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Now showing items 1 - 5 of 5

  • Symmetry breaking in UCA-based vortex waves

    Cagliero, Andrea  

    In literature, it is often said that a uniform circular array (UCA) composed of a sufficient number of radiating elements is able to generate a vortex wave with arbitrary topological charge. While providing a very simple and intuitive solution without the need for any synthesis method, the excitation of UCAs by means of a progressive phase shift does not always guarantee that vortex waves are correctly generated, since a major role is played by the symmetry and radiation properties of each individual element which constitutes the array. When the UCAs are employed in vortex communication links, these symmetry properties strongly affect the orthogonality of the channel modes and, therefore, the communication efficiency. In this work, the symmetry breaking associated with the radiation of vortex waves by UCAs and its impact on the mode orthogonality are explored in detail.
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  • On the Spectral Efficiency Limits of an OAM-Based Multiplexing Scheme

    Cagliero, Andrea   Gaffoglio, Rossella  

    As reported in several recent publications, a spatial multiplexing involving the transmission of orthogonal waves carrying orbital angular momentum (OAM) is unable to provide spectral efficiency improvements with respect to the conventional techniques. In this letter, we emphasize how the limits of an OAM multiple transmission between antenna arrays can be derived from the Shannon capacity formula, taking as a reference the performance of a multiplexing method based on the higher order channel modes. Our approach clearly indicates that the two techniques offer the same on-axis performance. Conversely, small misalignments in the arrays positions affect the OAM scheme, highlighting the greater robustness of a traditional multiplexing method in the context of radio communications.
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  • A New Approach to the Link Budget Concept for an OAM Communication Link

    Cagliero, Andrea   De Vita, Assunta   Gaffoglio, Rossella   Sacco, Bruno  

    Following on from the increasing interest for electromagnetic waves carrying orbital angular momentum (OAM), different configurations of antenna systems able to generate such beams have been proposed. However, in our opinion, a traditional radiation pattern approach does not provide the right picture of an OAM-based communication link. For this reason, we propose a new general concept, the "OAM-link pattern," which takes into account the peculiar phase structure characterizing these waves. Focusing on OAM transmissions between antenna arrays, we introduce a formula for the link budget evaluation that describes the whole communication link and directly leads to a "classically shaped" main lobe pattern for a proper rephased reception in the case of uniform circular arrays.
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  • A New Approach to the Link Budget Concept for an OAM Communication Link

    Cagliero, Andrea   De Vita, Assunta   Gaffoglio, Rossella   Sacco, Bruno  

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  • OAM multiple transmission using uniform circular arrays:Numerical modeling and experimental verification with two digital television signals

    Gaffoglio, Rossella   Cagliero, Andrea   De Vita, Assunta   Sacco, Bruno  

    In this work we present the outcomes of a radio frequency orbital angular momentum (OAM) transmission between two antenna arrays performed in a real-world context. The analysis is supplemented by deep simulative investigations able to provide both a preliminary overview of the experimental scenario and a posteriori validation of the achieved results. As a first step, the far-field OAM communication link is tested at various frequencies and the corresponding link budget is studied by means of an angular scan generated by the rotation of the receiving system. Then, on the same site, two digital television signals encoded as OAM modes ( = 1 and =- 1) are simultaneously transmitted at a common frequency of 198.5MHz with good mode insulation.
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