组合幂调频信号的时频移估计

为了准确估计接收信号的时频移参数和降低估计复杂度，设计了一种组合幂调频（CPFM）信号，该信号由具有时间间隔的正负幂调频（PFM）信号构成，并提出了基于CPFM信号的时频移估计算法。在算法中首先将CPFM信号降阶，然后独立地估计时延和频移，即采用三次相位函数（CPF）估计时延，通过正负PFM相位相消后再估计频移。相比于分数阶傅里叶变换（FRFT）时频移估计算法，所提算法避免了时延估计对频移估计的影响，而且仅需两次一维搜索，降低了计算量。仿真结果表明，该算法能准确地估计CPFM信号的时延和频移，并且频移估计均方误差（MSE）接近克拉美劳下界（CRLB）。

Time and frequency offset estimation using a combined power frequency-modulated signal

In order to accurately estimate the parameters of time and frequency offset of a received signal and reduce the computation complexity,a combined power frequency-modulated(CPFM) signal is designed,and the related estimation is derived. The CPFM signal is composed of positive and negative power frequency-modulated(PFM) signals with a fixed time interval. The time and frequency offset estimation with the CPFM signal includes two stages:firstly,the conjugate CPFM signal correspondingly multiplies the CPFM signal to reduce the signal power order;then time delay and frequency offset are estimated independently. The cubic phase function(CPF) is adopted to estimate the time delay. In addition,the frequency offset is estimated by the phase cancellation using the adjacent positive and negative PFM signals. Compared with the estimation by fractional Fourier transform(FRFT),the proposed method avoids the influence of time delay on the estimation of frequency offset,and only requires twice one-dimensional peak searching while the former requires searching in a two-dimensional domain. Simulation results show that the time and frequency offset of a CPFM signal can be estimated accurately. Besides the mean squared error(MSE) of frequency offset estimation is close to the Cramer-Rao lower bound(CRLB).