D.V. Ivanov1, V.A. Ivanov2, A.A. Elsukov3, N.V. Ryabova4, V.V. Ovchinnikov5, N.R. Isaev6

1-5 Volga State University of Technology (Yoshkar-Ola, Russia)

6 Scientific and Educational Center for Aerospace Defense “Almaz - Antey” n.a. Academician V.P. Efremov (Moscow, Russia)

1 IvanovDV@volgatech.net; 2 IvanovVA@volgatech.net; 3 ElsukovAA@volgatech.net; 4 RyabovaNV@volgatech.net; 5 OvchinnikovVV@volgatech.net; 6 inekitr9711@gmail.com

Ionospheric HF radio channel is a frequency-ordered set of multiple narrowband channels i.e. multi-channel. At any instant of time some of them are unavailable due to the adverse wave propagation conditions and the high interference level. Narrowband interferences and fluctuating noise have a negative impact on different radio-technical systems operating in the HF range. In this regard optimal signal reception requires their filtering. Moreover, automatic signal detection algorithms should be developed to improve performance of a system for diagnosing and estimating structural functions of ionospheric radio channels. Typically, removing interferences is carried out after signal demodulation. However, filtering prior to demodulation has several advantages especially for spread spectrum signals. For this reason, paper presents the findings of the research into advanced filtration algorithms of time-varying interferences (fluctuating and narrowband) that allow to increase processing gain of spread spectrum signals by means of software-defined radio (SDR) technology and “ADC to antenna” principle. It was shown that this algorithms effectively suppresses time-varying narrowband interferences even with a level exceeding 40 dB. However, due to the selected averaging period (10 s), resulting spectrum may contain residual interference components, not exceeding 10-15 dB. In addition to this, we studied Constant False Alarm Rate (CFAR) algorithms to improve automatic signal detection procedure when echoes are highly spread over delays. There are presented the results of full-scale experiments on verification of a complex adaptive algorithm for automatic interference filtration and sensor signal detection. Sounding was carried out over the Cyprus – Yoshkar-Ola propagation path. Findings showed that application of proposed algorithm yields images of the structural functions of multiple HF communication channels and the ionosphere, that are appropriate for automatic processing, because they contain information only on the echo. This allows automatically estimate the frequency dependences of the SNR and the scattering parameters, due to the improved quality of sensor data.

Applying SDR technology and “ADC to antenna” principle opens new perspectives for improving algorithms of digital processing of sounding signals. The presented results have a positive effect on the efficiency of long-haul communications using a variable propagation environment, contaminated with a variety of signals from various radio equipment that create mutual man-made interference.

Ivanov D.V., Ivanov V.A., Elsukov A.A., Ryabova N.V., Ovchinnikov V.V., Isaev N.R. Method and adaptive algorithms for narrowband interferences mitigation and automatic signal detection in the problem of sensor diagnosis of multiple HF radio channels. Radiotekhnika. 2023. V. 87. № 12. P. 158−170. DOI: https://doi.org/10.18127/j00338486-202312-17 (In Russian)

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