D.V. Ivanov1, V.A. Ivanov2, A.A. Kislitsin3, M.I. Ryabova4

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

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

The propagation of wideband wave packets (signals) through a transionospheric radio channel, characterized by its frequency and impulse response functions, leads to waveform distortion caused by the chirping effect. When spread-spectrum signals are employed in satellite communication systems (SCS), this waveform distortion results in pulse power loss, i.e., energy losses. New quantitative insights into these losses can be obtained by developing a propagation model for spread-spectrum signals in a wideband transionospheric channel that explicitly accounts for the chirping effect. The negative impact of chirping-induced energy losses plays a key role in the challenge of improving satellite communication quality through bandwidth expansion of complex-shaped signals. Therefore, a comprehensive investigation of chirping and its adverse manifestations remains a timely and relevant problem. The aim of this work is to present a comprehensive model for estimating energy losses in spread-spectrum signals that accounts for the chirping effect in a variable transionospheric propagation channel, as well as the results of their matched processing at the receiver. An approach to constructing a comprehensive model for estimating chirping-induced energy losses in spread-spectrum signals propagating through a transionospheric channel is proposed. The model represents the natural radio channel as a linear radio engineering system with Gaussian and rectangular frequency windows. It is shown that, in contrast to a rectangular window, the use of a Gaussian window yields more accurate asymptotic solutions for small values of frequency dispersion in a wideband channel. For large values of the dispersion coefficient, the losses are shown to increase inversely with the logarithm of the channel dispersion coefficient, while the chirp rate is inversely proportional to the group delay dispersion parameter. Experimental verification of the model under various geophysical conditions in reference channels with normalized bandwidths of 0.25 and 0.5 demonstrates new possibilities for investigating subtle effects in transionospheric channels. For a quiet ionosphere during nighttime hours, the energy losses due to chirping on a vertical path are approximately 2 dB in winter, 3 dB in spring, 6 dB in summer, and 3.5 dB in autumn. During summer daytime conditions, the losses may reach 9 dB. Increasing the channel bandwidth factor from 0.25 to 0.5 results in an additional loss of 4–5 dB. During periods of geophysical disturbances caused by X-class solar flares with a solar activity index in the range 9 ≤ SAI ≤ 10, the chirping-induced energy losses increase by 3–4 dB, while doubling the bandwidth of the reference channel leads to a further increase in losses of 4–5 dB. The presented results contribute to solving the problem of improving the energy efficiency of satellite communication systems by optimizing spread-spectrum signal processing methods with explicit consideration of the chirping effect in wideband transionospheric radio channels.

This work was supported by the grant № 25-19-00153 from the Russian Science Foundation.

Ivanov D.V., Ivanov V.A., Kislitsin A.A., Ryabova M.I. Development of a comprehensive model for the chirping effect in a trans-ionospheric wideband radio channel. Part 3. Power loss in spread-spectrum signals due to induced chirping. Radiotekhnika. 2026.
V. 90. № 2. P. 117−128. DOI: https://doi.org/10.18127/j00338486-202602-13 (In Russian)

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