改进多尺度Chirplet路径追踪算法在非线性调频信号估计中的应用

针对在低信噪比下雷达非线性调频信号(Non-linear Frequency Modulation，NLFM)瞬时频率估计精度不足的问题，提出一种基于多尺度线调频小波路径追踪算法(Multi-scale Chirplet Path Pursuit，MCPP)的拟合方法估计信号的瞬时频率。首先，该方法将时频平面分成二进制动态时间支撑区并形成多尺度线调频(Chirp)原子函数库；然后在每一个时间支撑区选择一个投影系数最大的Chirp原子，按照连接原则进行最佳路径连接；最后按时间支撑区顺序提取每个Chirp原子的起始和终止频率，采用最小二乘法进行瞬时频率拟合。仿真表明该方法在低信噪比下可以提高信号瞬时频率估计的精度。 

Improved Multi-scale Chirplet Path Pursuit and its Application in Instantaneous Frequency Estimation of Nonlinear Frequency Modulation Signal

To solve the precise problem of instantaneous frequency estimation for radar nonlinear frequency modulated signal(NLFM) in low SNR, a curve fitting method based on multi-scale chirplet path pursuit(MCPP) is proposed. Firstly, time-frequency plane is divided into binary regions of dynamic time supporting and the multi-scale chirp basis function library is formed. Then, the chirp atom which has the largest projection coefficient is chosen in every regions of dynamic time supporting and all chirp atoms are connected according to the rule of best path. Finally, initial frequency and final frequency of chirp atoms are extracted in order of regions of dynamic time supporting and the least squares curve fitting is adopted for instantaneous frequency estimation. Simulation indicates that the method can improve estimative precision of instantaneous frequency in low SNR.