A Technique for Planar Integration of Components of W-Band Backward-Wave Oscillator to Eliminate Misalignment

The alignment within the required tolerance between components like electron beam source, beam-wave interaction structure and spent beam collector is a major challenge in the realization of the high-power vacuum-tube sub-THz source. To overcome this major issue, a novel integrated W-band beam-wave interaction circuit along with spent beam collector and beam adapter region has been designed and developed on two planar metallic plates itself for the first time. It accomplished the level of required alignment of different components of a sub-THz source. This interaction circuit along with beam adapter region and spent beam collector has been developed on a single plate. These structures have been developed using optimized micro-milling techniques with achieved dimensional deviation less than <inline-formula> <tex-math notation="LaTeX">$ &lt; 7~\mu \text{m}$ </tex-math></inline-formula>. The average surface roughness is found to be around 100 nm, which is much less than the skin depth in the W band.