A Low Phase Noise K-Band VCO With a Threshold Voltage-Based Current Source

This letter presents a low-phase-noise voltage-controlled oscillator (VCO) with a threshold-voltage (
$V_{\mathrm {TH}}$
)-based current source. The proposed current source is insensitive to the supply voltage, and the flicker noise of the transistor in the current source is decoupled, leading to lower phase noise to the resonator. In addition, a small-size differential inductor is adopted to diminish the resonator loss and to increase the quality factor. Fabricated in a 130-nm CMOS technology, the proposed VCO demonstrates a tuning range of 23.8–26.3 GHz (10.4%). It achieved a phase noise of −74.73 dBc/Hz at 100 kHz and −107.36 dBc/Hz at 1 MHz offset frequencies from the 24.005-GHz carrier frequency, respectively. The figure of merit (FoM) reaches −188 dBc/Hz.