Frequency switching method

摘要

A frequency switching method is used to make switching among a plurality of frequency signal sources each providing a specific frequency range covering multiple bands. The method includes steps of providing a target frequency data; selecting one of the frequency signal sources to output a first clock signal; generating a first frequency data according to the clock signal of the first frequency to compare with the target frequency data; outputting a second clock signal with the highest band of another one of the frequency signal sources possessing a frequency range higher than that of the selected frequency signal source when the target frequency data is greater than the first frequency data; and outputting the second clock signal with the lowest band of the selected frequency signal source when the target frequency data is smaller than the first frequency data.