ABSTRACT. In recent years MEMS microphone market for consumer applications has been extensively growing pushing in the direction of high SNR, an increased DR and shrunk packages. In this scenario digital microphones have become more popular, i.e. for smartphones and wearables. In this paper a fully-differential digital microphone system with a full-scale of 140dB SPL capable of delivering a SNR of 67dB at the reference level of 94dB SPL based on a 3rd order hybrid modulator is presented. The proposed DAC architecture based on a voltage-mode subtraction results in a high input impedance of the modulator. This allows to use an on-chip voltage doubler to process signal swings of up to 2.5Vrms being powered from a 1.8V supply and having an acoustic overload point (AOP) at 136dB SPL. After introducing the topic and an overview about the sensor and package, the chosen architecture and its circuital implementation are discussed. The paper concludes with silicon measurements.

ABSTRACT. More than 25 years have already passed since Mark Weiser envisioned the concept of ubiquitous computing, corresponding to “one user-many computers”. This idea underlies under the paradigm of Wireless Sensor Networks, where several so called sensor nodes or motes are deployed in an application environment to massively collect data, enabling new applications that range from simple control systems to complex social behavior prediction, requiring a variety of technologies. In this context, during the last few years, a new picture has risen, encompassing the above mentioned technologies: the Internet of Things, which basically alludes to the access of objects through Internet. During the last ten years the technology related with the sensor nodes has evolved, appearing different platforms as commercial products and academic prototypes. Our research group has actively participated in this evolution, through the Cookies, a modular layered platform for WSNs and IoT. In this paper, the evolution of these networked embedded systems is reviewed, and some future trends are foreseen including the imminent apparition of 5G communications, the increased intelligence of the nodes and the dream of perpetual systems.

ABSTRACT. this paper describes system design and optimization for a complete interface circuit (readout and heater driving circuit) for MOX gas sensor. A Simulink-Matlab model has been used to simulate the complete system, including thermal and electrochemical effects of the heater. The readout interface is based on a resistance-to-frequency converter and covers the resistive range 100Ω - 1MΩ, with an equivalent 8-bit precision in a total measurement time of 1 second. This corresponds to a dynamic range of about 128 dB. The heater driving circuit is based on a simple on-off controller that controls duty-cycle of the heater resistance. Readout interface and heater driving circuit are implemented in a standard CMOS 130 nm technology. Power consumption and design strategy are optimized for mass production targeting consumer applications.

ABSTRACT. Once specific Smart Sensors are designed and manufactured in the newest nanoelectronics technology, and a Wireless Sensor Network is designed for being used on wearable applications (Cyber-Physical System) with optimum performance (data rate, power consumption, comfortability, etc.) the next step is the treatment applicable to the large amount of data collected. This can be a very general, and sometimes an unaffordable problem, but considering a system collecting physiological data from smart sensors on a human body, the range of possibilities is restricted to health or leisure but also to safety. In this case, a finite, and well-located, number of physiological sensors are producing few data per unit of time, which are locally processed for obtaining a reduced set of characteristics that are globally analyzed. In this paper, an analysis on different approaches for combining data from smart sensors attached to human body, with the purpose of determining the main emotion present in the person, is presented. Machine learning, selection of the best characteristics from raw sensor data, data bases for system training, etc. are the key aspects in this problem. The conclusions of the analysis will help in the design of a new application, where emotion detection can be used for personal safety (domestic violence, sexual violence, bullying, etc.). Attention is paid on the locally and globally data processing in terms of hardware and software, together with low-power behavior.

ABSTRACT. The use of MEMS sensors has been increasing in the last years. To cover all the applications many different readout circuits are needed. To reduce the cost and time to market, generic Capacitance-to-Digital Converter (CDC) seems to be the next step. This work presents a noise-shaping Integrating Dual-Slope (DS) Capacitance-to-Digital Converter (CDC), specifically designed for interfacing capacitive MEMS sensors. The sensor is built with a bridge of MEMS, where some of them are function of pressure. Then, the conversion is realized in two steps. In the first step the capacitance to voltage (C-V) conversion is achieved by a chopped preamplifier. Second, an Integrating DS converter is used to digitize this magnitude. The proposed converter works in the time domain and generate a multi-bit digital output stream. In addition, it performs noise shaping of the Quantization error to reduce measurement time. This article shows the effectiveness of this method by measurements performed in silicon. The designed prototype is fabricated using standard 0.13 μm CMOS technology. The measurements show that the CDC is able to achieve a resolution of 17 bits for pressure application, which means a pressure resolution of 1 Pa, while consuming 146 μA from 1.5 V power supply, with an effective area of 0.317 mm^2.

ABSTRACT. In this work, it is discussed the development of a simple closed formula that predicts the value of the sheet resistance due to the skin effect in metal strips. It is derived through the study of the current density distribution in the strip cross-section by means of an electromagnetic simulator. Using this formula, it is also shown the possibility to reduce the required number of mesh cells when performing the electromagnetic analysis of planar devices.

ABSTRACT. This paper presents the design of a variable-length transmission line for millimeter-wave integrated circuits, giving design considerations and comparing different approaches. The implemented line consists of a stub that is connected to ground using 7 different switches, which can be used to change the electrical length of the line. Measurement results show that the equivalent inductance of the line can be tuned between 74.8 and 110 pH, which corresponds to 47% variation. In terms of electrical length, it can be tuned between 20.73º and 29.15º. The presented variable-length transmission line can be used in self-healing systems and reconfigurable devices, as well as to implement adjustable matching networks in load-pull measurement circuits.

ABSTRACT. Abstract—This paper presents an analysis and review of digital redundancy techniques in Successive-Approximation-Register (SAR) ADCs for correction of comparator errors during the SAR search algorithm. The use of redundancy provides safety margin for dealing with incomplete settling in the DAC network, improving conversion speed and power, as well as relaxing switch sizes and comparator design. Techniques like binary- scaled, radix-based or arbitrary weighing capacitors with redundant bits are discussed using a unified nomenclature and modeling. The proposed unified description is closely related to the hardware realization eliminating the gap between theoretical and physical implementations, and allowing a clear identification of pros and cons of different approaches. For illustration purpose, several examples are modeled and simulated using the proposed description.

ABSTRACT. This paper presents a low power receiver front-end for the 2.4-GHz-band specified by the IEEE 802.15.4 standard in 65nm CMOS technology. This front-end adopts a low-IF architecture and it is comprised of a differential low-noise amplifier (LNA) and a double-balanced active mixer which have been stacked to reuse DC current and minimise power consumption. Current boosting techniques are also implemented to improve circuit performance. Depending of the current boosting technique that is applied, the receiver front-end achieves 25-23.3 dB voltage conversion gain and a 10.57-10.55 dB noise figure (NF), with -18 dB input matching and around -23 dB input third-order intercept point (IIP3), with a total power consumption of 2.47 or 2.2 mW.

ABSTRACT. This paper presents the design of an LDO-assisted DC-DC voltage regulator in Cadence Virtuoso® based on a 350-nm CMOS technology. This kind of voltage regulator consists of a switching converter together with a classic or LDO (low drop-out) linear voltage regulator. While the linear regulator provides the constant output voltage, the switching converter conducts nearly all the current provided to the output load, and keeping the regulator current close to zero where the higher efficiency is achieved. In addition, this paper shows the modeling in Matlab/Simulink. Notice that, this modeling is mandatory in order to predict and assure the stability of the circuit. In addition, it will help to improve the transient response and performance of the circuit.

ABSTRACT. It is essential for any embedded systems and increasing popularity of Internet of Things (IoT) be energy efficient. Such systems tend to work intermittently and reducing leakage in the idle time is essential. Energy reduction techniques bring the system to a low power mode which also provokes transition overheads. If such overheads are not considered, the task may not be schedulable under a given deadline. To get gain in energy savings, the idle state must be longer than a minimum required time. This time is referred as Break Even Time (BET). To properly design efficient algorithms and schedulers we must calculate and include the BET. In this paper, we present the first studies to examine the BET using accurate parameters extracted from a real chip using Silicon On Thin Box (SOTB) technology employing Body Bias Control (BB) energy saving technique. In this study, we demonstrate the BET range for SOTB microcontrollers, on the order of 0.5ms up to 1ms

ABSTRACT. This paper designs an off-line single-switch zero-voltage-switching inverter for the filament heating of cooker magnetrons. To drive the low-resistance cathode filament, a step-down transformer with high turn ratio is used. And, a single-switch zero-voltage-switching (ZVS) circuit is used to promote circuit efficiency and power density. With the ZVS circuit, the transformer leakage inductance and transistor output capacitance are all merged into the resonant tank. The transformer voltage drives filament load and the transformer energy provides ZVS operation. Through circuit analysis, a single-switch ZVS inverter is designed, and a prototype circuit for 30W/3V filament is implemented to verify the analyses of this paper.