Studying the Parameters of Frequency Dispersion for Radio Links of Different Length Using Software‐Defined Radio Based Sounding System

Abstract

Methods and relevant software were developed to study frequency dispersion parameters of wideband high‐frequency (HF) radio channels over propagation paths of different lengths: near vertical incidence skywave paths (up to 500 km) and long‐distance radio paths (from 1,000 up to 3,500 km). We developed a universal ionosonde (in terms of methods and signals) to do experimental research into HF radio wave propagation and dispersion using software‐defined radio technology and platform Universal Software Radio Peripheral N210. The multipurposeness of the ionosonde is manifested in the sounding methods used (oblique incidence and vertical incidence) as well as in the spread spectrum signals used (binary phase shift keying, frequency modulated continuous wave, and frequency modulated interrupted continuous wave). The characteristics of the megahertz‐bandwidth HF channels were studied. The dependences of the variation of the third‐order dispersion parameter on the time of day, the radio path length, and the channel carrier frequency were experimentally found.

Adaptive wideband equalization for frequency dispersion correction in HF band considering variations in interference characteristics and ionosphere parameters

“…FR is measured through the channel testing by a spread spectrum signal that allows its compression in the receiver. Previous studies [4] showed that a compressed signal is related to a channel IR. Procedure involves testing of a frequency-ordered set of adjoint narrowband ch  channels that constitute a wideband one.…”

“…Currently, the main approach to solving the problems of radio wave propagation is an equivalence principle. According to that principle radio channel can be modeled by an equivalent linear system [4][5][6][7]…”

“…at the channel output equals the transmitted signal spectrum ) [4]. However, narrowband interferences and fluctuating noise of different origin dominate in the HF band [8,9].…”

“…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].…”

Method of diagnosing frequency dispersion parameters for transionospheric propagation of wideband signals using GLONASS/GPS technologies

“…The variability of the propagation medium requires the development and study of the corrector training mode by means of data on sounding throughout the transionospheric radio channel. Previous research [2][3][4] showed that the frequency dispersion parameters, and, consequently, the transionospheric radio channel characteristics, depend on the total electron content (TEC) of the ionosphere. Since experimental estimates contain stochastic errors, it is crucial to perform an analysis of the influence of this factor on the correction performance.…”