Therefore, we characterise the symmetric T-network and Π-network by attenuation
rather than by gain.Attenuation in absolute value is given by e
α
. However, it has become
customary in filter engineering to specify attenuation in dB (decibel) units.
Thus, the attenuation in dB units in a two-port network is directly proportional to the
real part of its propagation constant. This explains why the real part (
α
) of
γ
is called the
attenuation constant. The unit of ‘neper’ is sometimes used for
α
.
16.10 CONSTANT-k LOW-PASS FILTER
We commence our discussion on passive filters designed using symmetric reactive two-
port networks from this section onwards. The ...
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