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US 2002/0171499 A1Published application
Varactor based differential VCO band switching
AssigneeBroadcom Corporation
InventorsAfshin Momtaz, Armond Hairapetian
Life of this patent
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Abstract
Method and circuitry for implementing VCOs with improved frequency band switching use differentially-coupled varactors to implement the different frequency bands. According to a specific embodiment, one side of a varactor couples to the tank circuit and the other side is coupled either to ground or to the positive power supply VDD without introducing any series parasitic resistance.
Claims22
A voltage controlled oscillator (VCO) comprising:
- a differential inductor/capacitor tank circuit connected between a first node and a second node;
- a first band-switching varactor connected between the first node and a S switching node;
- and
- a second band-switching varactor connected between the second node and the switching node,
- wherein, a frequency band of the VCO is modified by switching a signal at the switching node.
2 more elements
A method for switching a frequency band of a differential voltage controlled oscillator, the method comprising:
- adding a first capacitance to a differential tank circuit by applying a first signal to a common node of a differential pair of varactors;
- and
- adding a second capacitance to the differential tank circuit by applying a second signal to the common node of the differential pair of varactors.
A differential voltage controlled oscillator comprising:
- a differential LC tank circuit connected between a first node and a second node;
- a plurality of pairs of varactors each pair having a first varactor with a first terminal connected to the first node and a second varactor with a first terminal connected to the second node, second terminals of each pair connecting to a common node;
- and
- a plurality of switch circuits each connected to a respective common node of the plurality of pairs of varactors,
- wherein, each switch circuit is configured to switch its respective common node between one of a first voltage or a second voltage.
2 more elements
Dependencies are inferred from the claim text.