Question 11.1: An air line has a characteristic impedance of 70 Ω and a pha...

An air line can be regarded as a lossless line because \sigma\simeq 0 and \sigma_{c}\rightarrow \infty. Hence

R = 0 = G   and  \alpha =0

Z_{o}=R_{o}=\sqrt{\frac{L}{C}}                                (11.1.1)

\beta=\omega\sqrt{LC}                                          (11.1.2)

Dividing eq. (11.1.1) by eq. (11.1.2) yields

\frac{R_{o}}{\beta}=\frac{1}{\omega C}

or

C=\frac{\beta}{\omega R_{o}}=\frac{3}{2\pi\times 100\times 10^{6}(70)}=68.2 pF/m

From eq. (11.1.1)

L=R_{o}^{2}C=(70)^{2}(68.2\times 10^{-12})=334.2 nH/m