Q
Why do you specify jitter over multiple bandwidths?
A
Different applications care about different phase noise ranges. When driving a
data converter, phase noise from very close in (1 to 10 kHz) all the way out to
the Nyquist frequency of the converter affect the SNR performance capability of
the converter being clocked. In wired applications, the clock signal is
typically fed to another (‘downstream’) PLL. Since PLLs have loop filters,
they will filter off some portion of the jitter, meaning they only care about
specific bandwidths. 12 kHz to 20 MHz is a common band to measure over for
those applications.