3. TWO PORT NETWORK
• A two-port network (a kind of four-terminal
network or quadripole) is an electrical
network (circuit) or device with two pairs of
terminals to connect to external circuits
4. TWO PORT NETWORK
• A two-port network is regarded as a "black
box" with its properties specified by a matrix
of numbers.
• This allows the response of the network to
signals applied to the ports to be calculated
easily, without solving for all the internal
voltages and currents in the network
5. EXAMPLES OF TWO PORT NETWORKS
Examples of circuits
filters,
• matching networks,
• transmission lines,
transformers,
• small-signal models
for transistors (such as
the hybrid-pi model)…
6. TWO PORT NETWORK PARAMETERS:
1. Impedance parameters
2. Admittance parameters
3. Hybrid parameters
4. Inverse-hybrid parameters
5. Transmission parameters
6. Scattering parameters
7. Scattering transfer parameters
8. HYBRID(H)PARAMETERS
• Hybrid parameters are also
referred as h parameters.
• These are referred as hybrid
because, here Z
parameters, Y parameters,
voltage ratio, current ratio,
all are used to represent
the relation between
voltage and current in a two
port network
9. H PARAMETERS
• Hybrid parameters or h
parameters are very
much useful in analysing
electronics circuit where,
transistors like elements
are connected.
• In those circuits,
sometimes it is difficult to
measure Z parameters
and Y parameters but
Hybrid parameters can be
measured in much easier
way
10. H PARAMETERS
• Even in case of an ideal
transformer, Z parameter
can not be used Since, the
relations between
voltages and current in
that ideal transformer
would be
• It is impossible to analyse
a transformer with Z
parameters because a
transformer does not
have Z parameters
11. INDIVIDUAL VALUES
• h 11 is Short circuit
input Impedance
• h 12 is Open circuit
reverse voltage gain
• h 21 is Short circuit
forward current gain
• h 22 is Open circuit
output Admittance
12. CALCULATION
• For h 11 and h21 , the condition is that V 2 = 0
Which means that the right side of the two
port network is Short circuited.
• For h 12 and h 22 , the condition is I 1 = 0
which means that the left side of the two port
network is Open circuited.
14. Inverse Hybrid(G) Parameters
There is another set of parameters which is
closely related to set of h parameters.
The relations between currents and voltages
with g parameters are represented as,
17. T PARAMETERS
• A major section of power system engineering
deals in the transmission of electrical
power from one particular place (e.g.
generating station) to another
like substations or distribution units with
maximum efficiency.
• Thus the entire transmission system can be
simplified to a two port network for the sake
of easier calculations
20. INDIDVIDUAL VALUES
• A is Open circuit
Voltage ratio
• B is Negative short
circuit transfer
Impedance
• C is Open circuit
transfer Admittance
• D is Negative short
circuit current ratio
21. Parameter Specification Unit
A = VS / VR Voltage ratio Unit less
B = VS / IR Short circuit resistance Ω
C = IS / VR Open circuit conductance mho
D = IS / IR Current ratio Unit less
26. Types
1. Series connection
2. Parallel connection
3. Series - parallel connection
4. Parallel - Series connection
5. Cascade connection
27. CONDITIONS FOR INTERCONNECTION
• The combination rules need to be applied
with care.
• Some connections (when dissimilar potentials
are joined) result in the port condition being
invalidated and the combination rule will no
longer apply.
• A Brune test can be used to check the
permissibility of the combination
28. BRUNE’S TEST
• It is used to check the
permissibility of the
combination of two or more
two-port networks (or
quadrupoles) in electrical
circuit analysis.
• Tests whether the network still
meets the port condition after
the two-ports have been
combined.
Otto Walter Heinrich Oscar Brune
29. SERIES – SERIES CONNECTION
• When two-ports are connected in a series-
series configuration, the best choice of two-
port parameter is the z-parameters.
• The z-parameters of the combined network
are found by matrix addition of the two
individual z-parameter matrices.
32. BRUNE’S TEST FOR SERIES – SERIES
CONNECTION
• Voltage is applied to the input and the open-
circuit voltage is measured/calculated between
the output terminals to be connected.
• If there is a voltage drop, the two-port networks
cannot be combined in series.
• The same test is repeated from the output side of
the two-port networks Only if there is no voltage
drop in both cases, a combination of the two-
ports networks is permissible.
35. PARALLEL-PARALLEL CONECTION
• When two-ports are connected in a parallel-
parallel configuration, the best choice of two-
port parameter is the y-parameters.
• The y-parameters of the combined network
are found by matrix addition of the two
individual y-parameter matrices.
38. BRUNE’S TEST FOR
PARALLEL-PARALLEL CONNECTION
• Voltage is applied to the input and the open-
circuit voltage is measured/calculated between
the outputs that are short-circuited each.
• If there is a voltage drop, the two-port networks
cannot be combined in parallel. The same test is
repeated from the output side of the two-port
networks.
• Only if there is no voltage drop in both cases, a
combination of the two-ports networks is
permissible.
40. SERIES-PARALLEL CONECTION
• Two two-port networks with input ports
connected in series and output ports
connected in parallel
• The h-parameters of the combined network
are found by matrix addition of the two
individual h-parameter matrices
42. PARALLEL-SERIES CONECTION
• Two two-port networks with input ports
connected in parallel and output ports
connected in series
• The g-parameters of the combined network
are found by matrix addition of the two
individual g-parameter matrices.
45. CASCADING OF TWO PORT
NETWORKS
• Two two-port networks
with the first's output
port connected to the
second's input port.
• the best choice of two-
port parameter is the
ABCD-parameters.
46. CASCADING OF TWO PORT
NETWORKS
• The a-parameters of the combined network
are found by matrix multiplication of the two
individual a-parameter matrices,
• To combine a cascade of b-parameter
matrices, they are again multiplied, but the
multiplication must be carried out in reverse
order, so that
• A chain of n two-ports may be combined by
matrix multiplication of the n matrices
