REVISION B 3/25/15
83940D DATA SHEET
7 LOW SKEW, 1-TO-18
LVPECL-TO-LVCMOS / LVTTL FANOUT BUFFER
ADDITIVE PHASE JITTER
Input/Output Additive Phase Jitter
at 155.52MHz = 0.03ps (typical)
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
-150
-160
-170
-180
-190
1k 10k 100k 1M 10M 100M
The spectral purity in a band at a specifi c offset from the fun-
damental 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 specifi ed plot in many
applications. Phase noise is defi ned as the ratio of the noise
power present in a 1Hz band at a specifi ed offset from the fun-
damental frequency to the power value of the fundamental. This
ratio is expressed in decibels (dBm) or a ratio of the power in the
As with most timing specifi cations, phase noise measurements
have issues. The primary issue relates to the limitations of the
equipment. Often the noise fl oor of the equipment is higher
than the noise fl oor of the device. This is illustrated above. The
1Hz band to the power in the fundamental. When the required
offset is specifi ed, the phase noise is called a dBc value, which
simply means dBm at a specifi ed 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.
device meets the noise fl oor of what is shown, but can actually
be lower. The phase noise is dependant on the input source and
measurement equipment.
OFFSET FROM CARRIER FREQUENCY (HZ)
SSB PHASE NOISE dBc/HZ
