This paper reveals the periodic signature modulated by rotating structure of aircrafts in the air-defense radar echoes

and presents some methods of analysis and extraction of the periodic signature

based on induction mechanism

parametric model of modulation and echo characteristics.The stability and reliability of the periodic signature in the actual echoes is analyzed under different conditions including aircraft configuration and orientation

radar parameters and operation.The probability of identification of propellers based on the periodic signature is discussed.The analyzed results demonstrate that the periodic signature is reliably and steadily extracted from the air-defense radar echoes using the proposed methods

and can be used for identification of propellers.