Unformatted text preview: de an input impedance
that is proportional to the inverse of ZL :
X2
ZIN =
.
ZL
Another example of a 2port network that provides the impedance inversion function is a quarterwavelength
section of lossless transmission line. Denoting the characteristic impedance of the line is denoted by Zo , then
2
the input impedance is ZIN = Zo /ZL . 715 Solution
This problem can be worked using any of the 2port parameter sets. If we choose to use the Z parameters,
then the data tells us the following:
ZIN ZL →∞ = Z11 = 500 Ω
ZIN ZL =0 = Z11 − Z12 Z21
= 500 Ω
Z22 AV ZL →∞ = Z21
=4
Z11 ZOU T ZS →∞ = Z22 = 200 Ω From these data it is easy to determine that Z11 = 500 Ω, Z12 = 0, Z21 = 2000 Ω, Z22 = 200 Ω. This 2port
is unilateral because Z12 = 0, which is why the input impedance didn’t change when the load impedance
changed from an open circuit to a short circuit. With ZL = 50 Ω, the voltage gain is
AV = Z21 ZL
2000(50)
=
= 0.8.
Z11 ZL + Z11 Z22 − Z12 Z21
500(50) + 500(200) 3...
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This homework help was uploaded on 03/13/2014 for the course ECE 453 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.
 Spring '08
 Staff

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