太赫兹雷达直升机旋翼目标微动特性研究

直升机旋翼微动形成的微多普勒特征对于战场环境下直升机目标探测识别具有重要意义，掌握直升机旋翼的微动特性是雷达目标辨识的前提。太赫兹雷达波长短，多普勒效应显著，迫切需要掌握太赫兹频段旋翼目标微动特性。首先对偶数叶片和奇数叶片的螺旋桨目标进行建模，分别使用微波波段(3 GHz)与太赫兹波段(120 GHz,220 GHz)雷达对目标进行仿真分析，并从目标的回波信号特征出发提取多普勒频移信息，利用短时傅里叶变换进行时频分析，对比分析目标与雷达参数对其多普勒效应的影响及调制关系。仿真结果表明：在转速、视角以及直升机叶片长度均相同的情况下，太赫兹频段下的微多普勒效应比微波频段显著增强，多普勒曲线也更加清晰，叶片细节更加丰富。应用太赫兹雷达提取微多普勒信息能够为直升机目标识别提供重要特征。

Micro-motion characteristics of helicopter blades based on THz radar

Micro-motion of helicopter blades forms the micro-Doppler effect, which is a kind of important characteristic and is extremely important for identifying different types of helicopters in the battlefield environment. Determining the micro-motion characteristics of helicopter rotor is the precondition for the identification. Because of the short wavelength and significant Doppler effect of terahertz radar, it is urgent to determine the fretting characteristics of the rotor target in terahertz band. Firstly, the propeller targets with even and odd blades are modeled. Then, the targets are simulated by using the radar in microwave band(3 GHz) and terahertz band(120 GHz, 220 GHz), and the Doppler frequency shift information is extracted from the characteristics of the target echo signal. Using Short Time Fourier Transform(STFT) in time-frequency analysis, the influence of the target and the radar parameters on the Doppler effect and the modulation relationship are contrasted. The simulation results show that the micro-Doppler effect in Terahertz band is more significantly enhanced than that in microwave band, and the Doppler curve is clearer and more details of the blades can be observed under the condition of the same rotation speed, angle of view and blade length. Using terahertz radar to extract micro-Doppler information can provide significant features for helicopter target recognition.