H-Band High-Power and High-Efficiency Voltage-Controlled Oscillator IC and Waveguide Module

We present a high-power and high-efficiency voltage-controlled oscillator (VCO) integrated circuit (IC) and waveguide module operating at
H
-band (around 230 GHz) using a 250-nm InP HBT technology. The Colpitts oscillator with an
LC
emitter degeneration is adopted to reduce supply voltage and improve efficiency, where the inductance is implemented by the shorted transmission line. Capacitive feedback at the emitter is realized by the varactor consisting of the collector–base junction of the HBT. A common-base buffer amplifier is added to reduce the load-pulling effect of the Colpitts oscillator and increase output power. The optimum load impedance for high output power is determined from the load-pull simulations based on the large-signal oscillation analysis. To further increase output power, a low-loss on-chip balun is employed to combine output powers from each branch of the differential VCOs. On-wafer measurement of the fabricated VCO shows a peak output power of 6.8 dBm at 230 GHz with dc-to-radio-frequency (RF) efficiency of 6.0%. To build a stable and practical
H
-band source module, the fabricated VCO is mounted in a WR-3.4 waveguide. For this purpose, the on-chip balun is replaced with the dipole transition, which is also integrated into the InP substrate. The fabricated VCO module exhibits a peak output power of 6.4 dBm and dc-to-RF efficiency of 5.5% at 229.3 GHz. Oscillation frequency is tuned from 221.6 to 232.9 GHz. The phase noise is also measured to be −101.9 dBc/Hz at a 10 MHz offset at 230.3 GHz. To the best of the authors’ knowledge, these results demonstrate the best performance in terms of output power and efficiency among the reported
H
-band VCO ICs and modules.