An m-type backward-wave oscillator with photocopied delay line

Historically, microwave tubes have been fabricated from massive metal and ceramic parts. Recently, heavy emphasis has been made to lighten tubes for airborne applications. The requirements for lightweight, increased precision, and reduced costs have led to a novel approach to tube structure in which thin film technology including a photocopied process to produce a slow-wave structure on a ceramic substrate for an M-type backward-wave oscillator. Means for obtaining suitable bond of metal film to substrate without excessive rf loss is described. This paper will also discuss the problem of minimizing the sole sputtering phenomenon which degrades delay line propagation, and will report on operating performance of a 50 watt M-BWO having this type of delay line.