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  • Item type: Item , Access status: Acesso aberto ,
    T-RIS and R-RIS experimental characterization in the sub-THz band
    (2025) Jung, B.; Elesina, V.; Matos, S.; Koutsos, O.; Clemente, A.; Kurner, T.; Errico, R.
    sub-terahertz (sub-THz) communications is expected to be a key element for future wireless communications enabling extremely high data transmission rate. Its performance can be further emphasized by the use of reconfigurable intelligent surface (RIS), which provides the beamforming possibility of electromagnetic (EM) waves in a desired direction. The channel measurement is a fundamental element in understanding the characteristics of the propagation channel. To emulate a system composed of transmissive RIS (T-RIS) and reflective RIS (R-RIS), an electrically large transmit-array and reflect-array were designed. The paper presents the results of the single directional channel measurement of the sub-THz channel composing a concatenation of non-reconfigurable T-RIS and R-RIS. The results presented in this paper demonstrate the feasibility and scalability of establishing a sub-THz link by concatenating multiple RIS units for future applications.
  • Item type: Item , Access status: Acesso aberto ,
    Channel measurements involving passive RIS at 300 GHz
    (2025) Loeser, L.; Matos, S.; Kürner, T.
    he ever growing demand for data rates motivates the exploration of the low terahertz (THz) frequency bands for mobile communications due to the large available bandwidths. To mitigate the reliance on line-of-sight (LOS), the concept of reflective intelligent surfaces (RIS) has emerged as a promising technology. By reshaping the electromagnetic environment, RIS modifies the channel, necessitating new approaches to model key parameters such as the path gain. This paper proposes the bistatic radar equation as a simple yet accurate model to predict the path gain of a link that includes a RIS, even below the Fraunhofer distance. Chanel measurements at 300 GHz, incorporating a passive RIS, support the validity of this approach.
  • Item type: Item , Access status: Acesso aberto ,
    Monitoring plastic accumulations in a river environment using machine learning on Sentinel-1 SAR data
    (2025) Costa, T. S.; Felício, J.; Matos, S. A.; Costa, J. R.; Fernandes, C. A.; Fonseca, N. J. G.
    Plastic litter is a growing environmental issue. Microwave (MW) technology has the potential for an all-time and weather remote detection of floating macroplastics via satellites or airborne platforms. However, none of the early studies in the existing literature has addressed MW sensor requirements or the application of Machine Learning (ML) for automated monitoring with readily available data. In this study, we employ a supervised learning workflow to monitor, in a preliminary phase, floating macroplastic accumulation in a river environment utilizing polarimetric Sentinel-1 (S-1) SAR data. The combination of co-polarization (VV) and cross-polarization (VH), specifically VV-VH and VV+VH, resulted in detection accuracies exceeding 90%, without overfitting. Analysis of scattering behavior revealed that both VV and VH backscatter were sensitive to plastic patch size, with a linear relationship. This differs from the low-intensity scattering of river water. The findings highlight the importance of dual polarization for effective MW-based plastic monitoring missions.