DESIGN AND ANALYSIS OF ANALOG FILTERS A Signal ...

A Signal Processing Perspective 157
and
Note that (5.5) is the minimum attenuation for all When (5.5) is compared
with the general magnitude specifications for the design of a lowpass filter illustrated
in Figure 2.15 on page 52, setting equal to the negative of (5.5) results in
Several values of and corresponding values of are shown in Table 5.1. Note
that is the minimum attenuation in the stopband. At frequencies where the
numerator of (5.3) is zero, the attenuation is infinity.
Note that the magnitude-squared response of (5.3) is zero in the stopband
when The frequencies where the response is zero may be found as
follows:
from which
Section 5.1 Equiripple Stopband Magnitude