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-gm 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.
This paper describes a simulation method to compute oscillator phase noise which combines transient and periodic-transfer-function analyses, available in most of the commercial circuit simulators. The proposed calculation technique is simple to implement and provides the designer a deep insight into phase noise generation mechanisms for both stationary and cyclostationary sources, thus resulting a powerful tool to perform an optimum design in RF applications.