Ka-band MMIC voltage-controlled oscillators

A large-signal design procedure, along with simulated and measured results for two Ka-band MMIC voltage-controlled oscillators (VCOs), is described. These circuits were built for deployment in 28GHz local multi-point distribution (or communication) systems (LMDS or LMCS) and 38GHz communication applications. They were designed for the best phase-noise and spurious performance. The VCO for the 38GHz mobile communication systems was fabricated using a hetero-junction bipolar transistor (HBT) process. It provides an output power of OdBm at 40.5GHz with a 200MHz tuning range and has a free-running phase-noise of -83dBc/Hz at 100kHz offset. The VCO for the 28GHz LMDS/LMCS application was fabricated using a high-electron mobility transistor (HEMT) process. It oscillates at 29GHz, with a tuning range of 700MHz and buffered output power in excess of 20dBm, and has a free-running phase-noise of -62dBc/Hz at 100kHz offset. Once phase-locked using a 10MHz reference signal, the 29GHz VCO exhibits an improved phase-noise of -70dBc/Hz at 100kHz offset.