High-efficiency terahertz frequency triplers

Design and experimental analysis of high-power and high-efficiency frequency triplers to the 220 GHz and 440 GHz bands are presented. Test data for the 220 GHz tripler show 23 mW output power with 16 % efficiency. Test data for the 440 GHz tripler show 13 mW output power with 12 % efficiency. The 3 dB bandwidth for both triplers is about 7 %. This performance is comparable to the best reported in the literature, at these frequencies. There are no mechanical tuners and thus the triplers may be electronically swept to any frequency in the band. The triplers comprise a waveguide housing, a pair of quartz microstrip circuits and a Virginia Diodes (VDI) GaAs Schottky varactor chip. The simple circuit topology makes it easy to assemble the multipliers and bias the varactors. A version to 800 GHz has been designed and should be available for testing in 2007. The design is scalable to frequencies above 1 THz.