Our researchers

Héctor Solar Ruiz

Departamento de Ingeniería Eléctrica y Electrónica
Escuela de Ingeniería (TECNUN). Universidad de Navarra

Most recent scientific publications (since 2010)

Authors: del Río Orduña, David (Autor de correspondencia); Gurutzeaga Zubillaga, Iñaki; Beriain Rodríguez, Andoni; et al.
ISSN 1531-1309  Vol. 29  Nº 5  2019  pp. 351 - 353
This letter presents the design of a compact, wideband, and high-efficiency E-band power amplifier, integrated in a 0.13-mu m BiCMOS process and occupying 0.3 mm(2). It consists of a single-stage balanced amplifier, with HBT transistors in cascode configuration. The power amplifier (PA) is biased in class AB, with a dc consumption of 156 mW. A compact bias circuit is employed to achieve temperature robustness, while the layout is optimized for wideband and highly efficient operation. Measurements show a peak power gain of 15.3 dB at 83 GHz, with a 29.3% fractional bandwidth and less than 1-dB degradation over a 25 degrees C-85 degrees C temperature range. The peak output power at saturation and 1-dB compression is 18.6 and 13.6 dBm, respectively, and the maximum power-added efficiency (PAE) is 30.7%.
Authors: Villa, F., (Autor de correspondencia); Cortes, I.; Urain, A.; et al.
ISSN 1045-9243  Vol. 61  Nº 4  2019  pp. 90 - 96
This article presents the design of a complete radio system receiver to detect, in real time, the direction of arrival (DOA) of an incoming industrial, scientific, and medical (ISM)-band signal at 5.8 GHz. When a transmitter continuously sends a binary phase-shift keying (BPSK), modulated pseudo-noise (PN) code, the receiver estimates the DOA based on the received signal strength (RSS) and performs the channel sounding. The device that we describe includes a pattern-reconfigurable monopole antenna array, a front end, and a systemon-module (SOM). The SOM controls the antenna's main lobe direction by positive-intrinsic-negative (p-i-n) diode switching, configures the front-end modules, completes the data acquisition, and performs the digital signal processing (DSP) for the DOA estimation. The system has an average DOA resolution of 90° in the horizontal plane, with a success rate higher than 90%. It is presented as an educational platform for electrical engineering undergraduate and M.S. degree students.
Authors: Jauregi, I.; Solar Ruiz, Héctor; Beriain Rodríguez, Andoni; et al.
ISSN 1530-437X  Vol. 17  Nº 5  2017  pp. 1471 - 1478
The number of wireless medical wearables has increased in recent years and is revolutionizing the current healthcare system. However, the state-of-the-art systems still need to be improved, as they are bulky, battery powered, and so require maintenance. On the contrary, battery-free wearables have unlimited lifetimes, are smaller, and are cheaper. This paper describes a design of a battery free wearable system that measures the skin temperature of the human body while at the same time collects energy from body heat. The system is composed of an UHF RFID temperature sensor tag located on the arm of the patient. It is assisted with extra power supply from a power harvesting module that stores the thermal energy dissipated from the neck of the patient. This paper presents the experimental results of the stored thermal energy, and characterizes the module in different conditions, e.g., still, walking indoors, and walking outdoors. Finally, the tag is tested in a fully passive condition and when it is power assisted. Our experimental results show that the communication range of the RFID sensor is improved by 100% when measurements are done every 750 ms and by 75% when measurements are done every 1000 ms when the sensor is assisted with the power harvesting module.
Authors: del Río Orduña, David; Gurutzeaga Zubillaga, Iñaki; Solar Ruiz, Héctor; et al.
ISSN 0167-9260  Vol. 52  2016  pp. 208 - 216
This paper describes a method to design mmW PAs, by modeling the electromagnetic behavior of all the passive structures and the layout interconnections using a 3D-EM solver. It allows the optimization of the quality factor of capacitors (Q-factors > 20 can be obtained at 80 GHz), the access points and arrangement of the power transistor cells. The method is applied to the design and optimization of an E-Band PA implemented in a 55 nm SiGe BiCMOS technology. The PA presents a maximum power gain of 21.7 dB at 74 GHz, with a 3-dB bandwidth covering from 72.6 to 75.6 GHz. The maximum output P1dB is 13.8 dBm at 75 GHz and the peak PAE is 14.1%. (C) 2015 Elsevier B.V. All rights reserved.
Authors: Beriain Rodríguez, Andoni (Autor de correspondencia); Gutiérrez García, Íñigo; Solar Ruiz, Héctor; et al.
Journal: SENSORS
ISSN 1424-8220  Vol. 15  Nº 9  2015  pp. 21554 - 21566
This paper presents an ultra low-power and low-voltage pulse-width modulation based ratiometric capacitive sensor interface. The interface was designed and fabricated in a standard 90 nm CMOS 1P9M technology. The measurements show an effective resolution of 10 bits using 0.5 V of supply voltage. The active occupied area is only 0.0045 mm(2) and the Figure of Merit (FOM), which takes into account the energy required per conversion bit, is 0.43 pJ/bit. Furthermore, the results show low sensitivity to PVT variations due to the proposed ratiometric architecture. In addition, the sensor interface was connected to a commercial pressure transducer and the measurements of the resulting complete pressure sensor show a FOM of 0.226 pJ/bit with an effective linear resolution of 7.64 bits. The results validate the use of the proposed interface as part of a pressure sensor, and its low-power and low-voltage characteristics make it suitable for wireless sensor networks and low power consumer electronics.
Authors: Solar Ruiz, Héctor; Fernández Escudero, Erik; Tartarisco, G; et al.
ISSN 2190-7188  Vol. 3  Nº 2  2013  pp. 99 - 109
Authors: Fernández Escudero, Erik; Beriain Rodríguez, Andoni; Solar Ruiz, Héctor; et al.
ISSN 0026-2692  Vol. 43  Nº 10  2012  pp. 708 - 713
This paper presents a low power voltage limiter design for avoiding possible damages in the analog front-end of a RFID sensor due to voltage surges whenever readers and tags are close. The proposed voltage limiter design takes advantage of the implemented bandgap reference and voltage regulator blocks in order to provide low deviation of the limiting voltage due to temperature variation and process dispersion. The measured limiting voltage is 2.9 V with a voltage deviation of only +/- 0.065 V for the 12 measured dies. The measured current consumption is only 150 nA when the reader and the tag are far away, 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 0.35 mu m CMOS technology. (C) 2012 Elsevier Ltd. All rights reserved.
Authors: Gonzalez, J.; Solar Ruiz, Héctor; Adin Marcos, Íñigo; et al.
ISSN 0018-9480  Vol. 59  Nº 9  2011  pp. 2318 - 2330
A decreasing-sized pi-model electrostatic discharge (ESD) protection structure is presented and applied to protect against ESD stresses at the RF input pad of an ultra-low power CMOS front-end operating in the 2.4-GHz industrial-scientific-medical band. The proposed ESD protection structure is composed of a pair of ESD devices located near the RF pad, another pair close to the core circuit, and a high-quality integrated inductor connecting these two pairs. This structure can sustain a human body-model ESD level higher than 16 kV and a machine-model ESD level higher than 1 kV without degrading the RF performance of the front-end. A combined on-wafer transmission line pulse and RF test methodology for RF circuits is also presented confirming previous results. The front-end implements a zero-IF receiver. It has been implemented in a standard 2P6M 0.18-mu m CMOS process. It exhibits a voltage gain of 24 dB and a single-sideband noise figure of 8.4 dB, which make it suitable for most of the 2.4-GHz wireless short-range communication transceivers. The power consumption is only 1.06 mW from a 1.2-V voltage supply.
Authors: Solar Ruiz, Héctor; Bistue García, Guillermo; Legarda Macón, Jon; et al.
ISSN 1751-8725  Vol. 5  Nº 7  2011  pp. 795 - 803
A model for fully integrated CMOS linear power amplifiers (PAs) is presented. The model predicts the performance of the CMOS PA in terms of power-added efficiency (PAE) and output power (P-OUT) with respect to the main design parameters, such as supply voltage, current consumption, gain and inductor quality factors (Qs). In order to demonstrate the usefulness of the model, several studies showing the impact of these design parameters on the PA performance are presented. Finally, a 0.18 mu m fully integrated CMOS PA has been fabricated and compared with the model, showing good agreement. The fabricated PA presents 23 dBm of 1 dB compression point (P-1dB) and 27 dBm of saturated power (P-SAT) at 4.2 GHz with high maximum PAE of 32%.
Authors: Vaz Serrano, Alexander José; Ubarrechena Belandia, Aritz; Zalbide Aguirrezabalaga, Ibon; et al.
ISSN 1549-7747  Vol. 57  Nº 2  2010  pp. 95 - 99
A long-range UHF RF identification (RFID) sensor has been designed using a 0.35-mu m CMOS standard process. The power-optimized tag, combined with the ultralow-power temperature sensor, allows an ID and a temperature reading range of 2 m from a 2-W effective radiated power output power reader. The temperature sensor is based on a ring oscillator, where the temperature dependence of the oscillation frequency is used for thermal sensing. The temperature sensor exhibits a resolution of 0.035 degrees C and an inaccuracy value lower than 0.1 degrees C in the range from 35 degrees C to 45 degrees C after two-point calibration. The average power consumption of the temperature sensor is only 110 nW at ten conversions per second while keeping a high resolution and accuracy. These properties allow the use of the RFID as a batteryless sensor in a wireless human body temperature monitoring system.
Authors: Cranny, A.; Beriain Rodríguez, Andoni; Solar Ruiz, Héctor; et al.
Book title:  Systems Design for Remote Healthcare
2014  pp. 55 - 92
The four physiological measures of body temperature, pulse rate, respiration rate and blood pressure have for a long time been considered as vital signs in the diagnosis of a patient¿s health. It is also widely accepted that the routine measurement of other physiological or biological signals, possibly pathology specific, would help considerably in diagnosis and early stage treatment. Such measurements might include, for example, heart activity, brain activity, blood glucose level or mobility. Furthermore, the development of portable systems that can make a number of different health related measurements would prove beneficial in the monitoring of patients during treatment, recovery or rehabilitation. Technologies and instruments that can make these measurements have existed for some time, but factors such as their cost, lack of portability and in some instances, a requirement for expert knowledge, have restricted their wide scale use. Today, however, advances in information technology, communications and microfabrication techniques have made possible the realisation of truly portable systems for the measurement of a wide range of physiological signs at any medical intervention. This chapter describes the sensing technologies and systems currently being developed, or that are in use, for the measurement of a new, larger range of vital signs
Authors: Solar Ruiz, Héctor; Berenguer Pérez, Roque José
The work establishes the design flow for the optimization of linear CMOS power amplifiers from the first steps of the design to the final IC implementation and tests. The authors also focuses on design guidelines of the inductor¿s geometrical characteristics for power applications and covers their measurement and characterization. Additionally, a model is proposed which would facilitate designs in terms of transistor sizing, required inductor quality factors or minimum supply voltage. The model considers limitations that CMOS processes can impose on implementation. The book also provides different techniques and architectures that allow for optimization.

Teaching experience