3. Performance

3.1 Losses

Losses in guide structures and transmission lines can be classified into four types:

• dielectric losses;

• losses in the conductor;

• losses due to the surface roughness of conductors;

• radiation losses.

The first two have dissipative effects and result from the imperfection of the conductors and dielectrics that generally make up the guides. These types of losses have been discussed in detail in the article [E 1 171] . It is shown that, in the case of losses that are not too high, a perturbative approach can be...