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About

About

I have received the Licenciatura and PhD degrees in electrical and computer engineering from the Faculty of Engineering of the University of Porto (FEUP), Portugal. I am a researcher at INESC TEC with scientific interests in wireless transceiver architectures, low-power mixed-signal design, CMOS circuits for mobile communication systems, and wireless power transfer.

Interest
Topics
Details

Details

006
Publications

2021

Potential Non-Invasive Technique for Accessing Plant Water Contents Using a Radar System

Authors
Santos, LC; dos Santos, FN; Morais, R; Duarte, C;

Publication
Agronomy

Abstract
Sap flow measurements of trees are today the most common method to determine evapotranspiration at the tree and the forest/crop canopy level. They provide independent measurements for flux comparisons and model validation. The most common approach to measure the sap flow is based on intrusive solutions with heaters and thermal sensors. This sap flow sensor technology is not very reliable for more than one season crop; it is intrusive and not adequate for low diameter trunk trees. The non-invasive methods comprise mostly Radio-frequency (RF) technologies, typically using satellite or air-born sources. This system can monitor large fields but cannot measure sap levels of a single plant (precision agriculture). This article studies the hypothesis to use of RF signals attenuation principle to detect variations in the quantity of water present in a single plant. This article presents a well-defined experience to measure water content in leaves, by means of high gains RF antennas, spectrometer, and a robotic arm. Moreover, a similar concept is studied with an off-the-shelf radar solution—for the automotive industry—to detect changes in the water presence in a single plant and leaf. The conclusions indicate a novel potential application of this technology to precision agriculture as the experiments data is directly related to the sap flow variations in plant.

2020

Analysis and Design of a Polar Digitally Modulated CMOS PA Based on Switched Constant-Current

Authors
Gomes, R; Duarte, C; Pedro, JC;

Publication
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES

Abstract
Typical polar digital power amplifiers (DPAs) employ unit-cells operated in class-E or D-1, denoting a switched-resistance operation which degrades linearity. Besides introducing higher demand on digital predistortion (DPD), it also requires extra quantization bits, impacting the overall efficiency and system complexity. To address this, the present work makes use of an optimized constant-current cascode unit-cell which is combined with reduced conduction angle to achieve linear and efficient operation, while minimizing the effort on DPD and/or calibration. A design strategy is developed which focuses on the cascode bias voltage and transistor relative dimensions as design parameters, allowing cascode efficiency optimization without compromising linearity or reliability. A single-ended polar switched constant-current DPA is implemented in 180-nm standard CMOS. Continuous-wave measurements performed at 800 MHz demonstrate an output power of 24 dBm with a PAE of 47%. The DPA dynamic behavior was tested with a 64-QAM signal with 10 MS/s, achieving an average PAE of 20.9% with a peak-to-average power ratio (PAPR) of 8.7 dB and adjacent-channel leakage ratio (ACLR) = 40.34 dB. These results demonstrate comparable performance with the prior art while using only 6-bits clocked at 100 MHz baseband sampling frequency.

2020

Yield Analysis for Electrical Circuit Designs: Many Problems and Some Recent Developments in Electronic Engineering

Authors
Weber, S; Duarte, C;

Publication
IEEE Solid-State Circuits Magazine

Abstract
A high production yield, Y = 1 - pfail, and thus a low failure rate, pfail, is a key requirement for successful chip design and the design of many other technical products and systems. We focus on IC design in the analog and mixedsignal domains, where Monte Carlo (MC) techniques have been a standard method for many years (see "Important Monte Carlo Rules Engineers Should Know"). Circuits have to be reliable under certain ranges of environmental parameters, such as supply voltage (V) and temperature (T). Furthermore, the set of semiconductor technology parameters (P) varies significantly, from die to die (global variations) to device to device (local variations, called mismatch). Many circuit tricks are known to minimize all of these influences (for example, using cascodes for a high power-supply rejection, differential pairs to cancel out threshold voltages, special layout techniques, and so on), but at some point problems become hard to anticipate, and further improvements are difficult to achieve. We must accept such variations and need to analyze their impact on production yield, which is a function of these parameters and the specifications (such as design topology and component sizes, among others). © 2009-2012 IEEE.

2019

Design of an underwater sensor network perpetually powered from AUVs

Authors
Pessoa, LM; Duarte, C; Salgado, HM; Correia, V; Ferreira, B; Cruz, NA; Matos, A;

Publication
OCEANS 2019 - Marseille

Abstract

2019

Experimental Evaluation of Coupling Coils for Underwater Wireless Power Transfer

Authors
Duarte, C; Goncalves, F; Silva, M; Correia, V; Pessoa, LM;

Publication
2019 IEEE Wireless Power Transfer Conference (WPTC)

Abstract

Supervised
thesis

2020

Estudo e implementação de uma metodologia de estimação de potência de circuitos analógicos em modelos de System Verilog

Author
Francisco Bandeira Lobo de Àvila

Institution
UP-FEUP

2020

Hybrid CMOS/Memristor Circuits Emulator

Author
André Filipe Ávila Silva

Institution
UP-FEUP

2020

Implementation of Wireless Communication for IoT with Vortex Nano-Oscillators

Author
João Carlos Rodrigues Presa

Institution
UP-FEUP

2020

Ultra-Low-Power CMOS Oscillators

Author
Renato Alexandre da Silva Ferreira

Institution
UP-FEUP

2020

Analog Block Evaluation with BIST Instruments

Author
Carla Catarina Raposo Jorge

Institution
UP-FEUP