S.V. Elizarov – Ph.D.(Eng.), Head of Department, PJSC «Radiofizika» (Moscow); Associate Professor, Moscow Institute of Physics and Technology (State University)
S.A. Kiselev – Engineer, PAA Department, PJSC «Radiofizika» (Moscow)
E.V. Korotetskiy – Engineer, PAA Department, PJSC «Radiofizika» (Moscow)
A.V. Sokolova (Tikhonova) – Student, Moscow Institute of Physics and Technology (State University); Engineer, PJSC «Radiofizika» (Moscow)
This article discusses the reduction of interference signals by forming radar images using the ISAR (Inverse Synthetic Aperture Radar) method from the original backscattering diagrams with the subsequent reverse operation - obtaining backscattering diagrams from the radar images.
The aim of the work is to develop an algorithm for reducing interference signals by forming radar images of radar targets with cavities using the ISAR method from the original backscattering diagrams with subsequent reverse operation. Like any other type of images, radar image is also characterized by its resolution, that is, the ability to separate two closely spaced scatterer centers along the range or the cross-range direction.
To obtain the radar image, the measured object is rotated with a fixed angular step (in our case – 0.036 degrees) on the pylon with low-reflective form at a fixed position of the measuring antenna, located at some distance from the pylon. The reflected signal is measured at each angular position of the object. The bandwidth, frequency step and angular step of rotation are selected from the conditions of correctness of the subsequent formation of radar images. After the measurements, the inverse two-dimensional Fourier transform is performed over the accumulated data array (amplitude and phase of the signal depending on the rotation angle and frequency); the output is obtained by the radar image (backscattering diagram depending on the range [m] (down range) and the track [m] (cross range)).
After receiving the radar image, it is analyzed for the interference sources. Then the re-construction of radar images is performed in a narrow region of linear coordinates in X and Y, not including interference sources, followed by the recovery of backscattering diagram from the radar image using a direct two-dimensional (2D) Fourier transform. Formation of radar images of objects with the subsequent elimination of the interference signals is used in the measurements of backscattering diagram in anechoic chambers with poor anechoic conditions.
Thus, the formation of radar images, followed by the elimination of interference signals using the method ISAR (Inverse Synthetic Aperture Radar), and then obtaining backscattering diagrams from the radar images is an effective algorithm for determining reliable values of radar cross-section and backscattering diagrams of the radar targets with low levels of radar cross-section, including objects with cavities. Further optimization of the method is associated with reducing the time of the machine count by switching to the fast Fourier transform (FFT) algorithm, using «window» functions and choosing the optimal configuration of the measuring stand.
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