DocID025260 Rev 1

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AN4356

EMI and noise issues

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Figure 6 shows the spectral content of the USB2.0 signal. We can observe the carrier

frequency and its harmonics. It is interesting to notice that the first one is in the range of

frequencies used in mobile applications, such as 960 MHz, Rx band GSM960 (959.8 MHz).

The second one is near GPS frequency at 1.575 GHz.

Figure 6. Spectral content of a USB2.0 link without and with skew

The noise amplitude, and therefore its bad effects on the equipment, will depend on the

PCB layout and the proximity of the sensitive parts.