中文摘要：

近年来，对微多普勒效应的研究为目标的精确识别提供了一种新的途径，其在对直升机探测、分类和识别领域有着重要的应用前景。采用物理光学模型计算了直升机旋翼的雷达散射截面，改进了直升机旋翼回波的微多普勒模型。并基于该模型，分别计算了不同形状以及转速的双叶片、三叶片直升机旋翼的探测回波信号，利用短时傅里叶变换时频分析方法分析了微多普勒特征。研究结果表明，不同的直升机旋翼叶片数量、长度以及转速对直升机旋翼微多普勒的曲线形状、幅度以及周期产生不同的影响，为下一步对直升机的微多普勒识别提供了参考和借鉴。

英文摘要：

Recently, the research of micro-Doppler effect provides a new approach for accurate target identification, which possess an important application prospect of helicopter detection, classification and recognition. In this paper, the radar scattering cross section was predicted with the physical optics method, and micro-Doppler model of a helicopter rotor blade was modified. Based on the model, the echo signal of double blades and three blades with different shape and rotating speed was calculated and micro-Doppler effect was analyzed with STFT. The results show that different quantity, height and rotating speed have different influence on the curve shape, amplitude and period of the micro-Doppler, and some reference for helicopter identification by micro-Doppler is provided.