160 GHz Balanced Frequency Quadruplers Based on Quasi-Vertical Schottky Varactors Integrated on Micromachined Silicon

This work reports on an integrated frequency quadrupler operating at 160 GHz with maximum efficiency of 30% and corresponding output power of 70 mW. The quadrupler design includes two frequency doubler stages in cascade and is based on a balanced circuit architecture that addresses degradation issues often arising from impedance mismatches between multiplier stages. A unique quasi-vertical diode fabrication process consisting of transfer of GaAs epitaxy to a thin silicon support substrate is used to implement the quadrupler, resulting in an integrated drop-in chip module that incorporates 18 varactors, matching networks and beamleads for mounting. The chip is tailored to fit the multiplier waveguide housing, resulting in high reproducibility and consistency in manufacture and performance. Estimates of the varactor temperature for the multiplier were made using the diodes as integrated thermometers. These measurements estimate the operating temperature of the varactors in the quadrupler input stage to be 35 ^°C.