同步由锁相环完成,因此,根据内部时钟来同步到低频或高频就毫无问题.
后半句“主干”是: synchronizing (主语) works (谓语),整个后半句就是一个主谓结构而已.
真正的完整的主语是 synchronizing to lower and higher frequencies compared to the internal clock,第一个to后面是synchronizing的具体情况,compared to指的是需要同步的频率同步的标准是internal clock,修饰frequencies.
without any issues是状语,修饰works.