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 conductor surface roughness ;

• radiation losses.

The first two have dissipative effects and result from imperfections in the conductors and dielectrics that make up the guides in general. These types of losses were discussed in detail in the article [E1171] . We show that, in the case of not too high losses, we can use a perturbational approach and establish a general...