A design method of non-linear frequency diverse array is presented to generate the desired direction modulation for the array. The proposed method firstly sets the desired direction modulation, and then forms the desired transmit beampattern by adjusting the frequency of each array element in a non-linear manner. Theoretical analysis and numerical experiments have verified the effectiveness of the proposed method. Science Foundation of China under grant 61671304.

Free space optical (FSO) systems were usually designed according to the link budget analysis. However, the previous link attenuation estimations for fog channel were not precise. The link budget would be distorted, and resulting in the robustness degeneration of FSO system. Therefore, it is necessary to establish an accurate link attenuation model of fog channel. The previous models were mainly adopted by the Beer-Lambert law, or by classical Monte Carlo simulation combined with the fog drop size distribution. Unfortunately, the estimation deviation was eventually not fall within the acceptable range for FSO link budget analysis. We established a link attenuation model based on Monte Carlo simulation and Kim formula. Our model took the influence of multiple scattering and receiving parameters into consideration, and without the measurement of the fog drop size distribution and scattering cross-sections. The fog experiment was set up to verify the analysis results. And the experiment results revealed that the estimation deviation RMSE (root mean square error) < 1, which validated the accuracy of link attenuation model. The link attenuation model can be used to strengthen the link budget analysis of FSO system and guide the parameter design of future FSO communication system under fog channel.

In this paper, a stability control method based on active front steering control is proposed to steer by wire system (SBW). The proposed control system consists of an inner-loop angle tracking controller and an outer-loop controller. The inner-loop controller contributes to front steering angle tracking, and it is designed by PID control. The outer-loop controller restrains the effect of disturbance by feeding a compensation steering angle, and it is designed by using Improved Active Disturbances Rejection Control (IADRC) with less adjusted parameters than Active Disturbances Rejection Control (ADRC). Finally, the effectiveness of the proposed method is evaluated via numerical simulation and vehicle test. The obtained results show that the proposed controller can improve the handling stability of the SBW system. To a certain extent, the study results promote the research and application of SBW system.