Low noise and low power voltage-controlled oscillator (VCO) using transconductance (gm) degeneration

摘要

Certain aspects of the present disclosure generally relate to voltage-controlled oscillators (VCOs) using a lowered or an adjustable negative transconductance (−gm) compared to conventional VCOs. This −gm degeneration technique suppresses the noise injected into an inductor-capacitor (LC) tank of the VCO, thereby providing lower signal-to-noise ratio (SNR) for a given VCO voltage swing, lower power consumption, and decreased phase noise. One example VCO generally includes a resonant tank circuit, an active negative transconductance circuit connected with the resonant tank circuit, and a bias current circuit for sourcing or sinking a bias current through the resonant tank circuit and the active negative transconductance circuit to generate an oscillating signal. The active negative transconductance circuit includes cross-coupled transistors and an impedance connected between the cross-coupled transistors and a reference voltage.

主权项

1. A voltage controlled oscillator (VCO), comprising:
a resonant tank circuit; an active negative transconductance circuit connected with the resonant tank circuit, comprising:
cross-coupled transistors having drains connected with the resonant tank circuit; andan impedance connected between sources of the cross-coupled transistors and a reference voltage; and a bias current circuit for sourcing or sinking a bias current through the resonant tank circuit and the active negative transconductance circuit to generate an oscillating signal.