Percorrer por autor "Alves, Luís N."
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- All-digital reconfigurable STDCC radar baseband implementation in FPGAPublication . Duarte, Luís; Ribeiro, Carlos; Alves, Luís N.; Caldeirinha, Rafael F. S.This paper reports the architecture of an all-digital Swept Time-Delay Cross-Correlator (STDCC) baseband. Until recently, the sliding correlator technique has been mainly em-ployed for sounding the radio propagation channel. However, recent benchmarks have shown promising results in target detection context when compared to commercially available solutions. STDCC takes advantage of the sliding correlation properties of Pseudo-Noise (PN) sequences. Therefore, this paper presents the baseband generation for this new radar technique with on-the-fly sequence tuning using a Field-Programmable Gate Array (FPGA). The reconfigurable STDCC radar baseband generates both PN sequences digitally and requires a low-cost ADC to acquire the time dilated result. At the end, the proposed architecture is evaluated regarding resource usage efficiency and then the radar performance will be discussed in terms of the all-digital PN sequence spectrum and the real-time slide correlation. Our analysis confirmed a strong correlation between both sequence length and sampling frequency with radar detectable distance.
- Consumer LED lamp with ODAC technology for high-speed visible light communicationsPublication . Figueiredo, Mónica; Ribeiro, Carlos; Dobesch, Ales; Alves, Luís N.; Wilfert, OtakarOptical digital-to-analog converters (ODACs) were recently proposed to mitigate the non-linear characteristic of light emitting diodes (LEDs) and to simplify the transceiver in optical wireless communication systems. This paper describes the implementation and performance of an ODAC lamp built with commercial phosphor coated LEDs. It is shown to have sufficient performance to cope with data-rates compatible with those recommended for Ultra HD quality internet download speed (25Mbps), despite the very low bandwidth of these LEDs. Also, the structure of a low-cost and high-speed OFDM-based Visible Light Communication transceiver, based on commercial LEDs and off-the-shelf components, is presented. This solution does not require D/A conversion or complex LED driving circuitry in the transmitter, which are usually seen as limiting factors to the deployment of high-speed VLC systems in the consumer LED lighting market.
- Reconfigurable millimetre-wave RF front-end for radar and 5G applicationsPublication . Duarte, Luís; Reis, João R.; Leonor, Nuno; Ribeiro, Carlos; Alves, Luís N.; Caldeirinha, Rafael F. S.This paper proposes a reconfigurable RF architecture to cope with radar applications in autonomous driving vehicles and the next generation of communications (5G). A radio front-end architecture operating at frequencies between 24 and 27.5 GHz to deliver a small form-factor design that could easily be changed and ease future improvements, has been developed. Based on X-microwave ecosystem, a fully reconfigurable mmWave RF front-end has been designed and experimentally characterised. Due to the high modularity of the proposed front-end architecture, each mmWave RF component is tested and characterised in the frequency range of 24-27 GHz, allowing the final prototype to be used in future radar and communication systems. Results for the proposed architecture are presented at the component level, and, then with transmitter and receiver in back-to-back configuration. End-to-end testing and performance analysis clearly show the X-Microwave based solutions performance and the proper operation of the designed front-end in the up-/down-conversion of the baseband signal.