81250 Datasheet, PDF (28/64 Pages) Keysight Technologies – Agilent ParBERT 81250 Parallel Bit Error Ratio Tester

N4873A analyzer module
The analyzer features are:
• Acquire data from start
• Compare and acquire data
around error
• Compare and count
erroneous ones and zeros to
calculate the bit error rate
Receive memory for acquired data
is up to 64 Mbit deep, depending
on segment length resolution. The
stimulus portion of the channel
generates expected data and mask
data. Mask data is also available at
the maximum segment resolution
(32, 64, 128, 256, 512).
The analyzer is able to synchro-
nize on a received data stream by
means of a user selectable syn-
chronization word. The sync. word
has a length of 48 bits and is com-
posed of zeros, ones and Xs
(“don't cares”). The detect word
must be unique within the data
stream. Synchronization on a pure
PRBS data-stream is done without
a detect-word, instead by simply
loading a number of the incoming
bits into the internal PRBS gener-
ator. A pre-condition for this is
that the polynomial of the
received PRBS is known.
The input comparator has
differential inputs with 50 Ω
impedance. The sensitivity of
50 mV and the common mode
range of the comparator allow the
testing of all common differential
high-speed devices. The user has
the choice of using the differential
input with or without a termina-
tion voltage or as single-ended
input (with a termination voltage).
The differential mode does not
need a threshold voltage, whereas
the single-ended mode does. But
also in differential mode the user
can select one of the two inputs
and compare the signal to a
threshold voltage.
Table 21. N4875A analyzer timing: all timing parameters are measured at ECL levels, terminated
with 50 Ω to GND
Sampling rate
620 MHz to 13.5 GHz
Sample delay
Can be specified as leading edge delay in
fraction of bits in each channel
Start delay range
0 to 100 ns
Fine delay range
± 1 period (can be changed without stopping)
Delay resolution
100 fs
Delay accuracy
±10 ps ± 20 ppm relative to the zero-delay
(1)
placement
Relative delay accuracy ±2 ps ± 2% typ.
(1)
Skew between
20 ps after cable deskewing at customer levels (1)
modules of same type and unchanged system frequency.
(1) 25 °C - 40 °C ambient temperature
Table 22. N4873A pattern and sequencing
Analyzer auto-synchronization
On PRBS or memory-based data
Manual or automatic by:
Bit synchronization(2) with or without
automatic phase alignment
Automatic delay alignment around a start
sample delay (range: ± 10 ns)
BER Threshold: 10^-4 to 10^-9
(2) With PRBS data, analyzers can autosyncronize on incoming PRBS data bits.
When using memory-based data, this data must contain a unique 48 bit detect Word at the
beginning of the segment, and the generators must be on a separate system clock. Don’t cares
within detect word are possible. If several inputs synchronize, the delay diffference between
terminals must be smaller than ±5 segment length resolution.
Table 23. Parameters for N4873A ParBERT 13.5 Gb/s analyzer
Number of channels
Range of operation
Max input amplitude
Input sensitivity
Input voltage range
Internal termination voltage
(can be switched off )
Threshold voltage range
Threshold resolution
Minimum detectable pulse width
Phase margin (source: N4872A)
Impedance
1, differential or single ended, 2.4 mm (f)
620 Mb/s - 13.5 Gb/s
2 Vpp
50 mVpp typical @ 10 Gb/s, PRBS 2³¹ - 1,
and BER 10^-12
–2V … +3 (selectable 2V window)
-2.0 to +3.0 V
(must be within selected 2 V window)
–2.0 to + 3.0 V
(must be within selected 2 V window)
1 mV
25 ps typ.
1 UI - 12 ps typ.
50 Ω typ. (100 Ω differential, if termina-
tion voltage is switched off)
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