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摘要:
雷达回波穿过大气、飞行器外流场、天线罩后产生的波前畸变对主动雷达单脉冲测角误差有着重要影响。基于此,分析了湍流结构引起的折射率梯度对于波前畸变影响及网格分辨率对波动方程弱形式数值求解精度,提出电磁波动方程弱形式“显式”梯度项修正及涡球模型补充密度场小尺度结构的“梯度重构”方法,通过有限元方法进行了计算机数值仿真。仿真结果表明:雷达测角误差的重要原因之一是小尺度湍流造成的电场畸变,并且随着涡结构尺度减小、波长变长,电场畸变加强,测角误差加大。
Abstract:The wavefront distortion caused by the passage of radar echoes through the atmosphere, the external flow field of the aircraft, and the radome has a crucial influence on the angle measurement error of active radar single-pulse. The impact of the refractive index gradient caused by the turbulent structure on the wavefront distortion and the numerical solution accuracy of the weak form of the wave equation were analyzed. The “explicit” gradient term correction approach and the “gradient reconstruction” method of supplementing the small-scale structure of the density field with the turbulent vortex model for the weak form of the electromagnetic wave equation were proposed. Computer numerical simulation was conducted using the finite element method. The simulation results indicate that one of the significant causes of the radar angle measurement error is the electric field distortion induced by small-scale turbulence, and as the scale of the vortex structure decreases and the wavelength lengthens, the electric field distortion intensifies, and the angle measurement error increases.
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表 1 电磁波传输仿真参数
Table 1. Simulation parameters of electromagnetic wave transmission
工况 波长/mm 高度/km 马赫数 是否弱形式梯度
显式修正1 16 20 3 否 2 16 20 3 是 3 16 40 6 否 4 16 40 6 是 5 24 20 3 否 6 24 20 3 是 -
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