A 480-530 GHz Balanced Frequency Quadrupler Based on Schottky Varactor Diodes Integrated on a Micromachined Silicon Membrane

This work reports on the design and implementation of the first integrated, balanced frequency quadrupler operating in the 480-530 GHz frequency range, with measured efficiency of 4.9% and corresponding output power of 17 mW at 518 GHz. The design is based on the cascaded balanced doubler topology, utilizing a 90-degree waveguide hybrid and two stages of frequency doublers. The design incorporates 18 varactor Schottky diodes, with each doubler comprising a balanced configuration of three diodes connected in series. The quasi-vertical diode structure is used to minimize series resistance and improve power handling and thermal performance.