A novel self-oscillating HEMT-HBT cascode VCO-mixer using an active tunable inductor

Here we describe a unique Ka-band self-oscillating HEMT-HBT cascode mixer design which integrates an active tunable resonator circuit. The VCO-mixer MMIC integrates GaAs HEMT´s and HBT´s using selective molecular beam epitaxy (MBE) technology. The HEMT-HBT cascode active mixer operates similarly to a dual-gate mixer. The HBT of the cascode is used to construct a VCO by presenting the base with an HEMT tunable active inductor. The VCO can be tuned from 28.5 to 29.3 GHz while providing ≈0 dBm of output power. Operated as an upconverter, the MMIC achieves 6-9 dB conversion loss over a 31-39 GHz output frequency band. Using these active approaches, both VCO and mixer functions were integrated into a compact 1.44×0.76 mm² chip area. The active RF integrated circuit (IC) techniques presented here have direct implications to future high complexity millimeter-wave monolithic integrated circuits (MIMICs) for ultrahigh-speed clock recovery and digital radio applications