Jean-François Naviner

Designing a programmable analog signal conditioning circuit without loss of measurement range

Programmable analog signal conditioning circuits can be programmed in the field to permit their use in several applications with a variety of sensors with different output signal characteristics. The digital programming of the gain and dc level shift of a conditioning circuit can affect the measurement resolution and cause a reduction in the range of the measuring system in which it is employed. For a specified maximum acceptable loss in the measurement resolution, a procedure for defining and employing the programming values that guarantees the full measurement range is proposed. The proposed methodology takes into account practical implementation considerations and can be employed for designing either discrete or integrated circuits.

Design and prototyping of a /spl Sigma//spl Delta/ decimator filter for DECT standard

Deals with the design and prototyping of a decimation filter for DECT standard. Efficient implementation is obtained with a careful design of the filter and an FPGA structure oriented VHDL modelling, reducing power computation and routing needs. A filter prototype has been implemented in a programmable Altera circuit FLEX10K20.

Analog to digital conversion: technical aspects

An ideal radio communication receiver places the analog to digital conversion just after the antenna. It is an objective in a “software radio” perspective. The available silicon technologies do not provide the performance required by this application. We are able to evaluate the present limits and the gap between these limits and the ideal solution proposed. In this paper, we describe the present possibilities in terms of receiver architectures and we deduce theAdc specifications. Then we analyse differentAdc architectures adapted to this application. The choice is mainly between pipeline and sigma- deltaAdc. We compare them in terms of power consumption and we introduce a factor of merit. The future technologies will have an impact onAdc performance. Superconductor technology applied toAdc may be a solution and it is analysed at the end of this paper.RésuméPour la radio logicielle, la place idéale de la conversion analogique numérique est située juste après l’antenne de réception. Les technologies silicium disponibles ne permettent pas d’atteindre les performances imposées par une telle application. Nous pouvons évaluer les limites actuelles et avoir une idée du chemin qu’il reste à parcourir pour atteindre cette solution idéale. Dans cet article, nous présentons les possibilités offertes aujourd’hui par les architectures de récepteur et nous déduisons les spécifications duCan. Puis les diffé -rentes architectures de convertisseur adaptées à cette application sont analysées. Le choix doit se faire principalement entre les convertisseurs pipeline et sigma- delta. II est intéressant de les comparer en terme de puissance consommée. Connaître l’impact des technologies futures sur les performances de convertisseurs permet de montrer leur évolution dans les années à venir. La technologie des supraconducteurs appliquée à la conversion sera peut- être une solution et est envisagée à la fin de cet article.

Compensation of Mismatch Electrodes Impedances in Biopotential Measurement

The electric energy system power (50 or 60Hz) interference is one of the main noise sources in the biopotential measurement processes at the patient body surface. Even considering the use of high input impedance instrumentation amplifiers and high common mode rejection ratio (CMRR) values, the electrodes impedances mismatch implies common mode (noises) signals appearance that are amplified by the differential gain. Band-reject filters can be used for these interference signals attenuation. However, the interference frequency source can vary, becoming necessary the use of auto-tuner filters. Moreover, when the noise frequency is inside the signal frequency band that we are measuring, the use of this filter type can provoke the loss of important data from a clinical patient evaluation

Programmable gain and de level shift analog signal conditioning circuit: Microcontroller based implementation

Programmable analog conditioning circuits are very important for instrumentation systems since the same circuit can be used for different type of sensors. The main functions that must be provided for the analog conditioning circuit are gain and dc level shift. The conditioning circuit must be optimized, especially for systems on chip, in order to use reduced number of components, area and costs. In this work, we propose an architecture for a programmable gain and dc level shift circuit based on a procedure that yields the smallest set of passive components while guaranteeing the design specified performance in terms of maximum loss of resolution and no measurement range loss

Architectures of anemometers using the electric equivalence principle

Being an important parameter in the measurement of pulmonary function, the resistance of the respiratory tract is given by the relation between the pressure variation and the airflow variation measured near the patients mouth. The airflow determination may be accomplished by measuring the velocity of the respiratory stream with the aid of a hot-wire sensor. Due to its small dimensions, this type of sensor does not produce significant increase of mechanical resistance to the patients respiratory airflow. Furthermore, the sensor will be submitted to less contamination by the substances composing the respiratory fluid. In this paper, we present an evaluation of circuits employing constant temperature hot-wire sensors, in response to both fluid velocity steps and respiratory airflow in patients at rest.

Measurement system gain and DC level shift programming

An analysis of the effects of programming the gain and DC level shift in a conditioning circuit on the effective resolution and measurement range is carried out for a measurement system with configurable signal conditioning circuits. This analysis can be applied when designing such systems using discrete elements or integrated circuits. An example to illustrate the proposed analysis procedure is also presented.

Quantization effects in the resolution of the measurand in a measurement system

An analysis of the quantization errors propagation in a generic measurement system and a methodology to estimate the best resolution of A/D converters to obtain the desired resolution of the system, are presented in this paper. As application of the methodology, analysis of measurement systems using different sensors are presented.

Impact of charge injection on system-level performance of a discrete-time GSM receiver

The impact of charge injection on system-level performance of discrete-time systems is studied. A new model for MOS switches is derived from Y-parameter simulation and validated with less than 1% difference in respect to transistor. It is a SPICE-based model that helps analog system designers to predict the effects of charge injection on circuit performance. In this work, the model is tested on a discrete-time GSM receiver. The functions analyzed are the mixer stage and the channel selection filter. Results showed extra 0.5 dB side-band attenuation and 0.6 dB less out-of-band rejection in the frequency response of the filter stage.

A reconfigurable architecture suitable for adaptive multi-resolution processing

This work deals with adaptive multi-resolution processing. We present an adaptive filter bank structure for sub-band splitting of signals in order to match the system requirements. Reconfiguration of the filter bank is carried out according to an evolutionary algorithm. The architecture is designed to allow a dynamic reconfiguration of the number and the width of each sub-band.