科斯塔斯环 有助于载波同步的研究 锁相 载频3.563MHz，初始频率3.5628MHz 绘图显示具体的循环锁相过程 绘图显示相位变化-Costas reference for carrier synchronization fc0=3.563MHz,fc=3.5628Mhz show the process of synchronzation and phase change with figure.

这是一个用单片机做的频率计，外设需要配置一个同步门，之前可以实现精确的计频-This is a frequency counter to do with the microcontroller, peripherals need to configure a synchronization gate, before the meter can achieve accurate frequency