Henrique Salgado | Faculty of Engineering of the University of Porto (original) (raw)

Papers by Henrique Salgado

OCEANS 2016 - Shanghai, 2016

The use of high efficiency resonant coupling wireless power systems for subsea operations is here... more The use of high efficiency resonant coupling wireless power systems for subsea operations is here considered for the charging of autonomous underwater vehicles. In this paper, two architectures based on two different inductors are analysed for their potential as resonant wireless power couplers. Both systems were designed and optimised through electromagnetic 3D simulations, upon which two prototypes were constructed and measured. Efficiencies as high as 75% for distances up to 5 cm were achieved on experimental testing.

OCEANS 2019 - Marseille

In this paper we evaluate the long-term deployment feasibility of a large-scale network of abando... more In this paper we evaluate the long-term deployment feasibility of a large-scale network of abandoned underwater sensors, where power is provided by autonomous underwater vehicles (AUVs) in periodic visits.

Wireless Mesh Networks - Security, Architectures and Protocols

The radiative transfer equation (RTE) is a theoretical framework that can be used for predicting ... more The radiative transfer equation (RTE) is a theoretical framework that can be used for predicting and interpreting underwater light fields in terms of the constituents of natural water bodies. However, the RTE is a complex integrodifferential equation and deriving exact solutions for it is a difficult task. In this chapter, we aim to present some details regarding Monte Carlo simulations and how this method may be applied to solve the RTE numerically. By solving the RTE, one may accurately predict the received power and estimate the channel bandwidth and several other measurable parameters with regard to multiple water conditions. Simulations will also be presented.

2019 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC)

In this paper we describe the design of a dual polarized packaged patch antenna for 5G communicat... more In this paper we describe the design of a dual polarized packaged patch antenna for 5G communications with improved isolation and bandwidth for Ka-band. The results were validated using FEM and Momentum co-simulations in ADS. The novelty of the approach is the use of parasitic elements in the same layer to circumvent bandwidth limitations, thereby reducing the layer count in contrast to previous designs, combined with a differential feeding technique for improved isolation and radiation pattern stability, albeit at the expense of an increased complexity in the matching process. A peak gain of 5 dBi, isolation above 40 dB and a radiation efficiency of 60% were obtained.

Electronics, 2020

In this paper, we describe the design of a dual polarized packaged patch antenna for 5G communica... more In this paper, we describe the design of a dual polarized packaged patch antenna for 5G communications with improved isolation and bandwidth for K-band. We introduce a differential feeding technique and a heuristic-based design of a matching network applied to a single layer patch antenna with parasitic elements. This approach resulted in broader bandwidth, reduced layer count, improved isolation and radiation pattern stability. The results were validated through finite element method (FEM) and method of moments (MoM) simulations. A peak gain of 5 dBi, isolation above 40 dB and a radiation efficiency of 60% were obtained.

This work presents an Inverted-L antenna design using the fractal geometry for dual band WLAN (2.... more This work presents an Inverted-L antenna design using the fractal geometry for dual band WLAN (2.4/5.2GHz) USB dongle application. The proposed antenna has the advantages of compact size, wide operation bandwidth and easy fabrication. The experimental results show that it has a S11

André Oliveira Tekever, Portugal, andre.oliveira@tekever.com Pedro Sinogas Tekever, Portugal, pe... more André Oliveira Tekever, Portugal, andre.oliveira@tekever.com Pedro Sinogas Tekever, Portugal, pedro.sinogas@tekever.com Stefan Taing Munich Innovation Group, Germany, st@munich-innovation.com Jens Elsner Munich Innovation Group, Germany, je@munich-innovation.com Simon Watts Avanti Communications Group plc, United Kingdom, simon.watts@avantiplc.com Valentine Boissinot Avanti Communications Group plc, United Kingdom, valentine.boissinot@avantiplc.com Henrique M. Salgado INESC TEC and Faculty of Engineering, University of Porto, Portugal, henrique.salgado@inescporto.pt João Canas Ferreira INESC TEC and Faculty of Engineering, University of Porto, Portugal, joao.c.ferreira@inescporto.pt Luis Pessoa INESC TEC, Portugal, luis.m.pessoa@inescporto.pt José Machado da Silva INESC TEC and Faculty of Engineering, University of Porto, Portugal, jose.m.silva@inescporto.pt

Applied Sciences, 2021

The design of a uniformly spaced 1 × 4 linear antenna array using epitaxial layers of benzocyclob... more The design of a uniformly spaced 1 × 4 linear antenna array using epitaxial layers of benzocyclobutene over an InP substrate is demonstrated. The array elements are conjugately matched with a uni-travelling carrier photodiode at the input. The phased array is optimised to counteract mutual coupling effects by introducing metal strips with isolated ground planes for each radiating element. The proposed antenna array can provide a gain of 10 dBi with a gain variation of ±3 dB. The array operates over a bandwidth of 10 GHz (295–305 GHz) with a wide scanning angle of 100° in the broadside.

Electronics, 2020

In this paper, we describe the design of an electrically large anechoic chamber for usage on mill... more In this paper, we describe the design of an electrically large anechoic chamber for usage on millimetre-wave bands. Ansys Savant sotware was used to perform a simulation of the chamber, using physical optics coupled with uniform theory of diffraction (PO/UTD). Moreover, a method based on an open waveguide probe is described in this paper to obtain the electrical properties of the RF absorbers at millimetre-wave frequencies. Two different source antennas were simulated in this work and the corresponding quiet zones predicted. The largest quiet zone was 30 m m × 30 m m × 50 m m , for a chamber size of 1.2 m m × 0.6 m m × 0.6 m .

Optics Express, 2019

We report on the direct intensity modulation characteristics of a high-speed resonant tunneling d... more We report on the direct intensity modulation characteristics of a high-speed resonant tunneling diode-photodetector (RTD-PD) with an oscillation frequency of 79 GHz. This work demonstrates both electrical and optical modulation and shows that RTD-PD oscillators can be utilized as versatile optoelectronic/radio interfaces. This is the first demonstration of optical modulation of an RF carrier using integrated RTD-PD oscillators at microwave frequencies.

Microwave and Optical Technology Letters, 2019

Optical modulation characteristics of resonant tunneling diode photodetectors (RTD‐PD) are invest... more Optical modulation characteristics of resonant tunneling diode photodetectors (RTD‐PD) are investigated. Intensity modulated light excites the RTD‐PDs to conduct data experiments. Simple and complex data patterns are used with results showing data rates up to 80 and 200 Mbit/s, respectively. This is the first demonstration of complex modulation using resonant tunneling diodes.

Journal of Lightwave Technology, 2017

In this paper we further explore the concept of phase-conjugated twin waves (PCTW) for nonlinear ... more In this paper we further explore the concept of phase-conjugated twin waves (PCTW) for nonlinear cancellation in space-division multiplexed (SDM) systems. Previously, we demonstrated that the PCTW technique can successfully provide nonlinear cancellation in SDM systems. In this paper, we investigate the cases where two and four spatial modes are copropagating in a multimode fiber, considering three link lengths (1000 km, 3200 km and 8000 km). Weak and strong-coupling regimes are also evaluated. Our numerical simulation results show an average performance improvement >10 dB after a 1000 km transmission link.

Microwave and Optical Technology Letters

ABSTRACT

Optoelectronics - Materials and Devices, 2015

Radio-over-fiber technology, used in the transport of radio signals over optical fiber by means o... more Radio-over-fiber technology, used in the transport of radio signals over optical fiber by means of an optical carrier between a remote site and a central node of a cellular network, is an attractive solution for backhauling of a large number of remote antennas, enabling the shifting of the hardware complexity from base stations to a central station. Integration of both optical and wireless broadband infrastructures into the same backhaul network leads to significant simplification and cost reduction of base stations permitting equipment sharing and dynamic allocation of resources, which in turn leads to simplified system operation and maintenance. Wireless systems on the other hand are evolving rapidly and new standards are appearing, such as the Long-Term Evolution aiming at satisfying the required need for increasing bandwidth. Radio-over-fiber systems are known to be susceptible to noise and non-linear distortion in particular to the large peak-to-average power ratio of orthogonal frequency division multiplexing signals employed in these standards. In this work we compare, experimentally and through simulation, the performance of orthogonal frequency division multiplexing and single carrier frequency division multiple access signals, in radio-over-fiber applications, using directly modulated VCSELs.

Optics Communications, 2006

The underlying formation mechanisms and the properties of long-period gratings produced through a... more The underlying formation mechanisms and the properties of long-period gratings produced through arc discharges are intrinsically related to the temperature reached by the fibre during arc exposure. In this work, the determination of the fibre temperature was based on PlankÕs blackbody radiation law. The radiation emitted by the optical fibre during heating due to an electric arc discharge, detected using a Cronin spectrometer, was fitted to the emission spectrum of the blackbody radiation, allowing the estimation of the temperature range attained by the fibre. A peak temperature of 1400 ± 50°C was obtained.

Proceedings of SPIE - The International Society for Optical Engineering, 2013

ABSTRACT Achieving affordable high speed fiber optic communication networks for airplane systems ... more ABSTRACT Achieving affordable high speed fiber optic communication networks for airplane systems has proved to be challenging. In this paper we describe a summary of the EU Framework 7 project DAPHNE (Developing Aircraft Photonic Networks). DAPHNE aimed to exploit photonic technology from terrestrial communications networks, and then develop and optimize aircraft photonic networks to take advantage of the potential cost savings. The main areas of emphasis were on: multiplexing networks; providing standard components; simplifying installation; and reducing through life support costs. DAPHNE (fifteen partners from seven nations) finished in February 2013; and was supported by the European Commission‟s Seventh Framework Programme, although the consortium members are continuing with in-house developments.

Sensors, 2013

We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunn... more We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD's NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.

Optics Letters, 2005

Permanent long-period gratings were written using arc discharges in two aluminosilicate fibers, o... more Permanent long-period gratings were written using arc discharges in two aluminosilicate fibers, one of which was doped with erbium. Reversible gratings were also mechanically induced in both fibers. The thermal behavior of the arcinduced gratings was investigated at up to 1100°C. It was found that the shift of the resonant wavelengths exhibited a well-defined linear dependence on temperature up to 700°C.

Optics Communications, 2006

We have investigated the sensitivity of arc-induced long-period gratings to changes of ambient re... more We have investigated the sensitivity of arc-induced long-period gratings to changes of ambient refractive index. Two pure-silica-core fibres with different cladding diameters and a standard fibre were used in this study. For a 6 • 10 À3 change of the refractive index, a 240 pm shift of the resonant wavelength was achieved with long-period gratings written in the 125 lm cladding diameter pure-silica-core fibre.

Optics Communications, 2006

We have investigated the polarization properties of long-period fibre gratings fabricated using t... more We have investigated the polarization properties of long-period fibre gratings fabricated using the electric arc technique. It was found that the choice of the fabrication parameters (electric current, arc duration and pulling tension) affects the polarization dependent loss of the produced gratings. In particular, a non-monotonic dependence on the external pulling tension was obtained.

OCEANS 2016 - Shanghai, 2016

The use of high efficiency resonant coupling wireless power systems for subsea operations is here... more The use of high efficiency resonant coupling wireless power systems for subsea operations is here considered for the charging of autonomous underwater vehicles. In this paper, two architectures based on two different inductors are analysed for their potential as resonant wireless power couplers. Both systems were designed and optimised through electromagnetic 3D simulations, upon which two prototypes were constructed and measured. Efficiencies as high as 75% for distances up to 5 cm were achieved on experimental testing.

OCEANS 2019 - Marseille

In this paper we evaluate the long-term deployment feasibility of a large-scale network of abando... more In this paper we evaluate the long-term deployment feasibility of a large-scale network of abandoned underwater sensors, where power is provided by autonomous underwater vehicles (AUVs) in periodic visits.

Wireless Mesh Networks - Security, Architectures and Protocols

The radiative transfer equation (RTE) is a theoretical framework that can be used for predicting ... more The radiative transfer equation (RTE) is a theoretical framework that can be used for predicting and interpreting underwater light fields in terms of the constituents of natural water bodies. However, the RTE is a complex integrodifferential equation and deriving exact solutions for it is a difficult task. In this chapter, we aim to present some details regarding Monte Carlo simulations and how this method may be applied to solve the RTE numerically. By solving the RTE, one may accurately predict the received power and estimate the channel bandwidth and several other measurable parameters with regard to multiple water conditions. Simulations will also be presented.

2019 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC)

In this paper we describe the design of a dual polarized packaged patch antenna for 5G communicat... more In this paper we describe the design of a dual polarized packaged patch antenna for 5G communications with improved isolation and bandwidth for Ka-band. The results were validated using FEM and Momentum co-simulations in ADS. The novelty of the approach is the use of parasitic elements in the same layer to circumvent bandwidth limitations, thereby reducing the layer count in contrast to previous designs, combined with a differential feeding technique for improved isolation and radiation pattern stability, albeit at the expense of an increased complexity in the matching process. A peak gain of 5 dBi, isolation above 40 dB and a radiation efficiency of 60% were obtained.

Electronics, 2020

In this paper, we describe the design of a dual polarized packaged patch antenna for 5G communica... more In this paper, we describe the design of a dual polarized packaged patch antenna for 5G communications with improved isolation and bandwidth for K-band. We introduce a differential feeding technique and a heuristic-based design of a matching network applied to a single layer patch antenna with parasitic elements. This approach resulted in broader bandwidth, reduced layer count, improved isolation and radiation pattern stability. The results were validated through finite element method (FEM) and method of moments (MoM) simulations. A peak gain of 5 dBi, isolation above 40 dB and a radiation efficiency of 60% were obtained.

This work presents an Inverted-L antenna design using the fractal geometry for dual band WLAN (2.... more This work presents an Inverted-L antenna design using the fractal geometry for dual band WLAN (2.4/5.2GHz) USB dongle application. The proposed antenna has the advantages of compact size, wide operation bandwidth and easy fabrication. The experimental results show that it has a S11

André Oliveira Tekever, Portugal, andre.oliveira@tekever.com Pedro Sinogas Tekever, Portugal, pe... more André Oliveira Tekever, Portugal, andre.oliveira@tekever.com Pedro Sinogas Tekever, Portugal, pedro.sinogas@tekever.com Stefan Taing Munich Innovation Group, Germany, st@munich-innovation.com Jens Elsner Munich Innovation Group, Germany, je@munich-innovation.com Simon Watts Avanti Communications Group plc, United Kingdom, simon.watts@avantiplc.com Valentine Boissinot Avanti Communications Group plc, United Kingdom, valentine.boissinot@avantiplc.com Henrique M. Salgado INESC TEC and Faculty of Engineering, University of Porto, Portugal, henrique.salgado@inescporto.pt João Canas Ferreira INESC TEC and Faculty of Engineering, University of Porto, Portugal, joao.c.ferreira@inescporto.pt Luis Pessoa INESC TEC, Portugal, luis.m.pessoa@inescporto.pt José Machado da Silva INESC TEC and Faculty of Engineering, University of Porto, Portugal, jose.m.silva@inescporto.pt

Applied Sciences, 2021

The design of a uniformly spaced 1 × 4 linear antenna array using epitaxial layers of benzocyclob... more The design of a uniformly spaced 1 × 4 linear antenna array using epitaxial layers of benzocyclobutene over an InP substrate is demonstrated. The array elements are conjugately matched with a uni-travelling carrier photodiode at the input. The phased array is optimised to counteract mutual coupling effects by introducing metal strips with isolated ground planes for each radiating element. The proposed antenna array can provide a gain of 10 dBi with a gain variation of ±3 dB. The array operates over a bandwidth of 10 GHz (295–305 GHz) with a wide scanning angle of 100° in the broadside.

Electronics, 2020

In this paper, we describe the design of an electrically large anechoic chamber for usage on mill... more In this paper, we describe the design of an electrically large anechoic chamber for usage on millimetre-wave bands. Ansys Savant sotware was used to perform a simulation of the chamber, using physical optics coupled with uniform theory of diffraction (PO/UTD). Moreover, a method based on an open waveguide probe is described in this paper to obtain the electrical properties of the RF absorbers at millimetre-wave frequencies. Two different source antennas were simulated in this work and the corresponding quiet zones predicted. The largest quiet zone was 30 m m × 30 m m × 50 m m , for a chamber size of 1.2 m m × 0.6 m m × 0.6 m .

Optics Express, 2019

We report on the direct intensity modulation characteristics of a high-speed resonant tunneling d... more We report on the direct intensity modulation characteristics of a high-speed resonant tunneling diode-photodetector (RTD-PD) with an oscillation frequency of 79 GHz. This work demonstrates both electrical and optical modulation and shows that RTD-PD oscillators can be utilized as versatile optoelectronic/radio interfaces. This is the first demonstration of optical modulation of an RF carrier using integrated RTD-PD oscillators at microwave frequencies.

Microwave and Optical Technology Letters, 2019

Optical modulation characteristics of resonant tunneling diode photodetectors (RTD‐PD) are invest... more Optical modulation characteristics of resonant tunneling diode photodetectors (RTD‐PD) are investigated. Intensity modulated light excites the RTD‐PDs to conduct data experiments. Simple and complex data patterns are used with results showing data rates up to 80 and 200 Mbit/s, respectively. This is the first demonstration of complex modulation using resonant tunneling diodes.

Journal of Lightwave Technology, 2017

In this paper we further explore the concept of phase-conjugated twin waves (PCTW) for nonlinear ... more In this paper we further explore the concept of phase-conjugated twin waves (PCTW) for nonlinear cancellation in space-division multiplexed (SDM) systems. Previously, we demonstrated that the PCTW technique can successfully provide nonlinear cancellation in SDM systems. In this paper, we investigate the cases where two and four spatial modes are copropagating in a multimode fiber, considering three link lengths (1000 km, 3200 km and 8000 km). Weak and strong-coupling regimes are also evaluated. Our numerical simulation results show an average performance improvement >10 dB after a 1000 km transmission link.

Microwave and Optical Technology Letters

ABSTRACT

Optoelectronics - Materials and Devices, 2015

Radio-over-fiber technology, used in the transport of radio signals over optical fiber by means o... more Radio-over-fiber technology, used in the transport of radio signals over optical fiber by means of an optical carrier between a remote site and a central node of a cellular network, is an attractive solution for backhauling of a large number of remote antennas, enabling the shifting of the hardware complexity from base stations to a central station. Integration of both optical and wireless broadband infrastructures into the same backhaul network leads to significant simplification and cost reduction of base stations permitting equipment sharing and dynamic allocation of resources, which in turn leads to simplified system operation and maintenance. Wireless systems on the other hand are evolving rapidly and new standards are appearing, such as the Long-Term Evolution aiming at satisfying the required need for increasing bandwidth. Radio-over-fiber systems are known to be susceptible to noise and non-linear distortion in particular to the large peak-to-average power ratio of orthogonal frequency division multiplexing signals employed in these standards. In this work we compare, experimentally and through simulation, the performance of orthogonal frequency division multiplexing and single carrier frequency division multiple access signals, in radio-over-fiber applications, using directly modulated VCSELs.

Optics Communications, 2006

The underlying formation mechanisms and the properties of long-period gratings produced through a... more The underlying formation mechanisms and the properties of long-period gratings produced through arc discharges are intrinsically related to the temperature reached by the fibre during arc exposure. In this work, the determination of the fibre temperature was based on PlankÕs blackbody radiation law. The radiation emitted by the optical fibre during heating due to an electric arc discharge, detected using a Cronin spectrometer, was fitted to the emission spectrum of the blackbody radiation, allowing the estimation of the temperature range attained by the fibre. A peak temperature of 1400 ± 50°C was obtained.

Proceedings of SPIE - The International Society for Optical Engineering, 2013

ABSTRACT Achieving affordable high speed fiber optic communication networks for airplane systems ... more ABSTRACT Achieving affordable high speed fiber optic communication networks for airplane systems has proved to be challenging. In this paper we describe a summary of the EU Framework 7 project DAPHNE (Developing Aircraft Photonic Networks). DAPHNE aimed to exploit photonic technology from terrestrial communications networks, and then develop and optimize aircraft photonic networks to take advantage of the potential cost savings. The main areas of emphasis were on: multiplexing networks; providing standard components; simplifying installation; and reducing through life support costs. DAPHNE (fifteen partners from seven nations) finished in February 2013; and was supported by the European Commission‟s Seventh Framework Programme, although the consortium members are continuing with in-house developments.

Sensors, 2013

We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunn... more We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD's NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.

Optics Letters, 2005

Permanent long-period gratings were written using arc discharges in two aluminosilicate fibers, o... more Permanent long-period gratings were written using arc discharges in two aluminosilicate fibers, one of which was doped with erbium. Reversible gratings were also mechanically induced in both fibers. The thermal behavior of the arcinduced gratings was investigated at up to 1100°C. It was found that the shift of the resonant wavelengths exhibited a well-defined linear dependence on temperature up to 700°C.

Optics Communications, 2006

We have investigated the sensitivity of arc-induced long-period gratings to changes of ambient re... more We have investigated the sensitivity of arc-induced long-period gratings to changes of ambient refractive index. Two pure-silica-core fibres with different cladding diameters and a standard fibre were used in this study. For a 6 • 10 À3 change of the refractive index, a 240 pm shift of the resonant wavelength was achieved with long-period gratings written in the 125 lm cladding diameter pure-silica-core fibre.

Optics Communications, 2006

We have investigated the polarization properties of long-period fibre gratings fabricated using t... more We have investigated the polarization properties of long-period fibre gratings fabricated using the electric arc technique. It was found that the choice of the fabrication parameters (electric current, arc duration and pulling tension) affects the polarization dependent loss of the produced gratings. In particular, a non-monotonic dependence on the external pulling tension was obtained.