A.D. Kuchmy1, D.A. Yasentsev2, B.G. Tatarsky3

1-3 Moscow Aviation Institute (National Research University) (Moscow, Russia)

1 artem.kuchmy@yandex.ru, 2 yasentsev@yandex.ru, 3 boris-tatarsky@inbox.ru

In parallel with the development of systems of highly detailed mapping of the underlying surface, methods of ground moving targets indication (GMTI) were also improved. A dramatic improvement in the resolution characteristics of onboard radars occurred after the introduction of mapping modes with synthetic artificial antenna aperture. The advent of synthetic aperture radars (SAR) made it possible to detect ground moving targets (GMT) against the background of reflections from the underlying surface, which made it possible to further implement GMTI algorithms for detecting low-speed moving ground objects.

The simple way to carry out GMTI is if the observed target has a radial component of the velocity vector, which generates a Doppler frequency shift in the reflected signal. A more complex situation arises when it is necessary to detect targets moving at a tangential speed relative to the onboard radar. The difficulty of detecting targets moving at tangential speed is due to the fact that target movement in the direction perpendicular to the line of sight leads to deformation of the phase structure of the signal. This particular deformation manifests itself in the appearance of quadratic phase modulation of the reflected trajectory signal. With consistent signal processing in mapping mode, due to the appearance of quadratic phase modulation, the response of the observed moving target will be defocused.

To detect the presence of a moving target with tangential speed, it is proposed to use an algorithm similar to the well-known phase difference algorithm for autofocusing radar images. It consists in dividing the implementation of the trajectory signal into two parts, after which the bottom of them is subjected to a complex conjugation procedure. Next, the two implementations are multiplied with each other and the amplitude spectrum of the result of the multiplication is calculated. The shift of the maximum spectral density relative to the origin is proportional to the tangential velocity of the observed target. The sign of the shift (to the right or to the left) depends on the direction of movement of the GMT relative to the velocity vector of the carrier.

This algorithm was justified by an analytical method, then its mathematical modeling was carried out. In the case of observation of spruce trees by on-board radar with a high tangential velocity, the error in its estimation increases, which is due to the spreading of the spectrum of the signal reflected from the GMT to reduce the influence of this effect.

Kuchmy A.D., Yasentsev D.A., Tatarsky B.G. Estimation of tangential speed of ground moving targets in SAR. Information-measuring and Control Systems. 2024. V. 22. № 3. P. 38−48. DOI: https://doi.org/10.18127/j20700814-202403-05 (in Russian)

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