A Ka-band BiCMOS LC-VCO with wide tuning range and low phase noise using switched coupled inductors

This paper presents a wideband and low phase noise millimeter-wave (mm-wave) voltage-controlled oscillator (VCO) fabricated in 130 nm BiCMOS technology. The output signal can sweep from 29.6 to 35.5 GHz, which corresponds to 18.1% tuning range. The LC-tank of the VCO consists of two coupled inductors and a binary weighted varactor bank. The secondary inductor is terminated with a switch realized with heterojunction bipolar transistor (HBT). Depending on the switch state, the effective inductance of the LC-core can be changed which leads to significant improvement of tuning range. It is shown that the resistance of the switch in ON state can have a small effect on the LC-tank quality factor Q if the switch is properly sized. This results in a good phase noise performance over the whole frequency range. The measured phase noise at 1 MHz offset from the carrier is better than -97 dBc/Hz, which results in a figure-of-merit of -180 dBc/Hz. The VCO dissipates 20 mW and occupies 0.1mm² chip area.