DOI 10.18127/j20700814-201810-02

__Keywords:__MIMO synthetic aperture radar (MIMO SAR) generalized ambiguity function unmanned aerial vehicle (UAV) trajectory and orientation instability

E.F. Gibadrakhmanova - Head of Department, JSC RPA «Simonov Design Bureau» (Kazan); Post-graduate Student, Department RL-1, Bauman Moscow State Technical University

E-mail: endzhik@mail.ru

V.V. Chapursky - Dr.Sc.(Eng.), Senior Research Scientist, SRI of Radioelectronic Technics of Bauman Moscow State Technical University

E-mail: valch2008@yandex.ru

A technique for analyzing the resolution ability of the radio image of surface in MIMO synthetic aperture radars (SAR) in the presence of instability of the trajectory and orientation of the air carrier is proposed. The technique is based on the calculation of the generalized uncertainty function with respect to the plane coordinates for trajectory disturbances along the horizontal and altitude, and also in the absence and presence of a change in the orientation of the air carrier. Examples of analysis for the MIMO SAR placed on the UAV are given, in the case of circumferential maneuvers in the horizontal and vertical planes. The comparison of the generalized uncertainty function cross sections, based on the example of UAV, in the range and azimuthal coordinates with horizontal and vertical maneuvers, which had the same law of variation of the trajectory along the arc of the circle in the horizontal and vertical planes, showed the consistency of the technique and led to the following results. The width of the main lobe on the horizontal range corresponds, in this case, to the theoretical resolution determined by the total bandwidth of the signal and the geometric factor of observation. The blurring of the main lobe of the GUF and the resolution loss in the azimuthal coordinate in the case of a horizontal maneuver are approximately twice larger than vertical maneuvering, which is caused by the geometric factor of observation. It is also specific that, a separate analysis of the effect of horizontal and vertical maneuvering for MIMO SAR and classical SAR shows the same results in terms of the shape of the ОФН sections and the degree of the resolution loss in the azimuthal coordinate as compared with the lack of maneuvering. The considered technique also allows to take into account the effect of changing the orientation of the air carrier in the horizontal plane with respect to the rectilinear flight path of the carrier to the resolving power over the planar coordinates of the earth's surface in the MIMO SAR. Examples of analysis for MIMO SAR placed on an unmanned aerial vehicle (UAV) are considered, with two types of time dependence of the horizontal orientation angle of the UAV fuselage. When the orientation is changed, the main lobe of the processing response is split, which corresponds to the deterioration of the azimuth resolution with some quantitative differences. With the decrease in the amplitude of the course change, the bifurcation of the response disappears. As a result, the degree of deterioration of resolution depends on the intensity of the change in orientation in time. In the case of the classical SAR, there is no influence of orientation changes in the first approximation, but taking into account the shape of the ДНА, the further refinement of the result is required. The considered technique can be generalized, taking into account the accuracy of the estimation of the current coordinates and orientation of the carrier, formed by on-board systems of micro navigation. In this case, it is necessary to perform calculations based on the OКИ, in which the reference signal function is formed taking into account the data on the velocity vector, acceleration and orientation of the SAR carrier, including the SAR of the MIMO type.

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