Digital Signal Processing Reference
In-Depth Information
Chapter 4
High-Pass Filters
This chapter gives the filter coefficients and characteristics of a selection of high-
pass filters that are available in this offering. It is identical in format to those given
in the last chapter on low-pass filters with some exceptions that are highlighted
below.
4.1 FILTER TERMINOLOGY
4.1.1 Step Response in High-Pass Filters
The parameters given in the
Performance Features
table have the same meaning as
before. However, note that since high-pass filters do not support the DC
component in a given signal, the step response returns to zero after some
oscillations. Moreover, the step response is with reference to unit step input, and
as such the overshoot
Q
is given as a percentage of the input. For example, if a 2V
step input is fed into the filter
HPF99F0.175
, the output peak response would attain
±
41mV (i.e., 5% of
0.82V) in 12 sampling periods. Note too that there is no rise time
41% of 2V =
±
0.82V before settling down to less than
±
R
in
comparison to its low-pass counterpart since there is no apparent step on the
output. Figure 4.1 shows the relationship between the overshoot
Q
and settling
time
S
for the high pass filter.
Q
±
0.05Q
τ
S
Figure 4.1
Definition of overshoot and settling time for high-pass filters.
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