| 摘要 |
The frequency of a skew clock signal is dithered around a base frequency, thereby enabling this clock signal to comply with FCC requirements for electromagnetic emissions within a specified window. Delay is introduced such that the clock signals exhibits slightly different frequencies in successive periods. For example, the frequency of a 100 MHz clock signal can be adjusted to have frequencies of approximately 98, 98.5, 99, 99.5, 100, 100.5, 101, 101.5, and 102 MHz during different periods. Because the frequencies are spread in 0.5 MHz increments, only three frequencies are included in any 1 MHz window. As a result, 2/3 of the energy of the clock signal is not included when determining whether the clock signal meets the FCC electromagnetic emission requirements. By spreading the frequencies above and below the base frequency in a regular manner, the average frequency of the clock signal becomes equal to the base frequency.
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