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Question 9.2: A distortionless line has a characteristic impedance Zo = 50......

A distortionless line has a characteristic impedance Z_{o}= 50[Ω] and a propagation constant γ = 0.01 + j 4.0[m^{-1}] at frequency f = 100[MHz] . Find R, L, G, C, and v_{p}.

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From Eqs. (9-25c) and (9-25d), we have

\beta = \omega \sqrt{LC}                                                                      (9-25c)\\ Z_{o} = \sqrt{\frac{L (R / L + j \omega )}{ C ( G / C + j \omega )} } =\sqrt{\frac{L}{C} }                                   \text{(characteristic impedance)}                 (9-25d) \\ \beta = \omega \sqrt{LC} = 2\pi \times 10^{8} \sqrt{LC} = 4.0 \\ Z_{o} = \sqrt{L / C} = 50

From the above equations we obtain

L = 318[nH/m]

C = 127[pF/m]

From Eq. (9-25b) we obtain

\alpha = G \sqrt{L / C} = R \sqrt{C/L}                                                                   (9-25b)

\alpha = G \sqrt{L / C} = G Z_{o} = 0.01, and thus

G = 200[μS/m]

From the relation RC = GL we obtain

R = \frac{GL}{C} = \frac{200 \times 10^{-6} \times 318 \times 10^{-9}}{127 \times 10^{-12}} = 0.50 [\Omega / m]

Phase velocity is therefore

v_{p} = \frac{\omega }{\beta } = \frac{2 \pi \times 10^{8}}{4} = 1.57 \times 10^{8} [m / s]

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