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2-5
IM 704610-01E
Explanation of Functions
2
D-to-C Jitter <<For procedures, see section 4.1>>
Measuring Phase Difference
You can measure the phase (time) difference from the rising (or falling) slope of the data
signal to the first rising slope of the clock signal.
Measurement
Measurement
Data
signal
Clock
signal
Data
signal
Clock
signal
• Example
1
Data signal slope: rising
Clock signal slope: rising
• Example
2
Data signal slope: both rising and falling
Clock signal slope: rising
Measurement
Measurement
Measurement
Jitter
σ
, Jitter Ratio
σ
/T, and Average Value
A histogram (frequency distribution) is determined from multiple measured values of
phase difference, and the standard deviation
σ
from the histogram is calculated. This
standard deviation
σ
is the D-to-C jitter. The D-to-C jitter ratio is derived as a percentage
by dividing the standard deviation
σ
by the period T of the clock signal. The time-
averaged value of the measured phase difference signal is the D-to-C average value
AVE.
σ
=
Σ
(X
i
– AVE)
2
×
P
i
n
i = 1
AVE =
Σ
(
X
i
×
P
i
)
n
i = 1
n: Number of bins (histogram lines) of the histogram
X
i
: Class value of each bin
P
i
: Relative frequency
(Ratio of frequency Xi of a single bin with respect
to the total number of samples)
T: Period of the clock signal
(differs depending on the signal being measured since
it is measured at the same time as the data signal)
• D-to-C jitter
• D-to-C jitter ratio
σ
T
×
100(%)
• D-to-C average value
Regenerating the Clock Signal
The clock signal that is necessary in measuring the D-to-C jitter can be regenerated by
the PLL circuit of the instrument. D-to-C jitter measurements are carried out using the
regenerated clock signal. You can display the period T of the regenerated clock signal.
Note
By switching the displayed numerical values (see section 5.2) and making queries through
communication commands (see section 10.2.2), you can obtain statistical values other than
the jitter, jitter ratio, and average value.
2.3 Measurement Functions (Measurement Items)