V.A. Ivanov, D.V. Ivanov, M.I. Ryabova
Quasiantiaircraft propagation (NVIS) solves the problem of radio communications on short distances (40 - 400 km) and is most often used for strategic purposes, and for telemedicine. The requirement of high reliability, secrecy and speed of information transmission, reducing transmission power of connected and transmitted signals leads to the need for systems with spread spectrum. To estimate the dispersion of distortions arising from the NVIS, it is important to investigate the differential dispersion characteristics and the coherence bandwidth of channels with different mean frequencies for the NVIS.
Marks of parameters of a frequency and time dispersion for terrestrial and spatial waves are presented at quasiantiaircraft propagation. The technique of synthesis of dispersive characteristics and differential dispersive characteristics for multilayered quasiparabolic model of an ionospheric layer is developed.
Marks of the maximum frequency of following of elementary parcels (chips) for NVIS systems with DSSS are received. The factors leading to distortion of signals with DSSS are investigated. The model of the broadband channel for NVIS taking into account a frequency dispersion of the environment of distribution is developed.