The design and analysis of 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) are described. These circuits were built for deployment in 28GHz local multipoint distribution (or communication) systems (LMDS or LMCS) and 38GHz communication applications. They were designed for optimum 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 0dBm 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 from the carrier.