S. Garcia-Alonso

Low power voltage limiter design for a full passive UHF RFID sensor

This paper presents a low power voltage limiter design that avoids possible damages in the circuits of the analog front-end of the RFID sensor due to voltage surges whenever reader and tag are very close. The proposed voltage limiter design takes advantage of the implemented bandgap reference and voltage regulator in order to provide low temperature and process deviation of the limiting voltage. The measured limiting voltage is 2.9V with a voltage variation of only +/−0.025V for the four measured dies. The current consumption is only 150nA when the reader and the tag are far away one to each other, not limiting the sensitivity of the tag due to an undesired consumption in the voltage limiter. The circuit is implemented on a low cost 2P4M 0.35µm CMOS technology.

Low-power MEMS pressure sensor for wireless biomedical applications

Reducing power consumption leads to improve wireless sensor autonomy, increase battery life, and reduce radiated power. State-of-the-art blood pressure sensors based on piezoresistive transducers in a full Wheatstone bridge configuration uses low ohmic values because high sensitivity and low noise approach. In this work, the piezoresistance values are increased in order to reduce one order of magnitude the power consumption. The noise introduced by this improvement was proved that does not limit the accuracy for 8-bit applications. Therefore, a low power consumption pressure sensor with high sensitivity and low noise is proposed. Power consumption versus sensitivity tradeoff is analyzed in detail.

Multi-objective genetic algorithms applied to low power pressure microsensor design

Purpose – The purpose of this paper is to explain in detail the optimization of the sensitivity versus the power consumption of a pressure microsensor using multi-objective genetic algorithms. Design/methodology/approach – The tradeoff between sensitivity and power consumption is analyzed and the Pareto frontier is identified by using NSGA-II, AMGA-II and ɛ-MOEA methods. Findings – Comparison results demonstrate that NSGA-II provides optimal solutions over the entire design space for spread metric analysis, and AMGA-II is better for convergence metric analysis. Originality/value – This paper provides a new multiobjective optimization tool for the designers of low power pressure microsensors.

Electro‐Quasistatic Analysis of an Electrostatic Induction Micromotor Using the Cell Method

An electro-quasistatic analysis of an induction micromotor has been realized by using the Cell Method. We employed the direct Finite Formulation (FF) of the electromagnetic laws, hence, avoiding a further discretization. The Cell Method (CM) is used for solving the field equations at the entire domain (2D space) of the micromotor. We have reformulated the field laws in a direct FF and analyzed physical quantities to make explicit the relationship between magnitudes and laws. We applied a primal-dual barycentric discretization of the 2D space. The electric potential has been calculated on each node of the primal mesh using CM. For verification purpose, an analytical electric potential equation is introduced as reference. In frequency domain, results demonstrate the error in calculating potential quantity is neglected (<3‰). In time domain, the potential value in transient state tends to the steady state value.

New Constitutive Matrix in the 3D Cell Method to Obtain a Lorentz Electric Field in a Magnetic Brake

In this work, we have obtained a new constitutive matrix to calculate the induced Lorentz electric current of in a conductive disk in movement within a magnetic field using the cell method in 3D. This disk and a permanent magnet act as a magnetic brake. The results obtained are compared with those obtained with the finite element method (FEM) using the computer applications Getdp and femm. The error observed is less than 0.1173%. Likewise, a second verification has been made in the laboratory using Hall sensors to measure the magnetic field in the proximity of the magnetic brake.

Generation of New Detection Codes for GPS Satellites Using NSGA-II

In this paper we obtain new detection codes, to determine whether a GPS satellite in particular is visible, using NSGA-II as multi-objective optimization engine. Our approach takes into consideration the length of the code and the sampling frequency in comparison with other approaches found in the literature that fix those design parameters. The obtained new detection codes produce an improvement of the 19 % in terms of CPU execution time. Results demonstrate that both design parameters must be taken in consideration to obtain high quality detection codes.

Optimization of the Dimensionless Model of an Electrostatic Microswitch Based on AMGA Algorithm

In this paper a micro genetic algorithm for multi-objective optimization (AMGA) is used to minimize the number of function evaluations of the dimensionless model of an electrostatic microswitch. A non-dimensional dynamic model is proposed, and three objective functions are defined: the closing dimensionless time of the first impact, the maximum dimensionless speed and the maximum dimensionless displacement of the first impact. This work has been carried out using dimensional analysis. Results demonstrate an interesting methodology based on AMGA for optimizing the closing time and displacement of the first impact in a microswitch.

Lite GPS pseudo-code generation using genetic algorithms

Purpose – In a global positioning system (GPS) receiver, one of the most time-consuming tasks is to identify and track the visible satellites. The paper aims to propose and examine in detail new and shorter identification patterns or lite pseudo-codes – pseudo-random numbers (PRNs) – that allow GPS receivers to reduce dramatically the computational effort to identify and track GPS satellites. Obtaining lite pseudo-codes is a multi-objective optimization problem that the paper resolves using genetic algorithms (GAs). Design/methodology/approach – The lite PRNs are obtained by using NSGA-II and omni-optimizer multi-objective optimization techniques. Findings – The new PRNs obtained with the proposed single/multi-objective solutions are always better than previously presented when the highest detection peak (DP) is required for the GPS receiver. Originality/value – Results demonstrate that the problem of “obtaining lite pseudo-codes” is a multi-objective optimization problem. In other words, the solutions ob...

Wireless and batteryless blood pressure sensor

A low-power invasive blood pressure transducer has been designed. It is based on a structure of four high resistive strain gauges in a full Wheatstone bridge configuration. For obtaining the required sensitivity, the gauge was allocated performing a careful mechanical simulation of the membrane behaviour. The electronic conditioning circuit and the ADC were optimized to compensate the noise introduced by the high resistive gauges. A batteryless RFID tag designed to incorporate and to supply the sensor was fabricated and measured. It power supplies the sensor at a distance longer than 50 cm from a standard reader, while the reported ranges —to the best of our knowledge— are shorter than 10 cm. This wireless and batteryless sensor is especially suitable for surgery rooms and intensive care units.

Analysis of spatial harmonics in a polyphase electrostatic induction micromotor

This paper analyzes the influence on the force density of the spatial harmonics of the excitation voltage signal on each electrode of an electrostatic induction micromotor. We have used the lumped parametric equivalent circuit [7] and demonstrated that the spatial harmonics are attenuated from stator to rotor.