针对动态飞行测量实验,分别从时域、频域以及时频域对实测直升机回波信号进行了分析。结果表明,在时频联合域可以更清楚地揭示直升机旋翼的调制特性。根据其时频特征信号,可以判断旋翼叶片数的奇偶,并且可以测定调制回波的闪烁周期,从而确定旋翼叶片的数目和转速,实验还验证了叶片倾斜角对其调制回波的影响。这些特征对于直升机雷达回波信号仿真以及检测和识别具有重要的价值。

Based on measurement in dynamic flying experiment,the radar return signal of helicopter rotary blades was investigated in the time domain,frequency domain and time-frequency domain respectively. The results demonstrated that the modulation characteristics of the rotary blades can be seen more clearly in the joint time-frequency domain. From its time-frequency signature,the parity of rotary blades can be observed,and the interval between modulation flashes can be measured,which is determined by the number of rotary blades and its rotation rate. Also,the effects of blade pitch on the radar return signal was testified. These features are of great importance to the simulation of helicopter’s radar return signal and the detection and recognition of helicopter target.