In recent years the development of radio communication and of allied techniques such as radar and television has involved the use of higher and higher frequency signals. This trend has arisen, either from the need of more channels in the useful frequency spectrum, or, as in radar, from the need of directional antenna systems of reasonable size. In tubes of conventional design the upper limit of the useful frequency range is set by considerations of transit time of electrons, radiation losses and inductance of leads.

Wagner, S. (Supervisor)