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PHYSICAL DESIGN AND DEBUGGING
SOURCE
231732i11-20
Figure 11-20. Daisy Chaining
11.4.2.3 gO-DEGREE ANGLES
Another major cause of reflections are 90-degree angles in the signal paths, which cause
an abrupt change in the signal direction.
It
promotes signal reflection. For high-
frequency layout of designs, avoid 90-degree angles and use
45
or 120-degree angles
as
shown in Figure 11-21.
11.4.2.4 VIAS (FEED THROUGH CONNECTIONS)
Another impedance source that degrades high frequency circuit performance
is
vias.
Expert layout techniques can eliminate vias to avoid reflection sites on PCBs.
11.4.3 Interference
Previous sections discussed reflections in high-frequency design, their causes, and tech-
niques to minimize them. The following sections discuss additional issues related to high
Receiver
Driver
Driver
BAD
GOOD
231732ill-21
Figure 11-21. Avoiding gO-Degree Angles
11-24