spread spectrum clocking_xilinx pre-production_Free running(3)

1, thus interfering with the WWAN communications in the laptop computer or other computing device。 The range of frequencies with which minimal interference is desired is referred to herein as the “target band” (the GSM900 band, in this example)。

Utilizing the technologies described herein, an adaptive SSC clocking mechanism may be implemented that reduces peak EMI levels while minimizing radiated electromagnetic energy in one or more target bands. According to embodiments, the adaptive SSC clocking mechanism varies the rate of change in clock frequency, or the “modulation rate,” in the SSC scheme. By applying a higher modulation rate for clock frequencies within the deviation range that produce interference in the target band and a lower modulation rate for clock frequencies that do not interfere, the electromagnetic energy radiated by the clock signal is spread in an uneven spectral fashion over the frequency domain, with lower radiated energy in the frequency range that is interfering with the target band, while retaining the advantages of SSC for lower peak EMI levels.

FIG. 2 provides an overview of adaptive spread spectrum clocking methods and processes described herein. Specifically, FIG. 2 illustrates one routine 200 for adaptive spread-spectrum clocking to limit interference in a target band, according to some embodiments. Portions of the routine 200 may be performed by the SSC clock circuit of an HDD or other electronic device, for example. According to some embodiments, the SSC clock mechanism may provide an operational clock for one or more components of the device, such as processors, memory, communication components, and/or the like. The SSC clock circuit may comprise hardware components, software components, or any combination of the two.

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