Studying Impulse Response Peak Power Losses in a Satellite Communication Transionospheric Radio Channel with the Use of GPS/GNSS Data

The paper presents the findings of the research into the effects of frequency dispersion and impulse response peak power losses in a transionospheric radio channel depending on channel coherence bandwidth and total electron content of the ionosphere. We proposed a widely used approach when wave propagation through the ionosphere can be modeled by a linear system and its associated frequency response (FR), impulse response (IR) and dispersion characteristic (DC). When a transionospheric radio channel is represented as a linear system, the transformation to the frequency domain is attractive for studies in the case when an impulse response has a rectangular shape and a parabolic phase dependence on frequency, i.e., an impulse response is chirped. We considered a problem when a frequency response is defined in a frequency bandwidth with a mid-band frequency as well as phase-frequency characteristic (PFC) could be represented as a polynomial. In this case dispersion characteristic (first-order derivative of PFC) and second-order dispersion parameter (second-order derivative of PFC) are used. It is assumed that a channel is dispersive and an IR is distorted when second-order dispersion is taken into account. For this case we obtained equation for estimating impulse response peak power losses as well as proved its relation with transionospheric channel coherence bandwidth and total electron content of the ionosphere. There is presented results of experimental studies into daily variations of IR peak power losses for different seasons. It was experimentally proved that IR peak power losses increase with the decrease in the operating frequency and decrease from summer to winter for the channels with the same fractional bandwidth. The findings of the research seem rather promising for solving the problem of compensation for dispersion distortions in wideband transionospheric radio channels.