Tuning circuit for inductor capacitor (LC) tank digitally controlled oscillator
AssigneeMarvell International Ltd.
InventorsFernando De Bernardinis, Luca Fanori, Antonio Liscidini
Life of this patent
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Abstract
In one embodiment, an apparatus includes a first circuit of a digitally controlled oscillator (DCO). The first circuit has a loss component. A second circuit is coupled to the first circuit and configured to transform a positive impedance into a negative impedance in series with a negative resistance. The negative impedance includes an adjustable reactive component used to adjust a frequency of an output signal of the DCO. An equivalent reactance seen by the first circuit is less than a reactance of the adjustable reactive component.
Claims20
An apparatus comprising:
- a first circuit of a digitally controlled oscillator (DCO), the first circuit having a loss component;
- a second circuit coupled to the first circuit, the second circuit comprising:
- a first cross coupled pair of transistors coupled to the first circuit;
- and
- an adjustable reactive component coupled to the first cross coupled pair of transistors, the adjustable reactive component configured to adjust a frequency of an output signal of the DCO, wherein the second circuit is configured to transform a positive impedance into a negative impedance and provide a first negative resistance;
- a third circuit coupled to the first circuit, the third circuit comprising a second cross coupled pair of transistors coupled to the first circuit, wherein the third circuit is configured to provide a second negative resistance and does not include a reactive component,
- wherein:
- an equivalent reactance seen by the first circuit is less than a reactance of the adjustable reactive component, and
- the second circuit and the third circuit are between the first circuit and a supply.
An apparatus comprising:
- a first circuit of a digitally controlled oscillator (DCO), the first circuit having a loss component;
- and
- a second circuit coupled to the first circuit, the second circuit configured to transform a positive impedance into a negative impedance in series with a negative resistance, wherein the negative impedance includes an adjustable reactive component used to adjust a frequency of an output signal of the DCO,
- wherein:
- an equivalent reactance seen by the first circuit is less than a reactance of the adjustable reactive component, and
- the reactive component comprises a matrix of varactors, wherein:
- a first set of varactors are coupled to a first reference voltage;
- a second set of varactors are coupled to a second reference voltage;
- and
- a variable varactor is coupled to a variable voltage signal.
A method comprising:
- providing a first negative resistance to a tank circuit using a first circuit;
- providing a second negative resistance to the tank circuit using a second circuit;
- receiving an error estimate of an output signal of a DCO, the error estimate determined by comparing the output signal to a reference signal;
- and
- adjusting a reactance of a reactive component included in the first circuit to adjust a frequency of the output signal based on the error estimate,
- wherein:
- an equivalent reactance seen by a tank circuit of the DCO is less than the reactance of the reactive component,
- the second circuit does not include a reactive component, and
- the first circuit and the second circuit are between the tank circuit and a supply.
Dependencies are inferred from the claim text.