24 documents found, page 1 of 3
Visible light communications for 6G wireless networks
Niarchou, E.; Boucouvalas, A. C.; Ghassemlooy, Z.; Alves, L. N.; Zvanovec, S.This paper outlines the potential use of visible light communications (VLC) in sixth generation (6G) wireless networks. In the first section of the paper, the technical aspects are identified as well as the research challenges which have raised the need to evolve from 5 to 6G. In the second section of the paper, we present a vision of 6G technology, focusing on its proposed requirements of future communication ...
Performance Analysis of 8-bit ODACs for VLC Applications
Dobesch, A.; Figueiredo, Mónica; Alves, L. N.; Wilfert, O.A discrete optical power level stepping technique in visible light communication (VLC), also known, as an optical digital to analog conversion (ODAC) has been proposed. This is an alternative concept for VLC front-end design, able to mitigate the LED intrinsic non-linearity. Additionally, it removes the need of an electrical digital to analog conversion (EDAC) in the driver stage. This paper provides an experim...
A low-noise CMOS front-end for TOF-PET
Rolo, M. D.; Alves, L. N.; Martins, E. V.; Rivetti, A.; Santos, M. B.; Varela, J.An analogue CMOS front-end for triggering and amplification of signals produced by a silicon photomultiplier (SiPM) coupled to a LYSO scintillator is proposed. The solution is intended for time-of-flight measurement in compact Positron Emission Tomography (TOF-PET) medical imaging equipments where excellent timing resolution is required (approximate to 100 ps). A CMOS 0.13 mu m technology was used to implement ...
A reverse GPS architecture for tracking and location of small objects
Andrade, T.; Alves, L. N.; Cupido, L.; Santos, D.A novel architecture for the location and tracking of small objects using a GPS-like architecture is described. Unlike the conventional GPS system, the proposed architecture places the emitters at the objects to be tracked and the receivers at fixed (earth) stations, so that the emitters can be made very simple and most of the intelligence of the system is located at the receivers. Due to the very low signal-to...
Design, development and performance analysis of DSSS-based transceiver for VLC
Terra, D.; Kumar, N.; Lourenço, N.; Alves, L. N.; Aguiar, R.L.This paper addresses and implements a Direct Sequence Spread Spectrum (DSSS) transceiver for Visible Light Communication (VLC) systems based on FPGA. A transceiver was implemented including a transmitter capable of driving an array of light emitting diodes (LED) and a Pseudo-Noise (PN) matched decorrelator. The receiver architecture uses a discrete FIR correlator for data synchronization and acquisition. In thi...
Visible light communication for intelligent transportation in road safety appli...
Kumar, N.; Terra, D.; Lourenço, N.; Alves, L. N.; Aguiar, R.L.This paper discusses the implementation of a light emitting diode based visible light communication system, for intelligent transportation in road safety applications. The signal processing of both, transmitter and receiver are realized in a field programmable gate array using two Spartan-3E development kits. The implemented modulation scheme is based on direct sequence spread spectrum techniques. The performan...
A new technique to achieve exact and controllable voltage gain relations in fee...
Alves, L. N.; Cura, J.L.This paper presents a new technique that allows the realization of exact voltage gain relations in feedback amplifiers. Basically, this technique exploits the imperfect subtraction characteristics of traditional differential amplifiers, as a means to nullify the closed-loop gain error of the complete configuration. The validation of the proposed technique was achieved following a simulation perspective, using a...
Design and analysis of the basic parameters for traffic information transmissio...
Kumar, N.; Alves, L. N.; Aguiar, R.L.This paper discusses system design considerations concerning the use of visible light communication (VLC) concepts in road traffic control systems. A simple traffic set-up model has been analyzed in order to optimize various important design parameters. This optimization is based on the gain variation over 100m transmission range. This approach will help to specify the needed gain for the receiver in the comple...
A time-delay technique to improve GBW on negative feedback amplifiers
Alves, L. N.; Aguiar, Rui L.This paper presents a new method to improve the GBW (gain-bandwidth product) on negative feedback amplifiers. The proposed method is based on the introduction of time-delay elements in the feedback loop, which can be exploited to retrieve significant bandwidth enhancements. This delayed feedback concept is analyzed, and considerations are presented for first-order amplifiers, based on theoretical analysis. The ...
General model for the deployment of time-delay elements in transistorized elect...
Alves, L. N.; Barbosa, L.; Aguiar, R.L.This paper presents a general model for the analysis of time-delay contributions due to right half plane (RHP) zeros in circuit's transfer functions. The presence of these RHP zeros is in general associated to Miller capacitances. These can be explored as a means of implementation of delay elements. A general discussion on the usage of these RHP zeros as means of designing usable delay cells is addressed, inclu...