Patent ID: 9559702
Date: 2017-01-31
CPC Classifications: H03B,H03L

Claim:
1. A circuit comprising: an oscillator to output an oscillator carrier, the oscillator including a differential tank circuit, an active device, and a common-mode reactance circuit, wherein the differential tank circuit includes a first variable capacitor and a second variable capacitor each coupled to a common-mode port of the differential tank circuit, wherein the common-mode reactance circuit includes a common-mode variable capacitor coupled to the common-mode port of the differential tank circuit, wherein a phase difference between a voltage of the oscillator carrier and a device current of the active device is adjusted to reduce upconversion of flicker noise of the oscillator, wherein adjusting the phase difference to reduce upconversion of the flicker noise is performed by adjusting, using the common-mode reactance circuit, a common-mode impedance of the oscillator to generate, at a second harmonic of a frequency of the oscillator carrier and according to an imaginary part of the common-mode impedance, a phase shift of a common mode current that is substantially equal to a negative of a phase shift of a differential mode current in the active device, the second harmonic being a frequency twice the frequency of the oscillator carrier, and wherein adjusting the common-mode impedance includes adjusting the common-mode impedance to have the imaginary part substantially equal to a value Z wherein g