A compact current-mode instrumentation amplifier for general-purpose sensor interfaces

The proposed amplifier architecture follows a consolidated topology based on second-generation current conveyors (CCIIs), optimized for fully-differential operation. The architecture uses gain-boosting to improve the offset and noise characteristics of a recently proposed design. Wide input and output ranges and high accuracy are obtained by designing the CCIIs according to an original two-stage architecture with local voltage feedback. Embedding of chopper switch matrices into the amplifier enables vector analysis of the input signal, expanding the application field. The main strengths of the proposed amplifier are compactness and versatility. Measurements performed on a prototype designed with a 0.18 μm CMOS process are described

Solid state neutron dosimeter for space applications

Personnel engaged in space flight are exposed to significant flux of high energy neutrons arising from both primary and secondary sources of ionizing radiation. Presently, there exist no compact neutron sensor capable of being integrated in a flight instrument to provide real time measurement of this radiation flux. A proposal was made to construct such an instrument using special PIN silicon diode which has the property of being insensitive to the other forms of ionizing radiation. Studies were performed to determine the design and construction of a better reading system to allow the PIN diode to be read with high precision. The physics of the device was studied, especially with respect to those factors which affect the sensitivity and reproducibility of the neutron response. This information was then used to develop methods to achieve high sensitivity at low neutron doses. The feasibility was shown of enhancing the PIN diode sensitivity to make possible the measurement of the low doses of neutrons encountered in space flights. The new PIN diode will make possible the development of a very compact, accurate, personal neutron dosimeter

Measurement of the magnetic field of an RF-encoding birdcage-coil design for magnetic resonance imaging

Magnetic Resonance Imaging (MRI) is a non-invasive imaging technique used in radiology to investigate the anatomy and physiology of the body in both health and disease. MRI currently depends on the use of magnetic field gradient coils to visualize tissue. However, there is an alternate method, which can only use RF to encode the image. The idea behind RF encoding is that it uses spatial phase variation in the RF transmission to encode spatial information in the MRI signal instead of using gradient magnetic fields. This alternate method of encoding with RF, without magnetic field gradients, allows for a much simpler hardware configuration for the MRI device. Therefore, it could become possible to design a cheaper and lighter portable MRI. In this study, a measurement device was designed and constructed for a DC model of an RF encoding birdcage coil design. When the appropriate currents were applied onto the legs of the coil, a magnetic field was generated as quantified by the Biot-Savart law. Herein we presumed that the wires are infinitely long. These currents were calculated according to the RF phase encoding method, aimed to produce a linear varying phase mapping along with one axis. By using the constructed measurement device, the experimental phase profile could be obtained. It was found that a linear spatial phase variation occurs along the axis, with the RF birdcage-coil setup. By comparing the theoretical phase map with the experimental, the difference was quantified. Then, we could reach the conclusion that the proposed RF coil design works as predicted by theory

Biotelemetry of the triaxial ballistocardiogram and electrocardiogram in a weightless environment

Biotelemetry of triaxial ballistocardiogram and electrocardiogram in weightless environmen

FIBRE OPTIC COUPLED, INFRARED THERMOMETERS FOR PROCESSES INCURRING HARSH CONDITIONS

This study undertook the development and testing of fibre optic coupled infrared thermometers (IRTs) that could substitute for thermocouples in harsh conditions that would affect contact temperature measurements deleteriously. The IRTs have been configured without photodiode cooling and signal chopping but achieved low minimum measurable temperatures, fast responses and good sensitivities. IRTs were configured with mid-wave infrared (MWIR) and short-wave infrared (SWIR) photodiodes, to measure over different temperature ranges. The thermometers had small footprints, therefore could be installed into constrained spaces and not cause interference with the process. The MWIR thermometers were substituted for thermocouples in high temperature conditions in end milling tool temperature measurements and reactive electrochemical conditions in Lithium-ion cell temperature measurements. The conditions into which the fibre optics were embedded would lead to inaccurate measurements from thermocouples, whereas the fibre optic and remotely positioned IRT offered immunity against these errors. Calibration drift is a major problem that afflicts thermocouple temperature measurements. There has been progress towards addressing this weakness with improved thermocouples. The SWIR thermometer used a zero drift operational amplifier to minimise offset voltage, drift and noise. The IRT was coupled to a sapphire fibre optic probe that had tin deposited onto the core to form an integral fixed point temperature calibration cell. This low drift IRT provided an increment towards creating a drift-free, self-calibrating IRT that would substitute for thermocouples with integral calibration capabilities. The feasibility of substituting thermocouples with embedded fibre optics coupled to IRTs has been demonstrated and potential improvements of these thermometers have been identified

CMOS Design of Reconfigurable SoC Systems for Impedance Sensor Devices

La rápida evolución en el campo de los sensores inteligentes, junto con los avances en las tecnologías de la computación y la comunicación, está revolucionando la forma en que recopilamos y analizamos datos del mundo físico para tomar decisiones, facilitando nuevas soluciones que desempeñan tareas que antes eran inconcebibles de lograr.La inclusión en un mismo dado de silicio de todos los elementos necesarios para un proceso de monitorización y actuación ha sido posible gracias a los avances en micro (y nano) electrónica. Al mismo tiempo, la evolución de las tecnologías de procesamiento y micromecanizado de superficies de silicio y otros materiales complementarios ha dado lugar al desarrollo de sensores integrados compatibles con CMOS, lo que permite la implementación de matrices de sensores de alta densidad. Así, la combinación de un sistema de adquisición basado en sensores on-Chip, junto con un microprocesador como núcleo digital donde se puede ejecutar la digitalización de señales, el procesamiento y la comunicación de datos proporciona características adicionales como reducción del coste, compacidad, portabilidad, alimentación por batería, facilidad de uso e intercambio inteligente de datos, aumentando su potencial número de aplicaciones.Esta tesis pretende profundizar en el diseño de un sistema portátil de medición de espectroscopía de impedancia de baja potencia operado por batería, basado en tecnologías microelectrónicas CMOS, que pueda integrarse con el sensor, proporcionando una implementación paralelizable sin incrementar significativamente el tamaño o el consumo, pero manteniendo las principales características de fiabilidad y sensibilidad de un instrumento de laboratorio. Esto requiere el diseño tanto de la etapa de gestión de la energía como de las diferentes celdas que conforman la interfaz, que habrán de satisfacer los requisitos de un alto rendimiento a la par que las exigentes restricciones de tamaño mínimo y bajo consumo requeridas en la monitorización portátil, características que son aún más críticas al considerar la tendencia actual hacia matrices de sensores.A nivel de celdas, se proponen diferentes circuitos en un proceso CMOS de 180 nm: un regulador de baja caída de voltaje como unidad de gestión de energía, que proporciona una alimentación de 1.8 V estable, de bajo ruido, precisa e independiente de la carga para todo el sistema; amplificadores de instrumentación con una aproximación completamente diferencial, que incluyen una etapa de entrada de voltaje/corriente configurable, ganancia programable y ancho de banda ajustable, tanto en la frecuencia de corte baja como alta; un multiplicador para conformar la demodulación dual, que está embebido en el amplificador para optimizar consumo y área; y filtros pasa baja totalmente integrados, que actúan como extractores de magnitud de DC, con frecuencias de corte ajustables desde sub-Hz hasta cientos de Hz.<br /

CMOS design of chaotic oscillators using state variables: a monolithic Chua's circuit

This paper presents design considerations for monolithic implementation of piecewise-linear (PWL) dynamic systems in CMOS technology. Starting from a review of available CMOS circuit primitives and their respective merits and drawbacks, the paper proposes a synthesis approach for PWL dynamic systems, based on state-variable methods, and identifies the associated analog operators. The GmC approach, combining quasi-linear VCCS's, PWL VCCS's, and capacitors is then explored regarding the implementation of these operators. CMOS basic building blocks for the realization of the quasi-linear VCCS's and PWL VCCS's are presented and applied to design a Chua's circuit IC. The influence of GmC parasitics on the performance of dynamic PWL systems is illustrated through this example. Measured chaotic attractors from a Chua's circuit prototype are given. The prototype has been fabricated in a 2.4- mu m double-poly n-well CMOS technology, and occupies 0.35 mm/sup 2/, with a power consumption of 1.6 mW for a +or-2.5-V symmetric supply. Measurements show bifurcation toward a double-scroll Chua's attractor by changing a bias current