Schottky frequency doubler for 140–220GHz using MMIC foundry process

Paper presents the design and fabrication steps as well as measurement results for a fixed-tuned full-waveguide band Schottky frequency doubler. The doubler consists of a GaAs MMIC chip embedded in a waveguide channel. The chip is fabricated using a commercial MMIC foundry process and two post-processing options, substrate thinning and etching around anode fingers, are implemented afterwards. The doubler is optimized for flat output power across the G-band (140–220 GHz) and for operation at low input power levels (0.5–10 mW). For example, with an input power level of 2 mW, two doublers with different post-processing options achieve output power flatness of 3.0 dB and 3.8 dB and average efficiencies of 4.0 % and 3.8 % at 140–220 GHz. The maximum measured efficiency and output power with 5 mW of input power are 6.4 % and −5.0 dBm at 204 GHz. To the authors' knowledge, these are the best published results for a full G-band frequency doubler using commercially available MMIC foundry process.