中文说明：
北斗二代接收机中的跟踪程序，模块有载波环（二阶FLL，三阶PLL），FLL辅助PLL,码环是用二阶DLL，再用载波环辅助码环。
English Description：
The tracking program of Beidou second generation receiver includes carrier loop (second order FLL, third order PLL), FLL auxiliary PLL, code loop uses second order DLL, and then carrier loop auxiliary code loop.