Voltage controlled oscillator
AssigneeBroadcom Corporation
InventorZhiheng Cao
Life of this patent
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Abstract
A bias loop is used to program LC tank common mode voltage to allow operation at two different supply voltages VDD (e.g., 2.5V and 1.2V), and two different tank swings. This also allows lower phase noise through optimizing Ids shape allowing class C operation for both voltages. The two different supply voltages allow operation using multiple communication protocols such as 802.11n and 802.11ac within a common VCO circuit. The VCO can form part of a transceiver to provide frequencies in multiple bands.
Claims20
A communications voltage controlled oscillator (VCO) comprising:
- a voltage controlled oscillator (VCO) comprising at least a tank circuit and core;
- a bias loop connected to the voltage controlled oscillator (VCO) comprising:
- a reference generator generating variable supply and saturation voltage sources;
- a constant current source connected to the tank circuit and reference generator;
- a power amplifier with first input connected to the reference generator, second input connected to the constant current source and output connected to the core, and
- wherein the bias loop programs tank circuit common mode voltage to operate the voltage controlled oscillator (VCO) using two or more supply voltages and two or more tank swings by lowering core bias.
A method to program LC tank circuit common mode voltage for a voltage controlled oscillator (VCO) with core to provide operation at two or more different supply voltages, and two or more different tank swings, the method comprising:
- generating variable supply and saturation voltage references in a bias loop,
- setting tank circuit inductance L at variable supply and saturation voltage reference generator output to achieve maximum tank swing, and
- using the bias loop to lower transistor gate bias of the VCO core.
A circuit arranged to operate a high swing voltage controlled oscillator (VCO) at two or more different supply voltages comprising:
- a high swing voltage controlled oscillator (VCO) comprising at least a tank circuit and core;
- a class C bias loop connected to the voltage controlled oscillator (VCO) comprising:
- a reference generator generating variable supply and saturation voltage sources;
- a constant current source operatively connected to the tank circuit, reference generator and core;
- a power amplifier with inputs connected to the reference generator and constant current source and output connected to the core, and
- wherein the class C bias loop operates the high swing voltage controlled oscillator (VCO) at the two or more supply voltages by lowering VCO core transistor gate bias.
Dependencies are inferred from the claim text.