Bolometers

Infrared Detectors and technologies are very important for a wide range of applications, not only for Military but also for various civilian applications. Comparatively fast bolometers can provide large quantities of low cost devices opening up a new era in infrared technologies. This book deals with various aspects of bolometer developments. It covers bolometer material aspects, different types of bolometers, performance limitations, applications and future trends. The chapters in this book will be useful for senior researchers as well as beginning graduate students

Statics and dynamics of electrothermal micromirrors

Adaptive and smart systems are growing in popularity as we shift toward personalization as a culture. With progressive demands on energy efficiency, it is increasingly important to focus on the utilization of energy in a novel way. This thesis investigates a microelectromechanical system (MEMS) mirror with the express intent to provide flexibility in solid state lighting (SSL). By coupling the micromirror to an optical source, the reflected light may be reshaped and directed so as to optimize the overall illumination profile. In addition, the light may be redirected in order to provide improved signal strength in visible light communications (VLC) with negligible impact on energy demands. With flexibility and full analog control in mind, the design of a fully integrated tip-tilt-piston micromirror with an additional variable focus degree of freedom is outlined. Electrothermal actuators are used to both steer the light and tune the focal length. A detailed discussion of the underlying physics behind composite beams and thermal actuators is addressed. This leads directly into an overview of the two main mirror components, namely the segmented mirror and the deflection actuators. An in-depth characterization of the dynamics of the mirror is discussed including the linearity of the thermal response. Frequency domain analysis of such a system provides insight into tunable mechanical properties such as the resonant frequency and quality factor. The degenerate resonant modes can be separated significantly. It is shown that the frequency response may be tuned by straining specific actuators and that it follows a predictable pattern. As a result, the system can be scanned at increasingly large angles. In other words, coupled mechanical modes allow variable damping and amplification. A means to determine the level of coupling is examined and the mode shape variations are tracked as a function of the tuning parameters. Finally, the applications of such a device are explored and tested. Such applications include reliable signal-to-noise ratio (SNR) enhancements in VLC of 30 dB and color tunable steerable lights using laser diodes. A brief discussion of the implications of dynamic illumination and tunable systems is juxtaposed with an explanation behind the integration of an electrothermal micromirror and an all digital driver

Current-mode processing based Temperature-to-Digital Converters for MEMS applications

This thesis presents novel Temperature-to-Digital Converters (TDCs) designed and fabricated in CMOS technology. These integrated smart temperature sensing circuits are widely employed in the Micro-Electro-Mechanical Systems (MEMS) field in order to mitigate the impact of the ambient temperature on their performance. In this framework, the increasingly stringent demands of the market have led the cost-effectiveness specification of these compensation solutions to an higher and higher level, directly translating into the requirement of more and more compact designs (< 0.1 mm²); in addition to this, considering that the great majority of the systems whose thermal drift needs to be compensated is battery supplied, ultra-low energy-per-conversion (< 10 nJ) is another requirement of primary importance. This thesis provides a detailed description of two different test-chips (mas fuerte and es posible) that have been designed with this orientation and that are the result of three years of research activity; for both devices, the conception, design, layout and testing phases are all described in detail and are supported by simulation and measurement results.This thesis presents novel Temperature-to-Digital Converters (TDCs) designed and fabricated in CMOS technology. These integrated smart temperature sensing circuits are widely employed in the Micro-Electro-Mechanical Systems (MEMS) field in order to mitigate the impact of the ambient temperature on their performance. In this framework, the increasingly stringent demands of the market have led the cost-effectiveness specification of these compensation solutions to an higher and higher level, directly translating into the requirement of more and more compact designs (< 0.1 mm²); in addition to this, considering that the great majority of the systems whose thermal drift needs to be compensated is battery supplied, ultra-low energy-per-conversion (< 10 nJ) is another requirement of primary importance. This thesis provides a detailed description of two different test-chips (mas fuerte and es posible) that have been designed with this orientation and that are the result of three years of research activity; for both devices, the conception, design, layout and testing phases are all described in detail and are supported by simulation and measurement results

Integrated reference circuits for low-power capacitive sensor interfaces

This thesis consists of nine publications and an overview of the research topic, which also summarizes the work. The research described in this thesis concentrates on the design of low-power sensor interfaces for capacitive 3-axis micro-accelerometers. The primary goal throughout the thesis is to optimize power dissipation. Because the author made the main contribution to the design of the reference and power management circuits required, the overview part is dominated by the following research topics: current, voltage, and temperature references, frequency references, and voltage regulators. After an introduction to capacitive micro-accelerometers, the work describes the typical integrated readout electronics of a capacitive sensor on the functional level. The readout electronics can be divided into four different functional parts, namely the sensor readout itself, signal post-processing, references, and power management. Before the focus is shifted to the references and further to power management, different ways to realize the sensor readout are briefly discussed. Both current and voltage references are required in most analog and mixed-signal systems. A bandgap voltage reference, which inherently uses at least one current reference, is practical for the generation of an accurate reference voltage. Very similar circuit techniques can be exploited when implementing a temperature reference, the need for which in the sensor readout may be justified by the temperature compensation, for example. The work introduces non-linear frequency references, namely ring and relaxation oscillators, which are very suitable for the generation of the relatively low-frequency clock signals typically needed in the sensor interfaces. Such oscillators suffer from poor jitter and phase noise performance, the quantities of which also deserve discussion in this thesis. Finally, the regulation of the supply voltage using linear regulators is considered. In addition to extending the battery life by providing a low quiescent current, the regulator must be able to supply very low load currents and operate without off-chip capacitors

Design and Simulation of Micro-Bolometer in MEMS Technology

Tato diplomová práce zkoumá problematiku detektoru infračerveného záření nazývaného bolometr. Cílem je pokrok v detekci infračerveného záření použitím odlišné absorpční vrstvy modifikovanou karbonovými nanotrubicemi. V teoretické části jsou uvedeny základní fyzikální pojmy z problematiky teplotního managmentu a základních fyzikálních vztahů bolometru. Design bolometru je představen a popsán. Teplotně mechanické simulace předvídají chování bolometru při detekci infračerveného záření. PSpice model je vytvořen a kombinuje termální a elektrické vlastnosti čipu bolometru. Dále je uveden proces výroby bolometru, které je detailně popsán.This master thesis studies the infrared detector called bolometer. The task is to improve the infrared detection by using different type of absorption layer modified by the carbon nanotubes. In theoretical part there are basic terms of thermal engineering and basics definitions of bolometer physics. The bolometer design is presented and described. The thermal mechanical simulations are evaluating the operation behavior. PSpice model of bolometer is created combing the thermal and electrical properties of the bolometer chip. The fabrication process is then presented and detailed described.

MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

System design of a low-power three-axis underdamped MEMS accelerometer with simultaneous electrostatic damping control

Recently, consumer electronics industry has known a spectacular growth that would have not been possible without pushing the integration barrier further and further. Micro Electro Mechanical Systems (MEMS) inertial sensors (e.g. accelerometers, gyroscopes) provide high performance, low power, low die cost solutions and are, nowadays, embedded in most consumer applications. In addition, the sensors fusion has become a new trend and combo sensors are gaining growing popularity since the co-integration of a three-axis MEMS accelerometer and a three-axis MEMS gyroscope provides complete navigation information. The resulting device is an Inertial measurement unit (IMU) able to sense multiple Degrees of Freedom (DoF). Nevertheless, the performances of the accelerometers and the gyroscopes are conditioned by the MEMS cavity pressure: the accelerometer is usually a damped system functioning under an atmospheric pressure while the gyroscope is a highly resonant system. Thus, to conceive a combo sensor, aunique low cavity pressure is required. The integration of both transducers within the same low pressure cavity necessitates a method to control and reduce the ringing phenomena by increasing the damping factor of the MEMS accelerometer. Consequently, the aim of the thesis is the design of an analog front-end interface able to sense and control an underdamped three-axis MEMSaccelerometer. This work proposes a novel closed-loop accelerometer interface achieving low power consumption The design challenge consists in finding a trade-off between the sampling frequency, the settling time and the circuit complexity since the sensor excitation plates are multiplexed between the measurement and the damping phases. In this context, a patenteddamping sequence (simultaneous damping) has been conceived to improve the damping efficiency over the state of the art approach performances (successive damping). To investigate the feasibility of the novel electrostatic damping control architecture, several mathematical models have been developed and the settling time method is used to assess the damping efficiency. Moreover, a new method that uses the multirate signal processing theory and allows the system stability study has been developed. This very method is used to conclude on the loop stability for a certain sampling frequency and loop gain value. Next, a 0.18μm CMOS implementation of the entire accelerometer signal chain is designed and validated