Keysight M8195A User Manual page 82

2 M8195A User Interface
82
 Thresholds
This drop-down list sets the level threshold convention for the measure
rise/fall time parameters. Choices are '20%/80%' and '10%/90%'. '20%/80%'
is the default selection for this control.
 Rise Time (UI)
Rise/fall times can be set-up through this edition field. Time must be
expressed in UIs (Unit Interval) as a fraction of the symbol duration. Rise time
can be set up for all the edges shapes except for the Raised-Cosine and
Square Root of Raised-Cosine shapes. Rise time is fixed for clock signals to
two sample periods in order to minimize clock jitter. 400mUI (0.4 UI) is the
default value for this field.
 Alpha
This edition field only shows up when the Raised Cosine and Square-root of
Raised Cosine edge shapes are selected. With it, the excess bandwidth
parameter (alpha) of the isolated pulses can be set up. Alpha = 1.0 is the
default value.
 Inverted
This checkbox (if checked) reverses the polarity of the output waveform.
Default state is unchecked.
Data Section: The sequence of data to be generated can be set up in this section. To do
so, the following controls are available:
 Source
This drop-down list allows the selection of different pseudo random binary
sequences as data sources for signal generation. Choices are PRBS 2
(Polynomial x +x
7 6
x 10 +x 7 +1), PRBS 2
2 (Polynomial x
10 10
(Polynomial x 15 +x
length. The 2 sequences add an extra '0' to the longest sequence of
x
consecutive '0' in the corresponding 2
 Seq. Length
This edition field may be used to set a given data length to be implemented by
the modulated signal. This field defaults to the maximum non-repeating length
of the selected PRBS. It also defaults to this value if the user types '0' (Zero).
Otherwise, the sequence will be truncated when the number of bits set by this
control is reached. If this number is longer than the PRBS maximum length,
the sequence will be re-started as many times as necessary. The actual
number of symbols (and record length) in the waveform memory will depend
on the line coding/modulation and record length granularity requirements.
The simultaneous generation of a clock signal can also influence the actual
sequence length as an integer number of clock cycles must be accommodated
to keep its integrity (i.e. ISI distortion free characteristics).

Seq. Shift
This numeric edition field adds a shift to the PRBS sequence being generated
by each channel. In this way, uncorrelated data streams may be generated to
simulate multi-lane links (i.e. to test the effects of crosstalk) or to emulate IQ
baseband channels to feed electrical or optical coherent quadrature
modulators. The shift added to each channel may be calculated (in bits) for
each channel using the expression Shift = (Channel Number -1) * (Seq. Shift).
Unshifted PRBS sequences always start with the longest run of '1' for that
particular sequence.
Keysight M8195A Revision 2 – Arbitrary Waveform Generator User's Guide
+1), PRBS 2 -1 (Polynomial x
9
7 (Polynomial x 7 +x 6 +1), PRBS 2
+x +1), PRBS 2 (Polynomial x
7 11
14 +1). The sequences are identified by its non-repeating
x -1 sequence.
7 -1
+x +1), PRBS 2 -1 (Polynomial
9 5 10
9 (Polynomial x 9 +x 5 +1), PRBS
+x +1), and PRBS 2
11 9 15