The graphs show an interesting quirk of RFI. In figure 2-1, the theoretical USB 3.0 emission spectrum has a zero at 5.0 GHz (equal to its signaling rate). In fi

The graphs show an interesting quirk of RFI. In figure 2-1, the theoretical USB 3.0 emission spectrum has a zero at 5.0 GHz (equal to its signaling rate). In figure 2-2 the measurement has a significant narrowband spike at 5.0 GHz. Never believe zeros in spectra, there's usually something lurking under them. 2nd harmonic distortion probably causes it here.