Rev A 7/10/15 7 LOW SKEW, 1-TO-6, DUAL CRYSTAL/LVCMOS-TO-3.3V, 2.5V LVPECL
FANOUT BUFFER
8536-02 DATA SHEET
Additive Phase Jitter
The spectral purity in a band at a specific offset from the
fundamental compared to the power of the fundamental is called the
dBc Phase Noise. This value is normally expressed using a Phase
noise plot and is most often the specified plot in many applications.
Phase noise is defined as the ratio of the noise power present in a
1Hz band at a specified offset from the fundamental frequency to
the power value of the fundamental. This ratio is expressed in
decibels (dBm) or a ratio of the power in the 1Hz band to the power
in the fundamental. When the required offset is specified, the phase
noise is called a dBc value, which simply means dBm at a specified
offset from the fundamental. By investigating jitter in the frequency
domain, we get a better understanding of its effects on the desired
application over the entire time record of the signal. It is
mathematically possible to calculate an expected bit error rate given
a phase noise plot.
As with most timing specifications, phase noise measurements has
issues relating to the limitations of the equipment. Often the noise
floor of the equipment is higher than the noise floor of the device.
This is illustrated above. The device meets the noise floor of what is
shown, but can actually be lower. The phase noise is dependent on
the input source and measurement equipment.
The source generator "SMA 100 Generator 9kHz – 6GHz as
external input to an Agilent 8133A 3HGz Pulse Generator”.
SSB Phase Noise dBc/Hz
Offset from Carrier Frequency (Hz)
155.52MHz
RMS Phase Jitter (Random)
12kHz to 20MHz = 0.149ps (typical)
