Development of Precision Alignment Techniques for Millimeter Wave Sources

High power generation at millimeter wave (mm-wave) frequencies is expensive and the concurrent need for wide bandwidths at these frequencies creates an extremely challenging problem. Currently the most stringent requirements for mm-wave power and bandwidth can only be practically met by vacuum electronics (VE) technology. At present, vacuum amplifiers with the required performance are prohibitively expensive due to the high precision machining and assembly processes involved. Specifically, the devices are constructed of metal and ceramic parts that require extremely tight tolerances be maintained across proportionally large dimensions of assembled piece parts. Therefore, mm-wave device development and deployment are significantly impacted by limitations in manufacturing techniques and processes, and devices providing state-of-the-art performance are expensive due to complex manufacturing steps with relatively low yields. Recent advances have demonstrated sub-micron level machining of individual parts but the assembly of multiple parts into complete devices, while maintaining the tolerances required, still presents a significant challenge in the manufacturing process. The use of precision alignment techniques, such as kinematic couplings, quasi-kinematic couplings and elastic averaging has the potential to transform the mm-wave devices fabrication process, by providing increased device performance while reducing fabrication costs. Traditional methods of assembly such as alignment pins and in-process machining have accuracies limited to the 10-micron range or above. High precision alignment techniques provide sub-micron alignment accuracies and eliminate the labor- and time-intensive traditional assembly processes using in-process machining and manual alignment of components by skilled assembly personnel.         The utilization of precision alignment techniques in the fabrication of mm-wave sources will provide improved alignment of the components and allow for generation of higher quality electron beams, these improvements will result in higher device efficiency and increased beam transmission through the mm-wave generating circuit. Increased beam transmission translates to reduced beam interception and reduced thermal loading on the circuit, decreased operating temperatures, improved device stability and increased operating efficiencies.  In addition to the device performance improvements, the use of precision alignment techniques will decrease production costs by eliminating the time consuming alignment labor from the assembly process. These new manufacturing techniques will reduce W-band device part count, thereby improving reliability and robustness and allowing for additional unit cost reduction.  High precision alignment techniques will improve reproducibility between mm-wave sources, minimizing power and efficiency variations from device to device.