Hameg Instruments HZ530 Manual Del Usuario página 39

suppression measure is not noticeable.
The next step is to insert a 47 Ω, 100 pF, 47 Ω T-filter.
Figure 4 shows that the change is quite noticeable when compared
to Figure 3. The frequency range is now practically reduced to 200
MHz. At the same time the risetime is significantly slowed down.
The approach may be questionable if this slow risetime influences
the digital operation. In this case, the component values may be
varied to find a compromise between desired EMC characteristics
and digital functionality. This suitable example demonstrates the
effectiveness of the measurement procedures recommended here.
Several complete signal-line filters are commercially available. The
effectiveness of these filters can be evaluated using the same
procedures.
Figure 5 shows the use of a three-pole capacitor used as a signal-
line filter in the same circuit as used in the previous examples. The
results are disappointing: Even though the risetime is significantly
reduced, the frequency spectrum is only marginally reduced. This
results from the generally poor ground connection of a three-pole
capacitor which is relatively high in inductance compared to a R-C-
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