HF-guiding structures: Technology and applications

This article addresses a fundamental point of view, which in itself justifies the development of the digital techniques already outlined in [E1171] and the fundamental theory of guiding structures in general, outlined in [E1170] . Indeed, the general aim of these two articles, it should be remembered, is to lead to the actual implementation of planar-microwave and millimeter-wave circuits. An important aspect of this is the practical and technological aspects of these structures. It has been pointed out that the shape of the guides depends on a number of factors, such as the operating frequency, the transported power and the application, which sometimes requires low costs and/or implementation on substrates dedicated to integration with other components for greater compactness. This is why, in the first stage, we will present the material aspects of the technology (materials and physico-chemical manufacturing techniques). In the second stage, we'll look at techniques to help with circuit design. In fact, a guide or any other component can be represented by a distribution matrix linking the transmitted and reflected powers to the various ports. When these are connected to other modules, it is possible to represent the overall distribution matrix, taking internal connections into account. Next, performance in terms of attenuation due mainly to dielectric and conduction losses is outlined, with other types of loss briefly discussed. In addition, we look at power limitation due to heating and breakdown phenomena, briefly describing their mechanism and giving some numerical examples. Finally, the fields of application and prospects for microwave and millimeter-wave circuits will be presented.