125 GHz Frequency Doubler Using a Waveguide Cavity Produced by Stereolithography
Talal Skaik, Colin Viegas, Jeff Powell, Byron Alderman, Peter G. Huggard, Hui Wang, Carl Leonard, Yi Wang
Abstract
This article reports on the first Schottky diode frequency doubler with a split-block waveguide structure fabricated by a high-precision stereolithography (SLA) printing process. The printed polymer waveguide parts were plated with copper and a thin protective layer of gold. The surface roughness of the printed waveguide parts has been characterized and the critical dimensions measured, revealing good printing quality as well as a dimensional accuracy that meets the tight tolerance requirements for subterahertz active devices. The 62.5 to 125 GHz frequency doubler circuit comprises a 20 μm thick GaAs Schottky diode monolithic microwave integrated circuit (MMIC) in the waveguide. The measured doubler provides a maximum output power of 33 mW at 126 GHz for input power of 100 mW. The peak conversion efficiency was about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$32\% $</tex-math></inline-formula> at input powers from 80 to 110 mW. This doubler performance is compared with and found to be nearly identical to the same MMIC housed in a CNC-machined metal package. This work demonstrates the capability of high-precision SLA techniques for producing subterahertz waveguide components.