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- Long distance real-time echo cancellationPublication . J. Ferreira, Artur; Marques, Paulo; Carvalho, HélderThis paper describes an implementation of a long distance echo canceller, operating on full-duplex with handsfree and in real-time with a single Digital Signal Processor (DSP). The proposed solution is based on short length adaptive filters centered on the positions of the most significant echoes, tracked by time delay estimators. To deal with double talking situations a speech detector is employed. The floating-point DSP TMS320C6713 from Texas Instruments is used with software written on the C++ programming language using some compiler optimizations to reduce execution time. The resulting algorithm enables long distance echo cancellation with low computational requirements. It reaches greater echo return, loss enhancement and shows faster convergence speed than the conventional solu tion. Our experimental results also approach the CCITT G.165 recommendation for echo cancellers.
- Evaluation of a low-cost COTS bio radar for vital signs monitoringPublication . Silva, Fábio; Almeida, Rita; Pinho, Pedro; Marques, Paulo; Lopes, Sérgio IvanWith the beginning of the COVID-19 pandemic, there was a need for the Health Care Workers (HCW) to pay more attention to the vital signs of their patients. One way for this to happen, while respecting the social distance, is using contactless technologies, e.g. the bio radar. This way, the HCW will be able to monitor the respiration and heart rates of the patient, without getting close to him. For this to be possible, the best radar configurations were studied, as well as other important aspects that should be taken into consideration while monitoring a patient, for the results obtained to be reliable.
- Velocity estimation of moving ships using C-band SLC SAR dataPublication . Radius, Andrea; Marques, PauloA new algorithm for the velocity vector estimation of moving ships using Single Look Complex (SLC) SAR data in strip map acquisition mode is proposed. The algorithm exploits both amplitude and phase information of the Doppler decompressed data spectrum, with the aim to estimate both the azimuth antenna pattern and the backscattering coefficient as function of the look angle. The antenna pattern estimation provides information about the target velocity; the backscattering coefficient can be used for vessel classification. The range velocity is retrieved in the slow time frequency domain by estimating the antenna pattern effects induced by the target motion, while the azimuth velocity is calculated by the estimated range velocity and the ship orientation. Finally, the algorithm is tested on simulated SAR SLC data.
- Design of pulsed waveforms for space debris detection with ATLASPublication . Pandeirada, João; Bergano, Miguel; Marques, Paulo; Barbosa, Domingos; Freitas, José; Coelho, Bruno; Ribeiro, ValerioATLAS is the first Portuguese radar system that aims to detect space debris. The article introduces the system and provides a brief description of its capabilities. The sys tem is capable of synthesizing arbitrary amplitude modu lated pulse shapes with a resolution of 10 ns. Given that degree of freedom we decided to test an amplitude mod ulated chirp signal developed by us and a nested barker code. These waveforms are explained as well as their ad vantages and drawbacks for space debris detection. An experimental setup was developed to test the system re ceiver and waveforms are processed by digital matched filtering. The experiments test the system using different waveform shapes and noise levels. Experimental results are in agreement with simulation and show that the chirp signal is more resilient to Doppler shifts, has higher range resolution and lower peak-to-sidelobe ratio in compari son with the nested barker code. Future work in order to increase detection capabilities is discussed at the end.
- New SST optical sensor of Pampilhosa da Serra – studies on image processing algorithms and multi-filter characterization of space debrisPublication . Coelho, Bruno; Barbosa, Domingos; Bergano, Miguel; Correia, A.; Freitas, José; Marques, Paulo; Pandeirada, João; Ribeiro, ValerioAs part of the Portuguese Space Surveillance & Tracking (SST) System, two new Wide Field of View (2.3ºx2.3º) small aperture (30cm) telescopes will be deployed in 2021, at the Pampilhosa da Serra Space Observatory (PASO), located in the center of the continental Por tuguese territory, in the heart of a certified Dark Sky area. These optical systems will provide added value ca pabilities to the Portuguese SST network, complement ing the optical telescopes currently in commissioning in Madeira and Azores. These telescopes are optimized for GEO and MEO survey operations and besides the required SST operational capability, they will also pro vide an important development component to the Por tuguese SST network. The telescopes will be equipped with filter wheels, being able to perform observations in several optical bands including white light, BVRI bands and narrow band filters such as H(alpha) and O[III] to study potential different object’s albedos. This config uration enables us to conduct a study on space debris classification/characterization using combinations of dif ferent colors aiming the production of improved color in dex schemes to be incorporated in the automatic pipelines for classification of space debris. This optical sensor will also be used to conduct studies on image processing algo rithms, including source extraction and classification so lutions through the application of machine learning tech niques. Since SST dedicated telescopes produce a large quantity of data per observation night, fast, efficient and automatic image processing techniques are mandatory. A platform like this one, dedicated to the development of Space Surveillance studies, will add a critical capability to keep the Portuguese SST network updated, and as a consequence it may provide useful developments to the European SST network as well.
- (Virtual) Agents for running electricity marketsPublication . Trigo, Paulo; Marques, Paulo; Coelho, HelderThis paper describes a multi-agent based simulation (MABS) framework to construct an artificial electric power market populated with learning agents. The artificial market, named TEMMAS (The Electricity Market Multi-Agent Simulator), explores the integration of two design constructs: (i) the specification of the environmental physical market properties and (ii) the specification of the decision-making (deliberative) and reactive agents. TEMMAS is materialized in an experimental setup involving distinct power generator companies that operate in the market and search for the trading strategies that best exploit their generating units' resources. The experimental results show a coherent market behavior that emerges from the overall simulated environment.
- Opportunity targets as references for phase correction on passive radar channelsPublication . Marques, PauloThis paper considers the problem of phase correction on Passive Radar using opportunity targets present in the target area. The proposed technique has very low hardware and computational requirements and can be applied to configurations where it is desirable, or necessary, to have dispersed receivers, such as in a multistatic passive radar system, avoiding the use of costly methods. The main idea is to take advantage of a reference target, with a known position, to correct the phase error on the several channels. Simulation results illustrating the effectiveness and limitations of the proposed methodology are presented.
- Directional Moving Target Indication for Civil Traffic Monitoring Using Single Channel SARPublication . Marques, PauloThis paper presents a novel moving target indicator which is selective with respect to a direction of interest. Preliminary results indicate that the obtained selectivity may have high interest in civil traffic monitoring using single channel SAR data.
- Low-carbon cement with waste oil-cracking catalyst incorporationPublication . Costa, Carla; Marques, PauloThe present paper shows preliminary results of an ongoing project which one of the goals is to investigate the viability of using waste FCC catalyst (wFCC), originated from Portuguese oil refinery, to produce low carbon blended cements. For this purpose, four blended cements were produced by substituting cement CEM I 42.5R up to 20% (w/w) by waste FCC catalyst. Initial and final setting times, consistency of standard paste, soundness and compressive strengths after 2, 7 and 28 days were measured. It was observed that the wFCC blended cements developed similar strength, at 28 days, compared to the reference cement, CEM I 42.5R. Moreover, cements with waste FCC catalyst incorporation up to 15% w/w meet European Standard EN 197-1 specifications for CEM II/A type cement, in the 42.5R strength class.
- Development of the first portuguese radar tracking sensor for space debrisPublication . Pandeirada, João; Bergano, Miguel; Neves, João; Marques, Paulo; Barbosa, Domingos; Coelho, Bruno; Ribeiro, ValerioCurrently, space debris represents a threat for satellites and space-based operations, both in-orbit and during the launching process. The yearly increase in space debris represents a serious concern to major space agencies leading to the development of dedicated space programs to deal with this issue. Ground-based radars can detect Earth orbiting debris down to a few square centimeters and therefore constitute a major building block of a space debris monitoring system. New radar sensors are required in Europe to enhance capabilities and availability of its small radar network capable of tracking and surveying space objects and to respond to the debris increase expected from the New Space economy activities. This article presents ATLAS, a new tracking radar system for debris detection located in Portugal. It starts by an extensive technical description of all the system components followed by a study that estimates its future performance. A section dedicated to waveform design is also presented, since the system allows the usage of several types of pulse modulation schemes such as LFM and phase coded modulations while enabling the development and testing of more advanced ones. By presenting an architecture that is highly modular with fully digital signal processing, ATLAS establishes a platform for fast and easy development, research, and innovation. The system follows the use of Commercial-Off-The-Shelf technologies and Open Systems which is unique among current radar systems.