Nicola Massari - Academia.edu (original) (raw)

Papers by Nicola Massari

IEEE solid-state circuits letters, 2020

In this letter, a stitched array of <inline-formula> <tex-math notation="LaTeX&quot... more In this letter, a stitched array of <inline-formula> <tex-math notation="LaTeX">$768\times 64$ </tex-math></inline-formula> pixels for X-ray dental imaging is presented. The sensor architecture allows to increase the frame rate up to 900 fps thanks to a pipeline approach that minimizes the deadtime between consecutive frames. A column-based ADC converts pixel values in digital form while an external FPGA performs the operation of time-delay integration accumulation, thus increasing the signal-to-noise ratio. Internal programmable gain allows to achieve a maximum sensitivity of 2.6 LSB/nGy and, at the same time, to extend the dynamic range of the sensor in case of high intensity. The final system consists of two sensors each one having a size of <inline-formula> <tex-math notation="LaTeX">$74.5\times 9$ </tex-math></inline-formula> mm, assembled in a PCB and coupled with a high sensitive columnar thallium-doped cesium iodide (CsI(Tl)) scintillator for X-ray conversion. The sensor, fabricated in a standard CMOS 0.15-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> technology with a stitching approach, shows a pixel size of 97 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>.

In the present paper we describe the design of a quantum random generator based on a new concept ... more In the present paper we describe the design of a quantum random generator based on a new concept of a single photon position sensitive device (PSD). In this scheme, the PSD should identify the position of an impinging photon between a couple of SPADs. The front end circuit is then able to process the signal and extract the random bit reducing the non-idealities introduced by the system. The device has been designed and fabricated using a 0.15boldsymbolmumathbfm0.15 \boldsymbol{\mu} \mathbf{m}0.15boldsymbolmumathbfm CMOS technology and now it is under test for characterization.

Proceedings of SPIE, Oct 13, 2015

The present work is focused on the description of a SPAD-based pixel suitable for random bits ext... more The present work is focused on the description of a SPAD-based pixel suitable for random bits extraction. Compared to the state-of-the-art, the proposed approach aims at improving the performance of the random generator with respect to possible photon flux variation. Thanks to the adopted methodology, the entropy of the output is maintained almost constant over a wide range of operating conditions. The principle has been validated through simulations and implemented in a compact pixel, suitable for array implementation.

Journal of Instrumentation, Apr 1, 2022

Digest of technical papers, Feb 1, 2008

A 641times128-pixel vision sensor, whose pixels estimate and perform a 1b quantization on the loc... more A 641times128-pixel vision sensor, whose pixels estimate and perform a 1b quantization on the local contrast with a low energy budget is presented in this paper. The pixel-embedded time-adaptive visual processing is based on a charge-transfer mechanism, featuring no DC power consumption. The asynchronous readout process takes 147 mus and dispatches the column address of each asserted pixel, significantly reducing

Journal of Low Power Electronics

2017 New Generation of CAS (NGCAS), 2017

ESSCIRC 2008 - 34th European Solid-State Circuits Conference, 2008

A CMOS interface for a piston-type MEMS capacitive microphone is presented. It performs a capacit... more A CMOS interface for a piston-type MEMS capacitive microphone is presented. It performs a capacitance-to-voltage conversion by bootstrapping the sensor through a voltage pre-amplifier, feeding a third-order sigma-delta modulator. The bootstrapping performs active parasitic compensation, improving the readout sensitivity by ~12 dB. The total current consumption is 460 uA at 1.8 V-supply. The digital output achieves 80 dBA-DR, with 63

IEEE Transactions on Electron Devices, 2016

IEEE SENSORS 2014 Proceedings, 2014

Background light can be a critical issue in a Time of Flight (ToF) camera system, because it can ... more Background light can be a critical issue in a Time of Flight (ToF) camera system, because it can saturate the pixel destroying the depth information held on it. In this paper a new circuit aimed at increasing the dynamic range of a ToF sensor, based on photodemodulators, is proposed. The used approach consists of a compact low-power pixel-level circuit able to suppress the background light contribution. The proposed circuit, enabled by a digital clock signal, periodically injects a controlled common-mode charge to the integrated signals during the exposure time while preserving the depth information. This fast operation, executed in parallel to all the pixels, extends the dynamic range by a factor proportional to the clock frequency Fck. The pixel, implemented in a CMOS 0.18μm technology, counts 19T and exhibits a size of 10×15μm2 with a fill factor of 15%, while the overall power consumption is estimated to be 60nW @ 10KHz of Fck.

IEEE Solid-State Circuits Letters, 2020

IEEE Journal of Selected Topics in Quantum Electronics, May 1, 2020

Different electronic devices nowadays exploit random number generators either to create the seed ... more Different electronic devices nowadays exploit random number generators either to create the seed for simulations, for gaming or to encrypt the communications. Particularly for cryptography applications, there is an increasing effort to realize a truly random number generator, based not on mathematical algorithms but exploiting randomness of physical processes. Among them quantum processes, provide intrinsic unpredictability, for example exploiting the arrival time, the number or the properties of photons. In this work we focus on photonic quantum random number generator (QRNG), and we analyze different approaches and entropy extraction methods to realize a fully integrated, CMOS compatible, QRNG with photon-emitter realized on the same chip and very close to the detectors of single photons. Non-idealities of the emitter and the detector have to be studied and depends on the structure. They can be mitigated with robust extraction methods which however should not introduce complex algorithms or secondary entropy sources that can make the device no longer quantum based. The ultimate goal is to realize a CMOS building block that can be implemented as building block, with low power consumption and robust to environmental conditions.

The present paper describes a time-based technique for resistive detector. Thanks to the comparis... more The present paper describes a time-based technique for resistive detector. Thanks to the comparison with a reference resistance, the circuit easily compensate the baseline contribution, thus extending the dynamic range of the measurement. The implemented circuit is based on a resistance to time converter followed by a time comparator for signal comparison. Differently from existing time-based technique, the proposed approach allows increasing the sensitivity of the detection by increasing the time of the measurement. The circuit exhibits a measured resolution in the order of 20ppm with a nominal value of resistance of about 3MΩ while the maximum dynamic range is of about 40dB.

This paper presents the complete gamma characterization of the SPADnet-I sensor, a novel, fully d... more This paper presents the complete gamma characterization of the SPADnet-I sensor, a novel, fully digital SiPM array for PET applications. Each SPADnet-I pixel contains 720 SPADs and counting and timestamping logic, resulting in pixel dimensions of 0.6 × 0.6 mm2 and 42.6% fill-factor. Moreover, the sensor provides a real-time output of the total detected energy at up to 100 Msamples/s, which is internally used by a discriminator to distinguish gamma events from background noise. Results for the pile-up identification, crystal image and discriminator efficiency are presented. An energy resolution of 10.8% and a coincidence resolution time of 288 ps are reported.

A robust true random number generator (TRNG), able to assure high quality output at different wor... more A robust true random number generator (TRNG), able to assure high quality output at different working conditions, is an attractive solution in secure communication application, because it increases resilience against possible external attacks. Among different TRNGs, quantum RNGs (QRNG) represent a good candidate for such systems, because of their compactness, low cost and performance [1-6]. They typically consist of a source of photons, such as an attenuated LED, coupled to a detector with single photon capability (SPAD). Many works in the literature have used a single detector [1-4] for random bit extraction. These devices are characterized by a limited bit rate [1], which can be increased by exploiting the arrival time of photons at the cost of circuit and system complexity [2-4]. Recent works [5-6] proposed to implement an array of detectors based on SPAD working in parallel thus extending the speed of QRNG up to 5 Gb/s [5]. Despite the high bit rate, the main drawback of [5] is the strong dependence of each pixel bias on the impinging light intensity which forces the system to work only for a narrow range of photon flux that poses several constraints on the design of the final QRNG system, e.g. the need of a feedback control loop to maintain a constant flux of photons, and of a uniform distribution of light over the entire sensor. Moreover, it is impractical to implement algorithms for bit extraction to all detectors of the array because of different responses and mismatches among SPADs.

ABSTRACT Positron-Emission Tomography (PET) is a nuclear imaging technique that provides function... more ABSTRACT Positron-Emission Tomography (PET) is a nuclear imaging technique that provides functional 3-dimensional images of the body, finding its key applications in clinical oncology and brain-function analyses. The typical PET scanner is composed of a ring of scintillator crystals that absorb gamma rays and emit photons as a result, coupled to photon-sensing devices. The photons hit the sensors with a certain spread in space and time, depending on the material and geometry of the crystals. The sensors must then estimate the energy, the time of arrival (ToA), and the axial position of incoming gamma rays. Most commercially available scanners use photomultiplier tubes (PMTs), which are sensitive to magnetic fields, as the sensing element, making the integration of these systems with Magnetic-Resonance Imaging (MRI) impossible. A significant amount of research has focused on replacing PMTs with solid-state detectors, such as Silicon photomultipliers (SiPMs) [1], which can be integrated with MRI while maintaining the high-sensitivity of PMTs.

$Research paper thumbnail of A <inline-formula> <tex-math notation="LaTeX">$16\times 16$ </tex-math> </inline-formula> Pixel Post-Processing Free Quantum Random Number Generator Based on SPADs$

IEEE Transactions on Circuits and Systems Ii-express Briefs, May 1, 2018

Single-photon avalanche diodes (SPAD) are increasingly being used in a number of applications whe... more Single-photon avalanche diodes (SPAD) are increasingly being used in a number of applications where the timing information carried by the captured light is crucial. In this paper we will analyze which challenges need to be addressed in order to integrate SPAD devices into a CMOS system-on-chip. The analysis will span three levels of abstraction, from the device integration in CMOS technology, to the implementation of time-resolved arrayed electronics, to the architectural level design. A perspective on future developments, involving use of advanced technologies such as 3D stacking, is given.