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Article

Спектральный анализ сигнала, отраженного аэродинамической целью

The problems arising in the theoretical investigation of the signal spectrum reflected by the rectilinearly
flying radar target (RT) are considered. Using the Doppler frequency analysis (DFA) method,
which allows to associate the structure of the secondary Doppler spectrum with different target parameters
and the processing method of the signal under study, it can be shown that the reflected radar signal represents in the spectral region a set of harmonic components from individual scattering centers (SC).
Applying the basic provisions of the DFA, analytical dependencies describing the structure of the spectral
portrait are obtained. When analyzing Doppler frequencies to ensure high resolution and the necessary
dynamic range of measurements of the radar cross-section (RCS) of local scatterers of at least 35
dB, it is advisable to use the window functions of Kaiser-Bessel, Blackman-Harris and the like, as they
combine a relatively low level of side lobes with a narrow main peak. In mathematical modeling, it is
preferable to use the Kaiser-Bessel window function, since it has a simpler mathematical description in
the frequency domain, it is easy to calculate the Fourier series expansion coefficients and the possibility
of reducing the level of the side lobes. It is shown that as a spectral portrait of a RT for research and
application in mathematical modeling, it is expedient to use the one-sided amplitude spectrum of the
reflected signal, formed in convolution with the Fourier transform of the window function. The presence
of amplitude and phase noise caused by deliberate enemy interference, trajectory instabilities of target
flight, internal noises of the receiving path, etc., leads to transformations of the spectral portrait of the
target obtained by the DFA method, which is expressed as a change in the amplitude of Doppler harmonics
(due to the amplitude noise), and in the random displacement of their central frequencies.