Solar-Ruiz, H. (Hector)
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- A 22-m operation range semi-passive UHF RFID sensor tag with flexible thermoelectric energy harvester.(IEEE, 2022-10) Solar-Ruiz, H. (Hector); Del-Rio-Orduña, D. (David); Berenguer-Pérez, R.J. (Roque José); Beriain, A. (Andoni); Rezola-Garciandia, A. (Ainhoa)This article presents a wireless temperature sensor tag able to work in both fully passive mode and in semi-passive mode when assisted by a flexible thermoelectric generator (TEG). The sensor tag consists of an EPC C1G2/ISO 18000-6C ultrahigh-frequency (UHF) radio frequency identification (RFID) integrated circuit (IC) connected to a low-power microcontroller unit (MCU) that samples and collects the temperature from a digital temperature sensor. With a temperature gradient as low as 2.5 degrees C, the test results show that the TEG provides an output power of 400 mu W with an output voltage of 40 mV. By means of an up-converter in order to boost the TEG output voltage, this harvester supplies the power required to the sensor tag for a 2-conv/s data rate in semi-passive mode. Moreover, when the tag operates in semi-passive mode, a communication range of 22.2 m is measured for a 2-W effective radiated power (ERP) reader. To the best of our knowledge, the proposed TEG-assisted sensor tag shows the longest communication range and the only one that provides stable external power at low-temperature gradients. The measured performance and the chosen architecture allow using the wireless sensor in multiple industrial or biomedical applications
- Power management unit for solar energy harvester assisted batteryless wireless sensor node.(MDPI, 2022-10) Solar-Ruiz, H. (Hector); Berenguer-Pérez, R.J. (Roque José); Lopez-Gasso, A. (Alberto); Beriain, A. (Andoni)This work describes an energy-efficient monolithic Power Management Unit (PMU) that includes a charge pump adapted to photovoltaic cells with the capability of charging a large supply capacitor and managing the stored energy efficiently to provide the required supply voltage and power to low energy consumption wireless sensor nodes such as RFID sensor tags. The proposed system starts-up self-sufficiently with a light source luminosity equal to or higher than 500 lux using only a 1.42 cm(2) solar cell and integrating an energy monitor that gives the ability to supply autonomous sensor nodes with discontinuous operation modes. The system occupies an area of 0.97 mm(2) with a standard 180 nm CMOS technology. The half-floating architecture avoids losses of charging the top/button plate of the stray capacitors in each clock cycle. Measurements' results on a fabricated IC exhibit an efficiency above 60% delivering 13.14 mu W over 1.8 V. The harvested energy is enough to reach the communication range of a standard UHF RFID sensor tag up to 21 m.
- A 5.8-GHz-Direction of an arrival localization radio system with a reconfigurable monopole antenna array.(IEEE, 2019-08) Solar-Ruiz, H. (Hector); Villa-González, F. (Fátima); Urain, A. (Alvaro); Cortés-Vidal, I. (Iñigo); Valderas Gazquez, D.(Daniel)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.
- A high accuracy 3.1V voltage limiter for enabling high performance RFID sensor applications.(IEEE, 2019) Solar-Ruiz, H. (Hector); Del-Rio-Orduña, D. (David); Berenguer-Pérez, R.J. (Roque José); Beriain, A. (Andoni); Gurutzeaga-Zubillaga, I. (Iñaki); Rezola-Garciandia, A. (Ainhoa)This paper presents a low power voltage limiter design that avoids possible damages in the analog front-end of a RFID sensor due to voltage surges whenever the tag gets close to the reader. The proposed voltage limiter design takes advantage of the implemented bandgap reference block in order to provide a highly accurate limiting voltage in spite of temperature variation and process dispersion. The measured limiting voltage is 3.1V while showing a low current consumption of 100nA when the reader and the tag are far away, so that the sensitivity of the tag is not impacted due to an undesired consumption in the voltage limiter. The circuit is implemented in a low cost 180nm CMOS technology.
- 0.5 V and 0.43 pJ/bit capacitive sensor interface for passive wireless sensor systems.(MDPI, 2015-09) Solar-Ruiz, H. (Hector); Berenguer-Pérez, R.J. (Roque José); Beriain, A. (Andoni); Gutierrez, I. (Íñigo)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 mm2 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.
- A compact, wideband, and temperature robust 67-90-GHz SiGe power amplifier with 30% PAE(IEEE, 2019-05) Solar-Ruiz, H. (Hector); Del-Rio-Orduña, D. (David); Berenguer-Pérez, R.J. (Roque José); Beriain, A. (Andoni); Gurutzeaga-Zubillaga, I. (Iñaki)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%.