Reducing flicker noise up-conversion in a 65nm CMOS VCO in the 1.6 to 2.6 GHz band

The demand of voltage-controlled oscillators (VCOs) with a broad tuning range can lead to unacceptable degradation of the 1/f³ phase-noise component if traditional voltage-biased topologies are implemented. In this paper, a novel VCO architecture is proposed, where a segmented transconductor tailors the negative-g_m depending on the operating range to ensure that flicker noise up-conversion remains minimal. The implemented oscillator covers both 4G and WiMAX 2.5-GHz operation modes and achieves a 10-dB reduction of the 1/f³ phase noise without impairing the 1/f² phase-noise performance.