High-frequency conductors

The use of high-frequency conductors has evolved considerably since the end of the last century. The nanotechnology revolution, whose first manifestations were the development of the scanning tunnelling microscope and the discovery of nanotubes, is a case in point. However, conventional photolithography technologies and micromechanical processes have made it possible to reduce the lateral dimension of lines down to the micrometer. It's worth recalling Moore's Law , which still holds true more than forty years after it was first formulated: the number of transistors in an integrated circuit doubles every two years (eighteen months in the original article), despite the difficulties created by the molecular level of the smallest dimensions now reached. This implies a corresponding reduction in line widths and lengths. As a result, some of the problems that used to raise major difficulties, particularly concerning losses along the lines, are now much less so for this type of circuit, given the small size of the connections.

Furthermore, exponential advances in computing resources have gradually led circuit designers to exploit direct electromagnetic couplings, as they have become accessible to electromagnetic simulation and can therefore be controlled. The best-known and probably oldest example is the removal of the excitation rod from a patch antenna and its replacement by a radiating aperture in the ground plane . Since then, the use of frequency-selective surfaces in circuits and the variety of quasi-optical devices show that the traditional line or guide is in many cases no longer the only solution for building a circuit. Finally, we can see that metals are no longer the only option for producing conductors: screen-printing processes use conductive inks, and molecular or composite conductors are being developed, for reasons of cost but also flexibility in production - some are even flexible