Importance

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Abstract

Provided herein are apparatus and methods for reducing supply noise conversion to phase noise. In certain configurations, voltage controlled elements such as varactors are used to control a VCO output frequency. A VCO transfer function relating supply voltage noise to a common node of a varactor gives rise to a transfer function of value a representing a push coefficient. An intentional amount of supply noise can be added to a tuning voltage by injecting it at a tuning port of the VCO. By splitting an integration capacitance in a loop filter, an integration capacitance can be divided among a capacitor divider to create a transfer function of value β representing a compensating coefficient. The injected noise from the capacitor divider can reduce VCO pushing by canceling the value α. When the value β is set equal to the value α, the VCO pushing can be reduced to within the estimation or measurement accuracy of the value α.

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First Claim