Apparatus and method for reducing phase noise in oscillator circuits
AssigneeBroadcom Corporation
InventorRamon A. Gomez
Life of this patent
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Abstract
A resonant oscillator circuit includes an active device and a resonator that causes the active device to oscillate at a resonant frequency of the resonator. The active device includes one or more transistors that are DC biased using one or more resistors. The bias resistors generate thermal noise that is proportional to the resistance value. An external inductor circuit is connected across the output terminals of the active device and in parallel with the resonator. The external inductor circuit short-out at least some of the thermal noise that is generated by the bias resistors, and thereby reduces the overall phase noise of the resonant oscillator.
Claims18
A method of reducing phase noise at an output of an oscillator having an active device, the method comprising the steps of:
- (1) causing said active device to oscillate at a resonant frequency;
- and
- (2) providing a DC feedback path across output terminals of said active device.
A differential oscillator circuit, comprising:
- a resonator having a resonant frequency;
- an active device, coupled to said resonator, having a differential output that oscillates at said resonant frequency;
- an active bias circuit that provides DC bias for said active device;
- and
- a DC feedback path coupled to said active device and connected in parallel with said resonator, whereby said DC feedback path shorts-out thermal noise associated with said active bias circuit.
Dependencies are inferred from the claim text.