基于数据辅助的CPM信号捕获与频偏估计算法

Data-aided Algorithm of CPM Signal Acquisition and Frequency Offset Estimation

针对连续相位调制(Continuous phase modulation,CPM)信号同步问题,提出了一种基于给定导频符号的信号捕获和频偏估计算法。首先对由扩频码字组成的导频信号进行复数匹配滤波,将输出值取模,通过搜索峰值实现信号捕获。然后根据相关值对应的辅角利用最小二乘法实现频偏和初相估计,并分析推导了该算法在较低信噪比条件下的频偏估计范围和估计精度。仿真实验结果表明,频偏估计范围可达±0.25倍的符号速率,与传统伪码相关估计频偏算法相比,该算法估计精度高,在SNR为3.3dB时频偏估计精度接近克拉美罗下界。

To solve the continuous phase modulation signal synchronization problem, a signal acquisition and frequency offset estimation algorithm is proposed based on a set of pilot symbols. First, the pilot sig- nal composed of the spread spectrum codeword is complex-matching-filtered, then the output modulus value is obtained. The signal is captured by searching the peak to sync signal. Then the frequency offset and initialization phase are estimated based on the least squares method of argument of correlation re- sults. The range of the frequency offset estimation and the estimation accuracy are deduced in a lower SNR ratio. Simulation results show that the range of the frequency offset estimation is ±0.25Rb and the estimated accuracy is close to the Cramer-Rao lower bound when SNR is 3.3 dB.