D.V. Ivanov1, V.A. Ivanov2, N.V. Ryabova3, A.A. Kislitsin4

1-4 Volga State University of Technology (Yoshkar-Ola, Russia)

1 IvanovDV@volgatech.net; 2 IvanovVA@volgatech.net; 3 RyabovaNV@volgatech.net; 4 KislitsinAA@volgatech.net

The anomalous dispersion inherent in a transionospheric radio channel induces a chirping effect that restricts the use of wide frequency bands in satellite systems. This limitation constrains available frequency and power resources, degrading long-haul radio communication performance and preventing maximum-capacity data transmission, including for service channels. These challenges motivate the research presented in this paper. Our objective is to develop a model of the chirping effect in a transionospheric wideband radio channel based on a radio engineering approach and to determine its key parameters. We have developed an approach founded on the equivalence between wave packet propagation in a medium and its transmission through a linear system characterized by frequency and impulse responses. This framework provides a scientific basis for the difficulties encountered when using spread-spectrum signals in transionospheric satellite links. We establish that to avoid dispersion-induced distortion, the bandwidth of spread-spectrum signals must not exceed the channel's coherence bandwidth, which constitutes the limiting bandwidth. Violation of this condition triggers the chirping effect, which deforms the channel's impulse response into a near-rectangular shape. Moreover, an increase in the modulus of the dispersion parameter extends the chirp duration and reduces the limiting bandwidth. Experimental estimates of the limiting bandwidth at a reference frequency for vertical paths across different seasons confirm this effect. Numerical analysis establishes that for daytime conditions on transionospheric paths at a 1 GHz reference frequency, the limiting bandwidth narrows to 70 MHz. In contrast, nighttime conditions permit the use of frequency bands up to twice as wide. The results of our numerical and experimental analysis, conducted under anomalous intramodal dispersion, identify detrimental impacts on the channel's structural function (impulse response). This is critical for assessing system performance under complex, realistic scenarios that account for a dynamically changing propagation medium. Our findings enable the diagnosis and prediction of critical channel parameters, primarily the limiting bandwidth, to ensure stable data transmission and reliable communication via transionospheric channels subject to the ionosphere's variable and unpredictable influence.
This work was supported by the grant № 25-19-00153 from the Russian Science Foundation.

Ivanov D.V., Ivanov V.A., Ryabova N.V., Kislitsin A.A. Development of a comprehensive model for the chirping effect in a transionospheric wideband radio channel. Part 1. Radio engineering approach. Radiotekhnika. 2025. V. 89. № 12. P. 147−159. DOI: https://doi.org/10.18127/j00338486-202512-16 (In Russian)

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