Antonio Carlos Cavalcanti

MCA: one-port scalable microprogrammable ATM layer controller

This work proposes a flexible microprogrammable controller to perform the ATM layer functions of an ATM switch. The controller has as a main characteristic the flexibility to implement several algorithm types, by changing microinstructions programming only. The description and functionalities of the main blocks that compose the architecture are presented as well the preliminary chip blocks synthesis results.

Thin Teflon-FEP capacitors with open-tubular channels employed on low-pressure measurements for smart-grid monitoring systems

In order to improve quality and efficiency in electrical energy distribution, power supply companies have sought for better ways to monitor their equipment, stimulating research in smart-grid projects. Equipment subjected to constant monitoring are power and distribution transformers, in which severe faults can be avoided through preventive maintenance, such as, detecting partial discharges in early stages, conducting oil chemical analysis or monitoring transformer internal pressure. In the present contribution we discuss the use of thin voided capacitors made of fluoroethylenepropylene (FEP) films to measure pressure changes in sealed chambers, as in distribution transformers. Voided film structures are very sensitive to pressure variations due to their low mechanical resistance in the thickness direction. Here voided capacitors were fabricated using the same thermal lamination process reported to produce piezoelectrets with open tubular channels. In order to measure pressure disturbance an electrical circuit was specifically designed for detecting variations in capacitance and results correlating these changes with pressure increase are presented.

Comparative analysis between impulsive detection methods applied on partial discharge acoustic signals

Partial discharges (PD) plays an important role on power transmission lines and equipment failures therefore previously detect this high-voltage phenomena can prevent severe damages and avoid further outlay. Spark gaps discharges are among the most common PD in power transformers and other efficiency energy equipments. And in order to detect this effect optical and acoustic sensors are normally employed into monitoring systems. However optical sensors are expensive for transmission power lines and detecting acoustical signals from PD can be difficult since they are normally followed by other background sounds. In order to improve detection sound systems in this work we compare two methods that are regularly used on impulsive signal processing, the Variance Method (VM) and the Conditional Median Filter (CMF), to detect PD acoustic signals. From the presented results it is observed that the CMF is more appropriated for detecting impulsive PD although the VM detected less false positive discharge and can still be further optimized.

Comparison between three RTL implementations of the multiplicative inverse calculation of galois field elements based on a standard cells library

Most problems found during implementation of Galois Field (GF) arithmetic in Very-Large-Scale-Integration (VLSI) circuits, are the area occupied by the blocks responsible for the product of two elements and by the calculation of the multiplicative inverse of an element. This last, is the main routine applied on the S-Box and Inv S-Box functions of the Advanced Encryption Standard (AES) Rijndael algorithm. Therefore, on a complete implementation of the AES algorithm in hardware, one may expect that approximate 50% of the circuit area is occupied only with those instances. As an example, a simple pipeline implementation of the Rijndael algorithm may require more than 160 instances of the S-Box blocks, only in the encrypter of a GF (28). Since the multiplicative inverse applied in S-Box or Inv S-Box can be implemented by different methods and they consume considerable space in a VLSI implementation, it is desired to determine the most appropriated solution for VLSI circuits. Therefore, in this work we implemented three different approaches for the calculation of the multiplicative inverse in a GF (28) and map them into digital blocks. The digital blocks were then transcribed into a hardware description language (HDL), converted to Register Transfer Level (RTL) and synthesized over the same standard cells library. A comparison between these implementations regarding the estimated circuit area, the number of clock cycles and the maximum operation frequency, for a GF (28) of the AES are here presented.

Images from high-voltage impulse discharges evaluated with a developed graphical software

Power transmission lines are constant targets of high electrical discharges such as corona and lightning. This last is manly characterized as a high impulse voltage, which can rapidly cause severe damages to equipment in the lines. Therefore, detect the amplitude of these discharges in power lines is critical for the proper design of protective systems. Recently an impulse voltage sensor based on electret films was presented. The sensor employs a spherical electrode in direct contact with a grounded thin electret film. Whenever a negative electrical impulse voltage is applied on the spherical electrode, partial discharges occurs all around the electrode forming a circular pattern that can be visualized if toner is spread over the film. Depending on the discharge amplitude circles with larger diameter are formed. In this paper we present a software implementation through which the discharge images with circular patters can be measured and direct correlated to the impulse discharge amplitude, providing a reliable and fast method for measuring electrical discharges in the field. The software was validated performing measurements of the images diameter and correlating it with well defined discharges amplitude.

Acoustic detection of single and multiple air-gap partial discharges with piezoelectrets transducers

Electrical equipment installed in power transmission and distribution lines are usually subjected to abnormal conditions and intense electric fields, which eventually lead, among others phenomena, to partial discharges (PD). These, have been pointed as one of the main causes of equipment failures and premature aging. Therefore, detect PD became an important issue in the prospect of efficient and reliable electric energy. Concerning PD detection there are several sensors that can be employed e.g. optical, magnetic or acoustic, and each of them presenting particular advantages and limitations. One of the drawback of such sensors are their elevated costs for transmission lines equipments, which has restrict the PD monitoring to power transformers. Although, if the intention is only to detect the PD occurrence a new class of acoustic sensors implemented with piezoelectrets may be a feasible economic alternative. Therefore, in this work we have investigated the acoustic behavior of such transducers exposed to different PD conditions, for instance, the piezoelectret sensor was employed on the detection of PD produced by a single or multiple point-to-point electrode setup with different air gaps driven by high AC voltages. The recorded signals amplitudes were than correlated with the gap distance and voltage amplitude.

An MPEG-2 transport stream demultiplexer IP corecompliant with SBTVD

The design and implementation of a hardware architecture of an MPEG-2 Transport Stream demultiplexer is presented in this paper. This subsystem is directly applicable to set-top box (STB)designs compliant with SBTVD - Brazilian Digital Television System - broadcast environment. This project aimed to minimize the software support for common tasks such as clock recovery and table section filtering, frequently required from a complex main processor, not always suitable for STBs integration. This work covers the validation of design abstraction layers from the purel. behavioral high-level modeling, architecture, micro-architecture, finite state machines, up to RTL level. Models and testbenches were constructed in C/C++ and Verilog HDL. Each level were validated with corresponding testbench as well as its technology mapping in FPGA and ASIC. Hierarchical mode was used to schematic capture and layout of demultiplexer blocks.