12
Cable equalization feature
The U7232A software leverages the
equalization algorithms that were
implemented in HDMI. Though
not required in DisplayPort, these
algorithms can assist in the design
of receiver equalization methods by
comparing against a reference model
of equalization. Equalization models
exist for Cat 2 cable for 2, 5, and 10
meters, assuming standard models of
skin loss. Your own custom models are
possible using the “User-Specified”
equalization mode. Figure 17 illustrates
the performance of a non-equalized
DisplayPort cable versus equalization
for a 5-meter cable.
Figure 17. Cable equalization model for
receiver eye or cable analysis. Top: no
equalization. Bottom: 5-meter equalization
model applied.
W2621A DisplayPort test
point adapter
The W2641A DisplayPort TPA test
fixture simplifies the measurement
process by providing access to
the electrical measurement points
required for compliance tests. It
breaks out the DisplayPort data lanes
to pairs of SMP connectors for high-
bandwidth probing with either direct
connection to scope channels, or to
InfiniiMax SMA differential probes
through short SMP-to-SMA cables. Of
course, single-ended measurements
are supported as well. To support
DisplayPort AUX channel for device
control, two SMP connectors and
a digital connector allow for direct
connection to the AUX channel lane.
Measurement requirements
To use the U7232A electrical
performance validation and compliance
software with the Agilent W2641A
DisplayPort TPA fixture, you will need
at least one pair of the four SMP to
SMA cable pairs provided. Use of
differential probe amplifiers (1134A,
1168A, or 1169A) and appropriate SMA
probe heads (N5380A) is optional.
However, if you want connection
simplicity, consider these probes
for one-time setup and complete
characterization for all differential
measurements. If you are not using
the W2641A test fixture, you will
need to select the appropriate probe
head to interface with your fixture. For
instance, if the high speed signals are
only accessible through a terminated
50-ohm transmission line (for testing
silicon devices for example), you will
need to use the E2678A socketed
probe head, the E2677A, or N5381A
solder-in differential probe head for
high impedance probing and select
these in the scope channel setup
menu.
You can minimize test time by using
four InfiniiMax probes to measure all
four main link differential data lanes
(Lane0, Lane1, Lane2, Lane3) without
having to reposition or reconnect
probes. To use this capability, select
Connection Type: Differential Probe,
Number of Channels: Four Channels in
the Setup screen.
DisplayPort
Figure 18. The Agilent W2641A
DisplayPort test point adapter fixture
(246 Seiten)
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