针对在无线电监测和认知无线电系统中,信号参数估计这一重要问题,证明了OFDM信号具有循环平稳性的必要条件是加循环前缀或有非矩形脉冲成型,并以线性周期时变变换(LPTV)模型为基础,推导了OFDM信号的循环谱表达式-For radio monitoring and cognitive radio systems, signal parameter estimation of this important issue, the necessary condition for the OFDM signal with cyclostationarity is the cyclic prefix increases or non-rectangular pulse shaping, and Linear Periodically Time-varying transform (LPTV) model, based on the cyclic spectrum of the OFDM signal expression is derived