ABSTRACT
In two-port synthesis, specifications are often given in terms of the transfer functions such as the transfer voltage ratio, transfer current ratio, transfer impedance, or transfer admittance. The actual realization, however, is accomplished by means of the
y
- or
z
-parameters. Figure 76.1 shows a two-port network driven by a voltage source with output terminating in an impedance
Z
(
s
). It is straightforward to show that the transfer voltage ratio function
G
(
s
) can be expressed in terms of its
y
-parameters
y
(
s
) or
z
-parameters
z
(
s
) by the equation
(76.1)
where
Y
(
s
) = 1/
Z
(
s
). When the output is open-circuited, (76.1) becomes
(76.2)
Likewise, the transfer current ratio
α
(
s
) can be expressed as
(76.3)
The
zeros of transmission
of a two-port network are defined as the frequencies at which the twoport results in zero output for a finite input. They play an important role in ladder development. There are many ways of producing zeros of transmission. One possibility to prevent the input signal from reaching the output is by shorting together all transmission paths or by opening all transmission paths by means of a series or parallel resonance. Another possibility is that signals transmitted by different paths cancel at the output.
