A5191HRTNGEVB
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Figure 14. Monte Carlo Analysis of the First Filter Stage for 10% (above) and 1% (below) Accuracy
In Figure 15 the measured filter characteristic of both
variations are shown next to a simulated result. These
characteristics are only of the first stage of the filter as the
output of the second stage is not accessible. We notice an
additional pole showing up at high frequencies. This only
improves the filter by rejecting high frequency noise, and is
too high in frequency to have an influence on the phase of
HART signals. Figure 16 shows the group delay of the total
filter. It is important that the difference in group delay
between the mark and space is minimal, so that the output of
the filter still has coherence between both signals. The plot
of Figure 16 shows that the difference is indeed minimal.
Figure 15. Measured and Simulated Filter Characteristic of the First Filter Stage
