220 GHz ultra wide band TWTA: Nano CNC fabrication and RF testing

Precision fabrication and RF testing of a 220 GHz GHz sheet beam TWTA based on the double vane half-period staggered slow wave structure design[1]is reported. NanoCNC Milling technology[2] was employed to precision fabricate the entire TWTA circuit in bulk copper, incorporating input and output couplers, sever ports, and the slow wave structure with matching. To accommodate an overhead input/output coupler design, the TWTA circuit was fabricated in a three layer process with dimensional tolerance of within ~1-2 μm and surface roughness ~50 nm. The TWTA circuit was diffusion bonded (at UC Davis) within an accuracy of less than 10 μm between two circuit halves. Initial TWTA cold tests employing a BWO based scalar network analyzer showed an in-band insert ion loss of ~ -5 dB with a bandwidth exceeding 50 GHz. The in-band return loss was <; -12 dB. These measurements were subsequently confirmed using an Agilent PNA-X VNA. The hot test setup is ready to test the TWTA being baked at CPI and the latest test results will be presented at the conference and added to the abstract.