Conditions for a transmission line to be of low loss are

Concept:

Propagation constant for the transmission line is given by:

\(\gamma = \alpha + j\beta = \sqrt {\left( {R + j\omega L} \right)\left( {G + j\omega C} \right)} \)

For lossless line α = 0

If R ≪ ωL and a ≪ ωC, the propagation constant becomes:

\(\gamma = \sqrt {\left( {j\omega L} \right)\left( {j\omega C} \right)} \)

\(\gamma = j\omega \sqrt {LC} \)   ---(1)

Comparing equation (1) with α + jβ:

α = 0. Hence the line is lossless.

Important points:

A transmission line is also lossless when:

R = 0 and G = 0.

\(\gamma = j\omega \sqrt {LC} \)

Here also α = 0 and the line is lossless

∴ The conditions for lossless line includes:

1) R = 0; G = 0, or

2) ωL ≫ & ωC ≫ G