1. Line elements and passive devices

The lines, which serve as junctions between these various circuits, and as substrates for some of them, are of various types:

• metal waveguides, which offer excellent performance but have the disadvantage of a three-dimensional structure, making it difficult to manufacture circuit elements with complex mechanical structures (notably multipoles), and coaxial waveguides;

• strip lines, slot lines and coplanar lines, whose performance is less good but which have the advantage of a two-dimensional structure (so-called planar lines), suitable for hybrid integration with active components and devices.

The passive elements of the circuits are :

• dipoles that reflect energy (short...