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Дата последнего поиска статьи во внешних источниках: 1 апреля 2017 г.
Аннотация:The precursor wave (often called the first arriving signal) in a layered waveguide is investigated. It
is known that the velocity of such a signal is close to the velocity of the fastest medium in the waveguide,
and it may be bigger than the fastest group velocity given by the dispersion diagram of the
waveguide. Usually the precursor pulse decays with the propagation distance. A model layered
waveguide is studied in the paper. It is shown that the precursor is associated with the pseudobranch
structure of the dispersion diagram. The velocity of the precursor is determined by the slope
of the pseudo-branch. The decay is exponential and it depends on the structure of the pseudobranch.
Three approaches to precursors are described in the paper: the Miklowitz–Randles
approach based on analytical continuation of the dispersion diagram, the leaky wave approach, and
the approximate technique based on the properties of the real dispersion diagram.