User guide
At 100MHz, the pulse period is 1/100 × 10
-6
s = 10
-8
s = 10ns; this is the unit interval
(UI). For example, a value - in fact, any parameter that is specified in time units -
of 37ns is equivalent to 37ns/10ns=3.7UI (time values are expressed as multiples
of the unit interval).
This makes it easy to analyze measurements at different frequencies: If the
measured phase margin is 8ns at 100MHz (1UI=10ns), and 4ns at 200MHz
(1UI=5ns): The phase margin is 0.8UI in both cases, and it is immediately obvious
that it does not depend on the system frequency.
The same is true for the delay resolution parameter in the DUT Output Timing/
Jitter and Eye Opening measurements: If you specify the delay resolution as 0.01UI,
the measurement software will always measure 150 points across the bathtub, no
matter what system frequency you choose (only if edge optimization is switched
off, of course). However, if you specify the resolution in time, the number of
measured points will change inversely proportional to the system frequency
(doubling the frequency results in half the number of measured points).
Syntax Requirements
All time-related entries understand both time and unit interval notation, regardless
of the UI/time selection made in the View tab of the Properties dialog box. You
can enter
17s
,
5ns
or
0.01UI
at any time. On run, the Serial BERT will automatically
convert all entries to time values, using the current unit interval. So, the UI is handy
if you want to set values independently from the system frequency.
All voltage-related entries understand
23mV
,
0.01V
, and so on.
All power-related values can be entered as
50mW
,
0.04W
,
6dBm
,and so on.
All dimensionless quantities understand decimal notations (
e.g. 10000000
,
0.0003
)
and scientific/engineering notation (
e.g. 1e9
,
1.7e-3
).
Marker Definitions
Markers are available for all measurements except of the Fast Eye Mask. They
make the analysis and tracing of the results more comfortable. Markers can be
switched on or off at any time when results are available in the graphical view. For
the DUT Output Timing/Jitter measurement, the software provides two types of
markers.
The following illustration shows the definitions for the markers and the values that
can be derived from the marker position.
6 Advanced Analysis
236 Agilent J-BERT N4903B High-Performance Serial BERT
Example
Measurements at different frequencies
Linear Markers