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Denoting the characteristic impedance of the line is

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Unformatted text preview: de an input impedance that is proportional to the inverse of ZL : X2 ZIN = . ZL Another example of a 2-port network that provides the impedance inversion function is a quarter-wavelength 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 . 7-15 Solution This problem can be worked using any of the 2-port 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 2-port 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.

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