Inverse synthetic aperture lidar (ISAL) has overcome the optical diffraction limit and realized radar imaging with centimeter-level resolution at ultra-long distances. Taking a two-dimensional Gaussian rough surface as an example, a method for calculating the scattered echo under the Kirchhoff approximation based on two-dimensional Fourier transform is proposed. ISAL imaging of planar rough targets (square and circular plates) is realized using the intensity and phase information of the scattered echo. Moreover, the ISAL imaging of large rough convex targets (cone) is obtained through a coordinate transformation, and the influence of different rough targets on ISAL imaging is analyzed, revealing that as the roughness decreases, the proportion of scattering produced by coherent scattering increases, resulting in a sharper target edge, whereas increasing target roughness leads to the image energy distribution becoming more uniform.
When a laser is transmitted in fog, and the water droplets will scatter and absorb the laser, which affects the intensity of the laser transmission and the accuracy of radar detection. Therefore, it is of great significance to study the laser transmission in the fog. At present, the main method of calculating the scattering and attenuation characteristics of fog is based on the radiation transmission theory, which is realized by a large number of numerical calculations or physical simulation methods, which takes time and cannot meet the requirements for obtaining the fast and accurate results. Therefore, in this paper established are a new laser forward attenuation model and backward attenuation model in low visibility fog. It is found that in low visibility environments, the results calculated by the Monte Carlo method are more accurate than those from most of the existing forward attenuation models. For the cases of 0.86-μm, 1.06-μm, 1.315-μm, 10.6-μm typical lasers incident on different fogs with different visibilities, a backscatter model is established, the error between the fitting result and the calculation result is analyzed, the backward attenuation fitting parameters of the new model are tested, and a more accurate fitting result is obtained.
With the rapid development of the fifth-generation (5G) mobile communication technology, the application of each frequency band has reached the extreme, causing mutual interference between different modules. Hence, there is a requirement for detecting filtering and preventing interference. In the troposphere, over-the-horizon propagation occurs in atmospheric ducts and turbulent media. The effects of both ducting and turbulence can increase the probability of occurrence of long-distance co-channel interference (CCI), in turn, severely affecting the key performance indicators such as system access, handover and drop. In the 5G era, to ensure communication channels and information security, CCI must be reduced. This paper introduces a scattering parabolic equation algorithm for calculating signal propagation in atmospheric ducts on irregular terrain boundaries. It combines Hitney’s radio physical optical model and Wagner’s nonuniform turbulent scattering model for calculating the tropospheric scattering in an evaporation duct or a surface-based duct. The new model proposes a tropospheric scattering parabolic equation algorithm for various tropospheric duct environments. Finally, as a specific case, the topographical boundaries between several cities in the East China Plain were considered, and the over-the-horizon propagation loss was simulated for various ducting and turbulent environments. The simulation results were used to evaluate whether CCI would occur between cities in a specific environment.
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