直升机旋翼桨叶外形对雷达特征信号的影响

Effect of Helicopter Rotor Blade Shape on Its Radar Signal Characteristics

应用一种将物理光学、等效电磁流和准静态法相结合的方法,开展旋翼桨叶外形雷达特征信号时频域谱特性的研究。首先开展翼型参数、桨尖后掠和下反角对旋翼雷达散射截面(RCS)的影响机理和响应特性分析;然后通过对比选择不同桨叶片数和桨尖后掠角时旋翼回波信号的时频域变化规律,获得实现旋翼RCS减缩的桨叶片数和强散射源分布特点,并结合时频域灰度图谱发现和提取旋翼动态RCS闪烁域出现的时机与次数。研究表明:后掠桨尖是旋翼重要的强散射源之一;采用3片或5片桨叶时旋翼的RCS峰值比4片桨叶时分别减缩2.32dB·m2和2.52dB·m2,有利于控制雷达散射回波的峰值响应;由薄翼型NACA0006构成旋翼的雷达最大探测距离是厚翼型NACA0024旋翼的38.6%和41.8%,综合隐身效果最好。

The time-frequency domain analyses about rotor blade shape on its signal echo characteristics combining the physical optics method,the equivalent currents method and the quasi-stationary method have been investigated.Firstly,the effects and response characteristics of the rotor radar cross section （RCS） with multi factors such as airfoil parameters,blade-tip backward swept and anhedral have been carried out.Then time-frequency domain changes of echo signal of rotor about different blade numbers and blade-tip swept angle have been presented,as a result,the scattering reduced blade number choice and strong scattering regions are obtained.Simultaneously,moment and times of rotor RCS flash are discovered and extracted from time-frequency domain information grayscale.It shows that blade-tip backwara swept is one of the important and strong scattering sources.Comparing 3 or 5 blades with 4 blades rotor,the peak of rotor RCS can be reduced by 2.32 dB · m^2 or 2.52 dB · m^2 respectively,which is conducive to control peak of rotor RCS.The maximum radar detecting distances about RCS peak value of rotor with NACA0006 airfoil are 38.6% and 41.8% of that of rotor with NACA0024 airfoil respectively,providing the best comprehensive stealth performances.