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 28 GHz local multi-point distribution (or communication) systems (LMDS or LMCS) and 38 GHz communication applications. They were designed for the best phase-noise and spurious performance. The VCO for the 38 GHz mobile communication systems was fabricated using a heterojunction bipolar transistor (HBT) process. It provides an output power of 0 dBm at 40.5 GHz with a 200 MHz tuning range and has a free-running phase-noise of -83 dBc/Hz at 100 kHz offset. The VCO for the 28 GHz LMDS/LMCS application was fabricated using a high-electron mobility transistor (HEMT) process. It oscillates at 29 GHz, with a tuning range of 700 MHz and buffered output power in excess of 20 dBm, and has a free-running phase-noise of -62 dBc/Hz at 100 kHz offset. Once phase-locked using a 10 MHz reference signal, the 29 GHz VCO exhibits an improved phase-noise of -70 dBc/Hz at 100 kHz offset