Open Access
Enhanced single-stage folded cascode OTA suitable for large capacitive loads
(IEEE, 2018) López Martín, Antonio; Garde Luque, María Pilar; Algueta-Miguel, Jose M.; Cruz Blas, Carlos Aristóteles de la; Carvajal, Ramón G.; Ramírez-Angulo, Jaime; Institute of Smart Cities - ISC
An enhanced single-stage folded cascode operational transconductance amplifier able to drive large capacitive loads is presented. Circuits that adaptively bias the input differential pair and the current folding stage are employed, which provide class AB operation with dynamic current boosting and increased gainbandwidth (GBW) product. Measurement results of a test chip prototype fabricated in a 0.5-µm CMOS process show an increase in slew rate and GBW by a factor of 30 and 15, respectively, versus the class A version using the same supply voltage and bias currents. Overhead in other performance metrics is small.
Open Access
Analog lock-in amplifier design using subsampling for accuracy enhancement in GMI sensor applications
(MDPI, 2023) Algueta-Miguel, Jose M.; Beato López, Juan Jesús; López Martín, Antonio; Ciencias; Zientziak; Institute of Smart Cities - ISC; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA2005
A frequency downscaling technique for enhancing the accuracy of analog lock-in amplifier (LIA) architectures in giant magneto-impedance (GMI) sensor applications is presented in this paper. As a proof of concept, the proposed method is applied to two different LIA topologies using, respectively, analog and switching-based multiplication for phase-sensitive detection. Specifically, the operation frequency of both the input and the reference signals of the phase-sensitive detector (PSD) block of the LIA is reduced through a subsampling process using sample-and-hold (SH) circuits. A frequency downscaling from 200 kHz, which is the optimal operating frequency of the employed GMI sensor, to 1 kHz has been performed. In this way, the proposed technique exploits the inherent advantages of analog signal multiplication at low frequencies, while the principle of operation of the PSD remains unaltered. The circuits were assembled using discrete components, and the frequency downscaling proposal was experimentally validated by comparing the measurement accuracy with the equivalent conventional circuits. The experimental results revealed that the error in the signal magnitude measurements was reduced by a factor of 8 in the case of the analog multipliers and by a factor of 21 when a PSD based on switched multipliers was used. The error in-phase detection using a two-phase LIA was also reduced by more than 25%.
Open Access
Monitoring structural transformations in metamagnetic shape memory alloys by non-contact GMI technology
(IOP Publishing, 2023) Beato López, Juan Jesús; La Roca, Paulo Matías; Algueta-Miguel, Jose M.; Garayo Urabayen, Eneko; Sánchez-Alarcos Gómez, Vicente; Recarte Callado, Vicente; Gómez Polo, Cristina; Pérez de Landazábal Berganzo, José Ignacio; Ciencias; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISC; Zientziak; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Different applications based on metamagnetic shape memory alloy (MSMA) require monitoring the evolution of the martensitic transformation (MT) to optimize the actuation mechanism. To avoid interaction with the active material, a non-contact technique would be ideal. Nevertheless, non-contact detection involves complex methods like diffraction, optical analysis, or electromagnetic technology. The present work demonstrates that the MT can be monitored without interaction with the active material using a low-cost technology based on the Giant Magnetoimpedance (GMI) effect. The GMI sensor is based on a (CoFe)SiB soft magnetic wire submitted to an alternating current and whose second harmonic voltage variation allows to detect changes in the strength of the stray magnetic fields linked to the metamagnetic phase transition. The sensor has been tested using the MT of a NiMnInCo MSMA. A specific application for environmental temperature control using the non-contact GMI sensor is proposed.
Open Access
Low-power ultrasonic front-end for cargo container monitoring
(IEEE, 2019) Algueta-Miguel, Jose M.; García Oya, José Ramón; López Martín, Antonio; Cruz Blas, Carlos Aristóteles de la; Muñoz Chavero, Fernando; Hidalgo Fort, Eduardo; Institute of Smart Cities - ISC
A low-power ultrasonic communication system conceived for cargo container monitoring is presented. Two piezoelectric transducers operating at 40 kHz are used for generating and acquiring an ultrasonic signal through the metallic wall, thus establishing a non-invasive inside-outside communication that preserves the container integrity. Both transducers are fixed by means of a novel magnetic case designed for optimizing data transmission. The acoustic and electrical characteristics of the ultrasonic channel are analyzed. An experimental measurement setup based on FPGA has been implemented for comparing some basic modulation and detection schemes in terms of Bit Error Rate (BER), also considering their robustness against undesired mechanical and electromagnetic perturbations. On this basis, a compact digital DBPSK modulator using a square carrier signal is proposed. Frequency and amplitude tracking algorithms are designed for optimizing the quality and robustness of the data transmission. Finally, a low-power low-rate (up to few kbps) architecture based on the previous elements is presented. All the proposed contributions are experimentally validated.
Open Access
Energy harvesting approaches in IoT scenarios with very low ambient energy
(European Association for the Development of Renewable Energy, Environment and Power Quality (EA4EPQ), 2019) López Martín, Antonio; Algueta-Miguel, Jose M.; Matías Maestro, Ignacio; Institute of Smart Cities - ISC
The feasibility of multi-source energy harvesting in Internet of Things (IoT) scenarios with low and intermittent ambient energy is addressed. As a relevant case study, application to a smart cargo container system is analysed. The most relevant features of the main energy sources available in this target application are identified, and various transducers adapted to such sources are evaluated. Measurement results indicate that combined piezoelectric and thermoelectric generation inside cargo containers can significantly extend the battery lifetime of IoT end nodes embedded in such containers.
Open Access
Energy-efficient amplifiers based on quasi-floating gate techniques
(MDPI, 2021) López Martín, Antonio; Garde Luque, María Pilar; Algueta-Miguel, Jose M.; Beloso Legarra, Javier; González Carvajal, Ramón; Ramírez-Angulo, Jaime; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Energy efficiency is a key requirement in the design of amplifiers for modern wireless applications. The use of quasi-floating gate (QFG) transistors is a very convenient approach to achieve such energy efficiency. We illustrate different QFG circuit design techniques aimed to implement low-voltage energy-efficient class AB amplifiers. A new super class AB QFG amplifier is presented as a design example including some of the techniques described. The amplifier has been fabricated in a 130 nm CMOS test chip prototype. Measurement results confirm that low-voltage ultra low power amplifiers can be designed preserving at the same time excellent small-signal and large-signal performance.
Open Access
A lock-in amplifier for magnetic nanoparticle detection using GMI sensors
(IEEE, 2024-09-30) Algueta-Miguel, Jose M.; Beato López, Juan Jesús; López Martín, Antonio; Gómez Polo, Cristina; Ciencias; Zientziak; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Institute of Smart Cities - ISC
A digital lock-in amplifier (LIA) for contactless magnetic nanoparticle (MNP) detection using giant magnetoimpedance (GMI) sensors is presented. The proposed approach is based on the simultaneous detection of the second harmonic amplitude and phase. A Xilinx Artix-7 field-programmable gate array (FPGA) has been employed for efficiently implementing the phase-sensitive detection (PSD) and the subsequent digital processing. The analog GMI sensor interface has been designed for minimizing the dependence of the excitation current on the GMI sensor impedance, also enhancing the rejection of the parasitic second-order distortion produced by the setup. A subsampling process of the analog outputs has been applied, both increasing the effective resolution of the analog-to-digital converter (ADC) and facilitating signal recovery. The proposed system improves the MNP detection capability reported in previous works using the second harmonic amplitude. Moreover, a characterization of the phase response, which had not been previously studied in the literature, is also provided.
Open Access
Class AB amplifier with enhanced slew rate and GBW
(John Wiley & Sons, 2019) Garde Luque, María Pilar; López Martín, Antonio; Algueta-Miguel, Jose M.; Ramírez-Angulo, Jaime; González Carvajal, Ramón; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
The design of a micropower class AB operational transconductance amplifier with large dynamic current to quiescent current ratio is addressed. It is based on a compact and power-efficient adaptive biasing circuit and a class AB current follower using the Quasi-Floating Gate (QFG) technique. The amplifier has been designed and fabricated in a 0.5 um CMOS process. Simulation and measurement results show a slew rate (SR) improvement factor versus the class A version larger than 4 for the same supply voltage and bias currents, as well as enhanced small-signal performance.
Open Access
1-V 15-μW 130-nm CMOS super class AB OTA
(IEEE, 2020) López Martín, Antonio; Algueta-Miguel, Jose M.; Garde Luque, María Pilar; Carvajal, Ramón G.; Ramírez-Angulo, Jaime; Institute of Smart Cities - ISC
A super class AB recycling folded cascode amplifier in 130 nm CMOS is presented. It combines for the first time adaptive biasing of the differential input pair, nonlinear current mirrors with current starving and dynamic biasing of the cascode transistors in the output branch. Measurements using a ±0.5V supply show slew rate and gain bandwidth product improvement factors of 26 and 112 versus the conventional topology for the same bias currents, yielding the highest combined FoM to date.
Open Access
Subsampling OFDM-based ultrasonic data communication through metallic channels for monitoring of cargo containers
(IEEE, 2019) García Oya, José Ramón; Algueta-Miguel, Jose M.; García Doblado, José; Muñoz Chavero, Fernando; Hidalgo Fort, Eduardo; Baena Lecuyer, Vicente; López Martín, Antonio; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
An enhanced ultrasonic communication system based on piezoelectric transducers for monitoring of goods in cargo containers is presented. The proposed system consists of several sensors placed inside the container, whose data are collected and transmitted outside it. Data transmission is carried out by an ultrasonic communication channel, in order to avoid drilling the wall of the container. The proposed data communication system is based on the transmission of a 128-OFDM signal. This modulation has been chosen due to its robustness to channels with frequency-selective fading and its spectrum efficiency. In order to increase the signal bandwidth and to reduce the power consumption at the internal node (transmitter), the proposed system exploits the non-linearity of the metallic channel to transmit at higher resonance frequencies. Moreover, power consumption at the external node (receiver) is reduced by using a subsampling based receiver, which allows its implementation by low-cost electronics.