Examinando por Materia "Redes de Bragg"

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    Insertion of random spaces in time domain for frequency hopping sequences for RF systems
    (Universidad EAFIT, 2020) Carmona Valencia, Augusto; Marulanda Bernal, José Ignacio
    Improvements over the communications protocols are always a continuous research. Fast Frequency Hopping is an important method still in use and orthogonal codes used in SFH-CDMA are the special interest in several areas of technology. This research uses one coincident orthogonal code with restrictive adjacent spectral distance for the design of RF correlation detectors based on planar resonators arrays. Inclusion of uniform time delays sections between adjacent resonators is a well-known method to improve the MAI, at expenses of decrease the data rate and finally the bandwidth of protocol. Another strategy is selecting random delays between symbols in the way of adjacent peaks in cross correlation function vanishes, improving the dynamic range of asynchronous detector and accordingly the user number sharing the channel of communications.
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    Ítem
    Obtención de estructuras de relieve en materiales de registro de haluros de plata
    (Sociedad Española de Óptica, 2013-01) Giraldo, L.M; Velásquez, D.; Giraldo, L.M; Velásquez, D.; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica Aplicada
    Diffraction transmission gratings were recorded in AGFA-8E75 film, chemically treated under processes with D-19 + potassium ferrocyanide and a chemical processing technique proposed for PE-2 film to obtain embossed stripes. Holographic structures were measured topographically by the technique of atomic force microscopy in noncontact mode (NC-AFM) and we observe changes in the depths under variations in exposures and used photochemistry. We find that the best performance in terms of relief depth obtained is given by the conventional process which reached depths between 0.15 m and 0.3 m for spatial frequencies of the order of 400
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    Ítem
    Obtención de estructuras de relieve en materiales de registro de haluros de plata
    (Sedoptica, 2013-09-19) Velásquez Prieto, Daniel; Giraldo Castaño, Lady Marcela; Velásquez Prieto, Daniel; Giraldo Castaño, Lady Marcela; Universidad EAFIT. Departamento de Ciencias Básicas; lmgc15@gmail.com; Óptica Aplicada
    Diffraction transmission gratings were recorded in AGFA-8E75 film, chemically treated under processes with D-19 + potassium ferrocyanide and a chemical processing technique proposed for PE-2 film to obtain embossed stripes. Holographic structures were measured topographically by the technique of atomic force microscopy in noncontact mode (NC-AFM) and we observe changes in the depths under variations in exposures and used photochemistry. We find that the best performance in terms of relief depth obtained is given by the conventional process which reached depths between 0.15 m and 0.3 m for spatial frequencies of the order of 400