K-band double-balanced mixer using GaAs HBT THz Schottky diodes

We report on a K-band double-balanced mixer using Schottky diodes made with our baseline (Foundry) GaAs HBT technology. The GaAs HBT MBE structure which yields a transistor f/sub max/ of 50 GHz, can also support Schottky diode structures with THz cut-off frequencies. A GaAs HBT Schottky diode double-balanced mixer achieves an upconversion loss of less than 6 dB over an RF output frequency band from 18-22 GHz, an LO frequency of 12 GHz @ +10 dBm, and an IF input frequency band from 6-10 GHz. An output IP3 of 9 dBm with an LO drive of 10 dBm was achieved. IF-RF and IF-LO isolations of >20 dB, and an LO-RF isolation of >30 dB were achieved over the broad band. In comparison to a HEMT Schottky diode implementation of the same identical design, the HBT Schottky implementation achieves lower conversion loss and higher IP3 for a given LO drive level and obtains similar isolation and intermodulation performance.<>