Apparatus and method for generating clock signal

A method for generating an output clock signal in response to a source clock signal with a source frequency and a reference clock signal with a reference frequency, comprising steps of:

• producing a counting value series by counting at intervals of a specified period determined by said source frequency of said source clock signal and a predetermined counting value;
• generating a measuring value according to said counting value series in response to said reference clock signal, wherein said measuring value is defined by a ratio of the difference between a latest counting value and the k-th counting value ahead of said latest counting value to k, and k is greater than or equal to 2;
• and
• producing said output clock signal according to said source frequency and said measuring value.

A method for compensating a frequency drift of an output clock signal, said output clock signal being generated in response to a source clock signal with a source frequency and a reference clock signal with a reference frequency, said method comprising steps of:

• sampling said reference clock signal at intervals correlating to said source frequency to obtain a series of sampling values;
• averaging said series of sampling values according to a first formula to obtain a compensating factor;
• and
• incorporating said compensating factor to said source frequency according to a second formula to obtain a compensated frequency of said output clock signal.