estimate the distance to a target when low-Q transducers are used. Furthermore, we present measurement results in which we show that the system is able to determine the zero-crossings of the received echo with a resolution of 0.169 mm.Electrical engineeringMicroelectronicsElectrical Engineering, Mathematics and Computer Scienc
An Energy-Efficient Reconfigurable Interface for Resonant Sensors Based On Ring-Down Measurement
No full textThis thesis discusses the theory, architecture design, circuit design and measurements of an ultra-low-energy reconfigurable interface circuit for resonant gas sensors. This interface circuit employs a transient measurement method. The resonant sensor is driven at a frequency close to its resonance frequency by an excitation source that is intermittently disconnected, causing the sensor to oscillate at its resonance frequency with an exponentially-decaying amplitude. From the associated ring-down signal, the frequency of the freely-oscillating sensor and its quality factor are obtained by means of a counting technique. A prototype readout circuit that senses the ring-down signal and performs the required level-crossing detection has been fabricated in a standard 0.35-?m CMOS technology. The experimental results obtained using this prototype in combination with samples of micro-machined clamped-clamped beam resonators show good consistency with the resonance frequency and quality factor obtained using conventional impedance analysis. Compared to prior implementations, the realized prototype is less sensitive to leakage currents, enabling a shorter measurement time, and provides a reconfigurable front-end circuit that allows it to be connected to resonators with different parameters. The circuit consumes an energy of 207.9nJ per measurement.MicroelectronicsMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Low-Power Readout IC for a PMUT-based bladder scanner
No full textElectrical Engineering, Mathematics and Computer ScienceMicroelectronic
Energy-Efficient Self-Timed Zero-Crossing-Based Incremental Delta-Sigma ADC
No full textMicroelectronicsMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
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