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About

About

I was born in Viana do Castelo, Portugal, in 1996. I came to Porto in 2014 to join the Degree in Electrical and Computer Engineering in Instituto Superior de Engenharia do Porto (ISEP). In 2017 I joined the Master in Electrical and Computer Engineering - Specialization in Telecommunications in the same institution.

My master thesis was carried out at INESC TEC, as a curricular trainee. Currently, I am a research assistant at INESC TEC, part of the Optical and Electronic Technologies (OET) group of Centre for Telecommunications and Multimedia (CTM). Currently, I am attending the MAP-tele Doctoral Program in Telecommunications at the Universities of Minho, Aveiro, and Porto.

My main interests include high-speed optical and wireless communications, underwater communications, electronic circuits, optoelectronic devices, and microelectronics.

Interest
Topics
Details

Details

  • Name

    João Henrique Araújo
  • Role

    Research Assistant
  • Since

    01st November 2018
  • Nationality

    Portugal
  • Contacts

    +351222094000
    joao.h.araujo@inesctec.pt
001
Publications

2023

Misalignment-Resilient Propagation Model for Underwater Optical Wireless Links

Authors
Araujo, JH; Tavares, JS; Marques, VM; Salgado, HM; Pessoa, LM;

Publication
SENSORS

Abstract
This paper proposes a multiple-lens receiver scheme to increase the misalignment tolerance of an underwater optical wireless communications link between an autonomous underwater vehicle (AUV) and a sensor plane. An accurate model of photon propagation based on the Monte Carlo simulation is presented which accounts for the lens(es) photon refraction at the sensor interface and angular misalignment between the emitter and receiver. The results show that the ideal divergence of the beam of the emitter is around 15 degrees for a 1 m transmission length, increasing to 22 degrees for a shorter distance of 0.5 m but being independent of the water turbidity. In addition, it is concluded that a seven-lense scheme is approximately three times more tolerant to offset than a single lens. A random forest machine learning algorithm is also assessed for its suitability to estimate the offset and angle of the AUV in relation to the fixed sensor, based on the power distribution of each lens, in real time. The algorithm is able to estimate the offset and angular misalignment with a mean square error of 5 mm (6 mm) and 0.157 rad (0.174 rad) for a distance between the transmitter and receiver of 1 m and 0.5 m, respectively.

2023

Sigma-Delta Modulation for Enhanced Underwater Optical Wireless Communication Systems

Authors
Araújo J.H.; Rocha H.J.; Tavares J.S.; Salgado H.M.;

Publication
International Conference on Transparent Optical Networks

Abstract
This paper presents an experimental investigation of sigma-delta modulation (SDM) as a means of improving the performance of underwater optical communication systems. The study considers the impact of the key parameters of SDM, including oversampling ratio, the system's signal-to-noise ratio, bandwidth, and optical link distance. The results of this study provide insights into the design and optimization of SDM-based underwater optical communication systems, paving the way for future research in this field. A fully digital solution, albeit operating at a lower bit rate than previously published OFDM counterparts, provides immunity against nonlinearities of the system and robustness to noise, which is relevant in harsh environments. Moreover, the proposed solution based on a first-order bandpass SDM architecture avoids the employment of a DAC at the receiver, simplifying its operation and reducing costs. An experimental investigation is carried out for the transmission of 16-QAM over SDM, and a transmission distance of 4.8 m over the underwater channel is achieved with a maximum transmission rate of 400 Mbit/s with an MER of 28 dB.

2023

TEC4SEA-Developing maritime technology for a sustainable blue economy

Authors
Monica, P; Cruz, N; Almeida, JM; Silva, A; Silva, E; Pinho, C; Almeida, C; Viegas, D; Pessoa, LM; Lima, AP; Martins, A; Zabel, F; Ferreira, BM; Dias, I; Campos, R; Araujo, J; Coelho, LC; Jorge, PS; Mendes, J;

Publication
OCEANS 2023 - LIMERICK

Abstract
One way to mitigate the high costs of doing science or business at sea is to create technological infrastructures possessing all the skills and resources needed for successful maritime operations, and make those capabilities and skills available to the external entities requiring them. By doing so, the individual economic and scientific agents can be spared the enormous effort of creating and maintaining their own, particular set of equivalent capabilities, thus drastically lowering their initial operating costs. In addition to cost savings, operating based on fully-fledged, shared infrastructures not only allows the use of more advanced scientific equipment and highly skilled personnel, but it also enables the business teams (be it industry or research) to focus on their goals, rather than on equipment, logistics, and support. This paper will describe the TEC4SEA infrastructure, created precisely to operate as described. This infrastructure has been under implementation in the last few years, and has now entered its operational phase. This paper will describe it, present its current portfolio of services, and discuss the most relevant assets and facilities that have been recently acquired, so that the research and industrial communities requiring the use of such assets can fully evaluate their adequacy for their own purposes and projects.

2020

LASER diode-based transmitter module for optical wireless communications

Authors
Araujo, JH; Kraemer, R; Santos, HM; Pereira, F; Salgado, HM; Pessoa, LM;

Publication
2020 12th International Symposium on Communication Systems, Networks and Digital Signal Processing, CSNDSP 2020

Abstract
In this paper, we present the design of an analog transmitter based on a blue LD targeting optical wireless communications, suitable for OFDM signals. The approach relies on a thorough characterization of the individual components of the module, whence a detailed circuit model is obtained to design an impedance matching circuit for improved performance, prior to fabrication. The impedance matching is based on non-uniform transmission lines and works well over a wide frequency range (100 MHz to 2 GHz). The results are experimentally validated by the transmitter response exhibiting an increased 6 dB bandwidth limit and 1 GHz bandwidth improvement. © 2020 IEEE.

2020

5.36 Gbit/s OFDM optical wireless communication link over the underwater channel

Authors
Araujo, JH; Kraemer, R; Tavares, JS; Pereira, F; Salgado, HM; Pessoa, LM;

Publication
2020 12th International Symposium on Communication Systems, Networks and Digital Signal Processing, CSNDSP 2020

Abstract
An OFDM transmission system is reported based on a directly modulated blue LASER diode, for high bit rate under-water optical communication applications. The 256 subcarriers 16-QAM signal is transmitted over a total distance of 2.4 m underwater with an EVM lower than -28.5 dB for a 250 MHz bandwidth and -16.5 dB for a 2 GHz bandwidth, the BER being lower than the forward error corrector limit. At the maximum bandwidth of 2 GHz a transmission rate of 5.36 Gbit/s is achieved. © 2020 IEEE.