In this paper, a multiple diffuse coding metasurface (MDCM) of independent polarization is designed to control the propagation direction of diffuse reflections under different polarizations and to improve the monostatic and bistatic RCS (radar cross section) reduction effect. First, a method for controlling the distribution range and propagation direction of the diffuse field is studied, and the diffuse field distribution of the random phase metasurface is optimized by a genetic algorithm to improve the uniformity of the diffuse scattering distribution. Then, the random phase distribution is superimposed on the periodic gradient phase distributions of the linear and hedge types in the orthogonal direction so that the main propagation direction of the diffuse metasurface deviates from the specular reflection region under different polarizations, showing single and two diffuse beams. Finally, the anisotropic unit cell with a rectangle inside and an improved Jerusalem cross on the outside is employed as the basic coding element of the MDCM due to its independent polarization phase response. The numerical and experimental results show that the MDCM features multiple diffuse scattering, independent polarization and angle insensitivity and can efficiently improve the monostatic and bistatic RCS reduction effect simultaneously. Because the scattered energies are redirected away from the specular reflection direction, the specular scattering reduction effect is better than the isotropic diffuse metasurface. The proposed method increases the difficulty of detection by single or netted radar and has the potential for the applications of stealth techniques.

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As for the non-modeling dynamics of the six-rotor UAV during the modeling process, and the presence of uncertain external interferences such as crosswinds during flight, the L1 adaptive control method is used to design the attitude controller of the six-rotor UAV. The force analysis of the six-rotor UAV is performed first to establish a nonlinear dynamic model, and then the nonlinear factors and coupling terms of the model are considered as time-varying parameters and disturbances. The low-pass filter is introduced based on the traditional model reference adaptive algorithm, and the L1 adaptive attitude controller is designed to effectively suppress the high-frequency interference caused by mechanical vibrations of the aircraft. Finally, simulation results show that the algorithm has good dynamic performance and robustness while ensuring system stability.

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