José Camargo da Costa

Nitridation of Si (100) made by radio frequency plasma as studied by in situ angular resolved x‐ray photoelectron spectroscopy

X‐ray photoelectron spectroscopy with variable takeoff angles has been used to study the nitridation of Si(100). The air‐oxidized layer on the silicon film has been cleaned off by an Ar radio frequency (rf) plasma, and nitridation was obtained at temperatures around 400 °C in a rf plasma of a NH3 (5%)‐N2(95%) mixture. N(1s) and Si(2p) photoelectrons lines have been analyzed as function of the angle θ between the surface of the sample and the detector slit at each step of nitridation to obtain depth profile. These lines have both been decomposed into two components due, on one hand, to the Si–N and the metallic bonds and, on the other hand, to the chemisorbed nitrogen and the N–Si bond. From the integrated intensities of these lines, concentration dependencies on depth and nitridation time have been studied; a nitridation kinetics has been deduced.

Considerations about Nanoelectronic GSI Processors

According to recent studies, the basic technologies presently adopted by the semiconductor industry for memory and processor fabrication should attain limits imposed by the laws of physics around the year 2010. Nanoscale sized devices like single-electron transistors appear as a highly promising option to replace conventional devices by that time. In this study, considerations about the realization of a GSI processor, based upon nanoelectronic devices, are presented.

System-level power consumption modeling of a SoC for WSN applications

Energy consumption is a critical issue for wireless sensor networks (WSN) because of the limited energy supply on the nodes. Therefore, performance evaluation is very important, especially at early stages of the design flow. In this work, we present the modeling and simulation of nodes composed by a typical system on chip (SoC) for WSN applications using SystemC/TLM. The SoC contains a MIPS-based processor, a memory, a bus, a timer, a transceiver and a battery. The model is intended to allow power estimation in WSN simulation. The battery module estimates the energy consumption of the node by computing the amount of electrical charge used by each block As a case study, we performed a star topology WSN simulation, showed the power consumption of each node, and presented a discussion about the computational load. This approach is flexible and can be adapted to simulate more complex systems and topologies.

Design of a PSWF impulse response filter for UWB systems

This work presents a method of UWB pulse generation based in Prolate Spheroidal Wave Functions (PSWF). The method consists of a numerical approximation, a Padé approach and a state-space optimization. Therefore, a filter with a PSWF impulse response for UWB systems is designed. The generated pulse from the filter can be used in multiple access schemes and have some advantages over the Gaussian monocycle pulses with respect to better matching with the spectral mask defined by the Federal Communications Commission (FCC) for UWB applications.

System-level modeling of a mixed-signal System on Chip for Wireless Sensor Networks

Due to the increasing advance on wireless communication and sensors, Wireless Sensor Networks (WSN) have been widely used in several fields, such as medicine, science, industrial automation and security. A possible solution is to use CMOS System on Chip (SoC) sensor nodes as hardware platforms due to its extremely low power, sensing, computation and communication capabilities. This work presents the modeling of a mixed-signal SoC for WSN using a system-level approach. The digital section was modeled using SystemC Transaction Level Modeling (TLM) and consists of a 32-bit RISC microprocessor, memory, interrupt controller and serial interface. The analog block consists of an Analog-to-Digital Converter (ADC) described in SystemC-AMS. An application was implemented to test the correctness of the model and perform the communication between the SoC and a functional level node model.

System-level modeling of a Reconfigurable System on Chip for wireless sensor networks applications

This paper presents the system-level modeling of a Reconfigurable System on Chip (RSoC) that is being currently developed in our institution. Although there is a wide range of possible applications, our system is initially aiming fruit monitoring system. The proposed RSoC contains a 32-bit RISC microprocessor, reconfigurable structures, analog and digital interfaces, an RF transceiver and an Active Pixel Sensor (APS) matrix whose function will consist basically on image acquisition. The modeling at a high level of abstraction has been used lately in the design and verification of SoCs due to the rising complexity of such systems. Virtual platforms using SystemC description language at Transaction-Level Modeling (TLM) allow efficient simulations including software and hardware. In this work, a preliminary evaluation of a system-level description of the RSoC is carried out. A JPEG compression algorithm was mapped and implemented as a case study to test the accuracy of the model. Future implementations will include the description of an RF transceiver and the communication between two RSoCs.

CMOS Image Sensor Device for Objective Evaluation of Video Quality in Mass Distribution Networks

This work aims to present a device for the objective evaluation of video quality from the user perspective, in mass content distribution networks. This simple and cost-effective device with an integrated image sensor and an embedded processor intends to be network pervasive while minimizing the network overhead, allowing quality measurements over the network with greater control of the content distribution throughout the video chain, from content producers, distributors and to consumers.

EProf: An Accurate Energy Consumption Estimation Tool

Energy efficiency is a primary concern in Wireless Sensor Networks because in general, wireless sensor nodes run on non-rechargeable batteries. Therefore, the estimating a expected node lifetime is indispensable. Thus, energy is an important issue that should be optimized by the application developer. However, in order for the developer to realize that the program may not be developed in accordance with this power restriction, it is important to estimate the energy that will be consumed by the application. In this paper we present Eprof, a cycle-accurate instruction level simulator developed to estimate the energy consumption of applications running on UNB-RISC16 processor. Eprof is able to measure detailed time-critical phenomena, and can be used to shed new light on design issues for large-scale sensor network applications.

Interconnect impact on the performance of a SET-based Network-on-Chip memory circuit

Generally, the memory module of a processor core occupies the most part of its area. In this sense, the power dissipation of that high density device module is an important issue for developing an integrated circuit, especially when considering the effects of dissipation due to interconnects. Nanoelectronic devices appear like an option for designing large integrated circuits, because of their lower power consumption compared to nowadays technologies. Among these nanoelectronic devices, single-electron transistors (SET) are known for their reduced area and power consumption features, which are orders of magnitude lower than CMOS devices. Taking that into account, this paper evaluates the performance of a SET-Memory based on NAND logic gates module considering the impact of non-ideal interconnects.

Methodology for Objective Evaluation of Video Broadcasting Quality using a Video Camera at the User's Home

In this work, a methodology for objective evaluation of the quality of video programs, without reference, recording these programs in the users’ residence using a video camera is presented. Themethodology is based on the use of a digital watermark embedded in the original program. The watermark is invisible to the user, but capturable by the video camera. The recorded video is handled by specific software that evaluates the watermark degradation. The measure of degradation of this watermark is used to estimate the quality of the video broadcasting system. A case study is presented to validate the methodology. The results of video quality metrics using this methodology were compared to a standardized full reference metrics and the linear correlation between these metrics was superior to 93%, which indicates a high convergence. The result of video quality metrics were also compared to a pixel based difference metrics, PSNR (Peak Signal to Noise Ratio) and the linear correlation was superior to 99%.