中文说明：
详细介绍FSK调制信号的循环互相关函数，以及其循环谱图，有三维坐标轴图和二维切片图，算法可用有效。
English Description：
The cyclic cross-correlation function of FSK modulation signal and its cyclic spectrum are introduced in detail. There are three-dimensional coordinate axis diagram and two-dimensional slice diagram. The algorithm is available and effective