20-06-2013, 02:11 PM
2 Port Network analysis
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Terminal, port
A pair of terminal at which a signal (current or
voltage) may enter or leave is called a port
A network having only one pair of such
terminals is called one port network
No connections can be made to any other
node internal to the network
One port network can be modeled by
thevenin or norton equivalent
One port network-2 terminals
For example, the determination of Thevenin's
and Norton's equivalents pertain to one-ports,
since there is one pair of terminals through
which we look into the network
Thevenin or Norton equivalent is sufficient
for determining the voltages and currents in
any branch or circuit connected externally to
the one-port.
A network with n ports of entry is called an
n-port.
2 port network—4 terminals
A large number of networks of practical
interest and importance have two ports of
entry.
An amplifier, for example, has a pair of
input terminals (the input port) and a pair of
output terminals (the output port).
There are four variables of interest in a twoport;
the current and voltage at the input port
and the current and voltage at the output
port.
The response of a two-port network is
studied by using parameter matrices that
express the interdependence of these four
variables.
The actual configuration of elements is of no
interest in order to analyze the relationship
between any external connections at the input
and output ports.
Need to study
The common occurrence of two-ports in
modeling electronic devices, electronic circuits,
and communication networks and systems
makes it important to study them in some
detail.
The attractive feature of two-port theory is
that the network is viewed simply as a black
box described by certain parameter matrices.
We can concentrate on the four variables
(currents and voltages at the two ports) and
any external connections to the two-port.
Reciprocal networks
Reciprocal networks. A network is said to
be reciprocal if the voltage appearing at port 2
due to a current applied at port 1 is the same
as the voltage appearing at port 1 when the
same current is applied to port 2.
Exchanging voltage and current results in an
equivalent definition of reciprocity.