Abstract
Paper presents the outcomes of the studies into the adaptive wideband equalization for frequency dispersion correction in HF band considering variations in interference characteristics and ionosphere parameters. The subject matter of the research were megahertz-bandwidth channels with single-hop F layer propagation mode. There are presented data on variations in the channel amplitude frequency response that are caused by the interference of magneto-ionic components (intramodal multipath). Test facility for carrying out full-scale experiments was developed with the use of Universal Software Radio Peripheral platform supported by the groundbreaking software-defined radio technology. Verification of the developed methods and algorithms was performed in the experiments on oblique sounding over the Cyprus-to-Yoshkar-Ola propagation path by the linearly frequency modulated continuous wave signal.
Highlights
Ionospheric radio channel characteristics significantly vary over slow time due to the influence of propagation medium
The aim of the research was to develop method and algorithm of adaptive equalization for frequency dispersion and interference whitening with training mode in wideband (1 MHz) HF communication radio channels with the use of data on channel sounding by linearly frequency modulated continuous wave (LFMCW) signal and software-defined radio (SDR) technology
It is appropriate to employ fast sounding to leave 90% of the stationarity time for the operation of a communication system in a wideband radio channel
Summary
Ionospheric radio channel characteristics significantly vary over slow time due to the influence of propagation medium. These variations can disrupt operation of wideband radio systems and corrupt information that is conveyed by signals. There are several negative factors that influence propagation of radio signals throughout the ionosphere corrupting their amplitude frequency response (AFR) and phase frequency response (PFR). The most harmful effects are intermodal multipath when multiple propagation modes exist, intramodal multipath due to the magneto-ionic splitting, frequency dispersion due to the dependence of the phase velocity of the wave propagation on its frequency and timevarying properties of the ionosphere that cause corresponding variations in the characteristics of radio channels [1,2,3,4]. Spreading the bandwidth provides the opportunity to radically solve the problem of stealthiness and noise immunity of HF communication
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