Analog Circuits for Signal Processing
The research activity in this topic spans from the pre-processing signal conditioning to data conversion and techniques to obtain non-volatile memories. Circuits for effective dc-dc conversion are also studied.
For analog preprocessing the key function is low noise low offset amplification. Market requirements lead to research on innovative solutions for chopper stabilized amplifiers with low power.
New methods and architectures for analog-to-digital and digital-to-analog conversion are widely investigated with significant results, especially for portable and low power applications.
Research also concentrates on the effective conversion of dc voltage. Portable and nomadic systems need multiple supplies and miniaturization. The research in this area enables the generation of many supply voltages with a minimum number of external components and small inductors for system-on-package implementations. This area is also important for the optimum operation of solar cells.
Integrated Circuits for Wireline and Optical Communications
Transferring, processing and storage of data require more and more advanced communication technologies. More integration of diversified components (optical and electrical), better power efficiency of the channel and an increase in the communication speed are the primary targets.
A key challenge for future interconnections is the high speed transfer over channels with large losses. Thanks to an efficient electro-optics conversion, the photonic on silicon technology (silicon photonics) represents a path to be followed in the future. It is expected that wireline communications will demand transfer rates in excess of 100 Gbit/s.
Integrated Circuits for Medical Diagnosis
Ultrasound imaging techniques are simple, accessible and non-invasive. The operation principle is the analysis of the received eco signal reflected by tissues. The operating frequencies are in the range of MHz. Most of the commercial instruments have a limited number of processing channels and transducers. For this reason, the reconstruction of 3D images is limited to slowly moving parts inside the body.
The need for 3D images of fast moving parts (like blood, heart) motivates the development of new ultrasound imagers based on dense matrices of transducers. This requires moving the electronic circuits for signal processing from inside the machine (console) to the probe. Low power and custom integrated circuits are key.
Research activities for the Ph. D. students in this framework are in the area of new receiver architectures with high dynamic range and high-power compact transmitters.
In this field, the activities are mainly concentrated on Flash memories and phase-change memories. Flash memory cells are based on a floating-gate MOS transistor: information is stored by trapping electrons on the floating gate of this device, which is electrically isolated from the rest of the chip. Phase-change memory cells are based on a chalcogenide material that can be reversibly programmed into a crystalline or an amorphous state, which show very different resistivity values. In both cases, the research activities are essentially focused on the design of analog circuits required for memory operation and the development of program and read algorithms suited to multilevel storage.
Multi-level devices can store more than one bit per cell, thus leading to an increase of storage density (and, hence, to a decrease of the cost-per-bit) for any given integration technology node. In particular, in the case of Flash memory devices, multi-level operation is obtained by trapping multiple amounts of electrical charge in the floating gate while, in the case of a phase-change memory device, multi-bit storage can be achieved by programming the chalcogenide material into states corresponding to different values of the crystalline fraction.
In addition, efficient dc-dc conversion is required in non-volatile memory devices, where high voltages and, in some cases, also negative voltages are needed for memory operation. Voltage elevators based on the charge pump principle are therefore investigated, having high power efficiency as a key target.
Low-Noise, High-Density Microelectronic Systems for Active Pixel Sensors
This research activity is focused on the development of low noise processing chains for high granularity capacitive detectors. This involves the design and characterization of mixed signal circuits including charge sensitive amplifiers, shaping filters, threshold discriminators and analog to digital converters, logic blocks for selective data readout, serializers and signal drivers.
A thorough characterization of state of the art commercial CMOS technologies is constantly carried out to assess their suitability for low noise applications and to evaluate scaling down effects on analog circuit performance. Degradation induced by ionizing radiation is also studied in view of applications to the readout of position sensitive detectors in high energy physics (HEP) experiments and to the space environment.
In order to satisfy the requirements set for particle trackers at the future experiments in terms of position and momentum resolution and of readout speed, monolithic active pixel sensors (MAPS) featuring data sparsification capabilities are studied and developed.
More advanced microelectronics processes, involving vertical integration techniques, are investigated to further enhance MAPS performance through functional density increase.
This research activity is focused on:
- Discrete electronic dc/dc power converters, in particular, for low-power applications where the containment of weights and volumes is strategic. Integrated dc/dc converters for distributed power supplies.Power electronic dc/ac Converters for industrial applications. This is an activity devoted to electronic components and control of these converters.
- Photovoltaic systems. The work considers the research problems associated with the photovoltaic generation and its applications.
- Electronic supply systems able to recover energy from the environment through energy harvesting techniques (using different energy transducers: piezoelectric, thermoelectric, photovoltaic, electromagnets) to supply wireless sensors.
- Integrated Microsensors and front-end circuitry to detect various chemical and physical quantity.
Microelectronics for Radio-Frequency Applications
The research activity in this field is devoted to the design of analog and mixed-signal circuits in scaled CMOS technologies (65 nm and beyond) for next generation wireless communications. Applications cover a wide frequency spectrum that goes from th 1-2 GHz frequency band for cellular and WiFi communications, up to 10 GHz for ultra-wideband communications, and over 60 GHz for wireless HDMI and other millimeter-wave applications.
Research programs carried out within the Microelectronics PhD program cover different aspects, from single circuit blocks such as digitally-controlled oscillators, low-noise amplifiers, power amplifiers, etc., to integrated sub-systems such as digitally-controlled frequency synthesizers, to complete fully-integrated transceivers.
Sensors and Microsystems
The research activity in this field deals with the design and the implementation of integrated interface circuits for microsensors and microsystems. In such devices, the sensors and the interface circuits are realized on the same chip or in the same package, using integrated circuit (IC) technologies, thus leading to complete miniaturized systems.
In particular, the research activity is focused on interface circuits for magnetic sensors, inertial sensors (accelerometers and gyroscopes), temperature sensors, optical and radiation sensors, as well as gas sensors, considering different applications. The interface circuits, typically, include a complete signal processing chain, from the analog front-end to the analog-to-digital converter and the digital back-end.
Particular attention, especially for portable applications, is devoted to the minimization of the power consumption, either at system level, and at building block level. Finally, in order to achieve autonomous microsystems, energy harvesting sources, power management circuits, and simple wireless data transmission protocols are studied, for supplying sensors and interface circuits as well as transfer the acquired data.
Microelectronics for mm-Wave Applications
An intense research activity toward the realization of integrated circuits and systems for mm-wave applications (60 GHz, 77 GHz, 94 GHz and beyond) is presently under way at international level. Expected applications are in the area of high rate Wireless LAN, anti-collision automotive radars and imaging for medical diagnostic.
In this field Ph. D. students cover all the aspects from system analysis to selection of the processing architecture to the design of components and blocks leveraging advanced CMOS technoliges (65 nm and 32 nm).