Agilent Technologies N5980A Manual do Utilizador descarregar pdf (Página 6)

Figure 8: Bit recovery mode for analyzing non-deterministic

traffic.

6 J-BERT N4903A High-Performance Serial BERT Data Sheet

Bit Recovery Mode (option A01)

This mode is useful for analyzing non-deterministic

traffic. This is helpful when you need to analyze

real-world traffic, for example in a PCI Express link

where so-called ‘skip ordered sets’ are added unpre-

dictably to avoid FIFO overflow. This simplifies set-

up by eliminating the need to set up expected data

for the error detector. Two analyzer sampling points

are used to measure a relative BER, which makes

the following measurements possible with relative

BER:

• BERT Scan including RJ/DJ separation

• Output levels and Q-factor

• Eye contour

• Fast eye mask

• Fast Total Jitter

• Spectral jitter decomposition

Automatic Alignment

The J-BERT N4903A High-Performance Serial BERT

is able to align the voltage threshold and the delay

offset of the sampling point automatically, either

simultaneously or separately. It is possible to search

for the 0/1 threshold automatically on command, and

to track the 0/1 threshold continuously.

Fast Total Jitter

Agilent implemented a new measurement technique

for TJ (BER), the Fast Total Jitter Measurement. This

method provides fast and feasible total jitter meas-

urements, around 40 times faster than a common

BERT Scan but with comparable confidence level.

Instead of comparing bits until the BER reaches a

defined number of bits or a defined number of

errors, it only compares bits until it can decide with

a 95% confidence level whether the actual BER is

above or below the desired BER.

Figure 9: Auto alignment (Center) simplifies correct

sampling even for stressed eyes.

Figure 10: Fast total jitter measurement for quick and

accurate total jitter measurements.

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Agilent Technologies N5980A Manual do Utilizador Página 6