81250 Datasheet, PDF (23/64 Pages) Keysight Technologies – Agilent ParBERT 81250 Parallel Bit Error Ratio Tester

A/D converter test
This last example, basically a
semiconductor test application,
is very interesting in such that a
parallel bit error tester, i.e. the
ParBERT is used although literally
a BER cannot be measured at all.
The DUT is an A/D converter such
as it is used in satellite commu-
nications. The problem that an
A/D converter as a DUT presents
to a BERT lies in the nature of A/
D conversion. Even if the A/D
converter works within its speci-
fication, quantization may have
an inaccuracy of at least a bit,
probably a few. This means, that
when applying an analog input
signal at the A/D’s input, its out-
put value can not be predicted
bit-wise. So the only way of test-
ing the performance of the A/D
converter is capturing its output
data, and doing an appropriate
post processing on the uploaded
data.
The analog input signal for the A/
D test may come from a signal
generator or, in a back-to-back
configuration, from an appropri-
ate D/A converter driven by
ParBERT generators. Analyzers
with their deep capture memory
are used to record the A/D’s
output data and make it available
for later post processing.
Although this set-up sounds sim-
ple, details such as setting a cor-
rect sample delay maybe tricky,
as the overall propagation delay
of the A/D converter or an indi-
vidual lane maybe unknown. All
the nice BERT-typical autosyn-
chronization features that
ParBERT offers do not work,
as they need expected data.
However, ParBERT solves this
problem in a very user friendly
way: its built-in CDR with its
CDR/channel feature enables
automated sampling at optimum
sample point for each channel.
ParBERT
E4873A or E4875A
analyzer modules
analog signal input
Signal
generator
differential digital data outputs
DUT:
A/D converter
Figure 20. Example measurement set-up for an 8bit A/D converter utilizing ParBERT's CDR/
channel feature for automated optimization of sampling point
ParBERT 81250 Main Overview
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