Hector Solar

Full Passive UHF Tag With a Temperature Sensor Suitable for Human Body Temperature Monitoring

A long-range UHF RF identification (RFID) sensor has been designed using a 0.35- ¿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°C and an inaccuracy value lower than 0.1°C in the range from 35°C to 45°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.

A 16-kV HBM RF ESD Protection Codesign for a 1-mW CMOS Direct Conversion Receiver Operating in the 2.4-GHz ISM Band

A decreasing-sized π -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-μm 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.

A low-power RF front-end for 2.5 GHz receivers

This paper presents a low power and low cost front end for a direct conversion 2.5 GHz ISM band receiver composed of a 16 kV HBM ESD protected LNA, differential Gilbert-cell mixers, and high-pass filters for DC offset cancellation. The whole front-end is implemented in a 2P6M 0.18 mum RFCMOS process. It exhibits a voltage gain of 24dB and a SSB noise figure of 8.4 dB which make it suitable for most of the 2.5 GHz wireless short-range communication transceivers. The achieved power consumption is only 1.06 mW from a 1.2V power supply.

UHF RFID Temperature Sensor Assisted With Body-Heat Dissipation Energy Harvesting

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.

Layout-aware design methodology for a 75GHz power amplifier in a 55nm SiGe technology

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 80GHz), 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 55nm SiGe BiCMOS technology. The PA presents a maximum power gain of 21.7dB at 74GHz, with a 3-dB bandwidth covering from 72.6 to 75.6GHz. The maximum output P1dB is 13.8dBm at 75GHz and the peak PAE is 14.1%. Method for layout-aware design and optimization of millimeter-wave PAs.Custom MOM capacitors with Q>20 at mm-wave frequencies are designed.The power transistor arrangement, access points and connections are optimized.The method has been applied to the design and optimization of a low-E-Band PA. Its most significant parameters (power gain, bandwidth, output 1dB compression point and efficiency) have been measured and compared to simulation results, with good agreement between them. The PA presents a maximum power gain of 21.7dB at 74GHz, and the 3-dB bandwidth covers from 72.6 to 75.6GHz. The maximum output P1dB is 13.8dBm at 75GHz, with a peak PAE at this point of 14.1%. These performance metrics are comparable to other state-of-the-art devices and make the PA capable of transmitting multi-gigabit signals over E-band wireless links.The method has been applied to the design and optimization of a low-E-Band PA.There is good agreement between simulation and measurement results.The performance metrics are comparable to other-state-of-the-art PAs.

A very low power 7.9 bit MEMS pressure sensor suitable for batteryless RFID applications

There is a strong motivation for the development of new low power sensors for wireless passive applications such as RFID. In this work, a combination of a MEMS capacitive pressure transducer and a capacitive to digital converter compatible with a sensor enabled RFID tag are presented. The MEMS transducer has been designed and fabricated using a MetalMUMPs process. Its characterization showed an output variation between 9.3 pF and 13.4 pF corresponding to a pressure variation between 0 kPa and 30 kPa, with a INL of 0,2%. On the other hand, the capacitance to digital converter has been implemented in a low cost 2P4M 0.35μm CMOS standard process. The interface measurements showed a resolution of 7.8 bit and an average power consumption of 16.56 μW. Combining both devices together with a sensor enabled RFID tag, a long range passive RFID sensor for pressure measurements up to 30 kPa could be implemented.

A robust, −40° to +150°C wireless rotor temperature monitoring system based on a fully passive UHF RFID sensor tag

A novel wireless temperature monitoring system for electric machines is presented based on fully passive UHF RFID sensor tags. The system is composed of a custom designed IC UHF RFID sensor tag connected to an external μP and ADC through a master-slave series-peripheral interface (SPI) connection. The sensing element is a NTC 10kOhm thermal resistor (-40° to 300°C). The sensor tag, which includes an optimized meander dipole antenna, an analog front-end with a power consumption of 4.3uA and a digital core, communicates the temperature value to two EM optimized PIFA antennas located inside the stator of the electrical machine. The signal received by the PIFA antennas is demodulated by a commercial 1W RFID reader. The sensor is able to sense from -40° to 150°C and robust to the presence of the high electromagnetic disturbances generated by the electrical machine. Measured data rates are higher than 1 sample per second.

Digital output MEMS pressure sensor using capacitance-to-time converter

In this paper, a MEMS capacitive pressure sensor and a capacitance to digital converter are presented. The MEMS transducer has been designed and fabricated using MetalMUMPs process from MEMSCAP. For an diaphragm area of 600×600 μm2 and an electrostatic pressure variation up to 30 kPa, the MEMS exhibits a capacitance change from 9.3 pF to 13.4 pF, with a INL of 0.2% A capacitance to digital converter has been designed and fabricated in a low cost 2P4M 0.35μm CMOS standard process as a digital interface to the MEMS sensor. The measured resolution of 7.9 bit and power consumption of 16.56 μW demonstrate that by combining both devices a long range passive RFID sensor for pressure measurements up to 30 kPa is achieved.

0.5 V and 0.43 pJ/bit Capacitive Sensor Interface for Passive Wireless Sensor Systems

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 150nW CMOS novel temperature sensor for remote patient monitoring based on an auto-resonant active inductor architecture

An ultra low power temperature sensor suitable for human body range monitoring has been implemented using a standard 2P4M 0.35 μm CMOS process. This sensor is based on a novel Time-to-Digital Converter (TDC) architecture, which makes use of an auto-resonant cascode gyrator-C active inductor. The fabricated sensor has an active area less than 200 μm × 300 μm. It has a 0.03 °C resolution and a ±0.15 °C inaccuracy and allows high data rates with a conversion time lower than 200 μs and a power consumption less than 150 nW @ 10 samples/s.